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TECHNICAL SUMMARY

Colloidal stabilisation of beer Colloidal instability in beer is caused through the interaction of proteins and polyphenols. To understand the th e mechanisms that underlie beer stabilisation it is necessary to examine the main changes which inevitably accompany the natural ageing of beer, and affect both its taste and clarity.

Technical Summary 1 The first of a new series of technical summaries for the Institute & Guild’s AME candidates. By Tim O’Rourke.

• Controlling the physical conditions in the brewing process

P

rofessor J. De Clerck 1 attributes three principal changes which occur in beer and which are brought about by the presence of polyphenols and tannins. • Increase in haze caused by the precipitation of protein substance. • Increases in harsh or unpleasant after taste in beer • Increases in colour, particularly following oxidation.

The first manifestation of the loss of colloidal stability is observed as chill haze, which is a reversible association between small low polymerised polyphenols and proteinaceous material. The tendency to form chill haze progressively increases over time. Oxidation of some polyphenols – flavanoids in particular, lead to the formation of condensed (polymerised) products. These are active precursors in haze formation, leading to permanent (irreversible) haze formation (see illustrations below). To avoid colloidal haze production the brewer has to control the brewing by the selection of brewing materials and production and storage of packaged beer. These steps can be divided into:

Controlling protein content Proteins in beer come from malt and some adjuncts such as wheat and barley. It is broken down during malting and mashing to produce haze precursors but is also the source of the amino acids necessary for yeast growth, hydrophobic proteins which produce beer foam and protein which give beer texture and mouthfeel. The brewer has to strike a balance between reducing protein content to improve colloidal stability and affecting fermentation and beer quality. Typical ways of reducing the protein content of a beer are: • Selecting malts low in nitrogen (typically 1.6 to 1.8% nitrogen) • Using adjuncts which are low or free from nitrogen e.g. maize flakes or brewing syrups. • Using under-modifi under-modified malts thereby reducing the amount of protein extracted, this will be

counter balanced by proteolysis in the mashing programme. • Proteins are also removed from the brewing process with the spent grains and as hot or cold break after wort boiling, during cooling and cold conditioning. The effi efficiency of separation will depend on the quality of boiling, performance of the whirlpool, and temperature of cold storage. • The performance of break separation can be improved through using kettle finings It is principally the acidic hydrophilic proteins containing prolein which bond with polyphenols to produce haze.

Controlling polyphenol content Polyphenols come from hops and husk of the malt. The polyphenols from hops are generally highly polymerised and are precipitated with hot and cold break before filtration and hence have little adverse effect on beer stability. The malt polyphenols are extracted during mashing and wort separation. During the brewing process may give beer some antioxidant protection, however there is little evidence that malt polyphenols protect bright beer from oxidation in package. Typical ways of reducing the polyphenol content in beer are by: • The use of adjuncts to dilute the amount of polyphenols coming from the malt. • Most malt polyphenol is extracted towards the end of the runoff. Extraction can be reducing by avoiding running to a low gravity Oxidised Tannoids

• Controlling the protein content of the beer Protein

• Controlling the polyphenol content in the beer Oxidised Flavanoids Simple Flavanoids

Protein

Protein

Haze free In freshly packaged beer there is no chill haze (<0.6 EBC) and the polyphenol haze precursors exist as simple flavanoid molecule which bond with proteins by hydrogen bonding.

Chill haze

Permanent haze

Oxygen catalyses the polymerisation of simple flavanoids which become three to four units long, and which are are able to bond with a number of proteins via hydrogen bonds to form chill haze.

As the polyphenols continue to oxidise larger complexes are are formed, and some of the polyphenol/protein polyphenol/ protein hydrogen bonds are replaced by more permanent ionic bonds. These bonds no longer break when the beer is heated and leads to the formation of permanent haze.

The BREWER International •

www.igb.org.uk • January 2002

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TECHNICAL SUMMARY

(greater than 1004 or 1° 1 ° Plato) and keeping the sparge pH low (below 7). Operations such as weak wort recycling may increase the concentration of extracted polyphenols.

TABLE 1: Summary of techniques used in colloidal stabilisation of beer Composition of Chill Haze Adsorption

• Proteins and polyphenols form complexes at low temperatures, and hence are removed during cold maturation and cold filtration.

Precipitation

• Bentonite • Silicagel

• Tannic Acid

PROTEINS 40-75%

Degradation

Carbohydrates 3- 13%

• Enzymes such as Papain

Ash 0.7-5% Cu, Fe traces

Adsorption

• Polyclar PVPP • Polyamide (Nylon) • High molecular weight insoluble protein (Casein)

• A new variety of malt (proanthocyanidin free) has been developed by Carlsberg and is now commercially available. This may permanently solve the polyphenol problem for the brewers.

Removal of Protein-Tannoid complex

POLYPHENOLS About 17%

Controlling the brewing process. Attention to the brewing process can reduce the level of the protein and polyphenols finishing up in the final beer, thus reducing the tendency to produce colloidal instability. The principal changes which improve beer stability are:

• Chilling • Formaldehyde

• Cold storage and cold filtration of the beer encourages the formation of chill haze. It is essential once cooled, the beer remains cold particularly in line to the filter as the chill haze can rapidly re-dissolve. Lower temperatures (-2° (-2°C) are better for final beer stability. • Haze is produced as a result of oxidation of polyphenols, and hence eliminating oxygen, particularly in package will reduce the rate of haze formation and increase beer shelf life.

Summary of stabilisation control during processing

Area of Application

Polyphenol Reduction

Protein Reduction

Process Optimisation

Barley / Malt

Proanthocyanadin free barley High adjunct ratio

Low protein barley High adjunct ratio

Low malt modification High temperature mash

Mashing Mash separati aration on

Fermentation Matur Maturati ation on

High cut cut off off gravity vity Low sparge pH Avoid wort & trub recycling Time of hop hop addit addition ion Hotbreak breakremo remova vall Cold break removal Lack Lack of agitatio t ation n

Filtration

Stabiliser addition

Stabilisati on

PVPP

Wort boiling Wort clarifi clarificatio cation n

Brigh Bright worts wortsrun run off off

Kettle Kettlefi finings Hot break breakremov removal Cold break removal Sedimentati ntation on Auxiliary finings

Silica gel Tannic acid Enzyme

Time and vigour of boil Whirlpool effi efficiency

Area of

Causative

• Poor beer handling or over carbonation, particularly when using reduced hop compounds, can result in particulates due to collapsed foam floating in the beer. • Poorly hydrolysed foam stabiliser (Polyglycol alginate) • Lack of calcium in the mash can result in the formation of oxalic acid crystal, which can also lead to gushing. The brewer has to control the whole process to produce small pack beer with the required shelf life. It is not possible just to rely on chemical treatment at the end of the process to consistently achieve the colloidal stability. It is also found that a balanced chemical treatment removing both proteins and polyphenols provides a more effi ef ficient and more cost effective stabilization regime. s Further Reading •Tim O’ O’ Rourke et al from poster presented at Perth Convention – Ferment June 1998 – p189 • Tim O’ O’ Rourke Back to Basics, Brewers Guardian February 2000 – p29 • Mike O’ O’Neill – Advances in Beer Stabilisation The Brewer July Brewer July 1998 – p293 and August – p 353 • De Clerck J. Brewers Digest August 1970 p 62– 62 – 64 • McMurrough I et al “Effect of PVPP dosage on the flavanoid content of beer and consequences for beer quality” quality” Brew Digest 59 (10) 1984.

Application

Factors

Factors

Metal ions H ig ig h s to to rra a ge ge t em pe pe ra ra tu tu re re s H ig hi np ac ac ka ge ge ox ox yg en en Shaking/agitatio n

Soften water C oo oo l st or or ag ag e L ow ow pr pr oc es es so xy xy ge n Anti oxidants

Trade

Stock rotation Extended shelf life High te temperatures Direct su sunlight

BBD/Package date Beer fresh in time Direct de deliveries Refrigerated storage & distribution

Made Made by acidi acidic polymerisat y merisation of of silicate c atesolutions. Two forms: forms: hydr hydrogel ogelss70% & xerogels 5% moisture. Adsorbs protein proteins basedon selective cont control rol of pore pore diame diameter – removes <40,000 MW DOSAGE: Add to CT at run down up to 50g/hl Add to filter powder slurry up to 100g/hl ADVA ADVANT NTAGES: AGES: Insol Insoluble u ble – easy to use DISADVANTAGE: Moderately expensive. ve. Generally suitable if a shelf life < 9 months is required.

ACTION: ACTION:

Proteolytic enzyme SOURCE: RCE: Usual Usually l y Papainprod produce uced fro from m the the latex of Carica papaya. papaya. ACTIO ACTION: Hydr Hydroly olysesprote proteins. ins. (Beer foam foam is prot protein ein) DOSAGE: 2 to 6 mls/hl to rough or bright beer DISADVANTAGE: Survives normal pasteurisation <20 PU ’s Continues in bright beer may effect foam Tannic acid SOURCE: ACTIO ACTION:

Natural Natural gallotan o tannins nins extracted from Chinese Chinese gall gall nuts nuts or Shumac leave e aves. Has Has man many y hyd hydro roxyl xyl group groups, attracts prote proteins ins – bonds with nucleophylic (SH-& NH-) protein groups in a similar manner to natural beer polyphenols to produce insoluble precipitate. DOSAGE: 5 to 8 g/hl to cold rough beer AD AD VA NT NTA GE Ve ry ry e ffi fficient stabiliser DISADVANTAGE: Added in line cold 0 to -10C Requires 5 to 10 minutes contact Produces voluminous bottoms Polyvinylpolypyrrolidone SO URCE : Cros sl ink ed P VP – made synthetically. ACTION: ACTION: Preferentially l y bond bonds s with polymeriz polymerized ed polyp polyphenols henols (tannins)thro nins)through ugh hydroge hydrogen and multi-site bonding. DOSAGE: Single use 10 to 30 g/hl. Regeneration 25 to 50 g/hl A DVANTAGES: Very effective stabiliser Selective for problematical polyphenols Insoluble – easy to use DISADVANTAGE: High cost for single ngle use. Capital investment for regeneration system.

Process aids to reduce proteins or polyphenols.

By optimising the brewing process it is possible to produce good which are stable for up to three months without additional treatment. However, if a longer shelf life is required chemical stabilisers are recommended. See Table 1, above left. Preventative

Packaging and distribution

Summary of the properties of different beer stabilisers Silica Gel SOURCE:

• The protein/ polyphenol interactions are dependent on electrostatic attractions between the two compounds. It is found that beers with higher pH, above 4.2, show bette r colloidal stability.

Time Time and and temp. of cold storage Coldfi Cold filtration Oxygen pick up Metal ions Contact time Temperature Contact

Summary of stabilisation control during packaging

• Oxidative reactions are catylised by metal ions (particularly Fe2+ and Cu2+ ) reduction of metal ion improve beer stability. Similar oxidative processes also accelerate staling in beer and colloidal instability is often associated with aged beer flavours.

particles in the bear either as a result of a breakthrough from the filter or filter aid.

Other possible causes of haze in bright beer As well as colloidal instability there are other hazes found in bright beer: • Polysaccharides such as starch and beta glucans not broken down during mashing, can produce a fine haze or cast in finished beer. As well as haze the presence of the complex carbohydrates often cause filtration problems.

ONLINE www.igb.org.uk Please visit our website for full information on all the IGB’ IGB’s activities and services

• Poor filtration and hygiene can lead to

24

January 2002 •


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WORT BOILING

The function of wort boiling T

he purpose of wort boiling is to stabilise the wort by:

• Killing spoilage micro-organisms. • Reducing the amount of coagulable nitrogen thus promoting colloidal stability. • Extracting the desirable principles of h ops to give beer its characteristic aroma and flavour. • Reducing undesirable volatile compounds through evaporation. Clarified wort is usually collected directly in the wort kettle or run to a wort receiving vessel (often called a pre-run or underback) before being transferred to the wort kettle. The wort kettle is fitted with heating, either using direct fuel combustion or indirectly, using steam. The wort in the kettle is first heated from wort separation run off temperature, which is between 65°C and 78°C, to boiling (usually just above 100°C, at atmospheric pressure because of the dissolved solids). The kettle contents are then boiled for between 30 and 120 minutes. Wort boiling has a high energy demand and accounts for as much as 40% of the energy consumption of a brewery.

Concentration of Wort

Sterilisation of the Wort

During wort boiling water is driven off as steam, thus concentrating the wort. The amount of water removed during the boil is directly proportional proportional to the rate of evaporation (and hence the amount of energy supplied) once boiling has been achieved. The effi efficiency will be affected by the design of the kettle, particularly the surface area. Traditionally, high gravity beers, such as strong lagers and barley wines had a long boil time, the major purpose being the evaporation of water to concentrate the wort. There are however other ways of achieving high gravity worts without excessive excessive wort boiling:

Brewing raw materials such as malt, hops and occasionally brewing water itself are infected by micro-organisms, and these have to be killed during the brewing process to prevent wort and beer spoilage. After boiling the wort is largely free from microbial contamination. Some microsp. and other organisms, primarily Bacillus sp. thermophilic bacteria are able to form spores which can withstand heat treatment, including boiling, and if present in the raw materials or the brewing water may persist into the finished beer.

• Parti-gylesParti-gyles- collecting different copper gravities. • Sugar adjuncts – direct addition of extract to the copp er. • Weak wort recycling – recovering the weak worts from the lauter tun to be re-used for mashing. • Dewatering grains – where the extract left in the grains is recovered and reprocessed for mashing, sparging or to be added to the kettle. High extract wort separation techniques

Technical Summary 2 The second in this new series of technical summaries for the Institute & Guild’ Guild’s AME candidates. By Tim O’ O’Rourke.

understand the principle changes which occurring in the wort during boiling.

25

TECHNICAL SUMMARY

(greater than 1004 or 1° 1 ° Plato) and keeping the sparge pH low (below 7). Operations such as weak wort recycling may increase the concentration of extracted polyphenols.

TABLE 1: Summary of techniques used in colloidal stabilisation of beer Composition of Chill Haze Adsorption

• Proteins and polyphenols form complexes at low temperatures, and hence are removed during cold maturation and cold filtration.

Precipitation

• Bentonite • Silicagel

• Tannic Acid

PROTEINS 40-75%

Degradation

Carbohydrates 3- 13%

• Enzymes such as Papain

Ash 0.7-5% Cu, Fe traces

Adsorption

• Polyclar PVPP • Polyamide (Nylon) • High molecular weight insoluble protein (Casein)

• A new variety of malt (proanthocyanidin free) has been developed by Carlsberg and is now commercially available. This may permanently solve the polyphenol problem for the brewers.

Removal of Protein-Tannoid complex

POLYPHENOLS About 17%

Controlling the brewing process. Attention to the brewing process can reduce the level of the protein and polyphenols finishing up in the final beer, thus reducing the tendency to produce colloidal instability. The principal changes which improve beer stability are:

• Chilling • Formaldehyde

• Cold storage and cold filtration of the beer encourages the formation of chill haze. It is essential once cooled, the beer remains cold particularly in line to the filter as the chill haze can rapidly re-dissolve. Lower temperatures (-2° (-2°C) are better for final beer stability. • Haze is produced as a result of oxidation of polyphenols, and hence eliminating oxygen, particularly in package will reduce the rate of haze formation and increase beer shelf life.

Summary of stabilisation control during processing

Area of Application

Polyphenol Reduction

Protein Reduction

Process Optimisation

Barley / Malt

Proanthocyanadin free barley High adjunct ratio

Low protein barley High adjunct ratio

Low malt modification High temperature mash

Mashing Mash separati aration on

Fermentation Matur Maturati ation on

High cut cut off off gravity vity Low sparge pH Avoid wort & trub recycling Time of hop hop addit addition ion Hotbreak breakremo remova vall Cold break removal Lack Lack of agitatio t ation n

Filtration

Stabiliser addition

Stabilisati on

PVPP

Wort boiling Wort clarifi clarificatio cation n

Brigh Bright worts wortsrun run off off

Kettle Kettlefi finings Hot break breakremov removal Cold break removal Sedimentati ntation on Auxiliary finings

Silica gel Tannic acid Enzyme

Time and vigour of boil Whirlpool effi efficiency

Area of

Causative

• Poor beer handling or over carbonation, particularly when using reduced hop compounds, can result in particulates due to collapsed foam floating in the beer. • Poorly hydrolysed foam stabiliser (Polyglycol alginate) • Lack of calcium in the mash can result in the formation of oxalic acid crystal, which can also lead to gushing. The brewer has to control the whole process to produce small pack beer with the required shelf life. It is not possible just to rely on chemical treatment at the end of the process to consistently achieve the colloidal stability. It is also found that a balanced chemical treatment removing both proteins and polyphenols provides a more effi ef ficient and more cost effective stabilization regime. s Further Reading •Tim O’ O’ Rourke et al from poster presented at Perth Convention – Ferment June 1998 – p189 • Tim O’ O’ Rourke Back to Basics, Brewers Guardian February 2000 – p29 • Mike O’ O’Neill – Advances in Beer Stabilisation The Brewer July Brewer July 1998 – p293 and August – p 353 • De Clerck J. Brewers Digest August 1970 p 62– 62 – 64 • McMurrough I et al “Effect of PVPP dosage on the flavanoid content of beer and consequences for beer quality” quality” Brew Digest 59 (10) 1984.

Application

Factors

Factors

Metal ions H ig ig h s to to rra a ge ge t em pe pe ra ra tu tu re re s H ig hi np ac ac ka ge ge ox ox yg en en Shaking/agitatio n

Soften water C oo oo l st or or ag ag e L ow ow pr pr oc es es so xy xy ge n Anti oxidants

Trade

Stock rotation Extended shelf life High te temperatures Direct su sunlight

BBD/Package date Beer fresh in time Direct de deliveries Refrigerated storage & distribution

Made Made by acidi acidic polymerisat y merisation of of silicate c atesolutions. Two forms: forms: hydr hydrogel ogelss70% & xerogels 5% moisture. Adsorbs protein proteins basedon selective cont control rol of pore pore diame diameter – removes <40,000 MW DOSAGE: Add to CT at run down up to 50g/hl Add to filter powder slurry up to 100g/hl ADVA ADVANT NTAGES: AGES: Insol Insoluble u ble – easy to use DISADVANTAGE: Moderately expensive. ve. Generally suitable if a shelf life < 9 months is required.

ACTION: ACTION:

Proteolytic enzyme SOURCE: RCE: Usual Usually l y Papainprod produce uced fro from m the the latex of Carica papaya. papaya. ACTIO ACTION: Hydr Hydroly olysesprote proteins. ins. (Beer foam foam is prot protein ein) DOSAGE: 2 to 6 mls/hl to rough or bright beer DISADVANTAGE: Survives normal pasteurisation <20 PU ’s Continues in bright beer may effect foam Tannic acid SOURCE: ACTIO ACTION:

Natural Natural gallotan o tannins nins extracted from Chinese Chinese gall gall nuts nuts or Shumac leave e aves. Has Has man many y hyd hydro roxyl xyl group groups, attracts prote proteins ins – bonds with nucleophylic (SH-& NH-) protein groups in a similar manner to natural beer polyphenols to produce insoluble precipitate. DOSAGE: 5 to 8 g/hl to cold rough beer AD AD VA NT NTA GE Ve ry ry e ffi fficient stabiliser DISADVANTAGE: Added in line cold 0 to -10C Requires 5 to 10 minutes contact Produces voluminous bottoms Polyvinylpolypyrrolidone SO URCE : Cros sl ink ed P VP – made synthetically. ACTION: ACTION: Preferentially l y bond bonds s with polymeriz polymerized ed polyp polyphenols henols (tannins)thro nins)through ugh hydroge hydrogen and multi-site bonding. DOSAGE: Single use 10 to 30 g/hl. Regeneration 25 to 50 g/hl A DVANTAGES: Very effective stabiliser Selective for problematical polyphenols Insoluble – easy to use DISADVANTAGE: High cost for single ngle use. Capital investment for regeneration system.

Process aids to reduce proteins or polyphenols.

By optimising the brewing process it is possible to produce good which are stable for up to three months without additional treatment. However, if a longer shelf life is required chemical stabilisers are recommended. See Table 1, above left. Preventative

Packaging and distribution

Summary of the properties of different beer stabilisers Silica Gel SOURCE:

• The protein/ polyphenol interactions are dependent on electrostatic attractions between the two compounds. It is found that beers with higher pH, above 4.2, show bette r colloidal stability.

Time Time and and temp. of cold storage Coldfi Cold filtration Oxygen pick up Metal ions Contact time Temperature Contact

Summary of stabilisation control during packaging

• Oxidative reactions are catylised by metal ions (particularly Fe2+ and Cu2+ ) reduction of metal ion improve beer stability. Similar oxidative processes also accelerate staling in beer and colloidal instability is often associated with aged beer flavours.

particles in the bear either as a result of a breakthrough from the filter or filter aid.

Other possible causes of haze in bright beer As well as colloidal instability there are other hazes found in bright beer: • Polysaccharides such as starch and beta glucans not broken down during mashing, can produce a fine haze or cast in finished beer. As well as haze the presence of the complex carbohydrates often cause filtration problems.

ONLINE www.igb.org.uk Please visit our website for full information on all the IGB’ IGB’s activities and services

• Poor filtration and hygiene can lead to

24

January 2002 •


www.igb.org.uk



WORT BOILING



• Killing spoilage micro-organisms. • Reducing the amount of coagulable nitrogen thus promoting colloidal stability. • Extracting the desirable principles of h ops to give beer its characteristic aroma and flavour. • Reducing undesirable volatile compounds through evaporation. Clarified wort is usually collected directly in the wort kettle or run to a wort receiving vessel (often called a pre-run or underback) before being transferred to the wort kettle. The wort kettle is fitted with heating, either using direct fuel combustion or indirectly, using steam. The wort in the kettle is first heated from wort separation run off temperature, which is between 65°C and 78°C, to boiling (usually just above 100°C, at atmospheric pressure because of the dissolved solids). The kettle contents are then boiled for between 30 and 120 minutes. Wort boiling has a high energy demand and accounts for as much as 40% of the energy consumption of a brewery.




Brewing raw materials such as malt, hops and occasionally brewing water itself are infected by micro-organisms, and these have to be killed during the brewing process to prevent wort and beer spoilage. After boiling the wort is largely free from microbial contamination. Some microsp. and other organisms, primarily Bacillus sp. thermophilic bacteria are able to form spores which can withstand heat treatment, including boiling, and if present in the raw materials or the brewing water may persist into the finished beer.

• Parti-gylesParti-gyles- collecting different copper gravities. • Sugar adjuncts – direct addition of extract to the copp er. • Weak wort recycling – recovering the weak worts from the lauter tun to be re-used for mashing. • Dewatering grains – where the extract left in the grains is recovered and reprocessed for mashing, sparging or to be added to the kettle. High extract wort separation techniques



25

WORT BOILING



• Killing spoilage micro-organisms. • Reducing the amount of coagulable nitrogen thus promoting colloidal stability. • Extracting the desirable principles of h ops to give beer its characteristic aroma and flavour. • Reducing undesirable volatile compounds through evaporation. Clarified wort is usually collected directly in the wort kettle or run to a wort receiving vessel (often called a pre-run or underback) before being transferred to the wort kettle. The wort kettle is fitted with heating, either using direct fuel combustion or indirectly, using steam. The wort in the kettle is first heated from wort separation run off temperature, which is between 65°C and 78°C, to boiling (usually just above 100°C, at atmospheric pressure because of the dissolved solids). The kettle contents are then boiled for between 30 and 120 minutes. Wort boiling has a high energy demand and accounts for as much as 40% of the energy consumption of a brewery. Most of the energy required to heat worts to boiling point is recovered during wort cooling through the use of heat exchangers, heating up the incoming brewing water (liquor) in preparation for the next brew. This gives a heat recovery efficiency of up to 99%. The additional energy required to evaporate the water vapour during the boil is generally lost up the chimney. chimney. It is by reducing this energy loss that real savings can be achieved. A variety of schemes are available to recover part of the energy from evaporation. The most effective ways to reduce energy consumption are by reducing % evaporation rates. The average % evaporation rates have fallen over the last 30 years from around 12 – 20% to between 4 – 8%. In order to appreciate the consequence of reducing evaporation rates it is necessary to

Figure 1




Brewing raw materials such as malt, hops and occasionally brewing water itself are infected by micro-organisms, and these have to be killed during the brewing process to prevent wort and beer spoilage. After boiling the wort is largely free from microbial contamination. Some microsp. and other organisms, primarily Bacillus sp. thermophilic bacteria are able to form spores which can withstand heat treatment, including boiling, and if present in the raw materials or the brewing water may persist into the finished beer. However beer does not support the subsequent growth of these organisms.

• Parti-gylesParti-gyles- collecting different copper gravities. • Sugar adjuncts – direct addition of extract to the copp er. • Weak wort recycling – recovering the weak worts from the lauter tun to be re-used for mashing. • Dewatering grains – where the extract left in the grains is recovered and reprocessed for mashing, sparging or to be added to the kettle. • High extract wort separation techniques – such as the Mash Filter achieve high gravity worts and high extract effi efficiencies.



Halting Enzyme Action Enzymes rely on their three dimensional structure for their activity. Above certain temperatures, (usually in the range of 5075° 75°C) the tertiary structure of the enzyme becomes denatured, and they lose their activity. By the time the wort has reached boiling point there is usually no residual enzyme activity. The continued action of enzymes after the normal mashing programme will alter the fermentability fermentability of the wort, and hence in a programmed mash there is a final mash temperature rise to between 76° 76° and 79° 79°C, which is suffi sufficient to halt the malt enzyme activity.

These techniques enable the production of high gravity worts, while still maintaining brewhouse yield without the use of unnecessary heat for wort concentration.

Isomerisation of Bitter Substances During boiling the insoluble alpha acid extracted from hops are converted to a more soluble iso-alpha acid. This reaction is accelerated by temperature. Isomerisation is a relatively rapid reaction with production of over 90% of the wort bitterness occurring within the first 30 minutes of boil. Maximum isomerisation usually occurs within 60 to 70 minutes of boiling and accounts for around 60% of the total alpha acid present. Iso alpha acid continues to be lost during the fermentation and maturation process and is lost in any foam produced so that the final conversion value of alpha acid into iso- alpha acid in the beer is around 40% (see Figure 1).

Figure 2


www.igb.org.uk • February 2002

17

WORT BOILING

Removal of Volatiles During the evaporation stage of wort boiling undesirable volatile compounds are driven off with the steam (see Figure 2). The principal malt derived volatile lost during wort boiling is DMS or dimethyl sulphide which comes from lager malts and gives lagers a taste described as “sweetcorn” sweetcorn ”. It is produced by thermal decomposition of S-methyl-methionine in a first order reaction, with a half life of around 35 minutes (see Figure 3).

• Temperature of wort • Vigour of boil • Surface tension • Condensation of volatiles in the vapour stack • Thickness of diffusion path • Duration of boil The kettle design will have a major infl influence on the factors listed above and it is found that more late hop character persists in gently agitated systems such as isometric kettle, than in more vigorous boiling systems with turbulent flow such as kettles fitted with an external wort boilers.

Figure 3 The DMS released during boiling is rapidly lost through evaporation. However, However, the breakdown of S-methyl methionine continues during the period between the end of boiling and wort cooling. The DMS released is not lost and persists into the finished beer. It is, therefore, possible to control the level of DMS by varying the duration of boil and whirlpool stage.

100 ppm will produce beer with around 40 ppm calcium. To assist in the f all in pH extra calcium ions in the form of calcium sulphate or calcium chloride are added to the kettle. An alternative method to decrease pH is through the direct addition of acids such as phosphoric or sulphuric acid which drop the wort pH. In Germany, where the addition of mineral acid is prohibited under the Reinheitsgebot the product of an acidifi acidi fied mash fermentation using lactic acid bacteria is sometimes added to the kettle to assist in dropping the pH and improving beer flavour. It is important to achieve the required decrease in pH (generally around pH 5.0) as it effects wort and beer character, character, in particular the fall: • Improves protein coagulation • Improves beer flavour in particular VDK (diacetyl) reduction •Encourages yeast growth • Inhibits the growth of many other contaminating organisms. • Lower pH results in poorer hop utilisation. • Lower pH results in less colour formation

Increase in Colour The colour of wort increases during the boil. The reactions responsible for colour development fall into three broad categories: • Maillard reaction between carbonyl and amino compounds (see Figure 4). • Caramelisation of sugars, which is limited in steam heated coppers. • Oxidation of polyphenols.

Methods of control DMS levels in beer: • use malt with low S- methyl methionine levels. • long wort boiling time to decompose precursor and vaporise DMS. • short whirlpool stand time to reduce decomposition of the precursor. precursor. • rapid wort cooling – reducing the time the wort is held hot. • use wort stripping after the whirlpool stand to remove DMS.

Oxidation during wort boiling increases the colour particularly with oxidation of the polyphenols, which also has the effect of decreasing the reducing power of the wort and beer (see later). Mash and wort produced with low oxidation produces lower wort and beer with lower colours and improved flavour stability.

(Note: not all DMS comes from the malt and small amounts are produced during fermentation and by beer spoilage organisms). It was found that by reducing the boiling time from 60 minutes to 45 minutes, with the same level of absolute evaporation, the survival of DMS precursor increased by 16% for a standard wort corrected to 1039° 1039° original gravity. Hop volatiles (hop oils) are also lost during wort boiling, and if present in too high a concentration will contribute a bitter,

vegetable grassy flavour to the beer. Most of the hop oil volatiles are lost during a standard 60 to 90 minute boil. Where late hop character is required in beer, a small amount (up to 20% of the total hop charge) of selected aroma hops can be added to the kettle 5 to 15 minutes before the end of the boil. The principal factors which effect the evaporation of volatiles include:

Reducing Wort pH Control of pH throughout the brewing process, from brewing water to final package, is fundamental for product consistency. consistency. Wort pH starts to decrease during mashing continues to fall during wort boiling. The principal fall in pH is due to the reaction of Ca 2+ compounds with phosphates and polypeptides to form an insoluble compounds releasing H + (hydrogen ions) See Table 1. At least half the calcium present in wort is precipitated by the end of wort boiling. Hence sweet wort with a starting concentration of

Reducing Wort Nitrogen Levels During the brewing process it is necessary to decrease the level of high molecular weight nitrogen, which comes from the malt, and if allowed to persist can effect the pH, colloidal stability (chill haze and permanent haze), fining and clarifying properties, fermentation and taste of the beer. beer. Wort boiling is only one, if an important stage, in the reduction of nitrogen, and the effect in reducing the amount of wort nitrogen (measured by the Kjeldahl method ) for a standard boil at 100° 100 °C are shown below. % Nitrogen removal after different boiling times for a standard boil Time of boil (hrs) 0 0.5 1 1.5 2 3

% nitrogen removal 0 5.4% 6.2% 7.7% 9.9% 10.4%

Ref: Hough, Briggs and Stephen “Malting and Brewing Science”

Because of the relatively small overall reduction in total nitrogen during wort boiling it is diffi difficult to obtain consistent results even from the same kettle with the same quality of wort. (for example, over 9 samples from individual brews, a result of 1.9 ± 2.3 mg/100

Table 1: Changes in pH which can occur during wort

Before boil

6.06 5.63 5.09

pH of wort After boil After 3 hours 5.69 5.39 4.99

After 6 hours 5.46 5.22 4.96

Ref: Hough, Briggs and Stephen “Malting and Brewing Science ”

Figure 4

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February 2002 •


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ml. was obtained at 95% confi con fidence level). However, However, using a more specifi speci fic test (gel electrophoresis) it is possible to separate the nitrogen compounds by their molecular weight, to show that wort boiling is more effective at removing the higher molecular weight fraction, which is also the fraction responsible for colloidal instability in packaged beer (see Table 2) The process of protein/polypeptide coagulation involves the replacement of intra by inter molecular bonds, thereby increasing the effective molecular weight of each molecule. Aggregates of different molecular weight molecules are built up during wort boiling as a result of inter-molecular bonding, provided that they are not disrupted by mechanical shear. shear. During the whirlpool phase, with suffi sufficient time and momentum, these aggregates continue to coalesce and sediment out as hot break. The degree of protein and polypeptide removed depends on the probability of individual molecules colliding and forming stable bonds during the boil, and this is directly proportional to the length and vigour of the boil for a given temperature. Traditional Traditional criteria used for evaluating effi efficient wort boiling are: • Temperature of boil (usually just above l00 °C when boiling under atmospheric pressure). • Length of boil • Evaporation % per hour Traditionally Traditionally conditions for wort boiling were a 90 minute boil with a minimum of 10% evaporation per hour. However, because of the need to reduce energy costs and to improve

Figure 5.

brewhouse effi efficiencies shorter boiling times with lower evaporation rates are now employed; typical modern kettles operate with a 60 minute boil with between 5% and 9% evaporation. A criterion not usually measured, but which has been shown to be of critical importance, is the degree of agitation or vigour of the boil. In traditional boiling systems the vigour or boiling intensity has been related to evaporation rate. If some other form of agitation through better design of heat exchange, exchange, mechanical rousing rousing or use of pumped or thermosyphoned system is used, then additional agitation independent of the evaporation rate can be achieved. This result is demonstrated in figure 5, which shows a similar decrease in the high molecular weight nitrogen fraction throughout a boil under atmospheric pressure with different evaporation rates, when the same level of agitation is supplied by an external wort boiler. boiler. These results suggest that, given adequate turbulence during the boil, the actual removal of the high molecular weight nitrogen fraction is a function of time and vigour, and can be relatively independent of evaporation rate for atmospheric boiling. Vigour is only one feature of importance for coagulation, since protein agglomeration is improved by intense vapour bubble formation. The actual wort surface temperature, and the duration of the intimate contact of the wort with the heating surface, may also be of importance. Although it is often stated that it is desirable to remove as much protein/polypeptides as possible, nitrogen compounds have an important role in the quality and fermentation performance of a beer and in providing foam compounds and mouthfeel. Excess protein/polypeptide removal could lead to poorer quality product.

Extraction and precipitation of tannins/ polyphenols

Molecular distribution of proteins/polypeptides measured by gel electrophoresis < 5,000

5,000 to10,000

Before boil 0.0336 0.195 After boil 0.0175 % removal 49% 32%

10,000 to 50,000

50,000 to 100,000

0.101 0.125

0.0023 0.004

96%

Ref: Hough, Briggs and Stephen “Malting and Brewing Science ”

> 100,000 0.0029

0.001 95%

100%

• Proteins which combine with oxidised polyphenols are insoluble in boiling wort and are therefore precipitated during the boil to form hot break. • Proteins which combine with unoxidised polyphenols are soluble in boiling wort but precipitate when chilled and can give rise to chill haze and cold break. The polyphenols may subsequently oxidise during beer processing and may produce colloidal instability in packaged beer. beer. Unprocessed hops contribute around 40% of the total polyphenol content to boiled wort, however most hop polyphenols are removed as hot and cold break. The rest of the polyphenols comes from the dry goods, (particularly the husk), and less p olymerized and hence less likely to be removed. Worts devoid of hop tannins give poorer wort clarity and have a lower reducing potential.

Producing Reducing Compounds Malt and wort contain a number of reducing compounds which if not oxidised during the wort production or processing stages can provide the packaged beer with oxygen scavenging protection which may delay the onset of stale flavours and the rapid production of oxidised chemical hazes. Many of these compounds come from the raw materials, such as tannins described above, but others such as reductones and melanoids are formed during wort boiling through the condensation between sugar and amino compounds. Darker beers with high addition of unprocessed hops tend to produce the greatest reducing power. Brewing systems with low levels of oxidation tend to preserve the natural reducing compounds in the wort, which can persist into package beer and delay the onset of ageing, improving colloidal and flavour stability.

Summary.

Simple hop tannins and most malt polyphenols are soluble in boiling wort and moderately soluble in cold water. water. Tannins/polyphenols are readily oxidised and polymerise to give an increase in molecular Table 2: Effect of boiling on the molecular weight distribution of wort proteins

weight. Tannin/polyphenols Tannin/polyphenols also combine with proteins to form protein/polyphenol complexes:

Wort boiling is a poorly understood but crucial stage in the stabilization of wort and t he beer derived from it. Changes in the boiling process can effect the stability and quality of beer. s

q Further

Reading

1. Moll “ Beers Beers and Coolers ” . 2. Hough, Briggs and Stephen “ Malting Malting and Brewing Science” . 3. O`Rourke The Brewer 1994. Brewer 1994. 5. Wilkinson R. Ferment p 397 Vol 4 No6 Dec 1991. 4. Fitchett, C. S. et al. Pauls & Whites Brewing Room Book , 1992/93. cal 5. Hudson, J. R. and Rennie, H. Rennie, H. M.B.A.A. Technical Quarterly , Vol. 9, No. 4.

0.0 6. Zanglando, T. Brewers Digest, Digest, April 1979. Buckee G.K. et al J.I.B. J.I.B. Vol 99, 1992. European Brewery Convention Manual of Good Practice cation. – Wort Boiling and Clarification.


www.igb.org.uk • February 2002

19

TECHNICAL SUMMARY

The role of oxygen in brewing We live in an oxygen-rich environment for it comprises 21% of the air we breathe. Oxygen is chemically very reactive and combines readily with nearly all other elements. Elements reacting with oxygen are said to be oxidized. oxidized. Oxidation reactions tend to be accelerated by heat with the most vigorous reactions leading to combustion and burning.

N

early all plants and animals require oxygen for respiration with the removal of waste gas, carbon dioxide. Oxygen is a key component of organic compounds.

Biological systems in brewing. The malting process involves the germination and partial growth of cereal seeds (usually barley). To survive these seeds have to live in an oxygen rich environment and the waste gas produced during respiration has to be removed. Air is blown through the grain at various stages in the malting process: • In barley storage air is blown through the grain to prevent carbon dioxide build up. • During steeping the wet steeps are aerated to keep the steep water saturated and to agitate the growing barley. During the air rests in steeping air is usually sucked through the bed to bring in fresh oxygen and to remove carbon dioxide. • During germination humidified air is blown through the bed to vent carbon dioxide and keep the piece cool. • Once the green malt is kilned the living part or embryo is killed and the malt has no further need for oxygen. The other living organism used in beer is yeast. Although fermentation itself is an anaerobic process (occurs in the absence of air – see below), yeast cells require oxygen for growth Anaerobic respiration: respiration:

of two stage wort cooler to benefi bene fit from the turbulent flow conditions of a plate heat exchanger. • Use of stainless steel and ceramic candles in the cold wort line to produce micro bubbles. • The use of in line static mixers to promote turbulent flow • The use of venturi systems which produce pressure increase to forcing gas into solution.

Technica echnicall Summary 3 The third in this series of technical summaries for the Institute & Guild’s AME candidates. By Tim O’Rourke.

as the Crabtree effect. In the presence of glucose sugars (above 1% by weight) yeast (Saccharomyces spp ) uses glucose to produce alcohol and uses the oxygen to produce the necessary lipid compounds. The presence of insuffi insufficient lipid compounds will lead to a defective fermentation due to inadequate yeast cell reproduction, which in turn will lead to: • Slow and sticking fermentations • Off flavours – e.g. poor removal of diacetyl and acetaldehyde • Poor yeast crop in terms of quantity and vitality • Low ester formation Excess oxygen will lead to: • Rapid fermentations • Excessive yeast growth and hence beer losses • Higher ester production – giving fruitier flavoured beers

Oxygenating the wort

In any system only part of the gas supplied is dissolved. A good aeration system should also include a measuring device appropriately located suffi sufficiently far from the injection point so that it accurately measures the dissolved oxygen and can feed back to control system. The amount of dissolved oxygen required depends on the yeast strain and the original gravity of the worts. wor ts. Traditional ale and lager worts were usually not collected higher than 1045 (12% Plato) and required 6 to 8 ppm dissolved oxygen. With high gravity brewing original gravities have increased up to 1080 (20% Plato) and require dissolved wort oxygen levels of 16 ppm or higher. From the table below it can be seen it is impossible to provide this level of dissolved oxygen from air alone and pure oxygen injection is used.

Oxidation reactions Oxidation and reduction reactions take place all the time. Since we live in an oxygen rich atmosphere products are continually being slowly oxidised. A molecule which loses electrons it is said to have been oxidised. If one molecule loses an electron then another molecule must accept that electron. The molecule which accepts the electrons it is said to be reduced.

Wort is usually aerated in line on transfer between the wort clarifi clarification vessel (whirlpool tank) through the wort cooler to the fermenting fer menting vessel prior to yeast addition. Most breweries oxygenate the wort on the Solubility of oxygen oxy gen in water and in wort at different cold side after the wort temperatures and at atmospheric pressure. cooler (see table below). It is surprisingly dif diffi ficult Temperature (°C) to get oxygen to dissolve in Oxygen concentration concentratio n (mg/l) 0 5 10 15 20 water (or wort). There are Saturated water 14.5 12.7 11.2 10.0 9.9 several systems available Saturated 12% Plato wort 11.6 10.4 9.3 8.3 7.4 which include: Ref Moll – Beers & Coolers • Aeration in the mid section

Comparison of benefi benefits between hot and cold wort aeration

Sugar ➔ Alcohol + Carbon dioxide + Energy Energy (ATP) (ATP) Molecular oxygen is taken up by yeast at the start of the fermentation and is used by the cell to synthesise sterols and unsaturated fatty acids which are essential components of the yeast’ yeast’s membrane. The need for oxygen can be removed if sterols (e.g. ergosterol) and unsaturated fatty acids (e.g. oleic acid) are added directly to the wort. In terms of releasing energy, aerobic respiration is more effi efficient than anaerobic respiration. However in yeast the temptation to use the available oxygen for aerobic respiration is suppressed through a mechanism described

Benefits from hot wort aeration Sterilises air Better mixing through wort cooler

Benefits from cold wort aeration Better oxygen solubility in cold Lower risk of wort oxidation Little oxygen is consumed due to chemical reactions with wort Lower risk of off flavours and instability

Limitations from hot wort aerations Lower solubility of oxygen Risk of wort oxidation Some of the oxygen will be consumed through wort oxidation reactions. Risk of oxidised off flavours (garlic and staling) developing in the beer

Limitations from cold wort aerations Air must be sterile before addition Separate oxygen mixing system is required


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45

TECHNICAL SUMMARY

In this context oxygen is willing to accept free electrons and hence acts as an oxidising agent, but in that process oxygen itself will be reduced. Oxygen usually exists in a triplet state ( 3O2 ) and in this form is not very reactive. Oxygen has to be activated by energy (light or heat) or catalysed by metals (copper or iron etc) when it forms highly reactive radicals such superoxides and hydroperoxyl radicals. The radicals rapidly react with wort and beer components to produce oxidized compounds some of which have an impact on the final product e.g: • Flavour staling compounds particularly carbonyls – for example trans 2 nonenal • Accelerated chill and permanent haze formation through oxidation of polyphenols. • Increase of beer astringency through oxidation of polyphenols • Increase in beer colour through oxidation of polyphenols. The proposed mechanisms for these changes is shown below.

Fig 1. Proposed beer staling mechanism

Taken from: Kaneda H. et al MBAA Technical Quarterly 1999 No 1. These oxidative changes are almost inevitable, and have a marked influence on the flavour and aroma of beer. The only control the brewer has is to influence the rate at which these changes occur and hence the length of time the beer can exhibit its optimum flavour profile. Flavour changes observed in a typical beer due to oxidation over time.

Fig 2. Typical changes in flavour character with ageing

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March 2002 •


Oxygen control and minimising product oxidation.

Brewing materials The processing and storage of brewing materials have been implicated in promoting staling There is particular reference in the literature to the production of lipoxigenase enzyme during malting which is thought to increase the lipid content of the wort. Possibly more important, is the role of raw materials is in providing compounds which promote staling such as lipids or providing compounds which give reducing power to shield the wort and beer from oxidation. (e.g. compounds such as melanoidins and polyphenols;)

flavour stability. However some process differences between the beers was noted: • A better lauter tun run off was obtained with less oxidized mash with lower levels of oxidised protein as a result of less disulphide bridging between the polypeptides. Oxidised proteins polymerise by forming disulphide bridges (see Figure 3). • Poorer beer foam performance was observed from the lower oxidised mash. The mash with less mash oxidation produced a beer with a higher reducing potential. • Higher levels of oxidation increased the colour of the wort and beer produced. The beer produced from mash with higher levels of oxidation had lower beer polyphenol content (not at a significant level)

Brewhouse

Fermentation

Mash and wort oxidation has been the subject of considerable study and most of the brewhouse manufacturers have designed brewhouse operating and transfer systems to minimize the uptake of oxygen: • Mashing and mash transfer systems to the bottom of the vessels • Sparge and lauter re-circulation systems to introduce the wort below the liquid level. • Avoidance of systems with forced aeration during boiling. All these designs reduce oxygen ingress. However by far the largest uptake of oxygen comes from the brewing water (in mashing and sparging) which unless de-aerated will contribute around 30 ppm oxygen per kilo of malt mashed. Brewhouse oxidation produces a measurable increase in oxidised compounds (lipids and polyphenols) but it is not certain how much this may contribute to ageing in the packaged beer. Oxidation will use up the reducing potential in the mash and wort, producing beers with lower reducing potential, which would notionally be more prone to more rapid oxidation. There are a number of contradictory articles in the literature dealing with wort and mash oxidation. In many systems the wort or mash was artificially aerated to produce an unnatural result. Research on a pilot scale looking at mash oxidation by comparing normal brewing (less than 40 ppm oxygen per kilo of malt mashed) with very reduced oxidation (1 ppm oxygen per kilo of malt mashed) did not produce beers with improved

Air or oxygen is added just prior to fermentation to stimulate yeast growth. Live active yeast has a huge capacity to adsorb oxygen and it is rapidly assimilated before any chemical oxidation can occur. At the end of fermentation the green beer is totally anaerobic and free from oxygen.

Fig 3. Oxidation of proteins through the formation of disulphide bridges

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Beer Processing After fermentation beer is venerable to oxidation. While active yeast is still in suspension much of the oxygen can be scavenged. In the absence of active yeast, oxidation will occur leading to the staling reactions described earlier. Measures must be taken to avoid oxygen ingress: • All tanks should be blanketed with inert gas (carbon dioxide or nitrogen) • De-aerated water should be used to chase through beer transfers. • All additions and dilutions should use deaerated water. • Flush all bends and fittings with de-aerated water • Attention should be paid to prevent leaks at pump surfaces, joints etc where air can gain access • Pipework should be designed to be fully purged. • Processing large volumes of beer into large tanks helps minimise oxygen pick up. • Automation should be used to turn off pumps when vessels and dosing pots run empty. • Inert gas used to undercover flush of centrifuges

Fig 4. How air can be trapped in a bend with poor design

• Effective oxygen removal from de-aerated water. Poor pipework design can lead to oxygen pickup (see Figure 4). Through careful operation and good process designs oxygen pickup can virtually eliminated. Beer should be presented to the packaging lines with less than 50 ppb dissolved oxygen.

Packaging (small pack filling) Inevitably during small pack filling (bottling and canning) a small amount of oxygen pick up is inevitable. Developments in packaging line design have been made to minimise exposure to oxygen: • Counter pressure filler bowl with inert gas • Flushing can or double pre evacuation of bottles with inert gas • Fobbing control and gas flushing to reduce air in head space • Packaging lines surrounded by inert gas tunnels • The use of oxygen scavenging barrier crown corks can provide protection against oxidation, With the latest technology designed to reduce oxygen pickup it is now possible to produce beers with less than 100 ppb total in package oxygen. All Brewers should be capable of achieving less than 500 ppb. total in package oxygen. Keeping the oxygen content down in the finished product makes a very significant contribution to delaying the onset of staling.

Anti-oxidants The brewer can also increase the anti oxidant capacity of the beer. Providing the beer with compounds, which compete with flavour active compounds to be oxidised by the oxidising agents present: • As stated earlier raw materials have a profound effect on the staling capacity of a beer. The use of dark malts and high hop grists give beer better keeping qualities. • Naturally conditioned beer has yeast present in the final package and the yeast cells are able to scavenge residual oxygen picked up during filling. • Sulphur dioxide is an anti-oxidant produced during fermentation. The levels of naturally occurring SO2 can be boosted during fermentation by deceasing yeast growth through: Lower fermentation temperatures Reduced wort aeration Reduced pitching rate Reduced original gravity Increased sulphate additions to the mash Producing bright worts • Anti oxidants such as sulphur dioxide and ascorbic acid (or sodium ascorbate) can also be added to the beer, usually prior to packaging. It is found that the two antioxidants added together is the most effective method of use. • Avoidance of metal ions, particularly iron and copper will reduce the rate of oxidation. This

can be controlled through specifications on materials such as syrups and kieselguhr, and by diverting pre-coat liquors to drain to wash the filter bed out.,

Beer in Trade Most beer leaving the Brewery shows little signs of ageing. It is during storage in the supply chain that flavour deterioration occurs. Most light beers (Lagers and Pale Ales) show symptoms of ageing within three months of packaging even though they are given a nominal shelf life of 12 months, sometimes more. The flavour stability of darker beers are better for the reasons listed earlier. Process improvements make a significant contribution to improving the flavour stability of beer in trade, but the major improvements could result through better handling of beer in the supply chain; • Does the beer have to have a 12-month shelf life ? The supermarkets can turn perishable products around in a few days. • The best before date gives limited information about the product. One major Brewer is now providing a packaging date enabling consumers to judge the freshness of the beer. • Cold / cool storage of beer in the supply chain reduces the rate of oxidation. • If cold storage cannot be achieved then it is certainly necessary to avoid warm storage. Beer held at 30°C will stale 25 times faster than the same beer held at 0 °C.

• The platinum electrode which is capable of detecting oxygen in solution and is available for both laboratory and in line use. The platinum electrode is the industry standard for measuring dissolved oxygen in line and in the laboratory (see Figure 5). However “It is not the oxygen that we should measure …rather the impact of the oxygen”. It is therefore necessary for Brewers to taste their products through the shelf life to assess how well the beer survives ageing.

Summary Oxygen has an impact throughout the malting and brewing process. It would not be possible to malt barley or ferment wort without the contribution from oxygen, and without oxygen we would not be around to enjoy the beer either ! However, oxygen reacts with many compounds present in mash, wort and beer, which have an impact on the final and keeping quality of the product. There is still some disagreement over the importance of oxidation of the mash and wort production, but there is no disagreement that oxidation post fermentation is damaging to both the taste and colloidal stability of the beer. s

However there is a note of caution. Not all consumers dislike the “oxidized/stale “ tastes of beer. Many North American consumers associate this taste with imported brands from Europe and other areas and are less impressed when presented with the fresh beer!

Measurement To be able to control something it is necessary to be able to measure it. There are a number of reference methods in IGB list of recommend methods. Two methods that are commonly use in the industry are: • Shake out air methods use caustic soda to adsorb the CO2 and measures the head space air. This method cannot be used with nitrogen gas top pressure or mixed gas carbonation. • The Indigo carmine method, where the indigo carmine dye reacts with oxygen to produce a blue colour.

q

Further Reading

1. Moll “Beers and Coolers” Prof Dr Annemuller G. et al Brauwelt International Volume 19 April 2001 O`Rourke T Australia and NZ Institute of Brewing Convention March 1992 Prof Bamfort C. Brewers Guardian April 2000 Kaneda H. et al MBAA Technical Quarterly 1999 No 1.

Fig 5. The platinum electrode


www.igb.org.uk • March 2002

47

TECHNICAL SUMMARY

Predicting colloidal stability in beer Beer stability can be judged by the degree to which a beer tastes and looks as good at the end of its shelf life as it did when it was first packaged. Most customers “drink with their eyes”. They are often more willing to accept a glass of beer which does not taste quite right, over a glass of beer which is hazy. Hence colloidal stabilisation is often considered a more important attribute than flavour stability.

I

n the first article of this series (January 2002) stability was related to both the flavour and colloidal instability which can occur in beer as a result of oxidation reactions principally during and after packaging. Through the use of modern colloidal stabilisers it is possible to produce beer which shows improved colloidal stability. This article will cover the measurement and prediction of colloidal stability. When it comes to assessing colloidal stability of a beer for the duration of its shelf life there are three principal methods:

therefore the expected shelf life of the beer. There are a number of factors which influence colloidal stability (see Technical Summary, January 2002), however given similar beer brands and brewery equipment, the principal variables will come from the protein and polyphenol content of the beer. These are usually measured when predicting colloidal stability.

Technical Summary 4 The fourth in this series of technical summaries for the Institute & Guild’s AME candidates. By Tim O’Rourke. its preferred method. A few are listed below: European Brewery Convention (1963 method). The beer is held at 60 °C for 7 days then cooled to 0°C for 24 hours and the haze measured. Harp method The beer is stored for 4 w eeks at 37°C followed by 8 hours at 0°C and the haze measured. In this method forced haze development is equated to normal storage time. One member of the consortium related 1 weeks forced aging to 1 month of storage under normal conditions, while another equated 4 weeks of forced storage to 6 months of storage under normal conditions. The forcing tests have to be correlated to normal storage conditions as shown in Figure 1.

• ABSOLUTE ACCURACY: - keeping the beer at ambient and measuring haze at the end of its stated shelf life (best before date – e.g. 12 months) • RELIABLE INDICATOR – using some form of accelerated ageing (forcing test) on the packaged beer (e.g. 4 weeks at 37°C is equivalent to 1 months storage at ambient) and relating the date to absolute results. • PREDICTIVE TEST – using a measurement usually related to the proteins or polyphenol content of the beer to predict the probable rate of production of haze and hence the shelf life. Typically bright beer is packaged with an EBC haze of less than 0.8 units. The critical haze for stored beer is usually less than 2 or 3 EBC units for beer at 0°C. Keeping beer to the end of its shelf life to evaluate its colloidal stability is pointless except as an assurance exercise but it is essential to calibrate rapid prediction methods. Accelerated ageing tests These tests are aimed at stressing the beer usually by subjecting the beer to either hot or cold conditions to produce “accelerated” aging. Almost every brewing company has

Looking at the protein (polypeptide) content Chilling test A sample of the beer is chilled below 0 °C to as low as -8°C without freezing (often alcohol has to be added) and left for 8 hours and chill haze measured. The lower the chill haze the greater the stability. The chill haze is principally the protein fraction. Sensitive Protein – Titration with tannic acid Tannic acid is a “super” polyphenol which readily forms insoluble complexes with protein. A given amount of tannic acid is titrated against a given volume of beer to give a haze measurement which relates to its stability Ammonium Sulphate Precipitation (SASPL) Saturated ammonium sulphate is titrated against a sample of beer where it forms an insoluble precipitate with larger molecular weight polypeptides (m.w. 210,000). The precipitate drops out and once all the proteins have been removed, the haze starts to increase giving an measurement of the amount of high molecular polypeptides in the beer.

Looking at the polyphenol content. Fig 1: Correlation between forced haze and absolute haze development. Cycle tests – European Brewery Convention (1975 method) The beer is kept overnight at 0°C and the haze read to establish the base line. The beer is placed in a heated water bath at 60°C and then kept overnight at 0°C and the haze checked again. This shows the rate of haze development and can be repeated over number of cycles. Although these methods are faster than the absolute test, they still take a number of days to several weeks to complete, by which time the beer has been released and found its way in trade. It is a reactive rather than a proactive test.

Titrating with PVP This is a nephelometric titration of soluble PVP (polyvinyl pyrollidone) solution. PVP has a similar structure to a protein molecule and readily forms an insoluble precipitate with polyphenols, particularly medium size molecular weight polyphenols often called tannoids, which are know to be haze active. When the PVP is titrated in beer a haze is formed. This increases to a maximum and then decreases by a dilution effect as PVP addition continues. The peak value gives a measure of the “tannoids” which can be correlated with chill-stability.

Predictive tests

High Performance Liquid Chromatography Polyphenols can be adsorbed on Sephadex LH 20 and can be identi fied using 4dimethylaminocinnamaldehyde as a chromogen. The individual polyphenols can then be measured directly.

What every brewer would like is a test, which can predict the colloidal stability and

These predictive tests can be used to


www.igb.org.uk • April 2002

41

TECHNICAL SUMMARY

Is this someone else’s copy of

produce rapid results for beer prior to packaging, but the results have to be correlated with actual storage data. For best results the data should be set up per brand (product quality) and per brewery to reduce the amount of outside influences distorting the stabilisation results. As well as predicting the potential shelf life of a beer, these methods are useful in determining the optimum dosage rate of a beer stabilisation treatment. See figure 2.

PT-STABILITY-INDEX PT-STABILITY-INDEX P...PROTEINS T...POLYPHENOLS P...PROTEINS T...POLYPHENOLS Protein-Reagent P40/ Polyphenol-Reagent T-125 Protein-Reagent P40/ Polyphenol-Reagent T-125

HIGH VALUE = HIGH COLLOIDAL STABILITY= HIGH VALUE = HIGH COLLOIDAL STABILITY= LESS HAZE FORMING COMPOUNTS LESS HAZE FORMING COMPOUNTS 100

Y T I L I B A T S N I E T O R P F O E S A E R C N I

C

HIGH PROTEIN STABILITY

90

B HIGH PROTEIN and POLYPHENOL STABILITY

80

70

60

50

E 40

D

The

30

20

HIGH POLYPHENOL STABILITY

A

10

0

Brewer

0

10

20

30

40

50

60

70

80

90

100

INCREASEOFPOLYPHENOLSTABILITY

BEER A

you’ re reading?

PT- INDEX 8 : 16

Both,proteins 8 : 16and polyphenols are very BEER A PT- INDEX unstable Both,proteins and polyphenols are very Predominat: Unstable proteins unstable BEERPredominately B PT-INDEX 95unstable : 80 proteins

Figure 2: Determining the optimum dose rate for a beer stabilisation treatment.

Both,proteins and polyphenols are very

stable,

well balanced,extreme high stability 95 : 80 BEER B PT-INDEX Both,proteins and polyphenols are very BEERstable, C PT-INDEX 90 : 25 Extreme high protein-stability well balanced,extreme high stability

Automated measurements

Low polyphenol stability

To help the brewer, some of the methods described above have been automated.

PT-INDEX : 95 PT-INDEX 9030 : 25 BEERBEER C D Extreme high polyphenol stability Extreme high protein-stability Fair protein stability

Low polyphenol stability

BEER E

Tannometer This instrument measures the turbidity of a liquid sample in the range of 0 to 300 EBC in units of 0.01 EBC. It works on t ransmitted light at 510nm and the instrument can control the sample temperature including cooling it down to -8°C. The Tannometer can produce automated results for: • Tannoid content • Chill haze • Sensitive Protein • SASPL

Make sure you stay on top of the industry, scientific and educational news and analysis. Order your own monthly copy of

PT Standard Uses a series of specially developed reagents to the measure the protein and polyphenol content of a beer through titration and the results can be simply displayed on a computer allowing the brewer to see immediately the relative stability of his beer and decide what further treatment – protein or polyphenol, could be used to achieve the required stability. See figure 3.

The Brewer International

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April 2002 •


PT-INDEX 30 : 95 Extreme high polyphenol stability Fair protein stability

BEER E

PT-INDEX 35 : 45 Good stability for proteins and polyphenols

e3

Figure 3: Predicting beer stability using PT standard.

must not only look at the predicted stability of the beer in the brewery, but consider the hazards the beer may be subjected to during storage and in the supply chain and take appropriate remedial action.

Summary

regular copy of the

The

PT-INDEX 35 : 45 Good stability for proteins and polyphenols

BEER D

There are a number of methods which can be used to predict colloidal stability and hence the shelf life of a beer. The principle reactions occur between the protein and polyphenol fractions and hence the most consistent results come by looking at the levels of both fraction. The test and storage data are usually collected under ideal (laboratory) conditions. Packaged beer faces a much greater extreme of conditions in the real world, particularly those in the export trade, and it is export beers which are usually those consumed near or at the end of their shelf life. For those brewers anxious to deliver their beer to the consumer in prime quality they

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q

Further Reading

Tim O’Rourke: Beer Stabilisation Brewer International – January 2002. Tim O’ Rourke et al: from poster presented at Perth Convention - Ferment June 1998 - p189. Tim O’ Rourke: Back to Basics, Brewers Guardian February 2000 - p29. Jurgen Schneider: Opto-electronic regulations of stabilisation inputs – Brewers Guardian July 2000. M Moll: Colloidal Stability of Beer – Brewing Science Vol 3 ed Pollock. I. McMurrough I et al: Effect of PVPP dosage on the flavanoid content of beer and consequences for beer quality – Brew Digest 59 (10) 1984.

TECHNICAL SUMMARY

The process of wort boiling The reasons for wort boiling were covered in Technical Summary No 2 published in the February edition of The Brewer International . This feature covers the methods used to achieve wort boiling.

W

ort boiling has the highest energy requirement of any of the brewing processes. It can account for as much as 60% of the total steam demand of the brewery (depending on the type of packaging operations). It is therefore hardly surprising that a great deal of effort has gone in to reducing energy consumption and recovering energy from boiling.

Wort Boiling Plant Fig. 1 Traditional direct fired kettles Fig 1 Traditionally, wort was boiled in direct-fired kettles, often made of copper, since this metal has particularly good heat transfer properties. Because the heat source was localised at the bottom of the kettle, it restricts the volume of wort which could be boiled at any one time to a maximum of 200 barrels (330 hectolitres) which probably explains why traditional breweries with larger brew-lengths used number of separate smaller size kettles. The principal disadvantage of traditional direct peat or coal fired kettles are that they are relatively inefficient in heat transfer and tend to be labour-intensive. The heating surface of the copper becomes very hot and tends to promote caramelisation and burning of the wort, requiring frequent cleaning usually every 2 to 5 brews to ensure effective heat transfer is maintained. High evaporation rates were required to produce sufficient vigour or turbulence in the boil and typical boils would take over 90 minutes with an evaporation rate over 10% per hour.

Kettles with Internal Heating Systems Fig. 2 The advent of steam coils and internal heating systems allowed the production of larger kettles, as it enabled the designers to provide Figure 1: Direct fired copper

Technical Summary 6 ’ By Tim O Rourke

The sixth in this series of technical summaries for the Institute & Guild’s AME candidates.

a larger heating area and, because it was surrounded by the wort, the heat transfer was more efficient. In many designs the heaters were upright and located in the centre of the kettle to give a turbulent boil. Some of the kettles also include base steam coils for preheating the incoming wort, and to avoid the creation of dead spots within the kettles. The disadvantage of internally heated kettles is that the heaters tend to be difficult to clean with conventional CIP, and were often manufactured from copper, which is dissolved by caustic cleaning. The internal coils in particular are prone to corrosion, which can result in steam leaks in to the boiling wort which are difficult to detect and repair. Because wort circulation relies on thermal currents within the kettle the turbulence over the heating surfaces is sometimes limited, resulting in wort caramelisation, which requires more frequent cleaning to ensure effective heat transfer is maintained. Kettles with external heating jackets Fig. 3 To overcome the difficulties with cleaning internal heaters, kettles with external heating jackets were designed. One of the most prolific designs was the Steinecker Asymmetric Kettle. They are generally made of stainless steel and achieve a rolling boil through the location of the heating jackets on one surface. They suffer from similar problems to the direct fired kettles in achieving effective heat transfer, with the higher volume kettles being rather long and thin. They require mechanical paddles to achieve the necessary agitation f or Figure 2: Steam heated kettle

a satisfactory boil. This design overcomes the cleaning problems of the kettles with internal heaters, and has a lower tendency to foul, but it still requires cleaning every 6 to 12 brews to ensure effective heat transfer is maintained. These kettles are also prone to fob formation during boiling and often use a cold air draught over the wort surface and an extractor fan to keep fob under control. Kettles with External Wort Boilers Fig. 4 A more modern design uses an external heater (external wort boiler) which takes the wort out of the kettle and passes it through a shell and tube or plate heat exchanger for heating. These wort boilers achieve high heat transfer through two phase flow and nucleate boiling, and operate at low steam pressure (at 3.0 to 3.5 bar) to heat the boiler. In these kettles vigour can be introduced mechanically, by wort circulation, and the classical 10% evaporation/hour with a 90minute boil, can be reduced to 5% to 6% evaporation/hour with a 60-minute boil without loss of wort/beer quality. This represents a considerable saving in energy. These kettles have other advantages over internal heaters since pre-heating can start once 15% of the total kettle contents have been collected, allowing the kettle to boil immediately it is full, thus improving vessel utilization. Since low pressure steam is used, the rate of fouling is decreased, allowing more brews to be processed between cleans. Typical installations can process 16 brews between cleans and this number can increase up to 32 brews. This decreases brew house downtime thus improving throughput. There are some hybrid kettles which use an internal heater but also recirculate the wort through an external pumped loop to improve mixing and increase the vigour of the boil. One of the negative aspects of external wort boiling involves having to pump the wort, where shear forces may damage the floc formation (trub or hot break particles). In appropriately designed installations this problem can be resolved by using the natural circulation of the thermosyphon effect. The boiler has to be primed during the pre-boil stage using a small circulation pump. Once boiling is achieved the circulation pump can be by-passed and the wort will circulate due to the energy and change of state resulting from the density change between incoming wort to the boiler at 98°C and the outlet wort and vapour from the boiler at around 105°C.

Overpressure Wort Boiling Both the internal and external boilers can be operated with an increased over pressure during the boil usually up to 1 bar. This elevates the boiling temperature to

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streams, and a number of brewers still reservations over quality.

TABLE 1: COMBINED WORT BOILING & STRIPPING – TYPICAL OPERATING CONDITIONS Wort boiling

Heating up Boiling Whirlpool rest Stripping

Time (mins)

Flow rate (hl/h)

Steam Pressure (bar)

Evaporation rate (%)

650 500 120

1.5 1.1 1.2

1 2 1

40 40 15 50

around 106° to 110°C, which has the effect of accelerating the various wort reactions, and allows the boiling time to be reduced. At the end of boil the excess pressure is released allowing the escape of the volatile compounds. Over pressure kettles are often operated with some form of vapour recovery energy systems. The advantage claimed from this system is that it allows a shorter boiling time and lower evaporation rates than might be considered necessary in a conventional boiling system. Combined wort boiling and stripping (Merlin) Fig.5 Merlin is a more recent development which uses a form of external wort boiling to boil the wort and then to strip out the volatiles after the whirlpool stand. Wort is pumped from the collection vessel across a conical heating surface, which is fed with live steam at 0.6 to 1.5 bar, thus giving a steam temperatures of the order of 110°C. The boiler is supplied with a large heating surface area – about 7.5 sq.m per 100 hl of wort. The heater operates by providing a large heating surface covered by a thin film of wort allowing gentle boiling and rapid elimination of aroma compounds. The system is able to produce good quality worts with 4% evaporation in 40 minutes. To strip any addition unwanted aroma compounds formed during the whirlpool stand the clarified wort from the whirlpool is passed over the heating cone on the way to wort cooling. This provides approximately an additional 1% evaporation. See Table 1. Continuous high temperature boiling Fig. 6 An efficient way of reducing energy demands is to use continuous wort boiling, where the energy used for boiling is used for heating up the incoming wort in a multistage process. The process operates as follows: q The wort from the lauter tun, feeds into a holding vessel where hop additions can be Figure 3: Jacketed Asymmetric Kettle

made. The wort runs through a specially developed three stage, reverse flow heat exchanger and is heated to approximately 135°C q The temperature is held for approximately 1.5 to 2.0 minutes in holding tubes. q The wort is held constant at 135°C by regulating the flow rate at the inlet to the first of two adjoining separators. q As the wort flows into the separator, the pressure is lowered to a set level. This enables the wort to boil and evaporate. q The latent heat (enthalpy) in the vapour is given up in the separators and is reused in heat exchangers I and II. Only heat exchanger III is heated with fresh steam (or hot water). q The wort from separator II runs through a booster pump to one of three whirlpoolcasting vessels. The effective volume of the whirlpools should be approximately equivalent to the capacity of one hour throughput from the boiler. q Each pair of whirlpool vessels are filled alternately. As one is emptied and cleaned the other is available to receive the wort. The higher boiling temperature of 135°C accelerates the chemical processes of: q Isomerisation of the hop alpha acids q Coagulation of the high molecular weight nitrogen compounds which are temperature dependent and are completed in 1.5 to 2 minutes. q

An effective evaporation of around 7% is required to remove the undesired aroma components. Continuous wort boiling allows the steam demand of the brewhouse to be maintained at a constant level, thus avoiding the peaks resulting from batch heating or boiling of the wort. Heat recovery is very efficient, requiring only prime energy input to compensate for the difference between the wort inlet and outlet temperatures and minor heat losses from the heat exchangers. However, continuous wort boiling is difficult to manage with a number of different wort Figure 4: External wort boiling with Thermosyphon

Wort stripping One of the principle functions of wort boiling is to remove unwanted volatiles such as hop oils and DMS (dimethyl sulphide) which come from the raw materials. Stripping of volatiles can often be the rate determining step for wort boiling and any reduction in boiling time or evaporation rate will have an adverse effect on the level of volatiles remaining in the beer. Similarly some volatiles, DMS in particular, continue to be formed in the hot wort after boiling is completed and the levels build up in the wort prior to cooling. The removal of unwanted volatiles after boiling can be split into two stages: q The first stage takes place in a conventional wort kettle, where the wort is boiled or heated to boiling point and the volatiles are removed with the water vapour evaporated, q The second stage occurs after wort clarification and before wort cooling, when the volatiles are stripped from the wort in a stripping column. The wort leaving the stripping column has the same or even a lower level of undesired wort aroma compounds compared to a conventionally boiled wort. Wort stripping should take place after (hot) wort clarification (e.g. whirlpool) and wort cooling. In the normal process wort volatiles continue to be formed after the end of wort boiling during the hot wort stand (clarification and cooling). However, in the absence of evaporation, they are no longer eliminated. Wort stripping is an effective method of removing some of these volatile substances. The Merlin wort boiling system offers a way of stripping the volatiles after the whirlpool stand.

Factors affecting boiling efficiency Wort boiling relies on the efficient transfer of energy from the heating source in to the wort. The efficiency is influenced by a variety of design characteristics such as: • heating area • material of construction • steam pressure (which directly relates to temperature). Traditional kettles were made from copper (hence their name) and copper has a much better heat conductivity than stainless steel (the current preferred material of construction) see Table 2. However as each brew is boiled small deposits of caramelised wort along with precipitated mineral from the hardness in the water are deposited on the heating surface building up a fouling layer, which acts as a barrier to heat transfer. This fouling layer has a much greater effect on heat transfer than any material of construction and is the principal resistance to heat flow. The formation of fouling on the wort side of the heater results in a steady fall off in heat transfer with each brew which can be followed by a decrease in evaporation. See Figure 7.


www.igb.org.uk • June 2002

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TECHNICAL SUMMARY

TABLE 2: THERMAL CONDUCTIVITY k FOR DIFFERENT MATERIALS OF CONSTRUCTION (W/m°C) 20°C

Copper (pure) 396 Ferritic Stainless Steel 25 Austenitic Stainless Steel 16.3

FIGURE 7: FALL OFF IN EVAPORATION WITH SUCCESSIVE BREWS BETWEEN A CLEAN

100°C

200°C

300°C

379 25.5

374 -

369 27.5

17

The key factor in reducing fouling include: • Soft water (ie; low hardness/ carbonates) • Whole hops (rather than pellets or extract) • Lower wort original gravity • Low differential heating temperature (hence moderate heat flux) • Avoiding excessive energy input, especially short term peaks • Thorough mixing of liquid adjuncts prior to entering the heater • Turbulent nucleate boiling (rather than film boiling). It follows for any kettle processing more than one brew between cleaning, and boiling to a constant time, there will be a difference in evaporation rate between the first and the final brews. To ensure a constant evaporation is achieved, some systems control wort boiling by the mass of steam delivered. This can be integrated so that it is evenly supplied through the allotted boiling span by means of proportional steam control value, thus ensuring that the evaporation rate is constant regardless of copper volume. Other systems control evaporation rate by the increase in original gravity or decrease in wort volume, or a combination of both systems.

Reducing the energy consumption during wort boiling All the sensible heat supplied to heat the incoming wort from lauter transfer (around 78°C) to boiling (at just over 100 °C) will be

Figure 5: Wort boiling combined with wort stripping ( Merlin system)

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recovered from wort cooling through the heat exchanger or paraflow. It is generally the energy supplied to evaporate the % evaporation from a standard boil for each brew as measured from the water (plus weight of steam supplied. Source: O’Rourke – The Brewer 1984. volatiles) from the wort which is not process using either mechanical vapour so easily recovered. The best way to reduce recompression (MVR) or thermal vapour this energy demand is not to use it in the first recompression (TVR). place, and there has been a gradual reduction in evaporation rates from 10 to 12% per hour Summary for a 90 minute boil (amounting to a total of 15 Wort boiling has the highest energy demand of to 16% evaporation per hour) to 5 to 6% all brewing operations, and hence has been evaporation for 60 minutes. This has been subject to considerable research into ways of brought about by designs and process control reducing its energy consumption. The prime changes detailed above. energy used to heat the wort to boiling point is There are a number of ways in which the recovered through the wort coolers for re-use brewer can recover or re-use the energy used in brewing. during evaporation. It is the energy used to evaporate the water A number of heat recovery systems produce which is more difficult to conserve. Over the hot water and the effectiveness of the system last three decades evaporation rates have depends on the brewery being able efficiently fallen by a factor of three, through better to utilise the low grade hot water recovered. process operations and improved kettle The typical schemes used recover the latent design. The opportunity for further decreases heat of evaporation from the wort boiling no longer exists and brewers are looking at process may be grouped into three types: ways of recovering the energy used in 1. Recovery of energy for use outside the evaporation and either recycling it in the brewhouse, e.g., either by a simple condenser boiling process or using it as a source of system exporting hot water or using energy for other processes in the brewery. s absorption refrigeration; 2. Recovery of energy for use in the brewhouse, e.g., q Further Reading using hot water from 1. Moll “Beers and Coolers” a vapour 2. Hough, Briggs and Stephen “Malting and condenser/energy Brewing Science” store system for wort 3. O`Rourke The Brewer 1994 preheating prior to 4. Wilkinson R. Ferment p 397 Vol 4 No6 Dec 1991 wort kettle; 5. European Brewery Convention Manual of Good 3. Recycling energy Practice – Wort Boiling and Clari fication. within the wort boiling

Figure 6 : Continuous wort boiling system.

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TECHNICAL SUMMARY

Getting a head Technical Summary 7 By Tim O’Rourke

The seventh in this series of technical summaries for the Institute & Guild’s AME candidates.

When ordering a pint the consumer will judge the beer by: • Clarity

When considering beer foam it is necessary to look at two complementary conditions in order to ensure a satisfactory foam performance:

• Foam Beer is a supersaturated solution of gas. In the case of lager this is carbon dioxide, but in the case of ales may be a mixture of carbon dioxide and nitrogen gas. When the beer is poured out (either from a bottle or draught) the gas bubbles break out from solution and rise to the top of the glass. This effect is called “tracing” and many beer glasses have roughened bases inside the glass, which act as nucleation sites, to encourage tracing. The foam in beer is generally considered to be the head on the top of the glass. There are also other important visual effects from the foam adhering to the side of the glass called “Cling” or “Lacing”. This effect is particularly noticeable in beers, which form larger heads and have better foam performance. In mainland Europe most draught beers can be served with large heads without attracting the wrath of Weights and Measures. Unfortunately in the UK the pint glass is a legal unit of dispense and unless over-measure glasses are used, this limits the amount of head permitted on a glass of draught beer.

Photo 1: Normal Beer Foam in a lager beer from CO2 the bubbles are larger and more open.

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• drainage • coalescence • disproportionation.

First impressions count. Most consumers drink with their eyes and appearance is often more important than taste.

• Colour

• bubble formation

• The head formation, which is the ability of beer to form a head when poured. • The head retention, which is the ability of beer to retain a head once it has formed, after dispense.

Bubble formation occurs where bubbles are formed from a supersaturated beer at nucleation sites in the glass. Gentle pouring and low beer surface tension encourage the formation of smaller bubbles, which produce more stable “creamy” type foam. After bubble formation drainage of beer from the foam by gravity starts to occur and the bubbles start to shrink and collapse. The rate of drainage can be reduced by factors such as small bubble size, the amount of hydrophobic interactions, reduced surface tension, and increased liquid viscosity. Other components, such as lipids from food or brewing materials, dirty glasses and some cleaning fluids disrupt the bubble film causing the foam to collapse. The final stage in foam collapse is due to disproportionation when the gas from smaller bubbles, which is under higher pressure, diffuses into the larger bubbles, which is under lower pressure, creating

It is necessary to have adequate head formation in order to ensure sufficient foam FIGURE 1: EFFECT OF HYDROPHOBIC PROTEINS IN remains during the REDUCING SURFACE TENSION consumption of the beer. In some markets bottle beer is drunk directly from the bottle and head has no impact on the quality perceptions of these beers.

The structure of beer foam The formation and breakdown of beer foam occurs in four stages:

Photo 2: A tight crisp foam on an ale which has both nitrogen gas and CO 2 producing a much creamier head.


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Photo 3: Foam sticking to the glass after the beer has been drink is called Cling or Lacing.

Dalkia ad CD at Holbrooks 25/6

11

PRODUCTION

larger “bladdery” bubbles, which collapse more quickl y. Nitrogen is less soluble in beer than carbon dioxide and hence the bubble size is smaller. This means that disproportio nation is slower for beers with mixed gas giving the “creamier” appearance and better foam stability.

Factors which improve foam performance Anything which encouragers the formation of gas bubbles and gas breakout improves the stability of the gas bubbles and will consequently improve the presentation and foam stability of the beer.

The presence of dissolved gas Bubbles have to be created in order to form a head. This requires a minimum level of dissolved carbon dioxide or mixed gas (mixed carbon dioxide and nitrogen). Typical values are: • Lager beers – between 5 and 6 g/l carbon dioxide • Ales – (usually but not always lower) at between 2.5 and 5 g/l. The carbon dioxide content is often supplemented by 15 to 20 ppm nitrogen gas for mixed gas dispense. Bubble formation will also be influenced by external factors such as temperature. The solubility of carbon dioxide in particular increases with a decrease in temperature, and hence beers dispensed at low temperatures (for example very cold lager dispense ) will produce less foam unless the carbonation level is increased proportionately.

Foam stabilization by reducing surface tension The main factor which reduces the surface tension in the foam and stabilizes the bubbles is hydrophobic (water hating) protein or polypeptides. These hydrophobic proteins come from the raw materials principally the malt (see figure 1). Only a small proportion of the malt derived protein is responsible for foam stabilization. The balance of the protein is used as yeast nutrients (amino nitrogen) or can cause colloidal instability (chill and permanent haze). Considerable research has been carried out to identify the exact fraction of protein responsible for improving foam stabilit y. Foam-positive proteins can be divided into two fractions based on molecular weight: • high molecular weight (HMW, 35–50 kDa) fraction containing mainly protein Z 23 • low molecular weight (LMW) fraction containing LTP1 (lipid transfer protein 1) and a mixture of hordein and glutelin fragments.

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Volume 2 Issue 7 2002 •

These proteins form a ring around each bubble reducing the relative surface tension and stabilising the foam. Factors which increase the amount of these proteins in the packaged beer and will subsequently improve the head retention :

DETERMINATION OF HEAD RETENTION BY THE RUDIN METHOD

• Grist with malt made from high nitrogen barley and all malt grist will contribute increased nitrogen to the wort. • Poorly modified malts have less protein breakdown resulting in worts with higher protein content. • It is necessary to avoid excessive wort boiling or excess use of kettle finings which increase the amount of protein removed as hot and cold break. • Every time the beer foams it uses up some of the precious foam stabilising proteins, which are left behind as a crust on the vessel walls. Avoiding beer fobbing during boiling and all subsequent transfers reduces the loss of foam proteins and ensures more continue into the packaged beer. • Protein compounds can also be lost during processing through maturation and tight filtration. Care in these areas will improve foam potential. • Foam proteins are susceptible to breakdown by proteolytic enzymes, which can come from the yeast particularly if the yeast has been stressed (old yeast or poor yeast handling) and these along with any other proteases added can seriously reduce the foam potential of the beer. • It is reported that there is a greater loss of foam potential in a beer brewed at high gravity when compared to the similar product brewed at sales gravity. It has been shown that foam potential proteins are lost more readily from higher gravity worts. Currently there is no simple explanation for this observation. In addition to the hydrophobic proteins, iso-alpha acids from the hops also exhibit hydrophobicity and hence make an important contribution to foam stability. The hops are thought to help bridge between the bubbles adding additional support. Some brewers use reduced hop compounds to improve foam stability.


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Reduced hop compounds such as tetraiso-alpha acids are made from hydrogenating the double bonds in isoalpha-acid. As well as giving the hop compound protecting against break down under ultra violet light it also makes the molecule more hydrophobic, thus increasing its foam stability when compared to standard isoalpha acid.

Factors which produce poorer foam performance It follows that anything (including grist composition), which has an effect on reducing the level of proteins and isoalpha acid, will tend to produce beers with poorer foam performance. However, the foam potential can also be reduced by the process conditions, for example excess foaming during transfers, which will reduce both protein and hop compounds and through the effects of protease enzymes, which will breakdown the foam proteins. Lipids, grease and detergent are detrimental to foam performance. Lipids can form a wall around the bubbles preventing the stabilising action of hydrophobic proteins and iso-alpha acids, thus increasing the surface tension causing the foam bubbles to collapse. The fatty compounds can be picked up during the brewing and dispense process, with one of the most common areas being poor quality glass washing. Beer contains a lipid binding protein, which comes from the raw materials and has the ability to reduce lipid induced foam collapse. However, many brewers chose to add propylene alginate glycol (PGA) as a process aid, which binds to bubble walls and protects them from penetration by lipids.

The measurement of foam stability There are two principle methods used for evaluating head performance:

DETERMINATION OF HEAD RETENTION BY THE NIBEM METHOD

Determination of Head Retention by Rudin

that it just rests on the surface of the beer foam. As the foam collapses the signal received by the electrodes reduces. The plate moves down to maintain contact with the foam. The more rapidly the needles move down to maintain contact, the less stable the foam.

Standard: A satisfactory head is one that lasts more than 260 – 280 seconds by Nibem. Since no additional gas is added this method will give an indication of the performance of the beer foam in trade.

Principle: it measures the length of time it takes for the foam from gassed up beer to collapse between two set points in a narrow tube.

Advantages • measurement gives a better indication of probable foam performance under real dispense conditions.

Method: Degassed beer is placed in a narrow tube and CO2 is introduced into the bottom of the tube. The beer is gassed up to form a foam head until a pre-set line is reached. The speed with which the foam collapses between two marked points is measured.

Disadvantages • can be difficult to get reproducible results.

Standard: A satisfactory head is one that lasts for longer than 90 seconds by Rudin method. This method is better at measuring the foam potential of the beer rather than the actual performance of the beer in trade since it introduces its own level of carbonation. Advantages • It measures beer intrinsic ability to foam – i.e. foam potential. • It eliminates the variations due to carbonation and as a dispense gas because CO 2 used to produce foam. Disadvantages • The narrow glass tube has large surface area to volume ratio and is not representative of the performance of the foam in a beer glass.Since additional CO 2 is added it does not truly reflect the actual performance of the beer in trade.

Determination of Head Retention by Nibem

• susceptible to drafts and temperature. Although these are the most common analytical methods used for measuring foam performance there are a myriad of other methods proposed and used to measure both foam collapse and assess lacing on the glass. Many of the methods rely on visual assessments of the foam for both head retention and cling. More sophisticated systems use computer and video camera technology or infrared analysis to automate the visual observations and to reduce the subjectivity of the methods.

Nitrogen of between 0.5 – 0.75% ensures sufficient amounts of hydrophobic proteins are present in final beer. An all malt grist with low malt modification with the addition of wheat or barley will increase the level of hydrophobic proteins. • Higher bitterness will increase the isoalpha acid concentration, which helps foam stability. Better results are achieved if part of the iso-alpha acid is replaced with a reduced version such as tetra-isoalpha acid to between 3.5 - 5 ppm). • Care is required in the brewhouse to avid excessive breakdown of proteins during mashing or loss as hot and cold break. This requires the use of appropriate temperature and pH conditions for mash to allow survival of sufficient amounts of hydrophobic proteins. • Care must be taken to avoid fobbing as this will result in the loss of both hydrophobic proteins and iso-alpha acids. • Yeast handling and removal of tank bottoms is a priority to prevent yeast stress and the leaking of protease enzymes, which can damage foam. • Better foam stability is obtained with beers brewed at sales gravity over those brewed at high gravity. Higher alcohol products (those with more than 7 or 8% alcohol by volume) tend to have poorer foam performance. • Addition of propylene glycol alginate to combat the negative effects of fatty compounds. • Good foaming beers can easily be ruined in trade. Good line cleaning and well rinsed glasses with approved glass rinse chemicals are required to avoid the risk of grease or detergent getting into beer. s

Summary of the key factors affecting foam stability Anything which encouragers the formation of gas bubbles and gas breakout and improves the stability of the gas bubbles will improve the presentation and foam stability of the beer. The following factors are important when producing the best foam on a beer: • The beer should have sufficient levels of dissolved carbon dioxide or gaseous nitrogen to produce a good foam head

Principle: it measures the time taken for the surface of foam to collapse by 10mm, 20mm and 30mm using conductivity.

• The dispense temperature should be sufficiently warm to allow normal gas breakout.

Method: A standard pour is used to pour the beer into a glass. A movable plate containing three electrodes is lowered so

• Small bubbles are required for the best head retention. • Good quality malt with total soluble

q

Further Reading

1. Moll Beers and Coolers . 2. Hough, Briggs and Stephen Malting and Brewing Science . 3. Evan Evans et al Institute of Brewing Asia Pacific 26th Convention, Beer Foam: Not Just Froth and Bubble.


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TECHNICAL SUMMARY

The role of pH in brewing pH is the measure of acidity which is the concentration of + hydrogen ions H in solution. Water naturally dissociates into its ionic components at a very low level to produce hydrogen ions H+ and hydroxyl ions OH -.

Understanding the factors The ratio of the concentration of t he products ([H+] and [OH-]) to the concentration of the starting material (H2O) is given by the equilibrium constant Kc which is expressed as: Kc = [H+(aq)]aqm x [OH-(aq)]aqm [H2O (l)]aqm

Technical Summary 8 By Tim O’Rourke

Continuing this series of technical summaries for the Institute & Guild’s AME candidates.

Brewing water Mash Boiled wort At end fermentation

pH 7.0 pH 5.6 pH 5.4 pH 4.0

(neutral) ±0.2 ±0.2 ±0.2

However as explained above the scale is logarithmic and hence the range of hydrogen ions H+ is much greater for the finished beer than it is in the boiled wort. • For wort with a pH of 5.4 ± 0.2 the range of ions H+ concentration will be 4 ppm (2.5 ppm to 6.3 ppm)

In 1909 the Danish Scientist Sorensen devised a simple numerical scale, the pH unit, which is the negative log10 of [H+]. In a neutral solution where the H+ = 10-7 then the - log1010-7 = 7, so the pH is 7.0 units.

• For the finished beer with pH 4.0 ± 0.2 the range of H+ ion concentration will be 100 ppm (63 ppm to 159 ppm)

With pH 7 as the neutral, then decreasing values from 7→ 0 means the concentration of H+ ions increases and the solution becomes more acidic. Conversely as the pH value increases from 7 → 14 the levels of H + fall and the solution becomes less acidic or more alkaline. See Figure 1. The negative log scale is also useful for measuring the hydroxyl ion [OH -] concentration:

The full range of pH is found in the brewing process are shown in Figure 2. The fall in pH is governed by the mineral composition of the brewing water and mineral treatment added to t he brewing water.

pOH = - log10 [OH ]

Since the concentration of water is constant, [H20 (l)]aqm can be incorporated into a modified equation constant Kw, where:

Knowing this, we obtain the following useful expression:

Kw = [H+(aq)]aqm x [OH-(aq)]aqm

pH + pOH = -log10 KW = 14.00

Kw is called the concentration product of water and at 20°C (which is 298°Kelvin) Kw is equal to 10-14. mol-2 l-2 . In pure water each water molecule dissociates to give to give one H+ and one OH- ion, hence at 20°C :

Since the pH scale is logarithmic, the intervals between each whole pH unit is not equivalent. pH units are usually given as mol/l which is also equivalent to µg/l and ppm. For simplicity the units will be shown as ppm. The effect of the logarithmic scale is shown in Table 1.

Controlling pH in the brewing process

Increasing Acidity The principal increase in acidity during mashing comes from the precipitation of phosphates and amino acids/polypeptides derived from the malt. The phosphates dissociate: -

1. H3PO4 → H+ H2PO4

2. H2PO4- → H+ HPO42FIGURE 2

[H+(aq)] = [OH-(aq)] since Kw = [H+(aq)] x [OH-(aq)] -

then substituting for [OH (aq)] Kw = 10 -14 = [H+(aq)]2

Measuring the acidity or pH of a wort and beer Beer along with most beverages is acidic (i.e. with a pH below 7.0). Typical pH for the brewing operation for a standard lager is shown as follows:

[H+(aq)] = 10-7 mol/l

FIGURE 1

Table 1 - The relationship between pH and [H+] over the range pH 3.1 – 6.0. pH

H+ ppm

pH

H+ ppm

pH

H+ ppm

3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0

789 631 501 398 316 251 200 159 126 100

4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.8 5.0

79.4 63.1 50.1 39.8 31.6 25.1 20.0 15.8 12.6 10.0

5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 6.0

7.9 6.3 5.0 4.0 3.2 2.5 2.0 1.6 1.3 1.0

Ref: Taylor D. MBAA T.Q No4 1990.



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TECHNICAL SUMMARY

especially if one or both of the ions are moderately acidic or basic. If a substance has a basic anion, such as Mg(OH) 2 and CaF2, its Wort pH solubility will be affected by the pH of the Before boil After boil solution. In general the solubility of slightly 5.5 5.4 soluble salts which contain basic anions, 5.8 5.6 increase as the pH is lowered. 5.1 5.0 Most of the reactions in brewing are organic 5.4 5.3 reactions in aqueous systems and these are effected by pH. Biological macromolecules act as acids and bases by donating and accepting protons. However, due to the size of these molecules, they often contain several Wort and beer as a buffer different groups that accept or donate Wort and beer are good buffers and are able to protons, thus having both acidic and basic withstand small additions of acids or bases groups rather than behaving as purely acids or without significant changes in pH. Buffered bases. solutions resist a change in pH when small These acidic and basic groups act as weak amounts of acid or base are added. acids and bases. Changes in the pH around Buffers contain acidic species to neutralise the macromolecule will determine which OH- ions and a basic species to neutralise H + groups are protonated and which are not, ions. However, these two species must be able which in turn determines properties of the to co-exist in a solution, without completely molecule. neutralising each other. For example beer is a weak acid (HX) and when it dissociates from A typical example is amino acids, which are its base (X) the following equilibrium occurs: small molecules containing both an amino + group and a carboxyl group. Since each amino HX (aq) ↔ H (aq) + X (aq) group can be protonated and each carboxyl group de-protonated, the structure of an If OH - ions are added they will remove H + amino acid depends on the pH of the solution ions to form water, thus increasing the pH. it is in. At pH 7, amino acids have the following However, the equilibrium reaction will shift to structure: the right as H + ions are released. The [H +] will therefore remain fairly constant, as will the pH. If more H+ ions are added, then the above reaction will shift to the left. Amino group Carboxylic acid group The effect of changing concentrations on equilibria can be predicted using Le Chatelier’s Principle. This principle states that if a system in equilibrium is disturbed then the equation moves in the direction which reduces t he disturbance. Hence in the system above, when more hydrogen ions are added the equilibrium will move towards production of HX in order to When in an aqueous solution, amino acids minimise the disturbance. This will cause the can act as both acids and bases, i.e. they are [H+] to decrease, to close to what it was amphoteric. before, and thus the pH will stay fairly If only positive charges or only negative constant. charges are present, the molecule is The most effective buffering solutions are described as either a cation or an anion those which have similar concentrations of HX respectively. However, both positive and and X , because then the buffer has the negative charges can be present at the same capacity to absorb both acid and base, with time. When this happens, the molecule is the same effectiveness in either direction. called a dipolar ion or zwitterion. All amino acids exist as zwitterions at pH The effect of pH 7.0. There is no pH at which both groups are on the brewing process. electrically neutral. pH has a major effect on the rate of reaction, Amino acids can be joined together to form solubility and electrostatic charge of many proteins and polypeptide molecules through molecules. This will have an important condensation or dehydration reactions influence on beer quality and production between the carboxyl group of one amino throughout the brewing process: acid and the carboxyl group of the next. This bond is called a peptide bond. • Physical e.g. colloidal stability of the beer It therefore follows that all the protein and • Chemical e.g. isomerisation of alpha acid polypeptide molecules in beer will be charged and this will effect physical properties such as • Enzymatic e.g. malt and yeast enzyme their ability to coagulate and settle out as hot activity. and cold break. Also their tendency to form hydrogen bonds leading to the formation of a. Physical chill haze and foam. The solubility of inorganic ions such as mineral Enzymes are complex proteins which rely on a salt may be affected by the pH of the solution,

Table 2 - The effect of the Mineral Composition of mash water on wort pH

Water composition

50 ppm Ca2+ 50 ppm Ca2+ & 100 ppm CO32350 ppm Ca2+ 350 ppm Ca2+ & 100 ppm CO32Ref: Taylor D. MBAA T.Q No4 1990.

3. HPO42- → 3H+ PO43-

If calcium ions are present then the phosphates precipitate as calcium phosphate leaving 3H+ in solution, thus increasing the acidity. 4. 3Ca2 + 2H3PO4- → 6H+ Ca3(PO4 )2↓

A similar reaction will occur with the amino acids and polypeptides present in the wort: Amino Group-COOH

→ 2H+ + Ca(Amino Group-COO)2 ↓

When calcium sulphate (CaSO 4 ) is added to brewing water, the amino acids and phosphates form an insoluble salt (as shown above) leaving hydrogen ions (H + ) and sulphate ions (SO42- ) in solution. The increase in hydrogen ion concentration means that the solution becomes more acidic. The change in mineral ion composition and precipitation of calcium salts account for most of the pH fall prior to fermentation. During fermentation the beer becomes more acidic (pH falls from around 5.2 to 4.0). A small amount of this fall will be due to further precipitation of calcium salts but the majority of the fall in pH is brought about by the excretion of organic acids by yeast.

Decreasing Acidity However other mineral ions present in water can react to impede the fall in pH, and t hese are the salts of carbonates (CO 3 ) and bicarbonates (HCO3 ) often called temporary hardness. 1. Ca(HCO3 )2 → Ca2+ + 2HCO3-

2. 2HCO3 + H2O -

3. H2CO3

→ H2CO3 + OH-

→ H2O + CO2 ↑

The production of hydroxyl ions (OH- ) “mops up” free hydrogen ions (H + ) to form water and hence limiting the fall in pH. It is therefore necessary to treat all brewing water to remove temporary hardness to ensure the correct fall in pH is achieved. The effect of the ionic composition on pH is shown in Table 2. Temporary hardness is also responsible for scale and must be removed from process water such as boiler feed water, CIP water and water used in bottle washers, pasteurisers and bottle rinsers to avoid unnecessary scale build up.

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three dimensional structure for their activity. Much of their structure is derived internal electrostatic bonding (e.g. hydrogen bonding) and hence they can only operate within a given pH range. (see later)

Summary

Figure 3

The role of pH is essential in beer production. It governs most of the physical and chemical reactions which occur and creates the necessary living environment for the yeast grow, flourish and complete the fermentation process. The acidity of the beer itself contributes to the taste and character of the b eer. Acid is one of the four principal tastes sensations and the pH will effect the way the other flavour compounds are perceived by the consumer. s

b. Chemical There are a few non-enzyme catalysed chemical reactions which occur in brewing, examples are:

• Isomerisation of alpha acid into iso alpha acid during wort boiling. This is a basic chemical reaction, which is favoured by higher pH (pH 8 to 10) where it is goes to over 90% conversion. At wort pH (pH 5.2) typical conversions are around 60% in the kettle giving final bitterness utilisations of 40%. It is not practical to alter the pH of the wort , but many brewers chose to use preisomerised hop products, where the isomerisation of alpha acid is carried out at pH 8 for maximum conversion and the isomerised extract added to the wort. • Colour is increased during wort boiling due to the Maillard reaction. This reaction is not favoured at lower pH thus limiting wort and hence beer colours. • The husk of the malt contains polyphenols and silica compounds which are more easily extracted under alkaline (pH > 7.0) conditions. Polyphenols can produce a colloidal instability and astringency in the beer. Most of the polyphenols are extracted during the latter stages of sparging. It is important to ensure all brewing water is at least neutral or slightly acidic. Some brewers add mineral salts to all the brewing water including the sparge to maintain a lower pH thus avoiding this risk. • An important reaction during maturation is the conversion of alpha-acetolactate excreted by the yeast into diacetyl in the fermenting beer. This is a natural decarboxylation reaction which occurs outside the yeast cell and the rate of decomposition is increased at lower pH. Many brewers acidify their wort to accelerate the reduction of acetolactate at the end of fermentation. • At beer pH oxalates produced from the malt form insoluble salts with calcium ions and precipitate as calcium oxalate thus reducing the tendency for haze and gushing in packaged beer and beerstone production. c.Enzymes The majority of the chemical reactions in brewing are catalysed by enzymes. As was explained earlier these are made up of chains of amino acids and rely on a three dimensional structure for their activity. The charge on amino acids is critical to its structure and most enzymes will only work within defined pH ranges (see Figure 3).

The optimum pH ranges for the brewing enzymes fit well within the range of the typical mash pH (5.8 ± 0.2), thus: • Alpha amylase which randomly hydrolyses starch – optimum pH 5.2 • Beta amylase which hydrolyses pairs of maltose sugar from non reducing end – optimum pH 5.5 • Proteases – hydrolyses proteins to polypeptides to amino acid – optimum pH 5.5 • Beta-glucanase hydrolyses beta glucans to reduce wort viscosity – optimum pH 6.0

As a result many of the process parameters which rely on efficient enzyme conversion will be affected by the pH of the wort, for example: 1. Proteolytic and amylolytic enz yme activity, which improves brewhouse extract. 2. Increases wort fermentability 3. Increases wort free amino and soluble nitrogen 4. Increases rate of mash tun run off The other major contributor o f enzymes is the yeast itself, which converts the sugars to alcohol through a complex series of enzymic reactions. The yeast as a living organism, is capable of regulating its own intracellular pH at around 6.5, but prefers to live in an acidic medium. It can tolerate pH as low as 2.0 for short periods of time, hence the use of acid washing. Bacteria on the other hand generally do not like acidic conditions and only a specialised group of organisms can g row and infect beer. Few bacteria can tolerate the low pH conditions of acid washing. Lower beer pH is one of the essential prop erties of beer, which gives it microbial and physical stabilit y. Very acidic beers such as Belgian Lambic beers which have a pH around 3.5 are perceived as sharp and acidic, while beers with high pH are often described as soft and lacking in mouthfeel.

q Acknowledgement

I would like to thank Dr Lisa Bradley for her invaluable help in preparing this text. q Further

Reading 1. Moll “Water ” in Brewing Science and Technology Series II published by the Institute of Brewing 2. O’Rourke “Water ” in Brewing Science and Technology Series III (in print) published by the Institute and Guild of Brewing 3. O`Rourke “Treatment and use of water in Brewing ” Brewers Guardian December 1998 4. Taylor D “The importance of pH control during Brewing” MBAA Technical Quarterly Vol 27 pp131 – 136.



23

TECHNICAL SUMMARY

The function of enzymes in brewing The nature of enzymes Enzymes are proteins with a special structure capable of accelerating the breakdown of different substrates. They act as catalysts to increase the speed of a chemical reaction without themselves undergoing any permanent chemical change. They are not used up in the reaction or appear as reaction products. The basic enzymatic reaction can be represented as follows: Substrate + Enzyme ↔ Product(s) + Enzyme. Energy is required for chemical reactions to proceed. The energy is called the energy of activation. It is the magnitude of the activation energy that determines just how fast the reaction will proceed (See Fig 1).


Continuing this series of technical summaries for the Institute & Guild’s AME candidates. In order to do its work, an enzyme must combine – even if ever so briefly – with at least one of the reactants. In most cases, the forces that hold the enzyme and its substrate are non-covalent, being an assortment of: • Hydrogen bonds • Ionic bonds • Hydrophobic interactions.

molecule binds to the enzyme like a key in a lock. This means that the structure of the substrate has to match the shape of the enzyme and explains the remarkable specificity of most enzymes. The necessity for a close fit between enzyme and substrate explains how the enzyme can be inhibited by molecules with a similar structure. Many enzymes require the presence of an additional, non-protein, co-factor. • Some of these are metal ions such as Zn 2+ (the co-factor for alcohol dehydrogenase), Cu 2+, Mn2+, K+, and Na+. • Some co-factors are small organic molecules called co-enzymes – for example the B vitamins.

Temperature sensitivity

How enzymes work Enzymes bind temporarily to substrate of the product they catalyse. In doing so, they lower the amount of activation energy needed enabling the reaction to proceed at more quickly at lower temperatures (See Fig 2).

Most of these interactions are weak and successful binding of enzyme and substrate requires that the two molecules are able to approach each other closely over a broad surface. The substrate

Like most chemical reactions, the rate of an enzyme-catalyzed reaction increases as the temperature is raised. (A 10°C rise in temperature will increase the activity of most enzymes by 50 to 100%). Variations in

Figure 1. Free Energy diagram showing how enzymes reduce the energy of activation of a reaction.

Figure 2 – Schematic of the mechanism for an enzyme binding with a substrate.

Figure 3. Temperature Sensitivity of Enzymes.

Figure 4. pH Sensitivity of Enzymes.

Figure 5. Effect of increasing enzyme concentration on the rate of reaction with unlimited substrate.

Figure 6. The effect on limited enzyme concentration on the rate of reaction

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reaction temperature as small as 1 – 2° may introduce changes of 10 to 20% in the results. In the case of enzymatic reactions, this is complicated by the fact that high temperatures adversely affect many enzymes. The reaction rate increases with temperature to a maximum level, then abruptly falls off with further increase of temperature. Many enzymes start to become denatured at temperatures above 40°C (See Fig 3). Over a period of time, enzymes will be deactivated at even moderate temperatures. Storage of enzymes at 5 °C or below is generally the most suitable.

pH sensitivity Enzymes are affected by changes in pH. The most favourable pH value – the point where the enzyme is most active – is known as the optimum pH (See Fig 4). Extremely high or low pH values generally result in complete loss of activity for most enzymes. pH is also a factor in the stability of enzymes, as with activity, for each enzyme there is also a region of pH optimal stability. The optimum pH value will vary greatly from one enzyme to another. Most of the brewing enzymes have an optimum pH in

Figure 7: Schematic showing the action of alpha- and beta -amylase in starch hydrolysis. the range 4.5 to 6.0 which is the operating range of most brewing process.

Enzyme concentration With an excess concentration of substrate,

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15

TECHNICAL SUMMARY

such as starch in a brewers wort, there is a linear effect of increasing the enzyme concentration upon the reaction rate (See Fig 5). Hence the if all other factors are kept constant, malts with higher enzymic power will break down the starch faster. The amount of enzyme present in a reaction is measured by the activity it catalyses.

enzyme activity in terms of rate of reaction (See Fig 6). In addition to temperature and pH there are other factors, such as ionic strength, which can affect the enzymatic reaction. Each of these physical and chemical parameters must be considered and optimised in order for an enzymatic reaction to be accurate and reproducible.

Substrate concentration

Biochemical changes during brewing

It has been shown that if the amount of the enzyme is kept constant and the substrate concentration is then gradually increased, the reaction velocity will increase until it reaches a maximum. After this point, increases in substrate concentration will not increase the velocity. It is thought that when this maximum velocity had been reached, all of the available enzyme has been converted to the enzyme substrate complex. This point on the graph is designated Vmax. This information can be used to calculate

Enzymes are essential in catalyzing the biochemical changes, which occur in the brewing process. There are two principal processes of interest to the brewer: • The break down the carbohydrate, principally starch in malted barley to sugars. • The fermentation of sugars and other nutrients under anaerobic conditions by yeast to release energy and producing ethanol as a metabolic by-product. These biological reactions are catalyzed

Table 1 Enzyme

Action

Optimum temp °C Optimum pH

Alpha amylase Random hydrolysis of starch Beta amylase Hydrolysis of pairs of sugars from the non-reducing end Proteases (various) Solubilises proteins and polypeptides Malt beta glucanase Breaks gum cell walls, reduces viscosity

67

5.2

62

5.5

52 (some higher) 56

5.5 6.0

Table 2. Effect of mash temperature on wort fermentability (all malt mash) Mash temp °C

% Extract

% Fermentability

Attenuation limit for a 1040 wort (10°P)

75.6 74.2 74.0

76.2 69.7 65.3

2.7 3.2 3.7

60 65.5 68.3

pH Optimum

Optimum Temp.

Temp. Inactive

4.5-4.8

37-45°C

55°C

4.7-5.0

40°C

63°C

6.3

60°C

73°C

Endo beta 1-4 glucanase Endo barley beta glucanase beta glucan solubilase

Table 4. Effect of mashing temperatures on the release of beta glucan. Temp °C

Wort beta glucan mg/l

45 55 65 75

1.2 2.8 6.3 9.7

Wort viscosity cp

Wort filtration rate volume in 30 mins

1.20 1.35 1.63 2.01

277 178 133 78

Table 5. Effect of adding exogenous beta glucanase on the filterability of wort

Beta glucanse as % of grist weight 0 0.01 0.05 0.1 0.2

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All malt mash Wort filtration rate vol in 30 mins 260 283 288 325 325


Wort viscosity cp 1.73 1.73 1.60 1.43 1.43


60% barley + 40% malt Wort filtration rate Wort vol in 30 mins viscosity cp 200 218 236 290 290

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Breaking down the carbohydrates Although malting and mashing are physically separate processes and usually take place in different locations, malting has a profound influence on the subsequent release of sugars during mashing. During malting the barley corn is allowed to germinate where it produces enzymes which break down the cell walls in the corn and produces enzymes capable of releasing the energy stored as starch in the endosperm. The starch, which is laid down in concentric granules surrounded by a protein matrix, has to be broken down during mashing before the starch hydrolysing enzymes, Amylases, can gain access to the enclosed starch store. There are three principal enzymic reactions in malt involved in the mashing process, which are listed below along the upper limits of their thermal activity.

Starch hydrolysis

Table 3. Temperature of beta glucan enzyme activity Enzyme

by enzymes from the barley and yeast respectively. Every organism is obliged to produce all the enzymes needed to break down its component molecules. Thus barley is able to produce all the enzymes needed to degrade starch, betaglucan, pentosans, lipids and proteins, which are the major compounds of concern to the brewer. It follows that it must be possible to produce malting and mashing profiles to allow all these reactions to take place. Table 1 shows how enzymes work best between specific pH and temperature ranges.

1.82 1.81 1.65 1.43 1.44

The principal enzyme reaction involved in mashing is the hydrolysis of starch to sugars by alpha- and beta-amylase. Before enzyme hydrolysis can occur it is necessary to exceed the starch gelatinisation temperature of malt. Therefore it is necessary to select the optimum conditions for the saccharifying enzymes to operate. This is achieved by stabilising the enzymes in a number of ways: • Optimising pH at mashing ( usually between pH5 and 6) • Adding calcium ions to stabilise the enzyme • Using thick mash (high concentration substrate to insulate the enzymes against denaturing) • Optimising temperature to favour the activity of both the alpha and beta amylase. The amylase enzymes are able to break the alpha-1,4 links in amylose and amylopectin to give a mixture of glucose, maltose, maltotriose and higher sugars called dextrins, which are unfermentable, to give a wort (malt derived sugar solution) which is about 70% fermentable. • alpha-amylase produces random

hydrolyses of starch to dextrins.

Most beta-glucan is water soluble, but a proportion is bound co-valently to cell wall proteins. If there is insufficient degradation of the cell walls, then enzymic access to the protein and starch will be restricted, and the extract from the malt reduced. Although much of the necessary betaglucanase activity occurs during malting, there is inevitably some survival of cell wall material (even in the most fully modified malt). This will be exacerbated if adjuncts such as barley and wheat are also used. Consequently it is necessary to ensure the continued activity of beta-glucanase during mashing, since the release of beta-glucan will continue through the activity of betaglucan solubilase which is more heat stable than the malt beta-glucanase which breaks down the beta-glucan structure. (See Table 3). The results of the different optimum temperature can have an effect on the

• beta-amylase attacks the starch and dextrins from the reducing end, stripping off pairs of sugars molecules (maltose) as shown in Figure 7. By varying the mashing temperature it is possible to preferentially favour one enzyme reaction over the other and hence influence the fermentability of the wort, with the lower temperatures giving higher fermentable worts as shown in Table 2.

Beta-glucan breakdown As well as starch there are a number of nonstarch barley polysaccharides. The most significant non-starch polysaccharide in barley and malt is beta-glucan which makes up more than 75% of the cell wall. The molecule has a distinctive linear structure in with roughly 70% beta-1,4 linkages and 30% beta-1,3 linkages.

Table 6: Effect of mashing temperature after 1 /2 hour stand on protein hydrolysis. Temperature °C

Nitrogen mg/100 ml

62.8 65.5 68.3

Head Retention Rudin (sec)

43 40 37

Shelf life (weeks)

88 100 99

12 10 8

Table 7: Common enzymes used in syrup manufacture

Type of enzyme

Action

Principal sugars produced

Heat stable alpha amylase

Endo-1,4 alpha bonds

Reduces viscosity – Maltodextrins Glucose syrup

Alpha amylase and glucoamylase Alpha amylase and beta amylase Alpha amylase and pullulanase

Alpha-1,4 bonds and alpha-1,4 & 1,6 bonds Alpha-1,4 bonds Alpha-1,4 bonds Alpha-1,6 bonds

Principally maltose syrup Principally very high maltose syrup

Based on information supplied by ABM – Rhone-Poulenc

The first aid kit Location

Symptom

Remedy

Cereal Cooker

Glutinous starch Retrograded starch Enzyme deficient malt Starch in wort Set mash – will not filter Adjunct brewing – wheat or barley

Heat stable alpha-amylase

Mash mixer

Fermentation

Maturation and filtration

Low wort nitrogen Poor wort fermentability Starch in fermenting wort High beer attenuation Rapid diacetyl removal Low sweetness Promote secondary fermentation Chill haze protection Poor filterability Haze from starch or glucans

Bottling

Resistance to oxidation or oxygen barrier

Bacterial alpha-amylase Heat stable beta-glucanase Alpha-amylase, protease & betaglucanse Neutral protease Fungal alpha-amylase Amyloglucosidase or pullulanase + beta-amylase Alpha-acetolacate decarboxylase Amyloglucosidase Amyloglucosidase Papain Fungal alpha-amylase or betaglucanase Fungal alpha-amylase or beta glucanase Immobilised glucose oxidase in crown liner

viscosity and hence the filterability of wort and beer (See table 4). If the large viscous beta-glucan molecules are not broken down during malting or mashing other process problems can also occur: • Reduced extract recovery • High wort viscosit • Poor run off performance • Beer filtration problems • Beer haze problems The high molecular weight beta-glucans released by beta-glucan solublilase contribute to wort viscosity and poorer extract recovery. Most brewers are very careful in selecting malt with low beta-glucan levels, and betaglucan degradation occurs during malting. However most initial mash temperatures are at or above the maximum stability temperature of the malt beta glucanase enzymes, and it is common practice in many breweries to add exogenous betaglucanase to decrease wort and beer viscosity and to improve filterability. The effects of enzyme addition on the breakdown of beta-glucan can be shown by an increasing in filter flow rate and decrease in wort viscosity. The effect will be more noticeable with higher concentrations of unbroken beta-glucans when using for example raw (un-malted) barley adjunct (See Table 5).

Hydrolysis of Proteins and Polypeptides While about 95% of the starch from malt is solubilised by the end of mashing, only about 35 – 40% of the malt protein (TN – total nitrogen) is solubilised. This is referred to as the TSN (total soluble nitrogen) in an unboiled wort. The permanently soluble nitrogen (PSN) is the nitrogenous material which remains in the wort after wort boiling (i.e. is not precipitated as break). The PSN is usually calculated as TSN x 0.94. The principal groups of enzymes involved in the breakdown of malt proteins are Endoproteases which break the large protein molecules into relatively large polpeptide chains, and the Exopeptidases which attack the polypeptides from a specific end stripping off small units to produce amino acids.

Endopeptidases They have a relatively low optimum temperature and hence with high temperature mashing (e.g. 65oC isothermal mashing) most of the protein breakdown will have taken place during the malting process, and randomly attack the protein chain Optimum conditions pH Temperature Inactivation temperature


3.9-5.5 45-50°C 70°C


17

TECHNICAL SUMMARY

Exopeptidases They are able to withstand higher temperature s and release the amino acids from the prolypeptide chains. There are two principal groups of Exopeptidase enzymes: • Carboxypeptidase which attacks the proteins from the carbonyl end. This enzyme is not present in raw barley, but is rapidly produced during steeping and is active at normal mash pH. Optimum conditions pH Temperature Inactivation temperature

3.9-5.5 45-50°C 70°C.

• Aminopeptidase, which attacks the proteins from the amino end, is much less active at mash pH and does not play a significant role in protein breakdown during mashing. Optimum conditions pH Temperature Inactivation temperature

4.8-5.2 50°C >70°C

Most of the proteolysis occurs during malting. It is impossible to completely compensate for a nitrogen deficiency in malt by introducing a prolonged mash stand at < 50°C without adding exogenous enzymes. Nitrogenous materials account for 5-6% of wort solids, which is equivalent to around 30-40% of the total nitrogen in malt. Good yeast growth and rapid fermentation requires 160mg/l of free amino nitrogen (at 12°P wort) – depending on the yeast strain. Carboxypeptidases can release amino acids in mashing provided that the endopeptidase has broken down the protein substrate during the malting process. The optimum temperature to produce free amino nitrogen production is 50°C. Proteins in the mash dissolve at these low temperatures and then precipitate at 65°C, which can inhibit lautering. Excessive proteolysis in malting and mashing will reduce foam stability and the pH of a normal mash is not optimal for proteolysis (See Table 6).

Typical types of protein material found in wort Proteins Large molecules with a unique identity. Much of the surplus protein is left behind in the spent grains, but when oxidised can form a protein “scum” which causes run off problems. Some of the soluble proteins play an essential role as enzymes catalysing the reactions described above. Polypeptides Long chain sequences of relatively high molecular weight amino acids, with two important groups in brewing, hydrophobic

18


polypeptides which make up beer foam and acidic polypeptides which can combine with polyphenols to produce hot and cold break, and if not removed, these contribute to colloidal instability in beer. This group of compounds are also probably important in contributing to the texture and mouthfeel of the beer. Peptides These are short chain sequences of amino acids usually 2 to 10 units long, and probably have a minor effect on body and mouthfeel. Amino Acids These make up 10 to 15% of the TSN and are an essential source of nutrient for yeast growth. The usual concentration of soluble free amino nitrogen (FAN) in wort is required to be above 160 mg/l; lower levels can lead to a defective fermentation. In addition to role of amino acids in yeast growth, they are also involved in a number of metabolic pathways, producing significant flavour active compounds, which contribute to the final flavour of the beer. The activity of proteolytic enzymes are effected by temperature of mashing, which in turn will effect the total nitrogen, amino nitrogen, head retention and shelf life stability.

Fermentation Most living organisms respire aerobically, converting sugars to carbon dioxide and water releasing the energy bound by photosynthesis in the carbohydrate (sugars) molecules. However some micro-organisms, including yeast, are able to respire anaerobically, but under anaerobic conditions they can only partially break down the sugar molecules to ethanol to release energy in the form of ATP (adenosine triphosphate). The role of yeast in the fermentation is that of a living catalyst, effecting the reaction without becoming part of the finished product. During the course of the fermentation the yeast cells grow and replicate up to 5 times. Although the yeast gains its energy from the sugar, which it converts to alcohol it can only utilise simple sugars. The sugars are taken up in a specific order, with the monosaccharides, glucose and fructose used first, together with sucrose. Although the latter is a disaccharide, it behaves like a monosaccharide since it is broken down to glucose and fructose outside the cell through the action of the yeast enzyme invertase. Once the wort glucose level falls, the yeast starts to use the disaccharide, maltose, which is usually the most abundant sugar in brewers wort. Maltose has to be transported into the cell, where it is broken down to glucose. Lastly most yeast strains can utilise the trisaccharide, maltotriose, but only slowly.


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Brewing strains of yeast cannot generally ferment the longer chained or branched sugars (called dextrins) which persist in to the finished beer as unfermentable extract to give the beer body and mouthfeel. As well as sugars, yeast requires nitrogen, which in wort comes from the malt in the form of soluble amino nitrogen. A healthy fermentation yeast requires more than 160 mg/l of soluble nitrogen. If there is insufficient soluble nitrogen, for example when high cereal or sugar adjunct are used, then additional nitrogen may be required in the form of simple ammonium salts.

Syrup manufacture A number of brewers use brewing syrups which are manufactured from hydrolysed starch solution. Since the starch is not malted, microbial exogenous enzymes have to be used and by selecting different enzyme combinations the syrup producer can control the composition and fermentability of the syrup. (See Table 7).

A brewers first aid kit It is the objective of most brewers to avoid the use of external enzymes and rely on the naturally produced enzymes from the malt and the activity of the yeast alone to produce their beer (See table on previous page for some first aid). s

q

Further Reading

O’Rourke “Mashing” in Brewing Science and Technology Series III (in print) published by the Institute of Brewing O’Rourke “Brewing” chapter 2.6 from Industrial Enzymology Ed 2 edited by Godfrey and West Macmillan 1996. O’Rourke “Mashing” Brewers Guardian December 1999

TECHNICAL SUMMARY

Malt specifications & brewing performance When buying malt, the brewery is looking for a product, which will yield the most economic extract (wort) and will operate satisfactorily under brewhouse conditions and throughout the brewing process. Malt, which is difficult to handle can cause quality and process problems involving additional costs. To ensure that an appropriate malt is supplied the brewer will set and agree a suitable specification with his supplier.

B

rewhouse performance of the malt is affected by the interactions between malt quality and: • The type of brewing process. • The type of brewhouse equipment. • Other materials that are used with the malt e.g. adjuncts. The brewer has certain objectives when purchasing malt: • To recover a high yield of sugar (extract) from the malt. • That the malt will operate satisfactorily in the plant without additional processing or treatments. • The malt will pass through the plant within the required cycle time (run off time). • The wort produced from the malt provides all the necessary nutrients to ensure a satisfactory fermentation. • The malt delivers the flavour and process requirements of the brewer and his customers.

All of these benefits are supplied on consistent and reliable basis.

Malt specifications Barley, and the malt produced, is derived from natural living material, and hence subject to all the variations which can occur as a result of genetic and environmental conditions. It follows that no two batches of malt are alike. Malt is analysed in accordance with standard industry tests such as the IoB, EBC and ASBC methods of analysis. However, standard malt specifications are not always a reliable indicator of how well the malt will perform in the brewery. Brewers and maltsters are continually looking for better predictions of brewing performance of a malt. Barley variety There is a list of approved barley varieties for malting. Each barley variety has its own

Both methods give a prediction of brewhouse performance. However under laboratory conditions mashing are not optimised which explains how extract recoveries of greater than 100% can be achieved with more modern mashing and wort separation techniques such as the modern mash filter.



The factors which favour high extract recovery include:

characteristics through its genetic make-up which will determine certain properties of important to brewing. Some varieties produce better malt than others. Barley variety will influence malt quality in terms of variables such as:

1. Varietial effects – different barley varieties give different yields 2. The total nitrogen content – the higher the nitrogen the lower the extract. 3. Corn size – large even corns size give better malting and milling performance. 4. Modification – the malt should be adequately but not over-modified – see later. 5. Enzyme capacity – the malt should have sufficient enzymes to degrade the starch and convert it to simple sugars. 6. Low in gums – extract recovery can be reduced by the presence of gums – particularly beta-glucans in the malt. This problem is often resolved by the addition of exogenous beta glucanase.

• % nitrogen or protein in grain (see later) • % beta-glucan after malting • Size and homogeneity of grain – plumper grains yield better extracts and are easier to malt and mill. Most brewers specify that all grains should be ≥ 2.2 mm • Not all barley varieties have similar abilities to produce enzymes, this can be important particularly when using high levels of adjunct. The environment also influences these factors, e.g. weather, soil type and the use of fertiliser. The barley variety used to make the malt is considered important not only because of its brewing properties, but because of special characters it gives to the finished beer. Today many traditional ale brewers still specify Maris Otter as they believe it makes better quality beer, even though this variety is no longer recommended because of its poor yield and agronomic performance. Extract Yield Extract is a measure of the amount of sugar recovered from the malt after mashing. The extract value is based on a laboratory mash. There are two basic laboratory procedures used for measuring extract. • The IoB method, which involves mashing 10% malt with, distilled water and letting the mash stands for 60 minutes at 65°C. The extract is measured as the specific gravity of the filtered solution at 20°C. The results are expressed as litre degrees per kilogram. • In the EBC (European Brewery Convention) method two mash stand temperatures of 45°C and 70°C are used. The Extract is expressed % sugar (sucrose) over total weight of malt Extract value for typical malt made from standard 2-row barley. Malt extract “dry” IoB l° /kg EBC °Plato Standard ale malt 305 – 315 81 – 82 Standard Lager malt 300 – 310 80 – 81

Malt Nitrogen (usually expressed as % nitrogen) The higher the level of nitrogen the lower the % extract. Therefore brewers specify the % nitrogen or protein in malt.

Typical % nitrogen is in the r ange of : Ale Malt – 1.6% 1.4 Lager Malt 1.6 – 1.8% (Nitrogen is sometimes expressed as % protein which is % nitrogen x 6.25) However nitrogen plays an essential role in the quality of the beer: • Nitrogen, in the form of amino acids, is required for yeast growth with typical values of 160 to 240 mg/l depending on yeast strain and wort gravity. • Hydrophobic nitrogen from the malt provide the beer foam and head retention in beer. • Some long chain polypeptides cause colloidal instability (chill and permanent haze) in beer and have to be reduced in the brewing process. • Proteins and polypeptides contribute to the texture and mouthfeel of the beer. Excessive removal leads to a thin tasting beer with poor foam. It is important to ensure a avoid excess nitrogen in the barley, but ensure sufficient of the nitrogen available is broken down to soluble nitrogen. The ratio of total to soluble nitrogen is an important indicator or brewing performance. Most of the nitrogen breakdown occurs during malting.



27

TECHNICAL SUMMARY

Moisture (usually expressed as % moisture) The lower the % moisture, the higher the extract in the malt. Malt specifications express the extract as “extract dry” or “extract as is” – which includes the moisture content. The darker the malt colour, the higher or longer the kilning time. This results in lower % moisture. Because of their darker colour ale malts tend to have a lower % moisture than lager malt. Kilning uses a large amount of energy. The next process stage after kilning is mashing when the malt is re-hydrated, There is no benefit in excessive moisture reduction and the trend is to move to higher lager malt moistures to reduce energy costs. For safe storage and good milling performance malt moisture should not exceed 6%. The higher the moisture, the lower the extract yield per tonne of delivered malt. This has to be adjusted in the price since the brewer wants to pay for malt not water.

observation of the endosperm and evaluate the degree of modification. It is found that these observations correlate well with brewing performance.

Figure 1 – Process of modification of a barley corn.

Figure 2. Before – showing the beta glucan cell walls surrounding the starch granules in the endosperm before in barley before malting.

Typical % moisture values for standard malts: Standard ale malt = 2 – 3% moisture Standard lager malt = 4 – 6% moisture Colour During kilning chemical reactions take place between the malt components to produce colour compounds. There are a number of colour and flavour reactions. The principal reaction is between amino acids and sugars called the “Maillard reaction” which produces both colour and flavour active compounds. The higher the kilning temperature, the greater the amount of colour compounds produced. As well as producing colour, these compounds also contribute to flavour. The colour of the malt is based on the colour obtained from the IoB or EBC mash using a 10% solution. This colour value provides an approximate indicator of final beer because it is based on a dilute laboratory mash with an original gravity of 1030° (8°Plato). Further colour develops during wort boiling. Modification Before the brewer can break down the starch in malt to sugars during mashing, the maltster has to break down the cell structure in the endosperm to make the starch granules accessible. This process is called modi fication and is the most important measurement when predicting brewing performance and extract yield from malt. Modification gives a measurement of how evenly the cell structure in the endosperm has been broken down during the malting process. Enzyme activity starts from the embryo and the aleurone layer surrounding the endosperm to break down the protein and beta-glucan cell walls surrounding the starch granules (see Figure 1). The process of modification has the effect of stripping away the cell wall structure and is shown in the two electron micrographs (Figures 2 and 3). The degree of modification can be measured

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Volume 2 • Issue 10 • 2002 •

Figure 3. After – showing how the cell structure has been stripped away exposing the starch granules, which can now be degraded by enzymes during mashing. Thanks to Professor G. Palmer, Heriot Watt University, for permission to use the electron-micrographs.

in a number of ways: Direct observation The electron micrographs clearly show the degradation of the cell walls. This is a complicated and expensive technique for routine analysis. However, the presence of cell wall material can be detected using a calcofluor stain. The calcofluor dye binds with beta-glucans (cell wall material) and fluoresces under UV light. Thus if sectioned grains are exposed to this dye those parts of the corn rich in beta-glucan will fluoresce. This technique can be used to determine both the proportion of corns t hat have modified as well as the extent of modification within individual corns. By taking a series of transverse sections through the gain it is possible to make direct

Indirect measurements Another way of measuring modi fication is assessing factors influenced by the breakdown of the endosperm structure in the grain: 1.During malting the protein matrix, which surrounds the starch granules inside each storage cell is broken down. The greater the value of soluble nitrogen, the higher the modification. The IoB analysis it is usually expressed as the “Soluble Nitrogen Ratio” (SNR), which is the soluble nitrogen/total nitrogen expressed as a %. The EBC method uses a similar ratio based the EBC mash where it is called the Kolbach Index. 2. Unless the malt is fully modified a number of cells within the endosperm will not be degraded and will remain intact with coarser milling. When the malt is mashed the enzymes will not be able to penetrate the cells and gain access to the starch. These cells are ruptured with fine milling and the extract can be recovered. Another measurement of modification is the course/ fine difference, which measures the difference in extract yield between finely and coarsely ground malt. The smaller the difference the better the modification. 3. During malting the cell walls in the endosperm are dissolved away making the grain softer and easier to mill. It is possible to use this property to measure the degree of modification, by measuring the amount of energy required to grind the malt (Friability). The method takes 50 grams of malt which is milled with a constant pressure over a mesh screen. The well modified grain will fall through the screen leaving the chunks of under-modified malt. The weight of ground malt indicates the degree of modification. It also measures the homogeneity or evenness of modification. 4. Cold water extract measures the amount of sugars broken down and released during the malting process. – higher cold water extracts indicate higher modification (see Table 1). It is important to use malt that has been correctly modified: In under-modified malt all the cell walls have

Table 1: Typical spe cification for modification in pale ale and well modified lager malt. Index of modification

Pale Ale Malt

Kolbach % (Sol N/Total N) Course/Fine difference (l° Friability % Homogeneity % Cold water extract %

38 – 39 /kg) – 6 ≥ 95 ≥ 88 1.8 – 2.0


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Lager Malt

40 – 43 23– 3 ≥ 95 ≥ 82 2.0 – 2.2

not been broken down, it usually has a lower soluble protein content (SNR is lower) and there may still be small starch granules present which can give starch conversion and haze problems. Under-modified malt will give brewhouse problems and give poor extract recovery. In over-modified malts the cell structure is fully broken down, the soluble protein is higher (high SNR), and most of the small starch granules have be broken down. It is much easier to recover but extract from over modified malt, but some extract may have been used up during the malting process. Excessive nitrogen breakdown may lead to loss of foam positive proteins and poorer beer foam performance. Enzyme Activity. The principal activity of malting is to encourage the barley to produce its own enzymes. Some of the enzymes are required during malting to modify the corn structure. The other enzymes, principally the Diastase enzymes (which break down starch) are required to work during mash conversion in the brewhouse. There are two principle diastatic enzymes:

the starch to produce shorter chains and reduces the viscosity. The activity of the enzyme is measured by the length of time required to break down a standard starch solution to a specific colour standard using an iodine indicator. The activity is expressed as dextrinizing units (DU). • The other enzyme, beta amylase attacks the non reducing end of the starch chain to produce maltose sugar. The enzymic power is measures as DP (Diastatic Power in °Lintner) in the IoB methods of analysis. The DP is around 35 – 40 for standard Ale Malts, but can be as high as 100 to 125 for lager malts and over 160 for some high protein six row North American malts. The latter malts have far more enzymic power than they require just to convert the starch from the malt itself and enable the brewer to use high levels of unmalted starch adjuncts (see a later series.) In EBC analysis the diastatic power is measured as °WK (Windisch-Kolbach units). The value of °WK can be converted to °Lintner by the formula: DP °Lintner = (°WK + 16) / 3.5

• Alpha amylase which randomly hydrolyses

The contribution of malt to flavour Malt is the principal ingredient in beer supplying sugar to the yeast which produces alcohol. In addition to sugar, yeast requires a variety of essential nutrients which are necessary for satisfactory yeast growth and nutrition. The typical components required include: • Simple sugars (glucose, maltose and maltotriose) for fermentation • Amino acids (free amino nitrogen > 150 mg/l) for yeast growth • Mineral ions for enzymes – typically zinc, copper etc • Vitamins for healthy growth • Some lipid material for cell wall production – although yeast manufactures most of these compounds using available oxygen in the wort. During fermentation yeast will produce a number of flavour compounds as a direct consequence of metabolising brewing wort. Changes in wort composition will in fluence this metabolism and hence the flavour of the beer produced. Malt also contributes directly to the appearance final character and taste of the beer:

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TECHNICAL SUMMARY

• Most of the colour of beer comes from the crushed malt or is developed during the brewing process from reactions between malt components. • The colour compounds also give beer a characteristic flavour from light biscuity for the lager malt to a strong burnt acrid taste for black malt and roasted barley. • The mouthfeel and texture of the beer comes mainly from the residual unfermentable sugars (dextrins) derived from the malt. • The pH of wort and beer is regulated through the precipitation of malt components with mineral ions from the water. • Beer foam is made up from hydrophobic proteins, which have their origins in the malt. • Other protein fractions are involved in beer haze and have to be removed to achieve long term colloid stability in small pack beers. • Malt also has an effect on beer flavour through certain flavour active compounds. Most of these factors other than colour, are not included in the malt specification. However there is one flavour active compound formed during malting which has to be controlled in the finished beer. DMS or Dimethyl Sulphide is a malt derived flavour compound with the flavour of “cooked sweetcorn” often associated with lagers. It has a flavour threshold of around 35 ppb. It is only noticeable in lightly kilned malts (lager) and is derived from a precursor, S-methyl methionine (SMM) produced during germination which is

Typical Specification for a Lager Malt. Specification

IGB (Institute & Guild of Brewing) methods:

Moisture Extract yield (dry wt) Corn size > 2.5 mm Colour Total Nitrogen Total Soluble Nitrogen FAN SNR Soluble nitrogen ratio Coarse/Fine difference Friability meter reading Homogeneity Diastatic Power Wort viscosity mPas @ 20°C DMS precursor Beta glucan mg/l Alpha Amylase du (dextrin units)

4.5 – 5.5 % > 305 l ° /kg 95% 2- 4 EBC 1.6 – 1.8% 0.57 – 0.66% > 160 mg/l 34 – 40 % 3 – 7 l° > 85% > 96% > 65° IoB 1.55 -1.65 2 – 8 mg/kg < 200 > 30

converted to DMS by heating. The levels of DMS precursor can be reduced during malting by: • Reduced proteolysis and rootlet growth during germination • Poorly modified malts have lower SMM • Higher kilning temperatures reduce SMM. The brewer will often set a maximum specification for SMM to reduce the beer DMS. However in some beer brands DMS is seen as a positive flavour and high SMM levels are encouraged by short, low temperature kilning conditions. Nitrosamines are chemical compounds containing the grouping N-NO and may be found in malt. They do not have a flavour

EBC (European Brewery Convention)

4.5 – 5.5 % > 80.5 % 95% 2 – 4 EBC 1.6 – 1.8 % 0.65 – 0.75% > 160 mg/l 38 – 44 % /kg – 2% 1 > 85% > 96 % > 220 Windisch-Kolbach 1.55 – 1.65 2 – 8 mg/kg < 250 > 30

contribution but are thought to be carcinogenic. Volatile nitrosamine in malt is produced as oxides of nitrogen (NOx) react with naturally occurring malt amines during kilning to produce N-nitrosodimethylamine, usually abbreviated to NDMA. NOx may be present either in the hot gases from combusted fuel where direct drying is used or even from general air pollution in indirectly fired kilns. The most active forms of NOx are N2O3 and N2O4. To avoid the formation of these compounds most maltsters use indirect heat to fire the kilns, low NOx burners or burn sulphur. Although there is no legal limit for NDMA in the UK there is an industry agreed standard of < 5 ppb. s


Important JIB news for members Please note that as an added service to members, the Journal of the Institute of Brewing (JIB) is now available online on the IGB website and may be downloaded from www.igb.org.uk Printed copies of the JIB will continue to be available to members who specifically request a copy. If you wish to continue receiving your copy by post please contact Nicky Baker at the IGB. Tel: +44 (0) 7499 8144

30

Volume 2 • Issue 10 • 2002 •


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email: [email protected]

TECHNICAL SUMMARY

Hops and hop products Although hops were not added to the first beers, now all modern beers are hopped. Hops contribute to the flavour and appearance of beer. They provide beer with its characteristic bitterness and aroma. The function of hops in brewing. Hops are exclusively used to provide aroma and bitterness in beer. They add the following properties: • Provide the bitter taste in beer (with alpha acid the principal precursor) • The oils provide aroma. • Modify yeast performance during fermentation. • Contribute to beer texture (mouth-feel) • The bacteriocidal properties protect beer against some biological spoilage organisms. • Reduce over foaming during wort boiling. • Aid in protein coagulation during the boil. • Act as a filter medium when a hop back is used. • Foam active agent in beer improving foam performance and cling. • Cone hops contribute tannins which may increase the reducing power of a beer, and hence its resistance to oxidative staling. Tannins may also contribute to a tendency to produce chill haze.

Hops (Humulus lupulus) belong to the family Cannabinaceae . The part of the hop plant used for brewing is the inflorescence (that is a modified branch) of the female plant, which matures to produce a strobile - commonly called a cone. This contains small yellow granules called lupulin glands. These glands contain the hard and soft resins and the essential oil. The soft resins are converted into the bitter substances in the beer and the essential oils impart the “hoppy” character .

Figure 1. Cross section of a hop cone. It is the soft resins (soluble in hexane) that are most important in brewing, and these consist of alpha acids, beta acids and uncharacterised soft resins. The alpha acids and beta acids provide the bittering principals. These acids are largely insoluble in cold water and are more soluble in boiling water. However during wort boiling, the alpha acids are isomerised into iso-alpha acids that are much more soluble. The beta acids are less soluble and are

lost in beer foam (fermenting heads) • Iso-alpha acid is lost in beer foam and absorption by the final filters.


Whole hops

Continuing this series of technical summaries for the Institute & Guild’s AME candidates. largely unchanged during wort boiling, and hence contribute little to the final bitterness of the beer, unless they are oxidised to hupulones in which case they will also contribute bitterness. See Figure 2. The amount of alpha acid added is calculated from the weight and concentration in the raw hops or hop product used, and when using hops added to the kettle, the utilisation decreases throughout the brewing process: Typical recovery rates of iso-alpha acid during brewing with cone hops. Process Stage Recovery of alpha acid At the end of Wort Boiling 50– 55% At the end of Fermentation 35– 40% Bright Beer 25 – 30% After dispense 20% of bitterness can segregate into foam.

Whole hops are added to the kettle, and separated through a hop strainer or hop back. Although used by a number of traditional brewers they can be difficult to handle and store in a modern brewery, and many brewers prefer to use hop products. Whole hops cones are cleaned to remove unwanted stems and leaves before being dried and baled. They are generally stored cold (circa

Figure 2. Isomerisation of alpha acid into isoalpha acid.

The reasons for loss of iso-alpha acid from conventional hops in brewing are: • The nature (duration and vigour) of the boil. • Only around 50% is isomerised from alpha to iso-alpha acid during wort boiling. • Iso-alpha acid is absorbed by the trub (hop debris/protein) during hot wort clarification. • Iso-alpha acid is absorbed by the yeast and

5°C) to reduce the loss of alpha acid. Since they are not usually blended each bale will have a unique alpha acid content depending on the variety season and growing area. Whole hops also tend to give the poorest alpha acid utilisation during boiling (25% to 30%) since they have higher quantity of vegetative material and the alpha acid is less readily available. The higher the content of vegetative material, i.e. the greater the bulk of hop debris, then the greater the potential to retain wort with higher wort losses during wort clarification at the end of boil. There is usually

Table 1. Summary of benefits from using whole hop Preparation Major use Method of use

Bales from growers Bitterness and aroma Direct addition to kettle during boiling or cask for dry hopping

Composition % Total resins 15 Soft resin – alpha acids (8) beta acids (4) Hard & uncharacterised resins (3) Essential; oils 0.9 Tannins/polyphenols 4 Protein (N x 6.25) 15 Water 10 Monosaccharides 2 Lipids and waxes 3 Amino acids 0.1 Pectin 2 Ash 8 Cellulose & lignin 40 Resins and oils will vary according to variety

Advantages: Traditional form Free from extraction solvents Standard aroma & bittering product Aids hot break formation & settling


Disadvantages: Bulky and expensive to store % alpha and aroma varies each year Subject to loss of alpha and aroma on storage Possible contaminates from debris and pesticide Low utilisation (25 – 30%) Higher losses of wort in spent hops Costs of disposal of spent hops

Volume 3 • Issue 1 • January 2003 • www.igb.org.uk

21

TECHNICAL SUMMARY

Table 3. Summary of benefits from using iosmerised hop pellets Preparation Major use Method of use

Magnesium oxide is added to milled hops and gently heated before being palletised and vacuum packed Bitterness with good aroma properties Direct addition to kettle during boiling – can be added part way through the boil

Composition Similar to Type 90 pellets

Almost all the alpha acid is converted to the equivalent magnesium iso-alpha acid. Slight reduction in beta acid content Presence of magnesium and magnesium oixide

Figure 3. Manufacturing process of pelletised hop products. an associated cost to remove the spent hop material. See Table 1.

Pelletised Hops Pelletised hops are made by milling whole hops and compressing the hops into pellets. These are generally packaged under vacuum or in an inert gas such as nitrogen to reduce the rate of deterioration. Pelletised hops are available as: • regular pelletised hop, (type 90 pellets) • enriched pellets (type 45 pellets), where some of the vegetative (non-alpha acid bearing material) is removed to give a constant product with a much higher alpha acid. See Figure 3. Hops of the same variety but with differing alpha contents are often blended to give a standard product with a constant alpha acid appropriate for each variety and growing season. Pellets are added to the kettle where the alpha acid is isomerised during wort boiling.

Pelletised hops generally yield 2 to 3 % improvement in utilisation over the equivalent whole hops (between 27% and 32% utilisation – but sometimes up to 40%). Milling makes the alpha acid more readily accessible, with less vegetative material there is also a lower entrained wort loss, which can be further decreased through a trub recovery system. Wort clarification is usually carried out in whirlpool vessel and the trub (including the spent pelletised hops) is often recovered and sold along with the spent grains. See Table 2.

Isomerised hop pellets The pellets for isomerised hop production are produced in a similar way to standard pellets (see Figure 3) with about 2% magnesium oxide added during the pelletising process. These “stabilised” pellets, packed in an inert atmosphere are heated to 50°C for approximately 14 days, when up to 99% of the alpha acids are isomerised in situ, giving wort utilisation rates of 80 to 90%, and final beer utilisation rates of up to 70% The handling and processing of isomerised pellets is similar to regular pellets. See Table 3.

Hop Products Beside whole hops (hop cones) and pelletised hops, other hop products and extracts are used either as alpha acids added to the kettle or as

Table 2. Summary of benefits from using pelletised hop Preparation Major use Method of use

Leaf hops are cleaned, milled, palletised and vacuum packed Bitterness and aroma Direct addition to kettle during boiling

Composition Type 90 pellets – similar to leaf hop but may be standardised for alpha Lower moisture content Better utilisation through ruptured resin glands

Type 45 pellets – increased alpha due to concentration of lupulin gland. Between 40 to 50% of vegetative material is removed Resin/oil concentration is approximately double.

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Advantages: Traditional product Free from extraction solvents Standard aroma & bittering product Aids hot break formation & settling Significant reduction in volume Improved storage properties Improvement in % hop utilisation Easier disposal of spent hop debris Disadvantages: Bulky than extracts Possible contaminates from debris and pesticide Low utilisation (25 – 35%)


Advantages: Similar to hop pellets Better keeping properties Better utilisation (50 to 60%) Disadvantages: Similar to hop pellets MgO could be perceived as a chemical addition Low utilisation (25 – 30%)

isomerised iso alpha acids added to the kettle or after fermentation. Hop oils and hop bittering products can be added after fermentation to give a dry hop character, or to modify the character of the final beer. Processed hop products represent a convenient and controlled system for adding both bitterness and aroma character to beer, and can be useful for adjusting beers produced outside specification. Their benefits include: • Reduced bulk • Reduced transport costs • Reduced storage costs • Potential for automating hop addition in the brewery • Uniformity - (can be standardised to % isoalpha acid value) • Greater stability (long term storage) • Improved utilisation (pellets up to 10%: Post fermentation bitterness up to 70% improvement) • Reduced beer and wort losses • Improvements in beer quality and consistency • Decreased level of polyphenols/tannins • Decrease (or absence) of nitrates • Decrease (or absence) of pesticide residues These potential benefits have to be balanced against: • Increased production/processing costs • Possible inclusions of solvents and toxic residues (not with CO2 extract) • Purist/public attitudes to the use of processing and solvents • Possible adverse effects on beer quality and taste. All of the products are derived from whole hops in the first instance, and are generally used to help the Brewer overcome the effects of aging, storage and consistency problems.

Hop extract It is possible to extract the soft resins in a variety of solvents, thus obtaining a concentrated solution of alpha and beta acids as well as uncharacterised soft resin. Two typical solvent systems are used: Organic: Principally Ethanol; and Hexane Carbon Dioxide: Liquid and Supercritical Carbon Dioxide. See Figure 4.

Table 4. Summary of benefits from using hop extracts Preparation Major use Method of use Composition

Total resin Alpha acid Beta acid Essential oils Hard resins Tannins Waxes Water

Figure 4. Process flow chart for the manufacture of hop extracts. The main organic extractants are strong solvents and extract plant pigments along with the soft resin. After extraction the solvents are boiled off, to leave concentrated resins containing alpha acids for addition to the kettle. Solvent extracts are increasingly falling from favour because of perceived problems with residue, although ethanol does not have this disadvantage. Carbon dioxide is a more selective extractant removing less of the water soluble components. Supercritical CO2 (operating typically above 250 to 300 bar and below 40 to 45°C) has the properties of both gas and liquid, and is a more polar solvent extracting more plant material than the sub-critical CO 2 . The latter often known as liquid CO 2 operating at 50 bar and 10 to 15°C is a relatively mild non-polar solvent, like hexane, but gives lower overall extraction efficiency with a higher yield of alpha acid. See Figure 5. The immediate availability of the hop resins in the extracts added to the wort is favourable for utilisation (overall in the range of 35% - 45%), and the material is free from or has greatly reduced nitrate and pesticide residues. Liquid CO2 extracts also contain much of the hop essential oils, but the immediate availability of the hop oils decreases their survival during boiling, which may be detrimental to beer flavour. Standardisation of alpha acids in hop extracts (normally 30% alpha, but sometimes 25% or 45%) can easily be achieved. A “pure resin extract” (P.R.E.) is usually obtained first using optimum extraction conditions to produce the best yield of alpha acids from a particular batch of hops (normally in the range of 40 - 55 % alpha in the P.R.E. extract). The P.R.E. is then diluted to the required standard before final packaging by the addition of either glucose or corn syrup, or, more rarely (because of storage stability problems) with a hot water extract of the hop material, which will contain some of the hop sugars, tannins, polyphenols etc. Further fractions of carbon dioxide extract

Resins and oils are extracted from the hops using solvents which are then driven off. To provide bitterness to beer Direct addition to kettle during boiling Whole hops

Organic solvent extract

12 – 20% 2 – 12% 2 – 10% 0.5 – 2% 2 – 4% 4 – 12% 1 – 5% 8 – 12%

Super critical CO2

15 – 60% 8 – 45% 8 – 20% 0 – 5% 2 – 10% 0.5 – 5% 1 – 20% 1 – 15%

Advantages: Less bulk storage Good storage properties (several years) Improved utilisation (45 to 65%) Reduced pesticide residues Minimal wort/beer losses

75 – 90% 27 – 55% 23 – 33% 1 – 5% 5 – 11% 0.1 – 5% 4 – 13% 1 – 7%

Liquid CO2

70 – 95% 30 – 60% 15 – 45 % 2 – 10% None None 0 1 – 10% 1 – 5%

Disadvantages: Different brewing operation compared to whole hops Solvent extract Solvent residue (minimal) Altered aroma profile Presence of “chemicals” Supercritical CO2 Altered aroma profile Highest cost of extraction Possible impurities Liquid extract CO2 Lower yield than supercritical Higher cost per unit alpha than other extracts.

Figure 5. Schematic of plant used to manufacture of hop extracts.



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TECHNICAL SUMMARY

Table 5. Summary of benefits from using isomerised kettle hop extracts (IKE) Preparation Major use Method of use Composition Supercritical CO2 Liquid extract CO2

Pure resins undergoes controlled heating with alkali metal salts which isomerises most of the alpha acid. To provide bitterness and late hop character to beer Direct addition to kettle during boiling Similar to pure resin extract- 90% of the alpha acid is isomerised Essential oil components absent High levels of purity Contains similar amounts of essential oils as the leaf hop

Advantages: Easy to handle and store Standardised constant product Precise control of bittering Retains aroma contribution High utilisation (50 to 75%) High purity/ minimal residues Minimal wort/beer losses

Disadvantages: Restricted to those varieties processed Considered to be “chemically processed”

can be used for separating the hop oil fraction from whole hops, so that the oils can be used for dry hopping. The alpha acid can also be used to produce isomerised kettle or post fermentation hop bittering extracts, thus enabling all the brewing properties of the hop to be recovered. See Table 4.

Isomerised kettle hop extracts. In order to improve utilisation it is possible to pre-isomerise the alpha acid before wort boiling. Alpha acid can be isomerised by heating with an alkali metal carbonate while still in the resin form to produce pre-isomerised kettle extract (IKE). If it is made with potassium salts it is usually called PIKE; if it is made with magnesium salts, MIKE. The benefit of isomerised kettle extract is its ease of use, standard utilisation being around 70%, but it is relatively expensive. See Table 5.

Isomerised hop extract. As well as adding the isomerised extracts to the kettle where there are still losses due to absorption by the trub and yeast, it is possible to add isomerised extracts post fermentation (PFB - post fermentation bitterness), when the utilisation of alpha will be higher. It is usual to use a pure alpha acid, which has been separated from the soft resin, purified and isomerised externally to produce potassium or magnesium salts of the iso-alpha acid by heating. The isomerised extract is water based and is standardised to 20% or 30% isomerised iso-alpha acids from which a utilisation of 70% to 95% or greater can be expected. The material left behind in the soft resin is called the “base extract” and contains oils, beta-acids, and other resin materials plus impurities; it is often added to the kettle during boiling to:

Figure 6. Production of light struck fl avours (3-methyl-2-butene-1-thiol).

1. prevent excess foaming or over boiling 2. to add tannins and hop oils 3. to provide a source of non isohumulone bitterness 4. to provide hop compounds to ensure fermentation proceeds normally As PFB isomerised extracts contain only isoalpha acids, they contribute no flavour character other than pure bitterness to the beer. The extracts are often used to adjust for lack of kettle bitterness or to supplement nonisomerised hops in high gravity brewing (thus achieving better utilisation). When PFB isomerised extracts are used as the sole source of bitterness, base extract should also be added to the kettle to give other elements of hop character to the beer. See Table 6.

Reduced hop extract

Figure 7. The production of reduced iso- alpha- acid compounds from iso alpha acid.

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In the presence of sunlight (UV/visible radiation), conventionally hopped beers produce a “skunky” or “light struck” flavour. For this reason many beers are packaged in light proof or brown glass which is opaque to the radiation. See Figure 6. Light struck flavours develop when the isoalpha acid molecule splits stimulated by UV

light, and the free side chain bonds with a free sulphur radical. If the weak double bonds are reduced the iso-alpha acid cannot be photolysed and the reduced hop compound is not susceptible to the light strike effect. A variety of reduced compounds have been developed from both alpha and beta acids which are not prone to light struck taints while at the same time providing bitterness to beer. The mechanisms and structures are shown in

Figure 7. As well as providing different levels of bitterness, some of the reduced humulones have an effect in enhancing beer foam character. The products are usually marketed at concentrations of between 5% and 20% in aqueous solution. If a brewery uses clear glass and reduced iso-humulone, it is necessary to exclude all

sources of conventional hop (iso-alpha acid) below 0.2ppm. Iso alpha acid can be carried over from all vessels, pipework and in pitching yeast. It is usual to keep a pure strain of yeast or use freshly cultured yeast to avoid any carry over. If it is only being used for its foam enhancing properties, the reduced iso material may safely be used in conjunction with conventional hopping regimes. See Table 7.

Table 6. Summary of benefits from using isomerised (post fermentation bittering (PFB) extract Preparation Major use Method of use

Hops and hop essence Most of the hop products considered so far have been used to enhance the bitterness fraction in beer, but hops are also a source of hop oil aroma and these can be separated by steam distillation or by CO 2 extraction. The oils are ideal for post fermentation addition where they give dry hop aroma to beer, retaining much of the aroma character of the original hop variety. Hop oils are usually added in the form of an emulsion (with a food grade emulsifier), marketed in concentrations between 1,000 and 10,000 ppm of pure oil, or by re-dissolving in liquid CO2 and directly injecting this solution into a beer main. Other developments of hop oil addition techniques involve the adsorption of oils on to the surface of finely divided silica, and the retention of oils inside the ring structure of bcyclodextrin molecules. Both these methods entrap the oil in a solid (powder) form, which readily releases the oils in to beer on contact with water. With column chromatography it is possible to fractionate the whole hop oil into late hop essence, which may itself be divided into spicy and floral fractions:

Alpha acid extract from the resin is convert to alkali metal salt of iso-alpha acid in buffered water solution. Provides all parts of the hop bitterness Added in line post fermentation

Composition Alpha acids (HPLC) Beta acids Aroma compounds Iso alpha acid (30% solution) Potassium carbonate buffer

Specification pH (1% solution) Haze (1% solution) Gushing test

% – 0.8 0 0 – 0.3 absent 29 - 31 68 - 70

9.0 – 9.5 0 – 5 EBC None

Advantages: Easy to handle and store No aroma contribution Standard bittering product High utilisation (70 – 95%) Easy adjustment of bitterness Disadvantages: Expensive No hop aroma contribution Reduced kettle hop addition which contributes to hot break Reduced hop character in beer “Chemically processed”

Table 7. Summary of benefits from using reduced hop compounds Preparation Major use Method of use

Reduction of iso-alpha acid or beta acids Light strike resistance and foam improvement in beer Added post fermentation

Advantages: Disadvantages: Traditional form Costly Free from extraction solvents Utilisation lower (45 – 55%) Standard aroma & bittering product Chemically processed Aids hot break formation & settling If aroma is required it has to be added separately

• Late hop essence Spicy – contains terpene and sesquiterpene oxides which produces spicy flavour in beer, improves mouthfeel and enhances perceived bitterness. • Late hop essence Floral - contains ketone fraction which imparts light floral notes improving the fragrance rather than the taste of the beer. See Table 8. s

The reduced iso compounds have different benefits Reduced iso product Standard iso alpha acid Dihydro - iso alpha acid Tetrahydro- iso alpha acid Hexahydro- iso alpha acid

Bittering power 100 60 – 80 160 – 180 100

Foam stability Standard + Much greater +++ Greater ++ Standard +

Resins and oils will vary according to variety

Table 8. Summary of benefits from using hop oils and late hop essence Preparation

Major use Method of use

The oil fraction from whole liquid CO2 extraction of hops is further extracted and purified by vacuum distillation. Essences are fractionated from whole oil by column chromatography. Enhance hop aroma and flavour in beer Added post fermentation

Composition Hop oils Late Hop Essence – Spicy Late Hop Essence – Floral

q Further

Reading

Neve R.A. – Hops published by Chapman and Hall IoB Blue Book on Hops O’Rourke T – IOB Blue Book – Brewhouse and Brewing Materials – (in print)

Pure varietal oils or blends, semi refined Principally terpenes and sequiterpenes Principally ketone fraction Advantages:

Easy to handle and store Standardised constant product Available in variety of specific or generic forms Provides means of precisely adjusting and controlling late hop character Less change in hop character over time than with cone hops

Morris Hanbury Jackson LeMay Ltd. technical literature

Disadvantages: Oil require top be emulsified before use Essences are very costly Some drinkers can detect the difference in dry hop character between hop oils and whole hops Extraction dosage rates are critical

Brewing Science Vol 1 ed J.R.A. Pollock – various sections Malting and Brewing Science – Hough, Briggs and Stephens New Brewer July 1994 Moir M (1988) Development in Hop Usage, Ferment Vol 1 No 3, O’Rourke T – Back to Basics – Brewers Guardian April 1998.



25

TECHNICAL SUMMARY

Mash separation systems Once mash conversion is completed, when all the starch has been broken down to sugar, it is necessary to separate the sugar solution from the malt solids to produce clear sweet wort.



to the plates. Unlike the other wort separation systems the mash in a mash tun floats on the wort, at least during the strong wort recovery. During the initial run-off, the flow rate is low to allow for the high viscosity of the wort and to prevent the floating bed of mash being drawn down on to the false bottom of the vessel. The flow rate can be increased during sparging as the wort viscosity falls.

Typical mash tun cycle

T

he basic principals of mash separation are the similar. The wort is strained through a filter bed made up of the husk and solid material remaining from the malt which is held on a course septum such as a screen or filter sheet. The principles of filtration are defined in terms of Darcy’s equation:

Mashing in Mash conversion stand Run off Drain down & Spent grains removal Total turn around time

Flow rate u = filter surface area (A) x pressure differential across filter (P) Beer viscosity x resistance to the flow of beer (L )

20 minutes 75 minutes 185 – 330 minutes 20 minutes 300 -–440 minutes

Excluding the time taken for the mash conversion, the mash tun is the slowest wort separating system. Mash tuns are well suited to their traditional use in producing wort from well modified malt. They are the cheapest system in terms of capital outlay and are the simplest to operate with little or no automation. Mash tuns can only use a single temperature for mash conversion and as a result poor quality malts or malts requiring a protein or glucanase stand cannot be handled. Mash tuns are also less well suited to modern large batch production where high brewhouse utilisation and extract efficiency are expected. When using a Lauter Tun or Mash filter the mash is converted in a separate mash conversion vessel often using a range of temperature stands. The function of the Lauter tun and Mash filter is purely to separate the solids.

Therefore the highest flow rate is achieved with: • Large filter surface area (A) • Increased differential pressure across the filter bed (P) • The lower the wort viscosity • The shallower the filter bed (L) Darcy’s equation describes the conditions for optimum flow not optimum wort quality. It is also necessary to obt ain the maximum recovery of extract (sugar) and to produce bright wort free from suspended solids. There have been a number of different designs of wort separating equipment, but currently three basic types are commonly used.

Isothermal Mash Tun This is a combined conversion and wort separation vessel. Since it has no form of agitation or heating it operates at a single temper ature in the range of 65°C. Mash tuns have the smallest filter surface area with the deepest bed depth (up to 1 meter deep) which applying Darcy’s equation will explain why it has the slowest filtration and poorest extract recovery. The poorer run performance is partially compensated by using a coarse grist but th is could lead to poorer extract recovery. It does produce the brightest worts. Extract performance is a result of the combined effects of the malt gr ist and the bed depth. The poorer potential performance of the mash tun is partially offset by using a low volume of water in mashing (water: grist ratio of 2:1) this allows a higher volume of sparge water to optimise the leaching effects. The flow rate of wort from a mash tun is usually controlled manually. The run-off taps are set and adjusted to prevent pulling the bed down on

Lauter Tun Before transferring mash from the mash conversion vessel a layer of brewing water or “underlet” is added to cover the plates in the lauter tun. The transferred mash is allowed to settle on the lauter plates. The bed in the lauter tun is shallower (around 0.5 m) and the vessel has a larger diameter (greater surface area) than the mash tun. This gives it a better filter performance and allows the use of finer grist, which helps extract performance. The initial wort collected from the lauter tun is re-circulated to ensure that only bright wort (haze less than 5 EBC) runs to the kettle. The medium fine grist used in the lauter tun causes an increase in the resistance of wort run off, which has to be compensated by the use of rakes to open the bed and allow faster filtration. The rakes must operate in such a way to avoid the sparge being channeled through the bed and to avoid the filter bed being totally disrupted. Slight increases in wort viscosity can have a dramatic effect on run off performance.

Isothermal Mash Tun.

Lauter Tun.


Volume 3 • Issue 2 • February 2003 • www.igb.org.uk

57

TECHNICAL SUMMARY

There are a number of different ways of running a lauter tun which vary according to beer type, installation and tun design. Raking can be continuous in a “wave”, or using a number of discrete steps The sparge can be added continuously or as a batch addition when it is often accompanied by a total break up and re-mash of the bed. Most lauter tuns are fully automated and as well as controlling the wort run-off rate, they also measure and control the differential pressure above and below the lauter plates. When this pressure falls below a set pressure it has reached a “set bed” condition. The run-off is stopped and the rakes are lowered to the bottom of the bed and used to beak up the bed for 5 to 10 minutes before normal filtration is resumed. To control a lauter tun run-off, the following properties can be measured: • Wort flow rate (which can be accumulated to give total volume of wort collected) • Flow rate and volume of underlet and sparge • Differential pressure which is the difference in pressure above and below the later tun false bottom. This directly measures resistance to flow through the filter bed. • Wort clarity – wort should have a haze less than 5 EBC with less than 1 mg per litre of suspended solids. • Wort density – as the density decreases, the wort viscosity also falls allowing the lauter tun to run off more quickly. • Temperature of sparge • Dissolved oxygen is reduced by gentle filling usually from the bottom of the vessel and through gentle operation. These measurements can be used to control the lauter through: • Controlling flow rate – rate of run off • Sparge rate, that is the rate of re-hydrating the bed and the amount of water on top of the bed. • Sparge temperature (higher temperature reduces wort viscosity, but also increases extract of unwanted husk compounds). • Raking and set bed routines (these are primarily to relieve the build up of differential pressure across the lauter bed). • Re-circulation – at the start of run off and often after a set bed the wo rts are re-circulated on top of the lauter tun until they are bright before running to the kettle.

The large number of plates and shallow bed depth gives a high filter flow rate and the fine grind coupled with a thin filter bed results in high extract efficiency without the reduction in wort quality. The sequence below shows the series of events during a mash filter run.

Filling Mash is pumped at low pressure from the mash conversion vessel Duration Pressure Volume of run off

5 mins 0.7 bar nil

Filtration The solids in the mash form a cake on the surface of the filter cloth. Clear wort is run off to the kettle. Duration Pressure Volume of run off

Filling

30 mins 0.7 bar 175 hl

Pre-compression After all the mash has been transferred from the mash mixing vessel, gentle air compression is applied to the membrane which forces the strong wort through the bed. Duration Pressure Volume of run off


Filtration

Sparging When most of the strong worts has been squeezed from the grain, the membrane pressure is slowly released and sparge water is pumped through the mash inlet;

A typical lauter tun cycle Stage Underletting Filling Re-circulation First worts Second worts Last worts Weak worts Drain down Grain removal Total

Time in mins 3 11 4 41 74 10 16 8 25 192

Volume Hl 23 20 205 475 141 179 93 l000

Duration Pressure Volume of run off


Pre-compression

Final Compression When all the sparge has been supplied the membrane is compressed at high pressure and the grain bed squeezed dry. Duration Pressure Volume of run off

10 mins 1 to 1.5 bar 20 hl

Modern Mash Filter The modern generation of mash filter is typified by the Meura 2001. This filter has a large surface area because of the number of filter plates. It uses a very thin filter bed a few millimeters thick, and operates at up to 1.5 bar pressure, which provides a significant driving pressure to aid filtration. Through its design, the mash filter is able to optimise the filtration conditions defined in the Darcy equation and is therefore able to handle very fine grist. Mash filter grist is produced using a hammer mill; the very fine grist ensures an excellent extract recovery. The mash filter is charged with converted mash from the mash mixer. The mash filter is fitted with fine pore polypropylene filter sheets suitable for fine grist, without particles bleeding through the sheets. The fine filter sheets and grind result in a tight filter bed which means that no recirculation is required before first worts are drawn off which can run straight to the kettle.

58


Cake discharge

Sparging

Once all the extract has been squeezed from the grain, the pressure is released and the filter is opened up. The gains fall into a grain hopper for removal. Duration Pressure Volume of run off

10 mins none nil

The new mash filter is able to use a very fine grist which allows a high extract recovery usually in excess of


Final Compression

a r u e M f o n o i s s i m r e p d n i k y b r e t l fi h s Discharging a m e h t f o s Summary of the advantages of a n o i t a r t Mash Filter s Property u l l I Extract efficiency Circa 102 %

Sparge volume Turn around Flexibilty Operation Footprint (10 tonnes) Maintenance Quality (under ) correct operation Spent grains Capital Cost

100% laboratory extract. In addition because it requires a lower sparge volume than the other systems it can readily produce high gravity worts from an all malt brew.

Spent Grains After wort separation is complete the waste material left behind called spent grains and is drained down and sold for cattle feed. The removal of the grains depends on the mash separation system: •Mash Tun – thrown out by hand, or removed by a mechanical arm which rotates over the false bottom of the tun and pushes the grains towards outlet ports. • Lauter Tun – usually combined with the lauter rake equipment, where either the rake arms turn to present a flat surface pushing the grains towards outlet ports, or a bar attached to the rake arms descends to achieve the same purpose.

mash filter over a lauter tun.

Less sparge – Higher gravity worts Circa 2 hours 12 brews/day Full charge + 5 % -10% No underlet Easier run off Small 3 x12m Low – few moving parts Good – improved foam stability Dry – moisture < 65 % Can be cheaper depending on civil costs

Lauter Tun Circa 97.5 % Higher sparge lower gravity wort Circa 3- 4 hours 8 - 10 brews/day Full charge ± 35 % More problematical run off

• Mash Filter – the filter is opened up and the grains fall out, occasionally with sticky grains the cloths may require scraping.

8m dia. Higher – more moving parts Good Wet – moisture > 78 %

After grain discharge the plates or cloths are usually hosed off, in preparation for the next brew, and the vessels will receive a full hot CI P at least once per week. The discharged grains are usually conveyed either by a screw conveyor or using compressed air to a storage silo, where they can be loaded into local transport for removal. The % solids of the grains is between 19 and 36% depending on wort extraction system and drainage, where there is no concern over ef fluent and when the brewery is adjacent to suitable agricultural sites, the grains are discharged wet and removed for storage and ensiling on the farm. If the grains cannot be taken away wet then it is necessary to dry the grains. In which case after draining down, the grains may be passed through a decanter centrifuge to remove excess moisture before being dried in a drum oven. s

One of the principal differences between the three separation systems is in composition of the grist required, which is shown below: Summary of the principal differences in grist composition based on the standard EBC Pfungstat Plansifter sieving of grist. q References and further reading

Mesh size (mm) >1.27 1.01 to 0.547 0.253 0.152

Fraction Husk Coarse Grits Fine Grits Flour

Mash Tun 20% 35% 35% 10%

Lauter Tun 15% 5% 30% 30%

Mash Filter <5% 5% 35% >45%

O’Rourke T -– IoB Blue Book – Brewhouse and Brewing Materials – (in print) Meura – technical literature Briggs – technical literature Malting and Brewing Science - Hough, Briggs and Stephens O’Rourke T – Back to Basics – Brewers Guardian July 1999.


ONLINE

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59

Efficiency – Line Philosophy

PEOPLE

MACHINES

MATERIALS

PROCESS

METHODS

MEASUREMENT

ENVIRONMENT

In 1992 I presented a paper titled ‘Development of a Packaging Line’ to the Brewers Guild in Blackpool, and then at the MBAA Conference in the Caribbean. I made reference to the first packaging line that I managed in Ghana from 1971 to 1973. The speed was 120bpm, efficiencies were 85% and waste was negligible. It was a doddle! So what’s gone wrong? The answer is simple. The modern line is faster, technology more complex and there is a multiple range of products. If you want a successful line today, it must be right – the line philosophy should be perfect. Is this too much to ask for – well it usually is! When starting from new, frustrations can evolve as a result of: • •

•

• •

• •

Inadequate budget. It is either arbitrarily cut or poorly constructed. Time constraint. Once a decision is made there never seems to be enough time, everything must happen now! The contract. It is important to have a contract but I find they are now overly complex. This does three things 1) makes the supplier nervous (they will probably seek legal advice), 2) leaves a tendency for simple things to be left out, and 3) can delay the project. What generally happens is the project goes ahead while the contract is still being sorted out – not the perfect situation. Second-rate machinery is purchased or insufficient research is carried out. Not enough work is done on studying the compatibility of the materials with the machine. Operators are not properly trained. There is not enough involvement with those who will be running it!

Good planning is the essence of achieving the right end result, if this is not achieved, there is a nightmare to follow, and there is not much sympathy around! Good planning also means that when you are challenged you have the answer, and the consequences of any change are immediately known. So before developing a packaging line ensure that all parties have been consulted, and that there is total agreement on the objectives. So whom should you involve? The simple answer is, the customer, but sadly there is not one but many of them. My list would include – planning/sales, marketing, manufacturing (production and engineering managers and shop floor), and finance. Make sure that the top person is approached in each area, and ask that he/she nominate individuals who will

1

be asked to sign off what has been agreed. There will then be a steering committee involving all these people and a project ‘owner’ who would normally be someone from manufacturing who will work with the project and then finally take it over. This may seem a bit petty but a lot of money is being invested, so it is important that a great deal of up front work is carried out. If the reader works for a small company all this may not be necessary, as communications are easier and ownership is extremely clear. It is also likely that the same people will be around throughout the project! However, a clear plan still needs to be put together. All this may seem extremely obvious, but so many fall at this hurdle. After the requirements have been established, the line layout and type of plant must be decided. Specifications therefore need to be prepared and discussions take place with suppliers. You should still remain reasonably flexible in your approach, as suppliers will often as not come up with good ideas. On one occasion I remember talking to a supplier after the installation of his palletiser. We in manufacturing had specified the patterns for palletisation, and these were duly given to the supplier who actually suggested a better pattern for one particular format. This was turned down by project because the pattern had already been specified! Later on, when we discovered this, we changed the pattern on the supplier’s advice, and it worked much better. So have an open mind – do lots of listening! Line layouts and speeds are of the essence to good line performance. There are many layout alternatives. The end result may depend on existing layouts but the modern objectives would include (Mnemonic- FEEL DEMO!): • • • •

• • • •

F ast changeovers (Less than 10 mins) E rgonomics E ase of maintenance and cleaning L ow manning levels D esign line to ‘pull’ product E ase of waste removal M aterials ingress and compatibility O n line Quality Control

The line needs to be designed around the heart of the line i.e. the machine that does the primary packaging. If this machine stops, the output is immediately affected. For a beverage packaging line this would normally be the filler. A graph is then drawn with the filler at the bottom of the graph – this is known as a ‘V’ graph (see fig 1). In cases where a tunnel pasteuriser is installed, this may be at the bottom of the graph. However, if this is

2

done the filler needs to be electronic to allow it to modulate. 'V' Graph for 1500Cpm C anning Line

2050 1950 1850 1750 1650 1550 1450 DEP ALLE T IS ER

FIL LER /S EAME R

C ODER

PALL ET IS ER

MACHINE

Fig 1

Machines before and after the filler are planned to run faster by increments of 5 to 8%. In this way the line stands the best chance of giving a good efficiency. The machine at the bottom of the graph gives you the rated output for the line. The faster the line, the less robust it is, and stoppages will also give a greater loss of output. This leads us to the next point, accumulation. For slower lines, <500cpm, accumulation is not as important, and also the ‘V’ graph can be flatter. For higher speeds, however, accumulation is required to give an effective line balance. There are two types, static and dynamic. The simplest form of static accumulation is the bi-directional table, which is fitted at right angles to the conveyor. The product accumulates, and is then released into the conveyor when the line restarts. The disadvantage of this type is that products maybe held on the table for some considerable time, as the product will only be slowly released onto the line. In fact on some tables, the product can sit on the dead plate at the end of the table until it is physically pushed onto the conveyer. At a recent exhibition, ‘drinktec interbrau’ in Munich, Gebo Industries exhibited an in-line accumulation conveyer table. This has the advantage of ensuring that no product is left behind and is a neat combination of the dynamic and static types. It also takes up less space than dynamic accumulation on the conveyor. Dynamic accumulation can take place on any conveyors more than one slat wide. Conveyors on a packaging line are divided into two distinct areas – upstream and downstream (see fig 2) Upstream Normal State: Conveyors Full

Filler/ Seamer

Downstream Normal State: Conveyors 50%Full

Fig 2

Upstream conveyors feed the core machine, in this case the filler, and downstream conveyors take product away from that machine. The upstream conveyors will normally run full, so if for any reason a machine feeding the filler should stop, there is a buffer of cans on the conveyor to keep the filler running. Conversely, the conveyors downstream

3

will run around half full which allows them to fill up when there is a stoppage downstream. So how much accumulation does one have? When it comes down to it, it is a matter of money and space. The best advice one can give is to analyse the most common stops on a line and relate the accumulation capacity to these. There are now some brilliant packages available that allow line performance to be simulated – there are companies around that can do this for you, conveyor manufacturers should also be able to do this for you. For an existing line it is worthwhile spending some time on ensuring that your line is in balance and that the accumulation space is being properly used. On many occasion I have seen people increase the speed of the filler and expect higher output, the reverse actually takes place. A line always runs better when it is allowed to run continuously at the correct rated speed. It may be that the line has to be re-rated, or that machines upstream and downstream need to be speeded up. I have seen new plant being installed on a line and as it runs at a different speed to the de-installed plant, it throws the line out of balance. Another consideration is the line layout. There are two distinct ways to go – a straight line or a ‘U’ shaped line (See figs 3&4). The latter gives the best solution from the ergonomic point of view, as machines are much more accessible and also more visible. However, this will not be the easy solution if straight lines are already in place, or when a range of different pack formats are required. Should the latter be the case, a comb layout will be necessary giving a choice of routes. Whatever is chosen the above objectives – FEEL DEMO - should be met in order to give a satisfactory performance. In conclusion, the competence of the operating crew is absolutely key to achieving good output, but I also believe that a well-designed and balanced line makes a big difference to both morale and therefore output. Good planning is the essence; then ensure it is in balance and, finally, look after it! The next article is about measurement of line performance with a little financial input.

4

Efficiency – Line Philosophy

PEOPLE

MACHINES

MATERIALS

PROCESS

METHODS

MEASUREMENT

ENVIRONMENT

In 1992 I presented a paper titled ‘Development of a Packaging Line’ to the Brewers Guild in Blackpool, and then at the MBAA Conference in the Caribbean. I made reference to the first packaging line that I managed in Ghana from 1971 to 1973. The speed was 120bpm, efficiencies were 85% and waste was negligible. It was a doddle! So what’s gone wrong? The answer is simple. The modern line is faster, technology more complex and there is a multiple range of products. If you want a successful line today, it must be right – the line philosophy should be perfect. Is this too much to ask for – well it usually is! When starting from new, frustrations can evolve as a result of: • •

•

• •

• •

Inadequate budget. It is either arbitrarily cut or poorly constructed. Time constraint. Once a decision is made there never seems to be enough time, everything must happen now! The contract. It is important to have a contract but I find they are now overly complex. This does three things 1) makes the supplier nervous (they will probably seek legal advice), 2) leaves a tendency for simple things to be left out, and 3) can delay the project. What generally happens is the project goes ahead while the contract is still being sorted out – not the perfect situation. Second-rate machinery is purchased or insufficient research is carried out. Not enough work is done on studying the compatibility of the materials with the machine. Operators are not properly trained. There is not enough involvement with those who will be running it!

Good planning is the essence of achieving the right end result, if this is not achieved, there is a nightmare to follow, and there is not much sympathy around! Good planning also means that when you are challenged you have the answer, and the consequences of any change are immediately known. So before developing a packaging line ensure that all parties have been consulted, and that there is total agreement on the objectives. So whom should you involve? The simple answer is, the customer, but sadly there is not one but many of them. My list would include – planning/sales, marketing, manufacturing (production and engineering managers and shop floor), and finance. Make sure that the top person is approached in each area, and ask that he/she nominate individuals who will

1

be asked to sign off what has been agreed. There will then be a steering committee involving all these people and a project ‘owner’ who would normally be someone from manufacturing who will work with the project and then finally take it over. This may seem a bit petty but a lot of money is being invested, so it is important that a great deal of up front work is carried out. If the reader works for a small company all this may not be necessary, as communications are easier and ownership is extremely clear. It is also likely that the same people will be around throughout the project! However, a clear plan still needs to be put together. All this may seem extremely obvious, but so many fall at this hurdle. After the requirements have been established, the line layout and type of plant must be decided. Specifications therefore need to be prepared and discussions take place with suppliers. You should still remain reasonably flexible in your approach, as suppliers will often as not come up with good ideas. On one occasion I remember talking to a supplier after the installation of his palletiser. We in manufacturing had specified the patterns for palletisation, and these were duly given to the supplier who actually suggested a better pattern for one particular format. This was turned down by project because the pattern had already been specified! Later on, when we discovered this, we changed the pattern on the supplier’s advice, and it worked much better. So have an open mind – do lots of listening! Line layouts and speeds are of the essence to good line performance. There are many layout alternatives. The end result may depend on existing layouts but the modern objectives would include (Mnemonic- FEEL DEMO!): • • • •

• • • •

F ast changeovers (Less than 10 mins) E rgonomics E ase of maintenance and cleaning L ow manning levels D esign line to ‘pull’ product E ase of waste removal M aterials ingress and compatibility O n line Quality Control

The line needs to be designed around the heart of the line i.e. the machine that does the primary packaging. If this machine stops, the output is immediately affected. For a beverage packaging line this would normally be the filler. A graph is then drawn with the filler at the bottom of the graph – this is known as a ‘V’ graph (see fig 1). In cases where a tunnel pasteuriser is installed, this may be at the bottom of the graph. However, if this is

2

done the filler needs to be electronic to allow it to modulate. 'V' Graph for 1500Cpm C anning Line

2050 1950 1850 1750 1650 1550 1450 DEP ALLE T IS ER

FIL LER /S EAME R

C ODER

PALL ET IS ER

MACHINE

Fig 1

Machines before and after the filler are planned to run faster by increments of 5 to 8%. In this way the line stands the best chance of giving a good efficiency. The machine at the bottom of the graph gives you the rated output for the line. The faster the line, the less robust it is, and stoppages will also give a greater loss of output. This leads us to the next point, accumulation. For slower lines, <500cpm, accumulation is not as important, and also the ‘V’ graph can be flatter. For higher speeds, however, accumulation is required to give an effective line balance. There are two types, static and dynamic. The simplest form of static accumulation is the bi-directional table, which is fitted at right angles to the conveyor. The product accumulates, and is then released into the conveyor when the line restarts. The disadvantage of this type is that products maybe held on the table for some considerable time, as the product will only be slowly released onto the line. In fact on some tables, the product can sit on the dead plate at the end of the table until it is physically pushed onto the conveyer. At a recent exhibition, ‘drinktec interbrau’ in Munich, Gebo Industries exhibited an in-line accumulation conveyer table. This has the advantage of ensuring that no product is left behind and is a neat combination of the dynamic and static types. It also takes up less space than dynamic accumulation on the conveyor. Dynamic accumulation can take place on any conveyors more than one slat wide. Conveyors on a packaging line are divided into two distinct areas – upstream and downstream (see fig 2) Upstream Normal State: Conveyors Full

Filler/ Seamer

Downstream Normal State: Conveyors 50%Full

Fig 2

Upstream conveyors feed the core machine, in this case the filler, and downstream conveyors take product away from that machine. The upstream conveyors will normally run full, so if for any reason a machine feeding the filler should stop, there is a buffer of cans on the conveyor to keep the filler running. Conversely, the conveyors downstream

3

will run around half full which allows them to fill up when there is a stoppage downstream. So how much accumulation does one have? When it comes down to it, it is a matter of money and space. The best advice one can give is to analyse the most common stops on a line and relate the accumulation capacity to these. There are now some brilliant packages available that allow line performance to be simulated – there are companies around that can do this for you, conveyor manufacturers should also be able to do this for you. For an existing line it is worthwhile spending some time on ensuring that your line is in balance and that the accumulation space is being properly used. On many occasion I have seen people increase the speed of the filler and expect higher output, the reverse actually takes place. A line always runs better when it is allowed to run continuously at the correct rated speed. It may be that the line has to be re-rated, or that machines upstream and downstream need to be speeded up. I have seen new plant being installed on a line and as it runs at a different speed to the de-installed plant, it throws the line out of balance. Another consideration is the line layout. There are two distinct ways to go – a straight line or a ‘U’ shaped line (See figs 3&4). The latter gives the best solution from the ergonomic point of view, as machines are much more accessible and also more visible. However, this will not be the easy solution if straight lines are already in place, or when a range of different pack formats are required. Should the latter be the case, a comb layout will be necessary giving a choice of routes. Whatever is chosen the above objectives – FEEL DEMO - should be met in order to give a satisfactory performance. In conclusion, the competence of the operating crew is absolutely key to achieving good output, but I also believe that a well-designed and balanced line makes a big difference to both morale and therefore output. Good planning is the essence; then ensure it is in balance and, finally, look after it! The next article is about measurement of line performance with a little financial input.

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Efficiency – the Materials In last month’s article I talked about the Ishikawa approach in defining a process, as follows: PEOPLE

MACHINES

MATERIALS

PROCESS

METHODS

MEASUREMENT

ENVIRONMENT

Most people tend to focus on the Machinery and People. Production blame the Engineers, Engineers blame the operators. Although this is a culture we would like to think has passed us by, unfortunately, when there is pressure on output, this rather unhealthy discourse tends to raise its head once more. When I visit operations that have not done a full study on their plant performance, I often find that the materials that they are using are the greatest cause of downtime. The frustration on the shop floor is enormous and the answers are often found there. A simple example that I came across was with a labeller that was applying pre-cut paper labels and the operator was struggling with the varying sizes of label. It turned out that the company was buying from two different suppliers and each company was cutting the label to a slightly different dimension. Materials are probably the most comfortable item to look at because it mostly involves people outside the manufacturing arena and also the results can be extremely rewarding! So what is the best approach? I have listened to lecture in which a person from Quality Assurance was saying that you need good specifications and that you ensure that the suppliers keep to them, so far so good but who lays down the specification and is the supplier really comfortable with it. In this instance the user wrote the specification and then told the supplier that this is what he wanted. This can lead to an uncomfortable relationship with the supplier and tends to set up a feeling of animosity. This goes back to the days of material inspection and AQLs (Acceptable Quality Limits). In my mind a component is either right or wrong – why should there be any failures? Interestingly the best approach is the one that favours the buyer and the manufacturer; that is to have a single supplier and partnership where the supplier works closely with the manufacturer to achieve the best result. Most suppliers are into this approach and like it as they can then ensure that they are supplying the best materials for your plant and understand why certain dimensions are critical – or not – as the case might be. Specifications These are important and can be divided into three parts. The first is an overall policy statement – it could relate to a restriction in chemical treatment or the use of compounds used which you, as the user, do not want to come into contact with your product. It would include the requirement for tests should the supplier wish to use a different form of treatment; for example, use a different lacquer inside a beverage can. This may also

include an environmentally based statement that requires a percentage of the supplied material to be recycled. This of course needs to be done with great sensitivity, as some materials will have a significantly reduced performance if there is a recycled content! The second part, which I call the ‘Leader Specification’, will cover all components that come under a common heading, such as bottles, cans, trays, cartons, film etc. This will cover the general description, technical requirements, quality and environment specific to this component. Finally the third part, the ‘Individual Specification’ which will specific to the actual component giving dimensions, type of material, barcodes, artwork and so on. This is agreed with the supplier with other players, such as marketing, sales and manufacturing being involved. There are other ways of putting specifications together but I have always liked this hierarchical approach. As components are added or changed there is less documentation involved – whether it is computer based or in a file. Each component is given a code – preferably alphanumeric but if you are unlucky and have SAP it has to be numeric! Getting the Specifications Right This is all about capability. Packaging is in effect a means of carrying your product undamaged to the consumer. But there is more – I use an aide-memoire, ‘Is Capable’ to help! I – Innovative S – Sells the product C – Collation of packs A – Appeal through good design P – Protects and preserves the measured contents A – An easy product to handle B – Best practice for pack integrity L – Labelling for identity and information E – Environmentally acceptable When specifying the packaging it is necessary to have some or all of the above points considered. Especially important is to consider its end destination and how it will be handled en route. Having said this it must ALSO be capable of running on the machine! Earlier in this article we mentioned the importance of dimensions. There will be others such as slip for board, cans and bottles; glue viscosity and temperature and so on. This capability is well demonstrated by a frequency distribution curve. The Lower Specified Limit (LSL) and the Upper Specified Limit (USL) are the tolerance limits for the machine – this is known as the Engineering Tolerance or ET. The range is calculated by multiplying the standard deviation by 6. This is known as the Normal Tolerance or NT. Capability is calculated using standard deviation – a function available on any scientific calculator. At least twenty readings are necessary to give good data. It is calculated using the following formula

Frequency Distribution showing a Process Capability (Cp.) of 1

Unfortunately another calculation is required known as Cpk which takes the mean or average result into account. The following graphs aptly demonstrate this:

Rejects or Waste

Graphs showing Capability Variation

Process Capability Graphs showing Capability within Specification I have had experience of a supplier adding up all his measurements, taking the average and then boldly stating that he has met the specification! This brings us to the final comment. Final Comment To achieve the best out of the plant the materials or components must be consistently correct. The specifications should be agreed with the supplier and signed off – perhaps using a Certificate of Conformance – this should be done at least annually. It is the suppliers’ responsibility to meet this specification as it is with the manufacturer to meet specifications for the final product! The best way of achieving this is to introduce ‘Exception Reporting’ with a points system relating to the severity of fault. The exception report will be instigated by the operator and followed through with the supplier by Quality AND the Buyer who if not directly involved should be aware. Audits are then carried out with suppliers as to their performance and at the end of the year a certificate can be awarded to the ‘Supplier of the Year’. Suppliers take great pride in being awarded with these. At the end of the day never forget the significance of materials in achieving better efficiencies. Also having received them on site, ensure that they are stored in the right conditions in a clean place and do not hold them for too long! Next month the article will be on People.

Efficiency – People

This month people is the theme: PEOPLE

MACHINES

MATERIALS

PROCESS

METHODS

MEASUREMENT

ENVIRONMENT

There is no doubt that the most important part of a good process is the people that run it – they can make or break an operation. I have never found a magic ingredient, but one thing for sure, most are guilty of not looking after this main asset properly – by this I do not mean conditions of employment, I mean ordinary things like communicating, interest in the individual, and being consistent. Management of people is one of the most written about subjects and many have made a great deal of money out of it. Management of people has changed from ‘control, direction, compliance, discipline, measurement, feedback loops and union meetings’ to ‘empowerment, self management, involvement, co-ordinating, facilitating, enabling and team meetings’ and the structures are now flatter. I have been through management change that moved from one extreme to the other, and there is no doubt that there are problems at both ends of this spectrum. The latter, however, has to be the healthier environment to work in. The difficulty is that some of the people who worked under the old regime often do not fit in to the new one. This leads to some hard decisions about the people who clearly no longer fit in the organisation. Empowerment and self-managed teams may be good things, but it also needs first class production management - even better than before. However, there is so often a lack of it, production managers run themselves into the ground chasing resources and seeking emergency fixes for problems; instead of giving themselves time to understand, observe, listen and then to improve the manufacturing process. So why is this? I would suggest it is because manufacturing has become so tight that resources have been stretched to the limit. There is always two streams of activity, firstly, the real job of manufacturing – producing good quality product as required - and secondly the constant change programmes that enshroud manufacturing today. It is difficult to do both well! Fifteen years ago it was ‘Unions’, today it is ‘Change’. Resources are geared to cope with production, ignoring change, but for change programmes, people in the manufacturing teams are needed. As most change programmes have such a significant future impact on the plant the best people need to be involved – therefore manufacturing suffers. This cycle will continue, and so change needs to be part of a team activity not something that is divorced from it. Often there are so called ‘change management teams’ but they are not always helpful to manufacturing. They tend to build up resistance to change; then they need internal help, so you end up with the same problem.

Coupled with this, manufacturing teams have become ‘flexible’. Apart from the obvious advantages, this has other connotations. With the dedicated operators of the past, machines were owned and cared for by specific individuals, now with flexibility the same dedication is not there, and as a result machines are not receiving the same level of attention. I was talking to a manufacturer of board a short while ago about flexibility and ownership, and he identified immediately with this problem. Two issues arise from this:  

The consistency of operation The aptitude of the individual.

To overcome this, training has to be good. Individual operators need to be trained and properly assessed. With bigger operations that run a number of shifts this is really key. The only way out is to have professional training – perhaps with the help of NVQs - and having done this, individuals operating the machinery need to be constantly assessed. I also favour the nomination of key operators for individual machines, and linking them to a technician, in order to bring some ownership back – they can still be flexible but will have a special interest – they will also be the trainers for their specific machine. In the next issue we will talk about maintenance and how initiatives like TPM (Total Productive Maintenance) also have an impact on people. At the end of the day people are a part of plant and process with which they are inextricably linked:

PEOPLE

PLANT

PROCESS

For this article I have chosen to talk about the issues that directly affect output. There are two excellent chapters on the subject of people in a new book called ‘Excellence in Packaging of Beverages’ produced by myself and Eric Candy and recently published by the Binsted Group. Tel 01256 764180.

Efficiency – Line Measurement

PEOPLE

MACHINES

MATERIALS

PROCESS

METHODS

MEASUREMENT

ENVIRONMENT

Line efficiency is one of the most emotional topics in a packaging plant. As a result it is important that figures are on time, calculated correctly and that they portray the correct message. Initially efficiency was measured over the time that was available for production. Take as an example a 2 x 8 hour shift operation running for16 hours per day. If it takes one hour to start up the operation and two hours to close down, with half an hour per shift allowed for breaks, the efficiency would be measured over 12 hours. This can result in the manipulation of the efficiency figures, thereby creating a false picture. Today, there is a much greater emphasis on yield, which is measured over the full period. Therefore, using the above example, it would be calculated over the full 16 hours. Terms like ‘sweating the assets’ have entered the vocabulary, and benchmarking has become the norm. It is therefore very important that there is no ambiguity, and when comparisons are made, it is like for like. The working day often starts with the question ‘What efficiency did we get yesterday?’ The yield figure is fine as a reply, but alongside this should be two other figures, operation efficiency and utilisation. If the yield figure is the only one that is given, it is open to too much interpretation and innuendo. Hours can be wasted discussing irrelevant information. I have actually seen figures over the years become less and less relevant to those that specifically require them, and senior management being overloaded with information through management systems such as SAP. This is not healthy, as it can be responsible for creating a blame culture. Investment in a real time measurement system would improve this, but again, only if it is done properly. It must be geared for use by the shop floor in order to allow improvement initiatives to be carried out at that level. So what is yield? This is the good production in the warehouse divided by the rated output of the line to give standard hours. This is then divided by the number of paid hours. So for a three shift x 8-hour operation, this would be 24 hours. Standard Hours = Production in the Warehouse Rated Output /Hour of the Line

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Yield = Standard Hours Paid Hours So, if a line produces 1000 cans per minute for 44cl cans, output is 26,400 litres. In the warehouse after 24 hours we have 45,000 trays x 24 x 44cl cans = 475,200 litres. So Standard Hours = 475,200/27,400 = 18 hours. Yield therefore = 18*100/24 = 75%. Depending on the activity, this figure could be really depressed. It is important therefore, to also show the Operation Efficiency. For this figure, the Operating Hours are used. The paid hours are adjusted for the number of planned hours that the line is down for. Planned Hours = Time allowed for changeovers (from measurement!), maintenance, meetings etc Operating Hours = Paid Time – Planned Time So if planned time is 2 hours, the Operation Efficiency is 18*100/(24-2) = 82% To keep a check on planned hours taken it is a good idea to record line utilisation during paid hours. Utilisation = Operating Hours Paid Hours So for this example, Utilisation = 22*100/24 = 92% The yield, operation and utilisation figures will provide useful data. For example, changeovers, an extra long meeting and maintenance time can be easily identified. However, there will be days when there are other reasons such as machinery breakdowns, component problems/shortages, shortage of labour, skill shortages and so on. This is where the controversy becomes an issue, and when good information pays dividends. To make matters worse, you are potentially discussing someone else’s shift, and they are not represented or involved in the discussion. For this reason, I advocate a good line monitoring system (LMS), something that not many companies have, either because they have had a bad experience with one, or they do not wish to spend the money. The good thing about a system today, is that the management information (MIS) can be fed into any management package such as SAP that is already in place, and at the same time the shop floor are motivated by receiving the information they need. I have recently come across one such system that provides the solution to these needs. This is produced by a Spanish company in Barcelona called Adbraintage. It is not cheap, but it is definitely worth the investment. The system will tell you where the problems have been, and also whether the line is working in balance or not. It is designed to be operator friendly and the information report is well laid out. (See figs 1&2) Figs 1&2 Examples: Adbraintage Screen Display?? So many systems only go half way and that is why they are often not used; or they can go to the other extreme and be far too complex.

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A correctly designed system ensures that managers spend the minimum amount of time in the office, thereby maximising their focus on line issues. Measurement in real time gives many other advantages as well; this would include informing component suppliers of the status of the production line; this ensures that components do not run out or become over stocked. The same goes for finished goods. A much more efficient form of communication can be set up with warehousing and transport as they will have ready access to production information. Another benefit is providing the finance department with ready data that allows, for example, a more accurate costing of individual products. This is especially important for products with short runs and long changeovers. The accuracy of information is important for many reasons. Preventative Planned Maintenance (PPM) relies on it – see November Issue of Canning & Filling. This information will also support Total Productive Maintenance (TPM) activities discussed in the same article. For TPM to be successful the correct machines need to be targeted for improvement, so that full analysis can be carried out. Furthermore, this accurate and easily accessible data allows properly informed decisions to be made on machinery and plant. This article would not be complete without mentioning financial measurement. Accountants can be perceived as being supportive or as a threat. They will always be there, so it is wise to keep them on your side. This is especially important today as data is not as visible as it once was. We need to know how the business is performing against the challenging targets that are set for us, and help the operation to keep them on track. Two measures, which I am familiar with, are PMDO (Costs of People, Maintenance, Depreciation and Others) and TDEC (Total Delivered Economic Cost). ‘Others’ would include items like site maintenance, canteen etc. TDEC would include the cost of materials and waste – the variable costs. These costs, and certainly the PMDO element, are often used for benchmarking and would be expressed against a unit of production; this could be, for example, per litre or hectolitre (100 litres) or per case. Where a good accountant can be extremely helpful, is in pinpointing where the variances are, making it much easier to find the source of a problem. Measurement is a wide-ranging subject and I hope the points made above will give some food for thought. The key is to ensure that complexity is kept to minimum, and that figures are on time, even in real time. If figures are not understood fully or they are late, continuous improvement will be hindered significantly

JJCB/12/01/02

3

Efficiency – Changeovers

This month changeovers is the theme: PEOPLE

MACHINES

MATERIALS

PROCESS

METHODS

MEASUREMENT

ENVIRONMENT

Changeovers have become a big topic over the past few years with diversification of products, globalisation and economic consumer response (ECR). ECR is all about fast response to consumer demand and taking inventory out of the supply chain. None of this helps the producer, and in fact there is very little over the last five years that has! Manufacturing has had to cope with reducing costs, which inevitably means less resource, shorter runs and more stock keeping units (SKUs). The manufacturer therefore needs all the help he can get. We have already discussed good maintenance; this is a vital ingredient to good line performance – especially after changeovers. Most manufacturers are now faced with too many changeovers, and ridiculously short runs. The appeal is for sensible planning, rationalisation of product - in order to reduce the level of changeovers, and innovation that fits as closely as possible to manufacturing facilities already available. On many occasions I have found that planning schedules could be changed – this is especially important with a difficult product when longer runs are needed for the line to settle down. Planners can be adamant as their focus is demand, but after discussion it can often be found that a product can be produced fortnightly rather than weekly. Planners are measured on Customer Service not Production Efficiency! The message for production is to do everything possible to limit changeovers in the first place. I know a company who recently installed a new bottling line. It was only at this moment that they looked at rationalising the different bottles used. Rationalisation need not mean every product going into the same bottle, it can also mean bottles produced with the same diameter. The project team worked with the glass manufacturers and marketing, and ended up saving significant sums on change parts and changeover times. Why wait for a new line? An activity programme for this approach is shown in fig 1. This can take different forms according to the components used, but a similar interrogation and result is required.

1

OBJECTIVE Reduce Changeovers

Changeover Times?

Same Beer?

How Many SKUs?

Do Not Know

Categorise SKUs

Collate Information

Same Bottle?

Similar Dress?

Bottle Sizes & Dimensions?

Short Runs <4 hours?

Opportunities?

Proposals

Meeting with Marketing/ Planning/Finance

Reduced number of SKUs & Changeover Times

Fig 1 Flow diagram showing approach to changeover reduction

Having carried out this exercise and being sure that you have the best you can get, work now needs to be carried out on the shop floor so as to ensure that the best situation for changeovers exist. What approach is therefore necessary to ensure that changeovers are carried out? One cliché that sticks in my mind is ‘A place for everything and everything in its place’. At Guinness we had a person who championed this and it went well. Coloured boxes were painted on the floor for components etc and cupboards were made to tidy away cleaning materials close to their point of use. This is certainly a good place to start. Today, you will hear more about the 5’S’s which have been central to the Japanese methods that have evolved since the end of the Second World War. The objective is similar but there are clearer messages enveloped in this approach. There are many translations of the Japanese words but the interpretations are similar no matter what you read! The 5’S’s are as follows: •

Seiri – Sort – the first important thing is to sort out what is and what is not needed. If an item is not going to be used during the next 30 days, take it away and store it in a separate location where it can be easily located at a later date. Other components or parts can be stored close by. The only items that should be directly visible in the workplace are those items directly associated with current production. The important issue here is that ‘the workplace is left uncluttered’

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•

•

•

•

Seiton – Straighten out or Orderliness – items that have been sorted out after Seiri need to be arranged in an orderly manner. Racks need to be made and these should be properly labelled. All parts must be easily accessed. Seiso – Scrub or Cleaning – this means clean everything – tools, machines, change-parts, floor, ceiling – it should all be impeccably clean. Seiketsu – Standard of Cleaning or Cleanliness – this extends the concept of cleaning to making it normal work practice that becomes a checking and active routine. It emphasises that it needs to be done daily, and that it is not a ‘one off’ exercise! Shitsuke – Sustain or Discipline – the four ‘S’s above need to be engaged within a standard for the plant so as to ensure that it is maintained. It should be constantly audited – more frequently after it has been introduced.

The above, when adopted, clearly assists in achieving smarter changeovers and prevents the panic when looking for parts that you were sure were there last time. Indeed, in my experience, it was probably another shift that did the changeover anyway making it easy to blame someone else! In the October edition of Canning and Filling the subject was ‘Maintenance’. Total Productive Maintenance (TPM) was discussed and it is through this that machines can be improved to give quicker changeovers by, for example, good settings and parts that fit properly, or even modifications to give faster setting up and settling down times. One simple thing that really helped us was having colour coded change parts. These are made tailor made to suit specific component sizes, e.g. 275ml, 330ml and 500ml bottles. Many manufacturers are now adopting this principle. The important thing is to ensure that a reputable company makes the parts, as they must be a good fit. I have dealt with one such company, Zepf Technologies. Apart from making change parts for existing machinery, they have agreements with filler and labeller manufacturers to make change parts on their behalf. We have now covered three activities: 1. Reduction in the number of changeovers 2. Sorting out change parts through the 5 ‘S’ philosophy 3. Making machines easier to changeover This leaves one outstanding activity, and that is the methodology. Enter the Japanese once more! Shigeo Shingo started carrying out some productivity improvement work at Toyota in the early 1950s. It was here, when trying to improve ways to improve the utilisation of large body presses, that he first had the idea of separating the changeover operations into two fundamentally different types, ‘Internal’ and ‘External’. Internal Set Up – such as mounting and removing dies that can only be carried out when the press is stopped External Set Up – such as transporting the old dies to storage or conveying new dies to the press, which can be carried out while the press is in operation.

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Shingo had immediate success and it took a further 19 years to really develop it. The final target was to reduce changeover times to less than ten minutes, hence the name given to the method – Single Minute Exchange of Dies (SMED). The objective is to convert as much of the internal time as possible to external set up time. Although the work was carried out in the automotive industry, its concepts are as equally applicable to any production process. One way to start this process is by recording each element of the changeover on a camera. This, however, can cause great consternation, as we found out! Many people do not like having their actions recorded on camera. Could it be used as evidence?! If you can do this or indeed persuade the team to film themselves doing it, it is worthwhile for analysis purposes. Here are two very useful exercises that will complement this activity: 1. Carry out a changeover study on a sheet that gives: Event order • Description of Event • Event Time (plus box for ‘total time’) • Elapsed or Cumulative Time (plus box for ‘total time’) • Bar Graph for Event Time against each activity • Box marking activity as Internal (I) or External (E) • See fig 2 CHANGEOVER STUDY – OBSERVATION SHEET Event Cum Event Event 20 40 60 Time Time No

80 100 120 140 160 180 200 220 240

‘I’or ‘E’

Total

Fig 2 Sample Sheet 2. A brainstorming session that involves everybody, or a good cross-section of those who takes part in the changeover. Each person is given two differently coloured blocks of post-its, and they write one activity on each post-it – one colour for internal, the other for external. These are then stuck onto a large sheet divided into two boxes, ‘Internal’ and ‘External’. There is then a debate as to what can be moved from internal to external and how much time can be saved with the combination of activities.

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From these studies, together with what has been learnt from the 5 ‘S’s and TPM, work instructions are prepared. This in my experience is so often not done, or if it is, it is not done properly. An individual needs to be nominated to take ‘ownership’ of the whole process, which includes the work instructions and the final and most important bit – the installation across all shifts, training, and the review! Then, once satisfied, hand it over for audit at an agreed frequency. It is important that this is done, otherwise the hard work put in will be wasted, and old ways will slip back! There is no doubt that it is difficult to put all this in place and sustain it, but the rewards are there. Figure 3 shows is a summary of the above approach. Activity Summary REDUCE SKUs

MACHINE STUDY

5'S's

SMED

WORK INSTRUCTIONS

DO IT!

In next month’s issue the subject is line philosophy.

5

Efficiency – Maintenance

This month maintenance is the theme: PEOPLE

MACHINES

MATERIALS

PROCESS

METHODS

MEASUREMENT

ENVIRONMENT

Maintenance is not the ‘sexy’ part of packaging, which is why perhaps it never receives enough attention. If a packaging line is under pressure, that maintenance slot is lost, and if this becomes a habit, the line performance becomes worse, confidence in the plant reduces, and morale is low. It becomes a vicious circle. Less Time for Maintenance

Additional Capacity Required

Equipment Condition Deteriorates

Increased Variability

Rework Increases

Poor Quality

The above demonstrates this dilemma well, and although it is not a position we like to find ourselves in, I suggest that there is not one reader who cannot identify with that situation. How can this be overcome? Let us assume that you are in this situation. Before you can do anything, it is important that you know your equipment. Machines are inclined to move in a cycle. When they are new or overhauled there is the teething phase – adjustments, alignments have to be made. The machine at this stage is receiving a lot of attention and will settle down. At this stage interests wane because another machine has become a problem, and many of the ‘learnings’ that have been made about the machine are forgotten. Planned maintenance schedules have probably been prepared but only 25 to 50% of these have been carried

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out. The machine then starts to become unreliable again and major work is required once more. Adjustments and Alignments

Overhaul

Lack of Attention

Breakdowns

This raises the question about planned maintenance. If the schedules are not adhered to the maintenance system is discredited and, indeed, the critical work may have been missed. The key to this is to know your machine and to look after it; if it is ignored the following will happen:     

Unplanned Downtime Catastrophic failures Collateral equipment damage Product quality suffers Every day is a surprise!!

Efficiencies also tend to follow the planned maintenance trend as the following graph illustrates:

90 80 70 e g60 a t n50 e c 40 r e P30 20 10 0

Efficiency Maintenance (PM%)

1

2

3

4

5

6

Weeks

2

So how do you start to bring yourself on track? Initially there must be a clear maintenance policy and it needs to be adhered to and measured. For example, as illustrated above, planned maintenance compliance is as important as line efficiency, as one will directly effect the other. Therefore, both should be reported together. The policy should include:     

Maintenance Approach Capability/Skills required to carry out work Resources – use of contract, own skill limitation etc Support – tools, spares, planning etc Training and Development

A lot of this work will hinge on knowing your equipment as already stated. So what does this entail? Firstly, a gathering of equipment history. Hopefully this is available – if not – this must also be addressed and data built up from existing knowledge, and this then updated as the facts emerge – use every available source of information including the manufacturers! The historical data needs to be sub-divided into two categories:  

Repetitive failures Major stoppages

Each will require a different approach and indeed may lead to machine modification in some cases. Modifications should not be entered into lightly. They are often felt to be the fun bit of maintenance and can go badly wrong. Any changes should receive as much attention as any project and be properly planned. Plan – Do – Check – Act. The data gathered will help to build up a sensible preventative maintenance plan and indeed change what is already in existence. The use of a CMMS (Computerised Management System) is recommended. Secondly, the involvement of the operator through activities like TPM (Total Prodructive Maintenance). It is important that there is ownership. Sadly this has been lost through operators now being flexible. I am suggesting that they should still be flexible but, at the same time, maintain an interest in one piece of equipment. TPM is an important factor in this as it provides a good systematic approach to understanding the machine and it involves people. There is clearly not enough space to describe the process here, but suffice to say that the process is designed to maximise the overall equipment effectiveness. This is done by establishing and sustaining the optimal relationship between people and their equipment. The objective is to eliminate the six losses as follows:

1. 2. 3. 4.

Breakdowns Excessive set-ups and adjustments Idling and minor stops Reduced Speed

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5. Reduced Yield through defects 6. Start Up losses The next stage is to go through the three cycles; the Measurement Cycle (historical and present performance), the Condition Cycle (assess and plan) and the Problem Prevention Cycle (develop and install). Overall Equipment Effectiveness (OEE) is defined as the multiple of three factors; Availability (losses 1&2), Performance (losses 3&4) and Quality (losses 5&6). So OEE = Availability% x Performance% x Quality% Thirdly, it is important that materials fed to the machine are consistent and that the operator follows work instructions. This really does not need explanation and is well covered in my previous articles on materials and people.

Another vital factor is the cleanliness of the machine in an uncluttered workplace, and the Japanese approach to this is perhaps the best. It is known as the 5 ‘S’s and this will be explained in the next article, which is about changeovers. This article would be unfinished if RCM (Reliability Centred Maintenance) was not mentioned. It provides another approach to putting together a maintenance plan and is very focussed on the equipment operation and the possible consequent failures. The approach is not unlike the FMEA (Failure Mode and Effect Analysis) which follows through every detail. It is a top down approach should come up with a sensible maintenance strategy, which is technically feasible and economically justified. However it takes a lot of resource and is time consuming. Within this strategy condition monitoring may be considered. This would include vibration analysis (pumps and shafts), oil analysis (particles, lubricant breakdown,, water) and infrared(IR) thermography (contacts in panels). This is expensive so needs to be very precise if used. Finally, if you get it right it is very rewarding. The following are the positive indicators:        

Operator and technician ownership and productivity Work is known and measurable Reduced overtime requirements Effective budgeting Better and more focussed overhauls Increased uptime/higher efficiencies Increased capacity Higher morale!

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The ownership or improvement cycle should look something like this: Performance

Analysis

Monitor

Identify Issues

Take Action

Decide Action

A much healthier state to be in!

5

AUTOMATION

AUTOMATION

Towards the lights-out brewery A brewer’s view of automation The top man says ‘We’ll build a state of the art, fully automated brewery’. These have been mostly large developments, often on ‘green-field’ sites, where consolidation of facilities produces large gains in productivity and reduced overall cost. Can it be that only in such circumstances that the high cost of automation can be justified when the ‘financial gurus’ run the figures through their laptops?

By Paul Buttrick Beer Dimensions

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rewers who have simple ideas to ‘automate’and improve quality and reliability in a small section of an existing brewery often fail to justify their ideas in hard financial terms, and only sacking some of the few operators they have left will produce these hard savings. In this article, I will look back at how automation has developed in the last 30 years and at how it might develop in the future. There will be examples from my own experience as well as opinions and ideas for people to mull over as they strive for utopia in their own brewery.

A brief history of automation in breweries I sat in an of fice in Warrington reminiscing on past times with Frank Ainsworth and Paul Mahony of CAL Systems. I had worked closely with CAL over many years at various Whitbread breweries, including Boddingtons. As the conversation continued, I began to reflect on some of the battles which I had had with brewery and project engineers in the past. We brewers were particularly hard on our pioneering engineering colleagues at times – do I sense a touch of guilt creeping in? Not really, I’m sure

they questioned our parentage on many occasions! Packaging lines and areas involving what I call ‘stop/start, on/off ’ control had always been seen as very clever and automated, but brewing was undertaken by operators having special skills to regulate the processes that needed better measurement and control. Relay logic and solid state CMOS Logic figured in early control systems, with huge electric cabinets and mimic panels. The coming of automation meant that in the huge breweries of the 1970s could be built with sophisticated modern looking brewhouses hidden behind marble walls and ‘space age’ control panels.(Fig 1) Much of the following process, except possibly CIP (in place cleaning), remained fairly manual up to the packaging line. The coming of the microprocessor gave rise to the first generation of PLCs (programmable logic controllers) bringing another major step forward. The program was entered into the PLC on something akin to a desk top calculator with a single line of text available to the programmer. Simulation was achieved by ‘hard wired’ connection of switches and lamps to the PLC inputs and outputs (i/o). Brewers were told that ‘anything was possible’; you could programme

a microprocessor and the plant would automatically carry out the programme faultlessly every time. What we brewers did not realise was that the plant would work consistently every time, it took us a long time to understand that if any changes – some maybe very simple - had to be made, these ‘chips’ or EPROMs as they were called had to be sent away for reburning or reprogramming as we understood it. In the mid 1980s, the arrival of the second generation PLCs (Fig 2) revolutionised automation and improvements in process control (P&ID-piping and instrumentation diagram control loops) really made full automation practical and flexible at plant level. Programs could be modified ‘on the hoof ’ bringing with it a new set of problems in software version control.

TOP: Figure 1: The past – a vast array of panels and knobs at Bass Runcorn’s ‘new’ brewery in the 1970s INSETS: Figure 1a and 1b: The present – all information is brought to a PC screen in the brewer’s office as in Adnams new brewhouse or available out on the plant like this tiny Allen Bradley mimic panel at Oakham Ales.

Brewery plant It was not just the control side which needed to improve to give full automation. Plant had to be designed and installed to give a fail-safe situation which did not spoil the beer

The BREWER & DISTILLER INTERNATIONAL •

Volume 3 • Issue 8 • August 2007 • www.ibd.org.uk

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AUTOMATION

Figure 2: A major step forward in automation and control in the brewhouse at Inbev ’s Magor brewery.

Figure 3: The original 1966 Tuchenhagen mixproof valve. (Photo supplied by GEA Process Systems Ltd)

if a failure occurred. The introduction of the mix-proof valve was an enormous step forward which allowed large numbers of tanks to be hard piped and automated without risk of improper mixing or contamination with water or detergents. I can remember that everyone wanted ‘Tuchenhagen’ valve matrices. Otto Tuchenhagen invented the mix-proof valve concept in 1966 (Fig 3, Fig 4) following an incident in Germany involving contamination of school milk. The range of valves still goes under the Varivent trademark name. The flexibility and control offered by PLCs, and mix-proof valve technology moved automation on from having the ability to work with less operators on bigger and more complex plant, to fully automated plant with operators having an overseeing brief ensuring the plant is working correctly and carrying out on-line quality checks. Most modern brewhouses are essentially fully automated from raw materials intake to wort chilling with one person (or part of a person) inputting data and taking samples for analysis. Adding hops was one of the last operations to be automated, this remained manual because there was always someone around to do it, but dosing of extract and pellets has been automated in a number of modern plants.

Automated tanks

Figure 4: The 2007 version of the Tuchenhagen mixproof valve. (Photo supplied by GEA Process Systems Ltd)

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Fermentation has long been automated as far as controlling temperature has been concerned. A number of breweries have tried control on the basis of automated present gravity and pH measurement, but these have often failed due to inconsistent measurement as well as the cost of


installation, maintenance and calibration of the instrumentation. Predicting the progress of fermentations has been easier and more productive than sophisticated control based on individual instrument readings. Full auto-routing of fermentation and cold storage/maturation vessels is still rare apart from the most modern highly capitalised breweries. With up to half a dozen mix-proof valves needed per tank, the dif ficulty in justifying the spend cannot be covered by the normal ‘hard’ production savings (e.g. manning, losses etc). Decisions such as when to remove yeast, and where to, can be too complicated in all but the simplest plant. A ‘lights out’ fermentation and maturation area is therefore unlikely to be common in the near future. Most large breweries seem to manage fermentation with very few people, and with some automation and pipework routing, could reduce the requirement to a single person per shift. Having said that, yeast propagation is an area where automation can be justified because precise control and complex operations are required to give consistency. For automation of tanks, many breweries make a decision based on residence time and frequency of valve movements. Bright beer tanks which may be filled and emptied a couple of times a day are the most commonly automated.(Fig 5) The modern BBT farm is often a ‘lights out’ area with everything from beer into tank, beer out to packaging line, blending and CIP being controlled by PLC.

Filtration Filtration using vessel filters (screen and candle filters) were automated at an early stage (Fig 6). The closed nature of the equipment made for easy automation using hard wired systems backed up by a turbidity meter. The plants are normally manned by a single operator, whereas breweries which opted for plate and frame filters tended to be more manual and had more staff. Full automation of large plate and frame filters was trialled by a number and failed by all! I have been involved in a number of potential filtration projects where the desire to move from a more highly manned plate and frame operation to a fully automated vessel filter plant, has failed because the


financial justification did not stand up. It seems that installing fully automated vessel filters could only be financially justified if a project was started from scratch, was volume driven, or the current plant grossly overmanned. With kieselguhr-free filters now establishing their credentials, and increasing problems with powder handling and disposal, we shall have to see whether breweries opt to jump from existing plate and frame straight to the new technology.

Justification for automation In many cases, automation is specified to keep manning to a low level and to give a consistent operation. Previously a reduction in manning was one of the only acceptable hard benefits of investing in pipework and routing installation. The improvement in monitoring equipment has widened what is achievable. With capacity being tightly managed, time means product, so the elimination of dead time in processes is now measurable and thus more easily costed. Automation and instrumentation for protecting the product – e.g. avoidance of contamination, with conductivity and pH probes on filling lines are far more easily managed in a fully automated plant where prescribed reactive processes can be programmed and automatically carried out. Beer losses often used to be costed on the basis of raw materials being lost, however the true cost should also include utilities and ef fluent charges, and in some tightly managed plants a labour element is included as well. The impact of poor publicity on a brewery which pollutes the environment with an unauthorised discharge is huge and it would be wiser safeguarding its reputation with well engineered instrumentation and failsafe automated responses rather than leaving things to a conscientious but not infallible operator.

Cost of automation Automation is still costly, but compared to 30 years ago is relatively more affordable. For example, in 1985, a 75 mm Tuchenhagen mix-proof valve and control head with feedback had a typical market price of £1261, compared to £1259 in 2007. Considering that costs have risen by

over 100% since 1987, the relative costs have reduced and the quality and reliability of the valve have increased substantially. Control equipment – e.g. PLCs, field instrumentation and programming have all reduced considerably in price since the early days.

A few tips for reducing automation costs

always used to its full effect. The control plant suppliers offer any number of parameters to trend, but these are not always configured on relevant pages and their scaling is often outside the useful range for quick and meaningful diagnostics. An example of this might be trending of dissolved oxygen and temperature on a filtration plant. How often is a scaling seen as 0-

10°C for temperature and 0 – 10 ppm for oxygen, when the target is likely to be 0°C for temperature and less than 0.10 ppm (100 ppb) for oxygen. I challenge people to go into their breweries and see whether their SCADA (Supervisory Control and Data Acquisition) trend graphs are optimally configured, I would only expect a handful of positive replies.

Figure 5 below: A modern Tuchenhagen valve matrix on a tank farm. Figure 6 bottom: An automated filter plant at SABMiller ’s plant at Poznan in Poland.

In my time I have become an expert in getting automation installed on plant where project engineers have been keen to keep overall costs to a minimum. Remember: • When planning a project, take account of any future projects and install as large a PLC as it is reasonable to justify; this will reduce future automation and control costs. If this is not possible, make sure what is installed is easily adaptable and expanded. • When looking at automation projects, take a really close look at how much plant is required. For example, how many tanks are required? Do we need three of these, can we work with two? The ef ficiencies afforded by automation very often reduce the requirement for extra plant; this cost saving can often be used to offset the cost of automation, especially when projects are engineered to a budget. Automation gives the opportunity • to build in flexibility, but how much of this flexibility will actually be used and how often? Over-engineering is often the cause of projects being too expensive. I recently visited a brewery with the most fantastic fully automatic yeast propagation plant. Every aspect was PLC controlled, with the absolute minimum of input required from the operators – except that the air supply for aerating the culture remained manual – not quite ‘spoiling the ship for a ha’p’orth worth of tar’, but a small anomaly on an otherwise perfect installation.

Trends The improvement in process control instrumentation, plant schematics (Fig 7) and trending of parameters provides useful information for plant operators. In my experience, trending data has always been part of the requirement of any plant control system, but the information is not



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Trending for process improvement In my opinion, a glance at a well configured SCADA trend screen is the quickest and easiest way to tell whether a process is under control. Each process will have a recognisable trend shape which, with frequent use, will be familiar to the operator. Any trace which is not following the right line or, has an unusual shape needs to be investigated and corrective action taken. Unless a problem is significant, it may otherwise not present itself until well after the event, so frequent monitoring coupled with a well thought out alarm system can significantly improve quality and ef ficiency. In normal production, trends are most useful for diagnosing problems, particularly when matched with sequence steps and process values. An example is trending for dissolved oxygen in processed beer, where any adjustments to plant and equipment are almost instantaneously recorded. Similarly plant faults, such a defective pump seal sucking in air, can be instantly picked up and rectified.

Utilities

Figure 7 top: A SCADA screen showing graphics from yeast tanks. Figure 8 above:Trend graph from a fermentation SCADA screen. (Images:FMA Process Engineering Ltd)

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Use of trending for plant commissioning Trending (Fig 8) is often one of the last items on the commissioning plan – it’s far more useful to have the trends properly set up early on to aid commissioning. One of my recent commissioning experiences was with some 500 hl/hr green beer centrifuges. The centrifuges would ramp up and down in flow according to the turbidity of the beer coming on to them. The start up procedure was set according to a predetermined ramp rate, but the timing and set points were such that the average flow of the centrifuges was below the required capacity of the plant. The maximum flow was easily achieved, but time wasted in stopping/starting the centrifuges and tank changeovers, meant that the daily volume requirements were missed. Once the trend graphs on the SCADA system were configured and scaled correctly, the ramping up and down of flow rate could be improved to increase the average transfer rate from 300 hl/hr to greater than 400 hl/hr.


My own early brewing world was dominated by malt extracts, losses, the laboratory report and packaging line ef ficiencies. I can remember being asked by Charles Tidbury, the then Chairman of Whitbread, how ‘my wort attenuation limits were on Mackeson Stout?’ Energy, water and ef fluent costs were well down the priority list. How that has changed, with these costs rising and now accounting for 20% of brewery costs. Legislation and response to global warming in the guise of IPPC (Integrated Pollution Prevention Control) permits feature highly. The IPPC permit may be looked on essentially as a license to manufacture. With the requirement to introduce ‘best available techniques’ when practical, and demonstrate year on year improvements in performance, automation and monitoring in utilities becomes justifiable. As with all these things, a virtuous circle is formed, with the legislation driving companies into investment which in turn reduces costs. In many cases the justification would not be there without the motivation of legislation. Integrated MIS (Management Information System) packages


developed from SCADA can indicate where and when waste and extra cost is occurring. They can therefore be used to reduce and optimise energy usage. The cost of utilities can be directly allocated back to the using process and accountable team. In the ideal situation, the cost of utilities supply would be the responsibility of the utilities team, the cost of usage would be the responsibility of the production team. It sounds easy in principal, but having the instrumentation and data collection correctly positioned and configured is a considerable task and very costly. Only the larger modern breweries could justify such a scheme, where utilities budgets run to £1.50/hl which would be £3.0 million for a 2 million hectolitre brewery.

‘I don’t trust computers!’ With automated systems being more flexible, process changes, improvements and enhancements can be made and tested on site. The old problem of not trusting computers is becoming less common. Blaming the software still happens, but the control system only does what has been programmed to do – nowadays it is normally an instrument or sensor that is faulty, or the programme was not quite right to start with. In a well managed project, a prescribed procedure for developing and installing the software takes much of the pain out of plant commissioning that was such a feature 10 years ago. Up-front work with customers giving a good process description (URS – User requirement specification) followed by a well developed P & I D ( process and instrumentation diagram) and HAZOP (Hazards and Operability Analysis) study gives the control company a sound basis to write an FDS ( Functional Design Specification) which is developed into the end software. Testing of the software with the client before it goes to site should give 98% of what is required with only a few minor issues to be sorted at site during actual commissioning. Software simulation packages are available which can fully simulate process plant system inputs and outputs (I/O) via ethernet connection to the PLC software. From experience again, any little awkward decisions that are avoided in the early stages,

will always be there, and are twice as awkward and costly to address on site, so my advice is to leave as little as possible till the last minute.

Figure 9: Schematic of modern brewery IT architecture showing ERP, MES linking in with SCADA and brewer PLCs.

The Top End ERP and MES Automation and reporting has been around for a long time using SCADA, but there was always dif ficulty bridging the information gap between what happened on the plant and what information (and its accuracy) reached the planners and executive management. Inputting data by hand that is readily available electronically in SCADA and numerous other systems was, to those who had to do it, a real ‘pain’. In the last few years systems have been developed and improved so that manual double entry is being replaced by electronic transfer in what are called ERP and MES systems. ERP (Enterprise Resource Planning) systems are the top layer, and handle ordering, planning, finance and HR while MES (Manufacturing Execution Systems) provides the electronic bridge to SCADA and the process itself (Fig 9). MES systems basically gather data and analyse it for management control and decision making. It can be said to have three main functions: 1) To provide an electronic paperless system and data flow. 2) Enables key performance indicators (KPIs) to be established and monitored within a brewery, and in large groups, if the data collection systems are comparable, between plants. 3) Recipe management in a controlled environment. One effect of a properly implemented MES is to force the brewery into rethinking its work processes. Running processes in ‘manual’ leads in inaccurate reporting, which has an adverse ‘knock on’ effect over the whole system.

The future I asked Paul Bunyan and Tony Goodman of FMA about their view of the future trends in IT and automation in breweries. Their view was that large breweries are collecting their ‘islands of automation’ into plant wide systems, with an emphasis on standards which will ease maintenance and bring consistency to information, which would allow realistic plant

and process comparisons to be made. Many breweries have ERP systems like SAP which are separate from production, There will therefore be increased investment in MES systems which will enable electronic transfer of data across the whole operation. This will improve overall ef ficiency and cost by reducing order time fulfilment, reducing manufacturing cycle times from ordering materials to shipment of order, improving inventory control, reducing rework from improved quality management. Breweries which have invested in ERP and MES will require and implement higher levels of automation with more rigid standards in order to maximise benefits from these systems; this in turn will lead to a continued reduction of staff, who will be more highly trained. The traditional departmental structure of brewhouse, fermentation, processing and packaging will probably give way to a simple brewing and packaging control structure, although packaging would remain more labour intensive due to the need for more manual intervention.

breweries. The ‘lights out’ philosophy will only exacerbate this and may not be totally desirable. Questions I often ask people if they have problems in a brewery are: what does it look like?, what does it taste like ?, have you felt the pipe to see if it’s hot? (there is a health and safety issue here if it’s too hot, but then HSE is a whole new ball game!). ‘Lights out’ operation may be less of a target to some brewery CEOs, but hectolitres per man will remain a key comparator for high level company assessment. In reality I think money is more likely to be invested in reducing the high areas of costs – namely energy, water and waste, and in ERP and MES systems which will improve cost and ef ficiency, and vital data flow over the whole operation. ‘Lights out’ is not ideal, maybe keeping a light on in the corner so that the new vigilant operators can still ‘walk the plant’ and experience and see a bit of what is going on is preferable. In any case who’s going to feed the brewery cat – or maybe even that can be outsourced? s

“There will therefore be increased investment in MES systems which will enable electronic transfer of data across the whole operation. This will improve overall efficiency and cost by reducing order time fulfilment, reducing manufacturing cycle times from ordering materials to shipment of o rder, improving inventory control, reducing rework from improved quality management.”

Those mouse-click Brewmasters I was talking to a German Brewmaster the other day about ‘mouse-click ’ brewmasters – that is brewers who work in automated plant relying on PLC feed back for all their information. We were in ‘grumpy old men mode’ and agreed that this new breed of brewer was technologically very competent, but in the real world were not exposed to the sounds, smell and vision of the process, and therefore missed out on having a true feel and understanding of what was happening in their

q Acknowledgements

My thanks go to Andrew Ball (Tuchenhagen), Frank Ainsworth (CAL Systems Ltd), Paul Bunyan and Tony Goodman ( FMA Process Engineering Ltd) and Robin Cooper for their help in writing this article



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BREWING SCIENCE

Recovery of beer from tank bottoms – a review Many early Beer Recovery Systems are still in use today. In the days before ‘duty at the gate’, most breweries in the UK had some sort of recovery system to reduce beer losses. With breweries becoming larger and waste disposal cost increasing, recovering high quality beer from yeast is again becoming a real topic for debate.

By Paul Buttrick Beer Dimensions

What are the financial benefits of recovering beer from surplus yeast? The following tables show approximate operational savings that can be made by recovering beer from surplus yeast. The figures are general ones, and each brewery will have to use its own data and costing conventions to get a more accurate value. See Table 1.

Figure 1: A one tonne yeast press in a British brewery with polypropylene plates and frames installed in the 1980s. complexity of the operation increased.

What happened next?

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eer recovery in traditional British breweries often involved the Scott yeast press system. In this process, yeast was skimmed by vacuum from the top of an open fermenter to a tank usually in a room below the fermenting room. The tank was then pressurised with air and the yeast slurry passed over a yeast press, where high value beer (excise paid) was recovered and returned to the fermentation vessel it came from. Pressed yeast (of about 25% dry weight solids) was either used for repitching or sold at a high price to a well known food manufacturer. However, the plant was difficult to clean, which resulted in a serious microbiological risk, and many breweries stopped returning beer because of this. With the advent of processed beers, lagers, and small pack beers, additional technology was used to improve the quality of the recovered beer. Beer was sometimes filtered and flash pasteurised before being returned occasionally to the fermentation vessel but more often to the cold store tank. Even though the risk of microbiological contamination was significantly reduced, there were problems: a) High beer oxygen levels, coupled with high pasteurisation time and temperatures, made the beer taste poor and had a negative impact on flavour stability, haze stability and beer foam. b) Despite the pasteurisation process, cleaning and sterilisation of the equipment continued to give problems; this area of the brewery was often away from mainstream production areas, and consequently did not always get the attention required to maintain quality standards. c) The running costs continued to rise, and the

The financial driver for recovering beer increased as beer duty rose significantly above the rate of inflation. Rotary vacuum filters, OMD filters, and large semi-automated presses (Fig .1) were installed which were able to handle increased volumes. A pressure squeeze from membrane presses increased beer recovery rates further. Both the rotary vacuum filter and OMD filter needed a filter aid to recover the beer, which also had high oxygen content. These investment returns certainly kept the accountants happy, but were not good for beer flavour and quality.

Where are we now? Despite the move to ‘duty at the gate’ and the value of recovered beer reducing from approx £70/hl (incl. duty at 5% abv at current duty rates) to £5–6/hl, many breweries are still using large presses to recover beer, but problems with beer quality, running cost and complexity are forcing brewers to look at alternative technologies. Few breweries outside the UK recover beer from surplus yeast mainly because returns on investment were poor, and the probably correct perception that beer quality would be compromised.

Surplus yeast as a ‘co-product’ not a ‘waste product ’ Although beer savings alone may not justify a beer recovery project, the costs associated with effluent and disposal cost for yeast slurry will pay an increasing part in the financial equation. As disposal sites become full and costs increase (probably including government charges – I think these are called taxes) breweries will be driven even more to reduce their ‘waste’. Companies are beginning to look at surplus yeast as a co-product producing an income stream instead of a ‘waste’ stream with a disposal ‘on-cost’. With food safety being high on the agenda, farmers are looking more at accredited food sources. Brewers’ yeast is an ideal high protein food for pigs for example. It does, however, have to compete with other feed, and can only be economic if slurries are concentrated before collection. As a basic rule of thumb, yeast slurry from fermentation vessels is about 10% dry weight (dw), from cold storage tanks approx 7% dw, and a positive cash flow is only available with slurries above 14% dw. Depending on circumstances, revenue of approx £1/%/tonne above14% dw, so yeast slurry despatched at 17% dw would attract gross income of £3/tonne. It is important to note that yeast sent for animal feed has to be dead before it is consumed – this means that either the brewer or the feed supplier will have to kill the yeast using heat or chemical addition. Because of the high cost of transport, slurry sent out at less than 14% dw is likely to incur a transport on-cost. (Fig.2)

Table 1: approximate volumes of waste yeast and recovered beer expected from different sized breweries, and the value of the recovered beer. Volume brewed khl

500 1000 2000

Surplus yeast/bottoms khl

20 40 80

Volume of beer recovered (65%) khl

13 26 52

Volume of yeast for disposal (35%) khl

7 14 28

Value (£) of recovered beer (£6/hl)

78k 156k 312k

The calculations are based on: Surplus yeast is 4% of site volume; the beer recovery rate from the yeast is 65%, leaving 35% surplus yeast; recovered beer is valued at £6/hl.

The BREWER & DISTILLER •

Volume 2 • Issue 4 • April 2006 • www.ibd.org.uk

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BREWING SCIENCE

Table 2: the calculated operational cost saving (including beer) if waste is sold as a “co-product” at £3/tonne as opposed to a “ waste” product with disposal costs of £1/tonne.

Figure 2: A 44-tonne tanker delivering 28 tonnes of yeast to a pig farm in the UK– photo supplied by Wheyfeeds Ltd.

What should a brewer’s approach be now? With costs being squeezed, brewers are being driven to reduce beer losses. Consolidation of brewing plants with increased capacity, makes beer recovery more financially attractive, and most companies are grappling with the ‘how are we going to reduce our losses and waste costs?’ question. The answers are not straight forward, even different plants within the same group come up with different solutions. Another signi ficant factor for UK brewers is that those breweries which already have established beer recovery facilities have great difficulty in upgrading to higher quality more efficient operations, because what they already have makes a considerable impact on their costs, and extra investment based on a straight ROCE is difficult to justify. From my experience, the question of what equipment and process to use will depend very much on what equipment already exists, the quality standards expected, and what level of investment can be justified.

Volume of beer brewed – khl

Operational saving( beer and disposal cost) – £k

500 1000 2000

£119 £238 £476

Table 3 shows the same calculation if waste disposal costs increase to £3/tonne Volume of beer brewed – khl

Operational saving( beer and disposal cost) – £k

500 1000 2000

the future. They may decide to concentrate surplus yeast but not return recovered beer to their beer stream. 2) Continue with existing press operations This may be possible for a time, but control of quality and maintaining aging equipment will eventually prove to be uneconomical and unacceptable from a quality perspective. The beer yield from presses is high, with yeast being concentrated to approx. 25% dw.

1) Do nothing Some brewers will decide that they do not want to return any recovered beer for quality reasons. These breweries will increasingly have to address the problem of where and how their surplus yeast will be disposed of in

3) Alcohol recovery from yeast slurries Many UK brewers recovered alcohol evaporated from surplus yeast in the 80s and 90s, and some continue to get good return for their efforts. GEA-Wiegand (Fig. 3) and Unipektin were the main suppliers of this equipment. The technology, based on falling film evaporation working at 60-70°C and reduced pressure, is also used for producing alcohol free beers. The yield is high (up to 94%) because alcohol is recovered from within the yeast cell as well as from the beer slurry. When the calculations are done, the volume of alcohol evaporated from surplus brewing yeast is very close to the maximum allowed to be blended back into beer in by HMCE. With good plant maintenance and carbon filtration of the distillate, there are positive quality aspects of this process, although there were some flavour issues in early plants, where the operational

Figure 3: A GEA-Wiegand 20hl/hr falling film alcohol evaporation plant for recovering alcohol from brewery yeast – photo supplied by GEA-Wiegand.

Figure 4: A Westfalia CB 506 decanter centrifuge for processing up to 40hl/hr of yeast – photo supplied by Westfalia Separator Ltd.

What are the options? There are a number of options and technologies available:

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and control parameters were not ideal. The distillate is biologically stable and has little effect on flavour, head retention and haze stability. Because the flavour is neutral, alcohol distilled from different brands need not necessarily be segregated and can be returned to beer on transfer to cold storage tank. A downside for this technology is the image of chemical’ brewing, particularly when premium brands are involved. ‘

4) Centrifuges There are a number of options where centrifuges can be used to recover beer from surplus yeast. These can be split into 2 main types of operation: Decanter centrifuges These machines have been improved in recent years to being more suitable for foodstuffs, and are in use in a number of large breweries. There have been issues with cleanliness and sterility, and manufactures say that these have been overcome. Due to their mode of operation, these machines are able to concentrate yeast slurries up to 25% dw. (Fig. 4) The ‘squeezing’ element from the decanter screw, is thought by some to cause damage to the yeast cells. The centrate does have high yeast counts and some brewers have a small clarifying centrifuge and flash pasteuriser in line after the main decanter centrifuge, to ensure quality is assured before beer is returned.

Figure 5: A FEUX-510 Alfa Laval continuous discharging nozzle disk owl centrifuge (yeast processing rate 20-80 hl/hr) – photo supplied by Alfa Laval Ltd.

The cost of a single decanter centrifuge may be attractive, but the extra equipment needed to ensure quality, increases cost and complexity considerably. Some brewers might decide that centrate with a high yeast count does not have a deleterious effect on quality, and therefore if cleanliness and sterility can be assured and the recovered beer can be blended back immediately, then extra equipment is unnecessary. Another claimed advantage is the ability to handle a range of slurry thickness fed to it; the control system needs to be very good to ensure consistent centrate out of the machine.

Figure 6: A single ‘head ’ , 40m2 , Pallsep Vibrating Membrane Filter (VMF) for cross fl ow filtration of yeast up to 18 hl/hr – photo supplied by Pall Europe Ltd.

Figure 7: Bright beer quality filtrate from yeast slurry processed on a Pallsep VMF.

Figure 8: Diagram and photo showing the 40m2 cross fl ow filter head of the Pallsep VMF – supplied by Pall Europe Ltd.

Disk bowl and Continuous Discharging Disk Bowl Nozzle Centrifuges Disk bowl and continuous discharging disk bowl nozzle centrifuges are sometimes considered for recovering beer from yeast slurries. Large disk bowl centrifuges are not often used, and manufactures more often recommend their decanter machines. Continuous discharging disk bowl nozzle centrifuges (Figure. 5) are compact hygienic machines that can be used to concentrate yeast slurries, eg of pitching yeast. In beer recovery situations they can also be used ‘online’ to concentrate yeast bottoms and simultaneously dosing the centrate back into the main beer stream, or as “off-line” stand alone machines. These machines have the disadvantage that the yield is variable according to the thickness of slurry put to the machine. Compared to 25% dw yeast from a decanter centrifuge, the yeast from this machine will be about 18-22% dw. The yeast count on the centrate varies according to the thickness of slurry pre machine and control parameters applied. Their advantage is that the machines are compact, easy to keep clean and sterile, and are not thought to cause undue stress to the yeast. If a brewer already had a yeast press achieving 25% dw yeast, then the yield from a continuous discharge bowl centrifuge would be less. However brewers who have no current beer recovery operation, would be attracted by the physical advantages of the machine as well as reducing their losses. 5) Cross flow filtration Cross flow filtration technology has been applied by a number of manufacturers, There are two applications a) crossflow filtration using static membranes and b) vibrating membrane crossflow filtration (Pallsep – VMF) sold by Pall. The main advantage of crossflow is, that due to the very small pore size of the membranes (typically 0.5-0.8 microns), the filtrate is close to bright beer quality, virtually yeast free, has good palate and physical parameters. The membranes are ceramic or polymer, and installations can be completely automated. With the VMF (using PTFE membranes) most of the energy applied to separate beer from yeast comes from the vibration of the membrane. This means that very little pumping energy is needed to


Fig. 9 - A Filtrox CERinox ceramic cross fl ow filter. The photo shows a 3 module plant, with each module of 40m2 capable of handling up to 18 hl/hr of yeast slurry – photo supplied by Filtrox AG. circulate the slurry across the membrane, consequently temperature rise is minimised and the yeast flow is very gentle and stress free. (Fig ures 6,7 and 8) With the static crossflow filter, high flow rates are the driving force behind the beer/yeast separation, and a heat exchanger is needed within the equipment to reduce yeast stress and prevent autolysis. These filters eg Kerflux, from Pall, and CERinox from Filtrox, (Figure 9) are based on robust ceramic membrane technology (Figure 10). Because cross flow filters rely on the pumping of yeast slurries around the membrane, the final thickness of the yeast is less than 20% dw at the end of a batch. In order to achieve an extract recovery equal to a yeast press of 25% dw, a ‘dia-filtration’ with deaerated water can be used to ‘wash out’ additional beer from the slurry. Control parameters need to be set so that the ‘diafiltration’ process does not wash out any undesirable material from the yeast. A new development in static membrane technology, is a plate and frame polymer based membrane from Alfa Laval (Figure 11). This equipment has 0.45 micron membranes and is designed to give low pressure conditions and keep energy consumption down This type of filter concentrates yeast slurry to approx 20% dw so yields are less than from some other plant alternatives. An initial disadvantage of membrane systems has been the cost of replacement membranes. The manufacture of the membrane has improved significantly, and the guaranteed life is now making this option more affordable. 6) Blending yeast slurry back pre-centrifuge This process involves taking yeast from the bottom of a vessel and dosing it back as b eer is transferred from a fermenting vessel via a centrifuge to a maturation vessel/cold store tank. The proportional dosing of the tank bottoms means that the centrifuge will be able to remove the yeast dosed back because the load is spread over a large volume of beer. This looks to be an ideal system – a simple


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BREWING SCIENCE

Figure 10: Filtration module from a ceramic cross fl ow filter – Photo supplied by Filtrox AG.

‘on-line’ process with little extra equipment, especially if green beer centrifuges are already in use. However there are a number of considerations: a) The centrifuge must be sized to handle the extra yeast dosed from the vessel at the required beer transfer rate. If the centrifuge is not big enough to handle the extra yeast, then investing in extra green beer can be very expensive (Figures 12 and 13). b) The dose back rate needs to b e kept at low levels to reduce the possibility of yeasty flavours in the beer. c) Planning within the brewery must be such that bottoms and beer transfer can be carried out simultaneously – this is not as easy as it sounds.

Filtrate/centrate blend-back rates? For centrate from presses and centrifuges, most brewers put a 3 -5% limit on blending back. This is chosen because any flavour or quality differences will be blended away and not be noticed in the final beer; it also happens to be approximately the amount of filtrate produced. With crossflow technology, producing bright filtrate, brewers have blended back at up to 10%. With alcohol blend back, the maximum is set by HMCE and is approx 2-3% depending on the strength of the beer.

Figure 12: Picture of two large Westfalia SC 150 disk bowl centrifuges rated up to 600 hl/hr suitable for a yeast dose back operation – photo supplied by GEA- Westfalia Separator Ltd. there is no yeast in the filtrate which will be autolysed by the hot conditions. The hot environment also has a pasteurising effect. This type of operation is not as straight forward as it seems, because recovered beer is not always produced in synch with brewing. Options for centrate with higher yeast count include being added to actively fermenting yeast in fermenter, where the purging effect of fermentation washes out any flavour defects. Most brewers add beer back between fermenter and cold storage tank, and some add beer from crossflow equipment to beer before filtration. There is an old brewer’s ‘rule’ which says that any addition to a beer should be made going forward in the process; the benefit here is that any quality issues are restricted to beer from the point off addition. When adding returned beer just before filtration, care must be taken to ensure that there are no issues with haze stability.

To sum up Recovery of beer from tank bottoms can be justified, with spent yeast from a recovery process considered as a co- product w ith

value instead of a ‘waste’ on-cost. There are numerous alternative technologies for recovering beer from bottoms. Each brewery needs to assess its own quality and operational requirements before deciding what is best for them. There is no ideal solution which can be universally recommended and applied. A word about total investment costs. The justification for installing beer recovery equipment can easily be made on the basis of a single piece of recovery equipment. However, the associated plant can increase the overall project cost at least 2-3 times, and brewers need to be very clever in identifying the minimum practical cost of this plant in order to justify their investment. s

q Acknowledgements

The author would like to thank the following companies for supplying photos, diagrams and information for this article: Alfa Laval Ltd, CAL Systems Ltd, Filtrox AG, GEA – Wiegand GmbH, Westfalia Separator Ltd, Pall Europe Ltd, Wheyfeed Ltd.

q The

Author

After a long career with Whitbread and Interbrew, including time as Head Brewer of Boddingtons and Stella Artois Brewmaster, Paul has started his own independent consultancy Beer Dimensions. Paul has an MSc in Brewing Science from Birmingham University and is one of only a handful of British brewers to have studied at Weihenstephan (T.U. Munich). You can contact Paul on [email protected] or www.beerdimensions.com

Where to blend-back? This is determined by the quality of filtrate/centrate and policy of the brewer. Some brewers add beer back to the w hirlpool or into the wort stream just before wort cooling. This can be successful as long as

Figure 11: A DSS M39-H Alfa Laval plate & frame polymer membrane cross fl ow filter capable of handling 35 hl/hr yeast slurry – photo supplied by Alfa Laval Ltd.

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Figure 13: Process diagram of a yeast dose-back pre-centrifuge process – Diagram supplied by CAL Systems Ltd.


BREWHOUSES

. n a m t u P r e g o R : o t o h P

The Huppmann brewhouse at Oettinger Brau in Germany has been installed within a no frills industrial building. Oettinger is a leading supplier to the supermarket trade.

A brewer’s view on a modern brewhouse project Mention building a new brewhouse and any brewer’s eyes light up and the ‘red mist’ descends at the thought of gleaming shiny vessels in a marble hall set off with murals of malt and hops and modern lighting effects. The reality is often quite different and a lot of thought, analysis and soul searching have to be done before the dream is realised.

permanent, and any fundamental mistakes very dif ficult and certainly costly to rectify. From the brewer’s perspective, there are five key requirements in specifying a new brewhouse – these are: a) Brand image. b) Capacity – how big should it be? c) Wort and be er quality – taste, head retention, flavour and haze stability d) Capital costs – plant choice and design. e) Running costs – brewhouse yield, raw materials energy costs, manning and other costs.

Brand image By Paul Buttrick Beer Dimensions

T

his article is written by a practical brewer and is not intended to be a thorough analysis of each item of equipment, but will look at the things anyone building a new brewhouse should c onsider. Brewhouses are expensive, basically

It is important that a company takes into account its brand and image when developing a new brewhouse. If beer quality and tradition is core to a brand image – particularly premium brands, then positive PR can be gained from a ‘showpiece’ brewhouse, but if a company is more commodity based, leading with price and does not have strong individual brands, then a different

approach can be made. With brand image and strength becoming more important, how many companies regret building functional brewhouses? After all, customers expect to see more than a ‘chemical plant’ when they visit the ‘home’ of their favourite beer. It does not always cost a fortune to make a brewhouse ‘smart’ instead of purely functional (Fig.1) Brand image may not only influence the look of a brewery, but also dictates the raw materials and processes used. In designing a new brewhouse, there must be a serious debate on the recipe of a be er, because this will decide the plant choice and the final cost of the project.


“The decision by SAB-Miller to retain the triple decoction process, a copper heat exchange surface, and direct gas firing for Pilsner Urquell is no doubt the result of a debate that puts the beer and traditional process used at the heart of the image demanded by this unique beer.”

Figure 1: A ‘showpiece’ Ziemann brewhouse at a Latin American brewery.

Volume 2 • Issue 2 • February 2006 • www.ibd.org.uk

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BREWHOUSES

. n a m t u P r e g o R : o t o h P

Figure 2: Pilsner Urquell brewhouse (2004). Note the copper clad vessels with one of two 10m lauter tuns in the back ground. Over 100,000 visitors a year inspect this view from an elevated walkway.

The decision by SAB-Miller to retain the triple decoction process, a copper heat exchange surface, and direct gas firing for Pilsner Urquell is no doubt the result of a debate that puts the beer and traditional process used at the heart of the image demanded by this unique beer. (Fig.2)

How big should a brewhouse be? “The beer recipe can significantly influence the capital cost of a brewhouse, and its effect on ongoing brewing costs. The degree of malt modification dictates wort and beer quality as well as brewhouse processes. In traditional lager brewing, under modified malt is processed using a decoction system, with mash boiling vessels being key plant items.”

The normal way to size a brewhouse is to take the peak weekly or monthly volume of the business and use this as the basis for the capacity calculation. It is also important to include an overall ef ficiency factor for the operation which would include plant cleaning, mechanical ef ficiency and other non-production down time. Extra capacity can then be added to take account of future volume growth. This can be done by leaving extra days or shifts available for peak working, e.g. five and seven day working, double or triple shift working or a planned option to decrease brew cycle times. A single brewery company will take a different view to a global/national one with a number of breweries. With multi brewery operations, the capacity and capability of all the breweries must

be taken into account, as is the decision about which plant is to be expanded. In these situations, an overall production and minimum cost sourcing exercise needs to be done to get the right economic answer, before taking other factors such as local marketing conditions and risks into consideration. The planned brew length will normally be dictated by the size of other plant in the brewery – especially fermenting vessels. However – the opportunity should be taken to review both brewlength and brewing gravity, because it will affect the capacity of the whole brewery. It is important in this exercise to make sure everything ‘fits’ and not get a mismatch of vessel size and brewlength – e.g. a 500 hl brewlength with 5000hl fermentation vessels or a 1000hl brewlength with 300 hl vessels would not be ideal. It is also important to ensure that yeast pitching can be properly managed. Brewers always like to build in flexibility, but at what level does this become uneconomic? Some breweries that are based on a two stream brewhouse, should consider whether a single stream plant is a better option. A single stream will be less complex, less costly to install, easier and more economic to run.

Raw materials The beer recipe can significantly influence the capital cost of a brewhouse, and its effect on ongoing brewing costs. The degree of malt modification dictates wort and beer quality as well as brewhouse processes. In traditional lager brewing, under modified malt is processed using a decoction system, with mash boiling vessels being key plant items. Many breweries are using temperature programmed mashes and some employ infusion

RIGHT: Figure 3: Equipment schematic for “wet ” and “dry” milling operation – diagram from Huppmann FAR RIGHT: Figure 4: The “ Dispax” milling system in a Dutch brewery – photo supplied by Ziemann

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mashing to produce lager wort. Current opinion and experience suggests that reducing the length and intensity of mash heating and copper boiling results in beers with improved flavour stability – little did ale brewers of the last century realise that they were at the forefront of 21st century brewing science! Malt is the main raw material, but adjuncts play a big part in dictating brewhouse plant and costs. For example, the use of un-gelatinised maize grits requires the use of a cereal cooker, but using flaked maize does not. Similarly, use of liquid sugar requires storage tanks, but does not take up conversion vessel or wort separation equipment capa city. Maize grits are less expensive than maize flakes, liquid sugar is the same cost as malt. Doing an exercise weighing up the cost of extra plant and complexity against raw material and energy cost needs to be carried out. Remember that cereal prices vary from year to year, so a spot calculation on a single year is not wise. The result of this can le ad to a bit of soul searching and wise decision making on behalf of the brand owners (more often than not the Marketing function who may have to manage the PR aspects of any recipe or process changes. Many people underestimate the part that hops play in beer flavour and quality, therefore the choice of hop products is important. Extracts produce a clean beer with little hop flavour or aroma and are easier to process due to less bulk; wort losses can be up to 1% lower than when using hop pellets. Hop pellets give more polyphenol content to wort and if added late impart aroma and hoppy flavour. Polyphenols add to the overall mouth-feel and body of the beer as well as improved flavour stability, but if in excess can detract

P h o t o : R o g e r P u t m a n .

Figure5: The dimpled surface on ShakesBeer conversion vessel – photo supplied by Steinecker

Figure 6: One of two centrally-fed 16 tonne Meura 2001 mash filters installed at InBev’s Magor plant in South Wales.

from haze stability. Hops whether from pellets or leaf are known to improve the quality of beer foam compared with beers brewed using extract. The correct choice of plant will influence the overall project cost, beer quality and how much it will cost to brew for the next 20 ye ars or more. With energy and waste costs rising, these will have an increasing influence on running costs. The latest techniques involving reduced wort oxidation and ‘thermal stress’ are also leading to improvements in flavour, flavour stability and head retention. Thermal stress is brought about by any process involving excess heat at high temperatures in any brewhouse process (eg excessive wort boiling) Over enthusiastic mixing in other brewhouse vessels such as conversion vessels also has a negative effect on flavour stability. The leading brewhouse manufacturers all offer their own interpretation and development on the latest available brewing knowledge and science.

order to get the 30% fine flour required, power consumption is up to three times that required by wet milling systems. Noise and explosion risks also need to be taken into consideration. Continuous steep milling is recommended by Steinecker (Variomill) and Hupp mann (Millstar) and can be used in conjunction with any lauter tun. Conditioning of the whole malt grain in a continuous warm water steep increases the water content of the husk to approx 15 % before milling. Advantages over dry milling are said to be better and faster wort separation with opportunities for increased lauter tun loading, less equipment and less explosion risk (no dry ground grist), less oxygen uptake due to mashing taking place at the same time as milling (Fig.3). Ziemann have recently developed their innovative “Dispax” dispersion mashing/milling system which is a compact ‘wet’ option mainly for use with mash filters (Fig.4)

Mash Conversion Milling There are three main options for milling. Dry milling normally uses six roller mills and is still popular with breweries using lauter tuns. The milling is independent from the mashing process and therefore a lower rated mill can be used so that the milling operation can utilise the conversion vessel cycle-time, whereas ‘continuous steep’ milling requires milling to take place in 20 minutes of the mashing process. It is also reckoned that mill adjustments available on the three sets of rollers give a better opportunity for optimisation of extract and run off. Hammer milling is only used in conjunction with the mash filter in

The key here is the choice of infusion/temperature programmed mashes and whether mash boiling and cereal cooking are part of the desired brew recipe. All manufacturers feature on low oxygen pick up, ef ficient mixing, heat transfer with latest design mixers and temperature control. Ziemann and Steinecker (ShakesBeer) have introduced dimpled heat surfaces inside the vessel (Fig.5) which gives improved heat transfer and hence faster temperature rises for programmed mashes. Along with hot water injection, heat rises of over 2°C/min as against 0.5– 0.9°C/min for a conventional conversion vessel can

be achieved. This would be important to any brewery whose mash cycle is the rate determining step in their brewhouse. For a temperature programmed mash starting at 45°C and rising to 75°C, an overall time saving of 30–50 minutes is very significant. Note that any operation using mash boiling or decoction will include more complex plant as well as increased energy costs.

Wort separation The big debate continues on the use of lauter tuns and mash filters. Historically mash filters had a brief rise in the late 1970s, but improvements in lauter tun design reasserted their ascendancy until the introduction of the Meura 2001 membrane mash filter (Fig 6). Ziemann continue to offer modern mash filters and lauter tuns. The Ziemann TCM (Thin layer Chamber Mash filter) produces up to 16 brews per day, the largest version taking a 21 tonne grist. At present there is no clear winner, except that each brewer must make the decision based on its own requirements. Breweries using unmalted adjucts and high gravity brewing often opt for mash filters, as do breweries with a low number of wort streams requiring fast throughput and high extract yields. Lauter tun manufacturers, Briggs, Ziemann, Steinecker (with Pegasus) and Huppmann (with Lauterstar) have continued to develop their equipment to increase loading (up from a “norm” of 160kg/m2 to over 200kg/m2) while reducing cycle times and increasing extract. An emphasis has been put on decreasing down time (like spent grain removal) with improvements in rake design, automated raking and run off control improving the


“Continuous steep milling is recommended by Steinecker (Variomill) and Huppmann (Millstar) and can be used in conjunction with any lauter tun. Conditioning of the whole malt grain in a continuous warm water steep increases the water content of the husk to approx 15 % before milling. Advantages over dry milling are said to be better and faster wort separation with opportunities for increased lauter tun loading, less equipment and less explosion risk (no dry ground grist), less oxygen uptake due to mashing taking place at the same time as milling.”


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BREWHOUSES

Figure 7: The underside of a modern lauter tun – take note of the number of wort run off pipes – photo supplied by Huppmann

Figure 8: The Symphony external wort boiling system – supplied by Briggs of Burton.

wort flow itself. A significant step forward has been to increase the number and positioning of run off ports incorporating a conical design (Fig.7). This has resulted in faster run off with an even extract recovery across the whole bed and less vacuum produced. Without getting into detail, the main differences between a lauter tun and mash filter include the following. The lauter tun is more flexible for loading – charges of + 50% to -30% are claimed with the mash filter only able to handle +10% to -20% of optimum loading. Smaller breweries with a large number of beer brands are more likely to favour lauter tuns because of this. The cycle time of the mash filter of 90–120 minutes has been consistently better than the lauter tun, although using the latest run off

technology twelve brews per day on a bed loading of 200 kg/m2 can be achieved with a lauter tun. Whatever mash separation device is used, the malt quality is vital to good performance, especially levels of beta glucans, with β-glucanase addition to the mash often used to maintain consistent run off performance on mash filters. A recovery of 100–101% of laboratory extract from a mash filter compared with say 98.5% on an optimised lauter tun can mean a saving in malt of around £150,000 per year at a brewery producing one million hectolitres of wort. There is, however, a debate about how much the extra 3–4% extract is of positive value from a beer flavour and quality perspective. Capital costs of lauter tun systems are claimed to be about 70% of an equivalent mash filter. The maximum size for a single mash filter has been around 11 tonnes of grist (approx 600 hl of high gravity wort) compared with up to 25 tonnes for a single lauter tun, although the 21 tonne Ziemann mash filter is catching up fast. Operating costs for mash filters are also higher. This is mainly due to higher maintenance costs, cleaning costs (cleaning required every 50–60 brews), replacement of filter sheets (every 2,000–3,000 brews) and membranes (every 5,000 brews). Unlike the Meura 2001, the Ziemann TCM has no membranes to maintain or replace.

Wort Boiling As energy costs rise, wort boiling will continue to be an area of increased attention. Modern understanding of wort boiling has enabled manufacturers to look at wort volatile reduction and protein denaturisation/ coagulation as separate processes. The idea of applying a minimum temperature difference between the heating medium and the wort by effectively increasing heating area and inducing two phase liquid/vapour bubbles in the wort means that wort evaporation can be reduced from over 8% to 4 –5%. Different approaches have been made by manufacturers, with some opting for a separate volatile reducing step after wort boiling. Beers produced have similar fermentation characteristics and volatiles as well as reduced DMS levels. Reduced thermal stress on

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the wort also predicts an increase in flavour stability, although results supplied by manufacturers are dif ficult to assess and compare because they are often from different tests and analyses. With flavour stability and beer freshness attracting more focus, relying more on tasting beer and using better understood analysis would be helpful. Reduced evaporation from less and lower heat input also results in improved beer foam. Less fouling of the heating surface also has the benefit that cleaning frequencies can be reduced. The introduction of a natural thermosyphon during boiling is becoming a feature in all modern wort boilers. There is a choice between internal and external wort boiling. The latter is a development of Briggs external wort boiling system and is called ‘Symphony’ (Fig.8) This involves increasing the specific heating surface of the boiler to 0.43m2 /hl which is five times more than for a typical internal heater, and twice as high as a standard external wort boiler. By using this increased area, the steam temperature and pressure can be reduced and a two phase, liquid/vapour driven thermo-syphon is produced. The wort, which is circulated eight to ten times during the boil, is returned to the copper in a tangential manner to reduce foaming and minimise trub break up. This arrangement of external wort boiler and tangential inlet to the copper is easily arranged into a combination copper/whirlpool. Other suppliers have developed ef ficient internal copper heaters. A ‘dynamic’ or ‘low pressure’ boiling technique has been introduced by Huppmann (Fig.9) which involves heating wort under pressure of 150 mbar, equivalent to a boiling temperature of 103°C. When this pressure is reached, it is rapidly reduced to 50mbar and the temperature drops back to 101°C. This takes place at least six times during each boil and the effect produces a flash evaporation with the formation of foam and bubbles within the wort kettle which strips unwanted volatiles and aids coagulation of hot break particles. In order to accommodate the flash evaporation, the copper volume needs to be 30% greater than for a standard system and the wort is circulated 20–30 times per hour. Ziemann offers a similar technology. The internal wort heater

as applied by Steinecker (Stromboli) creates a large heating surface within an internal heater which enables wort volatile removal and precise protein coagulation at low thermal load. The heater has a specially designed two part spreader for the heating and boiling part of the cycle. A natural thermo-syphon via a “ jet pump” above the central tube enables the heat input to be reduced(Fig 10,11) As with the Briggs Symphony system, fouling of the heater is reduced, resulting in a lower cleaning frequency( Fig 12,13) Huppmann introduced an internal heater with a natural thermosyphon called Jetstar in September 2005.

Figure 9:The temperature/pressure chart of “dynamic/low pressure boiling” process – supplied by Huppmann.

FAR LEFT: Figure 10: The “Stromboli ” internal copper heating wort up to boiling temperature. –

Volatile stripping from wort after boiling German manufacturers have developed equipment to improve energy ef ficiency, beer quality and flavour by stripping volatiles after the copper. This allows copper evaporation to be reduced to 3–5%. DMS and precursor reduction takes place after the copper, but before wort cooling. The Steinecker system, called ‘Merlin’ is a vertical cylindrical vessel with a steam heated, coned shaped interior over which a thin film of wort is pumped before it goes the whirlpool (wort evaporation is 1–2%) (Fig.14). Ziemann offers a different approach using a vacuum technique working at approximately 0.4 bar underpressure to strip out volatiles between whirlpool and wort cooler (Fig.15).

LEFT: Figure 11: The “Stromboli ” internal copper heating system in boiling mode including thermosyphon. Diagrams supplied by Steinecker.

FAR LEFT: Figure 12: The tubes of a conventional internal wort heater after 8 brews. LEFT: Figure 13: The tubes of a Stromboli internal wort heater after 80 brews – notice how the less intensive heating regime has reduced fouling considerably. Photos supplied by Steinecker.

Energy saving and wort boiling With UK gas prices reaching a peak of £1.40 per Therm (£0.013/MJ) in November 2005, the requirement to save energy moves from a financial “nice to do” to a definite “must do”. It would be sensible for any brewer to look at retrofitting energy saving equipment whether or not a full brewhouse development is being considered. Brewers should be as focussed on energy usage as they are on malt extracts. Large energy savings are possible, especially if energy recovered from a vapour condenser is used for preheating wort going to the copper. This technique involves installing an energy storage system, which comprises a hot water storage tank and heat exchanger for taking

Figure 14: The inverted heating surface cone of a Merlin boiling/ wort stripping system seen in an exhibition mock up – photo supplied by Steinecker.



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Figure15: A Ziemann vacuum wort “stripping” system positioned after the whirlpool but before wort cooling – photo supplied by Ziemann.

wort from approx 75°C after the wort separator to 95°C+ in the copper (Fig.16).

Trub separation

“It is easy to get carried away with new plant, but a dedicated project team and detailed planning needs to be in place from the beginning. Bringing the new plant on stream is not always as straight forward as first thought and a logical step-wise programme of trials to ensure beer flavour and quality match the specifications is fundamental.”

Table 1 shows the order of magnitude of costs for wort pre-heating and boiling for a one million hectolitre brewery (volume brewed) at both 5% and 10% evaporation as the cost of fuel doubles.

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The whirlpool remains the most popular and simplest method for separation of hot trub from boiled wort. The workings of whirlpools have been studied extensively with many theories and calculations showing the best design. A vessel height to diameter ratio of around 0.5, copper casting time of ten minutes, tangential inlet velocity of 3–4 metre/sec and stand time of 20 minutes normally works effectively. An often overlooked consideration is solids loading. In order to get good trub separation, it is said that hop pellet loading should not exceed 2.0kg/m2. Hop pellets also retain extract, so increasing or decreasing hop pellets and hop extract ratios can make a difference in yield. There are many designs for the run off system, floor shape, and trub removal, all of which are important to consider as long as the basic design gives a good result. Converting hop backs in traditional breweries to effective whirlpools is often easily achieved with minimal expenditure. Combined copper-whirlpools have been successfully installed in recent years, these tend to be a compromise in optimum design, Vessel configuration and the hop grist must be fully considered along with all other criteria. An advantage

Figure 16: Schematic of a brewhouse ‘energy store system’ , with heat recovered by a vapour condenser used to preheat wort on its way to the copper – diagram supplied by Huppmann. of a copper whirlpool is that a vessel to vessel transfer is eliminated, there is less trub particle size reduction, and it allows a faster start up of wort transfer to fermenter. The copper/whirlpool is a natural development from the Briggs Symphony system involving a tangential inlet to the copper and is branded as ‘Symphony Plus’

The author would like to acknowledge the help of the following for supplying information, diagrams and photographs for this article. Briggs of Burton (Paul Dowd), Krones/Steinecker (Peter Gattermayer), Huppmann (Thomas Bühler) and Ziemann Group (Volker Mewes). q

A final word It is easy to get carried away with new plant, but a dedicated project team and detailed planning needs to be in place from the beginning. Bringing the new plant on stream is not always as straight forward as first thought and a logical step-wise programme of trials to ensure beer flavour and quality match the specifications is fundamental. There should also be a comprehensive blending operation in place until all ‘stakeholders’ are satisfied with the result. It is important that the Marketing and Sales functions are included in this process and the success criteria for a successful flavour match is agreed beforehand, so there is no dispute when the time for the final sign off comes. s

q

The author

After a long career with Whitbread and Interbrew, including time as Head Brewer of Boddingtons and Stella Artois Brewmaster, Paul Buttrick has started his own independent consultancy Beer Dimensions. Paul has an MSc in Brewing Science from Birmingham University and is one of only a handful of British brewers to have studied at Weihenstephan (T.U. Munich).

TABLE 1 Operation

Approximate Energy usage MJ/hl

Cost per 1 million hl per Therm brewed with gas cost at £0.65 (£0.00616 per MJ)

Cost per 1 million hl brewed with gas cost at £1.4 per Therm (£0.0133 per MJ)

Wort pre-heating from 75°C to 95°C 5% wort evaporation 10% wort evaporation

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£73,900

£159,200

12 24

£73,900 £147,800

£159,200 £318,400



Meura ad



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FILTRATION

Filtration – the facts A survey of systems and methods “In my early When I first started in the brewing industry, filtration Whitbread days, it was something carried out down in the cellars or was always ‘Process across in the ‘packaging store’. Even in France where I and Packaging’ but worked in my first brewery, it was ‘dans les caves’. when the bigger Today, with take-home beer beginning to outstrip on breweries were built sales, beer with a 12 month shelf life required closer it became part of the brewing area, mainly attention to filtration and stabilisation. With consolidation of breweries and focus on capacity because filtration utilisation and efficiency of packaging lines, beer problems were often quality and filter problems are no longer acceptable. pushed back up‘Right first time’ is the requirement. stream in the brewery. We were brewing lager and see how filter design affects beer had to deal with beta By Paul Buttrick filtration. Beer Dimensions glucans which gummed up the Maximum pressure drop allowed works and yeast that across a filter have been an examiner for the refused to settle to On early 60cm plate and frame IBD Master Brewer examinations the bottom of tall for many years, and questions on filters, the maximum allowable inlet cylindroconical filtration were often poorly pressure was 3 bar, for later versions tanks.” answered and showed a lack of and 100cm frames, this went up to 7 experience and understanding, bar, so the newer filters gave a large potential increase in filter run compared to other areas such as brewhouse and fermentation. This lengths. It is easy to see how one of the easiest and most cost effective may have been due to where responsibilities lie for filtration and ways to increase filtration capacity there were debates about whether it in a small brewery was to replace an old 60cm filter with a more modern was a brewing or packaging The diverse nature of responsibility. In my early 100cm version. kieselguhr as seen under Whitbread days, it was always a microscope. Filter area: ‘Process and Packaging’ but when the bigger breweries were built it The 100 cm plate and frame filter gave the possibility of large filtration became part of the brewing area – mainly because filtration problems areas, so pressure drops were low and filter runs long. However with a were often pushed back up-stream in the brewery. We were brewing lager flow-rates of 2.5–3.5 hl/m2 /h, the and had to deal with beta glucans area needed to be large to get a fast which gummed up the works and flow-rate compared to vessel filters yeast that refused to settle to the designed for 5–10 hl/m2 /h, although bottom of tall cylindroconical tanks.

I

The basics Like all things, the laws of science dictate performance and Darcy from way back in 1856 still shows the way. The table below develops his law and applies it to filtration : Applying this equation, it is easy to

12


flow on vessel filters tend now to be nearer the lower rate. On vessel filters, the filtration area is dictated by the number of candles or screens. Flowrates on kieselguhr -free crossflow filters are slower at 0.5 – 1.0 hl/m2 /h Filter cake thickness: This is dependent on the solids content of the beer and dosing rate of body-feed powder. Breweries which install centrifuges reduce the solids presented to the filter, are able to make large increases in filtration performance and capacity. The ‘sludge capacity’, that is the amount of powder that can be put into a filter will dictate the filter run length and reducing the body-feed dosing rate enables more beer to be filtered. The frames of the larger plate and frame

Flow rate = Permeability factor × Pressure drop × Area of filtration surface Filter bed thickness × Liquid viscosity Pressure Drop = Flow rate × Filter bed thickness × Liquid viscosity Permeability factor × Area of filtration surface

Volume 3 • Issue 12 • December 2007 • www.ibd.org.uk

( P h o t o : P u r e s e p . )

frame filters. At Magor, now part of InBev, long runs of very high quality filtered beer are achieved using high area filters run at slow flow rates with quite low porosity powders. With these regimes it is possible to achieve yeast-free filtrate on a 100ml aerobic plating of beer from the outlet of the filter.

MAIN PICTURE: Four fully automated 600 hl/h Filtrox kieselguhr and PVPP candle filter lines installed in Becks brewery Germany in 2002. ABOVE: A 100 cm plate and frame filter, still used in many UK breweries.

Choice of powders

filters have comparatively more capacity than vessel filters. The standard frame was 40mm deep, and some companies increased this to 50mm to increase filtration run lengths Beer viscosity: I can remember, over 25 years ago, spending many hours in the Samlesbury Brewery brewhouse doing starch tests on wort – with my fellow brewer – the late Bill Barker – we were known as ‘Starchy and Husk ’ after a well know pair of American detectives. Better brewhouse procedures and a malt specification to reduce beta glucans in the wort, sometimes with the aid of added beta glucanase, made sure we were able to filter plenty of lager in the hot summers of the late seventies.

build up than coarser powder. A compromise was needed because the finer the powder used, the better and brighter the filtered beer. It is also important to remember that vessel filters which are run at faster flow rates generally use coarser filter powders to keep the pressure differential down. When all is considered, it is easy to see why some companies continue to use 100cm plate and

The choice of filter powders has not changed much over the years in that kieselguhr (diatomaceous earth) is still the preferred material. No other material gives quite the same filtration performance. Perlites made from volcanic rock are increasingly used for a first precoat, but few use it for second precoat and bodyfeed. The main driver for brewers moving away from kieselguhrs is health and safety, where particularly flux calcined-white powders (heated in the presence of caustic soda) contain high levels of crystalline quartz (crystoballite) which is known to cause serious lung diseases. The white flux calcined powders ( S c h e m a t i c : K r o n e s . )

Schematic of the Steinecker TFS filter. This filter is speci fically designed to give an even powder coating over the whole candle.

Permeability: The pressure differential across a filter bed is determined by the permeability of the filter bed, which is dictated by the size and porosity of the filter powder. Very fine powder produces a quicker pressure



13

FILTRATION

best not to make them too big (say a maximum of a day’s supply) because continual stirring can degrade particles which will block the filter rather than keep the bed open. Also because it is very abrasive, slurry pump design and maintenance is key to operations. It is also important to make sure that the stirrer in the tank is either backed up with a spare or alarmed because powders settle and set like concrete if they are not kept in suspension – digging them out is not fun.

The Pall ‘ Big Bag’ bulk handling system, using 0.5 tonne bags of filter powder at Reissdorf in K öln.

Big Bags

“The Pall ZHF Primus is equipped with ‘Durafi l’ screens of 30 micron size that only requires the equivalent of a working precoat. Other fi lters including some candle fi lters also have 30-micron gaps, although Filtrox have remained with a 70 micron gap which is said to be less prone to blocking and has better cleanability.”

have larger particles and are generally used for the first precoat. Perlites are now used for this purpose in many UK breweries. Perlites are dif ficult to manufacture in fine grades and do not have the absorptive properties of kieselguhrs which give brilliant beers. There are very few breweries who use a complete perlite regime and these use sheet filtration afterwards to give their beer its final brilliance. Many filters using kieselguhr do not use polishing filters, but go straight to packaging which includes either flash or tunnel pasteurisation. Some filter manufacturers have designed their filters to work without a ‘first’ precoat. The Pall ZHF – Primus is equipped with ‘Durafil’ screens of 30- micron size that only requires the equivalent of a working precoat. Other filters including some candle filters also have 30-micron gaps, although Filtrox have remained with a 70- micron gap which is said to be less prone to blocking and has better cleanability.

With filter powders, being classed as hazardous materials, companies have sought to protect their people from the dust. There have been many designs for handling 20kg paper sacks in a special cabinet with bag splitters and vacuum dust removers. Some have been more successful than others and some have been more dust dispersers than offering personal protection. The level of protection tends to go with the amount of powder used, with smaller users still putting powder directly into the dosing tanks, the operator being protected with a face mask specific for kieselguhr dust. Filter powders are only hazardous in powder form, so it is quite common to see powder slurries mixed with water in a separate area from the filter room and then transferred to the dosing tank when needed. Another method is to have a separate area above the filter room with powders sent directly into the dosing tanks below. A little advice from experience – when designing slurry tanks, it is

The KHS Kometronic system RIGHT: Diagram of a KHS Kometronic precoat filter using regenerable cellulose fibres instead of kieselguhr

( D i a g r a m a n d p h o t o : K H S . )

FAR RIGHT: A KHS Kometronic precoat filter using regenerable cellulose fibres on trial with only one chamber in the stack.

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Any reasonable size brewery should be thinking of using bulk powder supply rather than paper sacks. Health and safety issues are greatly reduced and man power in big plants can be redeployed. With approx 10hl filtered per kg of filter aid, a brewery of 500,000 hl will be using 50 tonnes of powder per year; about 100 halftonne ‘big bags’ a year. I don’t know of any brewery currently using tanker delivery and bulk silo storage of filter powders, the main problem here is the availability and cost of bulk powder tankers and the capital cost of a silo system. Even for ‘big bag’ handling, the number of powders used should be kept to a minimum, in most cases a ‘first precoat’, ‘second precoat’ and ‘body feed’ should be enough, and very often the second precoat and body feed is the same powder. Some filter aid suppliers recommend mixing powders, not something I am too keen on – to me it is a bit too much of a ‘black art’ or a ‘three of sand plus one of cement’ approach. The cost of supplying kieselguhr in ‘big bags’ is similar to that of paper sacks. Some quite cost effective powder fluidising and transfer systems have been installed and can be justified on health and safety as well as manpower savings for sack handling, although civil costs can be high. A large brewery


( D i a g r a m a n d p h o t o : N o r i t . )

using 200 tonnes of filter aid per year, would be handling 10,000 × 20kg paper sacks so it must make sense to reduce this to 400 halftonne ‘big bags’. The ‘big bags’ are made from woven polypropylene. They are not re-used in the food industry, but may be collected ‘free of charge’ or for a small fee for use in non-food applications. Robinsons of Stockport use ‘big bag’ supplied by Flexibulk, and Thwaites are about to install a ‘big bag’ powder handling system to be supplied by Mass Measuring Ltd.

Disposal Disposal costs for spent kieselguhr is an increasing part of the total filtration costs. With landfill being carefully controlled, costs will only increase. Soil injection is used by many companies in the UK. In parts of Germany spent kieselguhr is already considered as a ‘chemical waste’ which is extremely expensive to dispose of and more countries will follow suit. KHS are in final stages of developing a filter system called Kometronic incorporating a precoat filter replacing kieselguhr with regenerable cellulose fibres. I know that a number of companies are looking at manufacturing a replacement powder but they are not at the commercial stage yet. I am sure there will be long queues of interested brewers when they eventually come on the market as long as the economics are sound and the material can be used on existing filters.

Regeneration Pall Food and Beverage has developed a kieselguhr regeneration system called Befis which is used in conjunction with their Primus filter. This system works on the principle

Norit BMS. ABOVE: Schematic of a 600 hl/h Norit BMF, showing from left to right: cold store tank, stabilisation dosing, recirc/retentate tank, filter, buffer tank, carbonator, bright beer tank. LEFT: A 600 hl/hr (72 module) Norit BMF installed in a brewery in Belgium. of regenerating and cleaning the spent kieselguhr from a filter with caustic, acid and an enzyme preparation. This material is used as the body feed for subsequent filtrations. A fresh, new precoat is needed on each filter run. Overall kieselguhr savings of 70-80% are possible.

Which filter is best for me? In the UK, plate and frame filters were used extensively until the 1970s. The plates and frames were mostly 60 cm with flow rates limited to 100hl/hr. This gave a typical run length of 1000 hl in ten hours. The introduction of the Seitz Orion 100 cm2 filters enabled a step change in throughputs where flow rates over 320 hl/hr were possible. A maximum 6–7 bar inlet pressure allowed a differential pressure of 5 Bar (75 psi) and gave run lengths of over 4000 hl and with centrifuges and optimisation runs over 24 hours are achieved. The large sludge volume enabled much longer runs and even some 200 cm2 frame filters were introduced. The problem was that the downtime to wash off, clean and sterilise the filters was 4–6 hours and required a lot of manual input. Although attempts were made to automate cleaning of plate and frame filters, they were not successful, so

automated vessel filters were introduced. Candle filters and other screen filters were already in use on the continent. In the 1980s, candle filters and horizontal screen filters were most popular. Candle filters had comparatively small sludge volumes which restricted filter run lengths, they were the answer for breweries who wanted large volumes filtered in a short time. Also, because the vessel volume was large, losses were high because of the water-beer interfaces at the start and end of the run. A problem also associated with the large plate and frame filters. The introduction of large horizontal screen filters was a major step forward. This enabled long filter runs at fast flow rate and because the filter cake sat on a horizontal screen the filters could be emptied using carbon dioxide gas through low level ‘rest elements’ which were not used during the main filtration. The beginning and end of filter runs could be free of beer-water interfaces, so losses were greatly reduced. Because of the horizontal screens, the filtration could be halted – the bed was stable, whereas the bed on a candle would slip off. The same was true during a power interruption. The main manufacturers with the exception of Filtrox concentrated on


“Disposal costs for spent kieselguhr is an increasing part of the total fi ltration costs. With landfi ll being carefully controlled, costs will only increase. Soil injection is used by many companies in the UK. In parts of Germany spent kieselguhr is already considered as a ‘chemical waste’ which is extremely expensive to dispose of and more countries will follow suit.”


15

FILTRATION

( P h o t o : © P a l l C o r p o r a t i o n 2 0 0 7 . )

Membrane modules (each of 12m2) on a Pall Pro fi filter installed at Carlsberg in Fredericia which processes up to 480hl per hour.

horizontal-screen filters. It seemed that the candle filter was becoming outclassed. Horizontal-screen filters had many advantages, but changes to brewing practice and a need for simplicity has seen a come back by the candle filter, with many of the concerns being answered.

“The introduction of large horizontal screen fi lters was a major step forward. This enabled long fi lter runs at fast flow rate and because the fi lter cake sat on a horizontal screen the fi lters could be emptied using carbon dioxide gas through low level ‘ rest elements’ which were not used during the main fi ltration.”

16

Candle filters make a comeback The complexity of moving parts and seals on the screen filters produced engineering headaches for some, so the simplicity and lack of moving parts in the candle filter again became attractive. Filtrox (Synox), KHS (Getra Eco) and Steinecker (TFS) all looked at the more negative aspects of candle filters and came out with innovations, to improve the ef ficiency and running cost. New wedgewire designs replaced the scalloped ring candle which are easier to keep clean and give a more even powder coating. For example, in the Filtrox Synox PF candle filter launched at Brau 2004, an optimised version of the successful Filtrojet filter, the filter area was increased by introducing a 25 mm instead of a 33mm diameter candle. The smaller diameter candle enabled more units to be put into the housing. The overall effect was to allow more filtration area and sludge space and less relative ‘void’ volume which contributed to losses in the form of water-beer interfaces at the beginning and end of a filter run. The increased use of high gravity brewing meant that beer at the beginning of a filter run could be run into a tank at very low gravity (assuming deaerated water is used to charge and pre-coat the filter) which could be compensated for by


running in a precalculated volume of high gravity beer, thereby eliminating losses at start up. Similarly, at the end of the run, the blending water can be shut down early to compensate for weaker beer being run at the end of the run – although care should be taken to ensure proper mixing. The same system could also be applied to a large plate and frame filter and some brewers who installed horizontal screen filters never use the blow down facility. It must also be remembered that when a filter is blown down with CO2, the filter cake contains full gravity (often high gravity) beer, so the losses are not zero as some have claimed. Another development by Steinecker (Krones) is the TFS-Twin Flow System candle filter introduced in 2000. This filter is different in that there is no filtered beer section of the filter vessel. The rough beer comes into the vessel, filtered beer comes out through the candles into a manifold within the body of the filter which feeds directly into the filter outlet pipe. Ten percent of the flow through the filter is recirculated from the bright back to the rough side in order to give an improved distribution of filter aid particularly at the top of the candle. The TFS is also designed to be used without a ‘first’ precoat. So which powder filters are available and who makes them? The main filter suppliers have consolidated over the years, with only Filtrox remaining independent and having the same ownership. Pall bought Seitz-Schenk in 2002, while Steinecker became part of Krones and SEN became part of KHS. Table 1 shows the main manufacturers and


brand name of various powder filters.

Kieselguhr-free filtration The issues associated with powder handling and disposal of spent filter powder have led to companies developing kieselguhr-free systems based on cross flow technology. This technology is extensively used for cider and wine, so what is the situation with beer? Early attempts by APV in the 1980s to filter beer using ceramic membranes were unsuccessful, but at least three major players currently have systems in use in breweries. The 0.7- 1.0 hl/m2 flow rates on cross flow filters are slow compared with powder filters. The principal of cross flow filtration is straight forward with the unfiltered beer circulating across a polymeric 0.45–0.6 micron membrane. A cross-flow rate of approx 1.2 m/s has a pressure which is above the pressure on the filtered beer side of the membrane (this is called the trans-membrane differential pressure). The pressure difference between the rough and bright side of the membrane provides the force to push the beer through the membrane and take out any particles. Because there is a ‘fast’ flow across the membrane perpendicular to the flow through the membrane, there is little build up of solids. There is no ‘dead end’ filter bed to go through as in a conventional filter, so there is no static filter bed build up and hence little pressure build up. There will be some build up of solid material on the membrane which will cause a rise in the trans-membrane pressure, and the process will continue until a pressure difference of about 1.5 bar is reached. The manufacturers of cross-flow filters all use an interim ‘pulsing’ or ‘backwashing’ technique to disturb any solid build up and reduce the trans membrane pressure. A stage is reached when the trans membrane pressure will not reduce, in which case a chemical clean is carried out. If we are looking at the physics of filtration, the same principles apply – crossflow filtration is enhanced by a large surface area, thin filter bed, and slow flow rate/m2, so there is slower pressure build up compared with conventional filtration. The three systems presented by Pall, Norit and Alfa Laval, all use polyethersulphone membranes put together in a series of modules.

FILTRATION

( P h o t o s : A l f a L a v a l . )

Alfa Laval systems. RIGHT: A 300 hl/h Alfafine membrane filter in operation in a brewery in Western Europe since 2005 FAR RIGHT: A 0.7m2 ‘Sartocon’membrane cartridge used on a Alfabright membrane filter.

“Another development by Steinecker (Krones) is the TFS-Twin Flow System candle filter introduced in 2000. This filter is different in that there is no filtered beer section of the filter vessel. The rough beer comes into the vessel, filtered beer comes out through the candles into a manifold within the body of the filter which feeds directly into the filter outlet pipe.”

Norit and Pall use hollow fibre modules and Alfa Laval use a series of cassettes to make up the filter. A large recirculation pump is used to provide the fluid flow across the membrane. Table 2 compares the systems’ features (previous page). Cross-flow membrane filters produce a yeast free filtrate (due to 0.4-0.65 micron pore size) Suppliers have also reported improved hazes in bright beer as well as better flavour and haze stability due to reduced oxygen and iron pick up from filter powders. This is a good start, but only with longer term use and experience will these improvements be substantiated.

The cross-flow players Norit is a Dutch company which specialises in purification technology, including water and other beverages. The BMF-200 beer filter was introduced to the market

at Drinktec 2001, and extensive work has been carried out with Heineken. A filter with the capability of up to 200 hl/h has 24 filtration modules of 9.8m2 filtration area each. The membranes are 0.5 micron PTS (polyethersulphone), each consisting of 2800 × 1.5 mm diameter fibres. In process terms, the filtration flow rate is 0.8hl/m2 /h and the cross flow rate is 1.2 m /s. A system pressure of 3 bar gives a maximum trans membrane pressure of 1.2 bar. The filters have a typical average run length of 20 hours which includes a small number of back flushes, to reduce the trans membrane pressure a nd allow CIP. The chemical based clean using an oxidising agent and membrane cleaner takes 2.5 hrs and is carried out when the membranes become partially blinded. Pall Food and Beverage is a global company, well known to the

Table 1: Main manufactures and brand name of their powder filters Company

Plate and frame

Horizontal screen

Candle

Filtrox KHS Pall/Schenk Krones/Steinecker

Novox Orion Niro -

Filter-o-mat Cosmos Primus Steineker FS 130K

Synox PF Getra Eco Ecoflux Steineker TFS

brewing industry, which specialises in filtration technology. The Profi system was developed in conjunction with GEA Westfalia Separators and a great deal of development work has been carried out with Carlsberg. A filter with the capability of up to 240 hl/h has 20 filtration modules of 12 m2 filtration area each. The membranes are 0.65 micron PTS (polyethersulphone). In process terms, the filtration flow rate is up to 1.0 hl/m2/h. The system is designed in blocks of modules, which are taken out in sequence for cleaning, thus allowing a continuous operation. Because the beer solids are mostly removed by the centrifuge, no retentate buffer tank is required, and the volume of beer involved in beer changes is low. Beer changes and the end of batch operations are carried out by blowing out the system with CO2. Like the Profi system, Alfabright is based on a combination of a centrifuge from Alfa Laval and a membrane system supplied by German filtration specialist Sartorious. A typical system

Table 2 – Comparing available kieselguhr-free filtration systems

Configuration Module size Size/modules etc Membrane Pore size Flow rates Number in use

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Norit Batch or continuous 9.8 m2 Blocks of 24 modules up to max of 72 (600 hl/h) Polyethersulphone 0.5 micron 0.8 hl/m2 19

Pall Alfa Continuous 12 m2 Blocks of 20 modules (up to 240 hl/h per block) Polyethersulphone 0.65 micron /h – 1hl/m2 /h 0.5 11


Laval Continuous 0.7 m2 cassette Up to 432 cassettes (up to 300 hl/h) Polyethersulphone 0.6 micron 2 /h 0.7 hl/m 2

designed for 225 hl/hr based on 302m2 of filtration area (0.75 hl/m2 /hr). The membrane filter is made up of a number of 0.7 m2 ‘Sartocon’ cassettes with a 0.6 micron PES membrane. This design is different from Norit and Pall in that the membrane cassettes have a very narrow distance between membranes – 120 microns, which according to Alfa Laval enables the filter to be run using lower powered, smaller recirculation pumps. The compact design of the cassette is also said to give a more stable membrane and optimium cleaning characteristics which have a positive impact on membrane life. The filter system works continuously, with sections taken out for cleaning every 2-5 hours.

Do you need a centrifuge? There continues to be a debate about whether a centrifuge is required to clean beer before it is filtered on a crossflow filter. Pall and Alfa Laval

recommend using a centrifuge to reduce yeast load on the membranes. Norit argue against the need for a centrifuge because they believe a separator does not remove the small particles (< 0.5 micron) which are responsible for blocking pores on the filter. The Norit system includes a ‘retentate/recirculation’ tank where the solids removed from the beer are collected. In the Alfabright and Profi systems, the solids are mostly removed by the upstream centrifuge. Centrifuges are very costly to buy and operate and not having to include one in a new filtration scheme gives a big financial advantage to the Norit system. Like all new technologies, the debate will continue and only plant performance and experience will dictate whether centrifugation is necessary. Another unknown is the robustness and reliability of the membranes and until better

“ Another unknown is the robustness and reliability of the membranes and until better guarantees and replacement costs are substantiated, many brewers will not take the kieselguhr-free route.”

guarantees and replacement costs are substantiated, many brewers will not take the kieselguhr -free route. However there have been huge strides in membrane technology and it is widely used in other industries, so the time will come when brewers feel more confident to embrace the powder-free route. For companies with a longer term view of capital investment on strategic items, overall project lifetime costs may well be better on cross-flow than current powder systems, when everything including energy and environmental cost is considered. In the mean time, only continued development and experience will confirm whether crossflow is the future for beer filtration. s

q Acknowledgements

The author would like to thank those companies who supplied information and images in the preparation of this article

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Glossary of Brewing and Packaging Terms:Absorption Where chemical compounds are removed from a liquid by being retained on a solid surface – examples – proteins adsorbed by silica gel or organic compounds adsorbed by activated carbon. ABV Measure of alcohol content by volume - expressed as % alcohol by volume Acetaldehyde A flavour compound produced during fermentation – tastes of “raw apple skins” Acetic Acid Acid (Vinegar) produced by bacteria under aerobic conditions. Usually indicates the presence of Beer spoilage organisms. Acetobacter An aerobic bacteria produces an off flavour of acetic acid and turbidity in beer. Adjunct An addition source of extract (starch or sugar) which is not malted barley. Aeration Cool wort is aerated/oxygenated to provide oxygen for yeast growth. Alcohol Waste product produced by yeast during fermentation to be consumed and enjoyed by the customer. Ale Originally a term for un-hopped beer. Now used to describe most darker beers (top fermented) with ale yeast. (common in UK and Belgium) Alpha acid A natural hop resin which is isomerised to iso alpha acid during wort boiling and to give beer its bitterness. Amber Malt A medium brown grade of malt made by higher temperatures during the later stages of kilning. It provides beer with a crisp biscuit taste and aroma. Amino Acids Proteins are made up of long chains of amino acids. Amino acids are produced by the enzymic breakdown of proteins during malting & mashing. They are required as essential nutrients for yeast growth.

Amylase A general name for the enzymes that breaks down starch. Alpha amylase is an endo enzymes which liquefies starch by breaking long starch chains in smaller polysaccharides. Beta amylase is an exo enzyme which is a saccharifying enzyme by breaking pairs of sugars off from the non reducing end of starch and polysaccharide molecules to form maltose. •

•

Astringency A mouth drying/bitter harsh after tastes which are often produced by polyphenols derived from malt and hops. Attemperation A term used for controlling or cooling beer during fermentation Attenuation Limit A measure of the fermentability of wort tested by fermenting with an excess of yeast. It represents the amount of non-fermentable carbohydrates left in beer. Auxiliary finings Liquid finings made from alginate or silicate which helps to settle protein. It usually works best when added sequentially in combination with isinglass finings. Bacteria Small living organisms which lives by breaking down organic matter such as beer. Specific bacterial species infect wort and beer producing off flavours and turbidity. Barley A cereal a member of the grass family grows in temperate regions of the world. Barley is the most common cereal used to produce malt for beer. It has a thick husk which makes it robust in the malting process, and the husk forms a filter bed during mash separation. Barrel A traditional volume for measuring beer. The UK standard barrel contains 36 gallons of beer. Barrels are still used in measuring capacity but few full barrel containers (36 gallon casks) are still in use. Beer A drink produced by the fermentation of sugars derived from malted barley flavoured with hops Beta Glucan A gummy material which comes from barley cell walls. It is largely degraded during malting, but if present in wort or beer can cause filtration problems.

Bicarbonate An soluble salt which produces “temporary hardness” reducing the fall in acidity (pH), and generally has to be reduced in waters used for brewing. Bicarbonates decompose to form carbonates which form a scale on heating surfaces. Bitterness A taste associated usually associate with iso-alpha acids in beer (isomerised alpha acids from hop). Some traditional ales were bitter and hence the term is also used to describe types of ales with a high hop rate Black Malt Is made from pale malt which is then roasted in a malt drum. It gives beer a black colour and strong burnt flavour. Blending The mixing of beers to achieve quality or in high gravity beer. Bloom A deposit on bottles often due to carbonates in the water BOD BOD is the measure of the amount of oxygen in milligrams per litre of sample which is utilised over a five day period in the biological oxidation of the sample after suitable dilution. It is often written as BOD5 to reflect the 5 day duration of the test. BOD is an indication of the amount of oxygen which will be taken up from a watercourse due to microbial growth on discharge of the sample. Body Feed Filter powder added to the beer flow in line to improve solids loading and to aid filtration Boiling Wort A stage in the brewhouse process when clarified wort from mash separation is boiled to stabilise the wort, remove unwanted aromas and isomerise the alpha acids from the hops. Bottom Fermentation For a successful fermentation yeast has to be in suspension in the wort. Once the fermentation is complete (the final gravity is achieved) lager strains of yeast clump together or flocculate and sink and settle to the bottom of the fermentation vessel. Break This is the term given to protein/polpeptide molecules which for insoluble solids and settle to the bottom of the vessel. Hot Break or trub forms after wort boiling and also contains hop debris. Cold break forms in cooled wort and can often be collected at the bottom of fermentation vesses.

Bright Beer Beer that has been through filter to remove visible haze and most microorganisms in preparation for packaging. Brown Malt A roasted malt which produces a reddy brown colour and gives beer a rich malty, biscuit flavour. Buffer Tank Is any vessel used as a break between two processes eg between maturation vessel and filter is the filter inlet buffer tank. Calcium It is an important metal ion which is added to mash and has a number of beneficial effects in brewing – particularly in help to drop pH which is necessary for many enzyme activities and yeast growth and flocculation. Calorie A measure of energy. Beer has quite a low level of calories typically around 450 kcal or 1870 kJ per litre. Most of the calories in beer come from alcohol, hence the higher the % alacohol the greater the number of calories. Candle Filter Is a design of primary filter where rods or candles are used to support the filter aid. Caramel Dark burnt sugar which is usually added to beer to adjust colour. Carapils A continental darker malt used to add some colour but principally mouthfeel and texture to lagers. Carbohydrate Complex sugars which are generally found as a energy store in plants such as barley endosperm. Carbon Dioxide A gas which is produced during fermentation, under pressure it combines with water to form carbonic acid. A level of carbon dioxide is present in all beer and it proves beer with its “ fizz”. Carbonate A salt which dissolved in hot water but tends to precipitate in cold water producing a hard coat of scale or beer stone. Cask Conditioned Beer Beer that that remains unfiltered at the end of fermentation is conditioned and matured in a cask. It is usually clarified in trade through the addition of isinglass finings.

Centrifuge Equipment for clarifying beer by spinning it at high velocity separating the solids from the liquid. It is able to remove most yeast from beer in a matter of seconds.

Cereal Cooker A separate vessel used to prepare cereal adjuncts by heating (boiling) to gelatinise the starch (used for adjuncts which have a gelatinisation temperature greater than malt). Colloidal stability Haze causing colloids such as proteins and tannin must be removed from beer. This is done through good brewing practice and chilling the beer prior to filtration For beers which require a long shelf life adsorption stabilization agents which are insoluble in beer are used to reduce the haze forming compounds (principally protein and ployphenol) prior to filtration .

Chloride Is a anion often added as Calcium Chloride and gives beer smooth full palate. This is characteristic of many lagers and mild beers. Chocolate malt A dark roast malt used in dark beers and stouts CIP Cleaning in Place Automated system of vessel and line cleaning – Cleaning In Place. Clarification Separating suspended solids from wort or beer. Cling Where beer foam adherers to a glass Coagulation The attraction of solid (often protein) to each other resulting in the formation of solids during boiling COD A chemical method of measuring BOD used to look at the biological load in effluent. Collagen A protein also known as finings – usually derived from Isinglass and is added to clarify beer. Conditioning (Maturation) Is the process during which the raw flavours of fermentation are removed and

CO2 is formed which helps to carbonate the beer. Conversion A term used to describe the breakdown of starch into sugar in the brewhouse. Coolant A liquid used to cool beer or wort Copper (Kettle) A vessel used for boiling wort Copper (kettle) finings Material (usually Irish Moss) added to the copper kettle to aid coagulation and clarification of trub. COSHH Regulations for handling hazardous material Crown Cork A cap for sealing bottles Crystal Malt A malt prepared by stewing on the kiln to produce crystallised sugars. It adds colour and flavour to beer. Customs & Excise The regulatory body for collection of Excise duty. De-palletiser Equipment for offloading bottles, cans or kegs delivered on pallets Deaerated Liquor/Water Water where the dissolved oxygen stripped out or removed Decoction Mashing A method of heating the mash where part is taken out into a separate cooker and boiled before being added back to the mash to raise the temperature by a required amount. Detergent A liquid which is capable of dissolving soil (dirt) used for vessel and line cleaning. Dextrin Unfermentable sugar often left in mash because of the incomplete breakdown of amylopectin which has branched chains.

Diacetyl Diacetyl is a by-product of the metabolism of yeast during the fermentation process. The majority is removed by well controlled secondary fermentation. Small amounts of diacetyl in beer cause an unpleasant odour and taste of “butterscotch”. Diastase General name given to enzymes that break down starch. In Brewing these are mainly alpha and beta amylase. Diatomaceous Earth A powder made up of the mined skeletal remains of diatoms which is used as a filter aid in beer filtration. Dissolved Oxygen A measure of oxygen dissolved in beer DMS Dimethyl Sulphide A flavour compound derived from malt which gives a “sweetcorn” character. Dormancy A natural delay in the onset of barley germination Draught Beer Beer served from large containers (casks or kegs) Dry Hopping The process of adding hops to casks beer to provide hop aroma EBU (also called IBU) A measure of beer bitterness (based on the European Brewery Convention) Effluent Process waste stream which leaves the brewery – either for in house treatment or to municipal treatment (Sewage Works) Endosperm The starch food store of the barley corn which provides the extract for brewing. Esters A group of flavour compounds found in beer – generally produced during fermentation through the combination of acids and alcohols. They give beer strong fruity aromas and taste. Ethanol (ethyl alcohol) The main alcohol produced by fermentation. This is an important property which determines the “strength” of the beer.

Extract A measure of sugar potential or yield from the raw materials. Most extract comes from the malted barley but additional extract can be added in the form of adjuncts. False Bottom The slotted base of a mash or lauter tun Fermentation The process when yeast metabolises simple sugars to produce alcohol abd carbon dioxide (and some heat) under anaerobic conditions. Filtration The process of using a porous surface medium to hold back solids thus separating solids from the liquid beer. Finings A changed material added either as liquids or solids and used aggregate suspended particles in the beer to aid clarification. (eg Kettle finings, auxiliary finings and isinglass finings) Firkin A container or cask which holds 9 gallons capacity Flash Pasteurisation Pasteurisation (heating) through a plate heat exchanger to kill/reduce live micro-organisms Flavour Stability The extent to which a beer tastes as good on ageing as it did fresh when packaged. Foam The stable head/bubbles on beer formed by protein coating bubbles of carbon dioxide gas. Beer is the only beverage with a stable foam. Fob Excessive or uncontrolled foam Forcing Test A procedure for heating and holding samples at a higher temperature to check for flavour or microbiological stability. Gelatinisation The initial process in mashing when the starch has to unwind from its crystalline structure in order to make it accessible to enzyme degradation.

German Purity Laws The German Beer Purity Law or Reinheitsgebot is the world's oldest food law purity law. It was decreed by Duke Wilhelm IV of Bavaria in 1516. The decree states that only barley, hops and water may be used in the brewing of beer. Yeast was added subsequently but had not been identified as essential for fermentation in 1516 and natural "wild" yeast produced the necessary fermentation. Germination The growth or sprouting of the grain – second stage in the malting process. Glucose A simple sugar which forms the base unit of starch Gram Stain A procedure for differentiating between different species of bacteria. It relies on the structure of the bacterial cell wall. Green Beer Immature beer at the end of fermentation before it has been matured. Green Malt Germinated barley before it is kilned Grist A term for milled crushed malt ready for mashing. Gypsum Calcium Sulphate present in some brewing water such as Burton on Trent, and often added as a salt to water or mash as part of water treatment. It contributes to permanent hardness bringing out the dryer, bitter flavours in a beer. Haze Beer should be clear. Haziness or cloudiness in beer occurs because of suspended material which can be organic chemicals – colloidal haze or microorganisms – biological haze. Head Retention A measure of the foam stability of the head on beer (common methods used to assess foam are direct observation or instruments like Rudin & Nibem ) Headspace The volume of gas above the beer in a bottle. Part of this gas can be air or oxygen which contributes to beer staling. Hectolitre The usually volume of measurement in most breweries One hectolitre = 100 litres

High Gravity Brewing Many beers are brewed with an original gravity (OG) higher than sales producing beers with higher levels of ethanol. After processing the beer is dilutee to sales gravity using de aerated water, usually post filtration. Hogshead Is an oversize barrel or cask which holds 54 gallons. Few if any are still in use. Hop Back A vessel used for hot wort clarification after wort boiling when using whole (cone) hops which are used as the filter medium. Hop Extract An extract of the bitter and some times the aroma components of hops Hop Oil An extract of the hop aroma compounds Hops A perennial plant which produces hop cones in the female plant which contain bitter substances (alpha acids) and aromas and used to ‘bitter’ and add aroma/flavour to beer Horizontal Leaf Filter A beer filter with horizontal screens on which the filter aid is deposited and then used to filter rough beer.

Ice Beer Beer where the contents is partially frozen – ice is formed – to produce a smother flavour. Infusion A term for single temperature mashing traditionally used in mash tuns Ion Exchange A method of treating water to remove un wanted mineral ions. Isinglass Collagen, the active ingredient in finings made from the swim of selected fish Isohumulone Isomerised hop bitterness compounds iso-alpha acid is also called iso humulone. This is derived from alpha acids or humulone Jetting A small jet of hot water is often fired into a bottle after filling to cause it to froth up so that it is capped on foam to reduce dissolved oxygen.

Keg A metal container for holding beer (usually 11 gallon 50 litre or 22 gallon 100 litre – some are as large as 36 gallons or a UK barrel) Kettle / Copper The name given to the vessel used for boiling wort Keystone A bung which holds the tap in a cask of beer Kieselguhr A filter aid made up skeletal diatoms used in beer filtration

Kilderkin (Kil) A cask holding 18 gallons (half a barrel) Kilning The last stage in malting where the moisture is driven off to produce a stable malt with increase colour and flavour compounds. Krausening The process of enhancing warm maturation (secondary fermentation) by adding fermenting wort from a subsequent brew to the maturation tank of a beer on completion of primary fermentation. Labeller Equipment for labelling bottles Lacing The effect of foam clinging to a glass of beer as it empties Lactic Acid An acid produced by certain bacteria (lactic bacteria) which can effect the beer flavour Lactobacillus Species of lactic acid bacteria which produce acid and turbidity Lag Phase The stage at the start of a fermentation before the yeast start to replicate (bud) Lager Beer brewed using traditional ‘Continental’ methods (usually typified by using bottom cropping yeast and pale lager malt) Lagering The process of maturing lager beer traditionally the beer was stored for several months at zero or below.

Lautering The process of wort separation using a lauter tun which is a filter vessel with a false slotted bottom. Legionella A hazardous bacteria found in warm and cooling water assoacited with cooling towers and tunnel pasteurisers Lipids Fatty material in raw materials such as malt and produced by yeast when aerated at the start of a fermentation. Liquor A term used in the UK and Ireland for brewing water Losses The difference between the volume and strength of what you started with in comparison to the volumes and strength at the start and finish of a process Lupulin gland The resin gland of the hop cone which hold the acids and oils used in brewing. Maize Grits Broken embryo of Maize milled which has to be cooked in a cereal cooker before being mixed with the malt mash. Malting Variety A type of barley suitable for malting Maltose The principle sugar produced by conversion of starch to wort during mashing. Mash The process of mixing grist (ground malt) and water at the necessary temperature and mash thickness. Maturation Post fermentation processing – during warm maturation flavour development occurs – cold maturation is required for colloidal stabilisation. Micro-organism A very small living organism usually only visible under a microscope. Modification A term to describe the change of barley into malt and the extent to which the cell walls in the endosperm have been digested.

Nitrates Chemical salts found in water often indicating contamination. There are maximum permitted levels and many breweries use water treatment to remove nitrates. Nitrogen gas Inert gas used to eliminate air or to give beer a stable head (nitrogen is sometimes incorrectly used to describe proteins, polypeptides and amino acids, found in beer) Non Biological Shelf Life The time that beer remains free of non biological haze (protein/polyphenol complex chill haze)

OG Original Gravity. The specific gravity or density of wort before fermentation has started Oxygen Gas required by living organisms. It is added to stimulate yeast growth before fermentation starts. If present in finished beer it will cause beer staleness Palletiser Equipment for loading packs onto pallets Pasteurisation Procedure for heating beer to sterilise it Pasteurisation Unit A measure of the degree of pasteurisation (1 PU is the energy given by holding beer at 60 0C for 1 minute) Pediococcus An anaerobic of bacteria infecting beer Perlite A type of filter aid made from volcanic dust pH A measure of the acidity/alkalinity of a liquid (measures -log10 H+ ions) Pils/Pilsner A style of beer (lager) originally from Pilsen in the Czech Republic Pin A cask holding 4.5 gallons Pitching The process of adding yeast to wort to start fermentation

Plate and Frame Filter A vertical chamber used with filter aid to filter green beer Plate Heat Exchanger Counter current flow through a of plates for cooling or heating liquids flowing through Plato Unit of measurement of specific gravity expressed in percent based on a sucrose solution Polish Filtration Fine filtration of beer usually after a primary green beer filter. Polyclar PVPP A beer stabilising agent which adsorbs polyphenols in beer. Pre-coat Procedure for coating a filter with filter aid Primings Sugar added to fermented beer to fuel a secondary fermentation or sweeten the beer. Protein Complex organic compounds made of nitrogen, carbon and hydrogen important in malt quality and break down to provide compounds for beer foam, haze pre-coursers and yeast nutrition. Proteolysis The process of protein breakdown during mashing Pure Culture A procedure for producing high quality pitching yeast Racking The process of filling casks/kegs with beer Recovered Beer Beer recovered from yeast after fermentation Refrigeration The process of cooling beer down to lower temperature (usually below 0 0C) Respiration The process of oxygen use by living matter

Roast Barley An adjunct used in some dark beers and stouts to produce a very dark black colour and roast bitter taste. Rough or Primary Filtration Used to remove most of the particles – all yeast, most bacteria and settled haze top produce beer from green beer. Saccharification The process during mashing when starch is broken down into simple sugars principally through the activity of beta amylase enzyme Saccharometer An instrument for measuring specific gravity (see hydrometer) Saccharomyces Cerevisiae Yeast used in ale fermentation Saccharomyces Uvarum Yeast used in lager fermentation (sometime Saccharomyces Carlsbergensis) Secondary Fermentation A fermentation which occurs after the principle fermentation is complete usually at a lower temperature to improve flavour or increase carbonation. carbonation. Shelf Life The time during which a beer retains its marketable quality quality in terms of flavour and haze stability. Shive A bung that fits into the top of a cask Silica Hydrogel A material for stabilising beer it adsorbs protein Skimming Removal of top cropping yeast after fermentation particularly for ale brewing where the yeast is harvested from the top of the vessel. Sparge Water used to wash out extract from the mash after strong wort run off during mash separation. Spear The tube in a keg used for filling and emptying the keg Specific Gravity A measure of the relative density of a liquid

Spent Grain The brewery co-product which remains after all the wort is extracted and is used for cattle feed. Spray Ball Equipment fitted to a tank for spraying water and detergent during cleaning Stabilisation The process of processing beer to retain quality Staling The process whereby beer loses its fresh flavour usually due to oxidation Starch The carbohydrate food source of plants Starch Granules Starch is held as granules in the barley endosperm Steeping First step during malting which involves adding water to grain to start germination Sterilant Material for killing micro-organisms Sterile Filtration Fine filtration designed to remove micro-organisms micro-organisms Sucrose A simple sugar broken down by yeast outside the cell and used to fuel fermentation. Sulphate A salt dissolved in water often added to bitter beers as permanent hardness Sunstruck Flavour The ‘skunky’ flavour created when hopped beer is subjected to sunlight or UV light Tannin A substance in barley or other plants which affects beer stability (also called polyphenols) Top Fermentation Fermentation A fermentation where the yeast floats to the surface on completion of fermentation

Trub Solids protein and hop debris created when wort is boiled and separated in a whirlpool or hop back.

Tunnel Pasteuriser A chamber where hot water is sprayed on packaged small pack beers (bottles & cans) to heat them to kill any micro-organisms micro-organisms by pasteurisation. Turbidity A term for the cloudiness of beer Vertical Leaf Filter A type of beer filter Viability A measure of the number of live yeast cells usually done by staining Vitamins Substances essential for healthy yeast growth Water Softening A process for removing water hardness for boiler feed, CIP, and bottle washer. Brewing water may be softened to remove temporary hardness or have more extensive treatment. t reatment. Whirlpool Equipment for clarifying hot wort which is not bittered with whole hops after boiling Widget A smallpack insert for creating foam usually nitrogen gas Wild Yeast A yeast strain different from that approved approved for pitching pitching the beer. Many wild yeast strains affect flavour flavour and beer stability. Wort Extract of malt produced in the brewhouse before fermentation Yeast A single celled fungus - micro-organism micro-organi sm used to ferment wort Yeast Count A measure of the number of yeast cells in a sample

MATCHING BEERS

MATCHING BEERS

Palate matching A brewer’s answer to ‘provenance’? ‘Provenance’ is a word that has been used by beer aficionados when breweries are closed or famous brands moved. Palate matching has been successfully achieved by some, some have failed. Paul Buttrick shares some thoughts and considerable experience on this topical subject. By Paul Buttrick Beer Dimensions

I

n the past few years many brands – Draught Bass, Youngs, Old Specked Hen, Gales, Boddingtons and most recently Courage have been moved from their original brewery to other sites. Some have moved more than once. The word ‘provenance’ has been used to justify – or not – whether a beer can move home without changing its taste and character. What were the provenance issues, say in the case of Draught Bass, when this beer was moved from the large, modern, mostly lager-brewing Coors plant in Burton, down the road to the smaller and more traditional Marstons brewery? It is not only ales where the debate is taking place, premium lagers such as Stella Artois, Kronenbourg, and A-B’s Budweiser have all come under the spotlight for brewing beer away from the ‘home’ brewery. With constant change and consolidation in the industry, there is a need to manage such brand transfers effectively. It is not just major brewers who are closing breweries or moving location, small and medium sized companies are also setting themselves up for the future whilst at the same time improving quality and cost. In order to make the change, a handful of people, brewers and possibly sales and marketing get together and agree a plan. A number of trial brews are carried out and the group reconvene to taste the ‘test’ (trial), against the ‘key’ (reference) beer. The expectation from the trade is that the beers will taste exactly the same, because brewers have told them that they can achieve a match. The brewers think they can match the beers, but sometimes it’s not always as straight forward as first thought. A consensus is reached and the beer goes into the trade, where the ‘its not the same as it used to be’ brigade will make their voices heard in all the wrong places – such as the Chairman’s ear when he’s going round his pubs.

What can realistically be expected? In my experience, there are ways to manage changes in production location or plant, which take much of the stress and emotion out of the process. The first is for brewers to manage the expectations of their sales and marketing colleagues, the second is to have objective criteria, where both parties can agree that the matching process has been successfully completed. Whatever reason a beer company is moving a brand, a similar strategy should apply. In each case, customers will worry that ‘their’ beer might change – it is strange, but why is change so often perceived as negative? Companies do not intentionally move brands to make poorer beer, on the contrary, the reason for many investments is an improvement in quality. Brewer’s have a dilemma; matching beers is a skilled job, people want to know it can be done successfully in a reasonable timescale, but it is not an exact science. I suppose brewers would like people to see it as ‘a triumph of the brewer’s art’, but for themselves they would prefer a process with minimal risk!

How close a match is required? I have been involved in many matching processes, some sadly involving brewery closures, but others driven by expansion, logistics and marketing requirements. The first question for any brewer to ask sales and marketing is what they expect from a brand transfer. There are only really two answers, an ‘exact match’ or what I call a ‘commercial’ match. An ‘exact’ or perfect match means the beer will be identical to the original in every way. This type of match is usually required when a high profile brand is moved to another site. A ‘commercial’ match may be agreed for smaller brands of lower volume, where the beer should have a similar taste and character as the original, but need not be identical. It can be quite difficult to get brand owners to accept anything but an ‘exact match’ but there has to be some realisation that striving for perfection can take a lot of time and resources. In some cases where a ‘commercial match’ has been agreed, the new beer has been preferred to the original, and I think this is a good way for brand owners to feel comfortable with agreeing what they may see as a reduced status for their beer. Matching cask beers can be more difficult because of the changing flavour of cask beers during their shelf life. An ‘exact match’ can therefore be difficult to achieve, and the term ‘fully matched’ has been offered as a better description. The basic character of a cask beer at various ages should be similar, so a good match should be possible.


Start Early I would advise the process to start early, this can be difficult in sensitive brand moves perhaps involving a brewery closure, but it’s no fun being up against a tight timetable which cannot change, when the beers are not matched properly. The perceived easiest way to move a brand, is to brew it in exactly the same way as the original. This means the plant, raw materials and processes used are identical. Malt and hops are quite easy to manage, but what about the yeast? The discussion about using the original yeast or a different one already in use at the new brewery is always a lively one. Having had this discussion a few times, I come to the conclusion that there is no right answer. What must be taken into consideration is the flavour produced by the yeast in the original beer and the flavour produced by an alternative yeast in the new brewery. An ‘exact’ match can only be achieved if the original yeast strain is used, but a very good ‘commercial match’ is often attainable using a different strain. From a process control, continuity and capital investment perspective using a yeast already in use in the new brewery will normally be preferred. In some cases this is a more sensible option than trying to introduce a new strain and process into a new environment. My advice would be – if time permits, do a couple of trial brews early on and make an educated decision on whether using a different yeast is likely to produce a good match. If time is tight, there is really no other option but to use t he original yeast strain unless a ‘commercial match’ is acceptable. In the matching processes I have been involved with, all the major brand moves have involved retaining the original yeast strain. Even then, considerable skill and invention was required to get the required result, especially when beer was moved from conical fermenters to squares and vice versa. It is not just taste that consumers will notice, I have successfully matched beers for flavour, but have run into trouble because the head of the beer was not as it was – this can be a particular problem north of Watford Gap! How do we go about setting and agreeing criteria for a palate matching exercise? An aim must be for any criteria to be objective and give an unequivocal result. This means that the brewery must have objective tasting schemes in place, or should consider introducing them. Depending on resources, there are a number of techniques available to large and smaller companies. Larger companies can afford more sophisticated and statistically accurate techniques, but smaller companies can have quite simple systems that give very objective results, that are far more beneficial than what I

Volume 3 • Issue 3 • March 2007 • www.ibd.org.uk

27

MATCHING BEERS

call ‘ad hoc’ individual judgements.

The sophisticated panel Many years ago, brewers agreed on a common terminology for beer flavour terms. There are 122 of these which have been formed into what is known as the beer flavour wheel. These flavour terms have been cleverly formed into a wheel with simple descriptors as well as more detailed descriptions, which can be used for flavour recognition and training. The ‘flavour wheel’ adorns the walls and tasting tables of many breweries. Many brewing companies have sophisticated well-trained tasting panels based on the flavour-wheel characters. Beers are tasted – sometimes against as many as 2030 flavours and an intensity score is given to each flavour. Scores can range from 0 (absent) to 10 (extreme) with full scales ranging from 0–5 to 0–10 depending on the brewery. The results are plotted on a graph, with the average scores of the original beer plotted as a comparison (Fig 1). Statistical analysis of t he results can indicate where key differences are and if a beer is ‘true to profile’ This is the most objective method for analysing beer flavour, and goes into a lot of detail, but it does rely

Fig 1: A global lager showing one brand at three breweries in different countries. heavily on expert tasters and is often carried out away from where the action is. Only breweries with ample sophisticated resources can use these techniques.

The use of experts There are organisations and companies that specifically help companies set up t raining systems and train staff. FlavorActiV is probably the best known, and after ten years is

a world leading supplier of tasting systems to over 800 breweries in more than 160 countries worldwide. Originally only the larger companies were involved, but more smaller companies are now taking a more professional approach to maintaining the flavour of their beer. FlavorActiV’s philosophy is based on training people from all areas of a beer company to recognise beer flavours – both good, not so good, and flavours that should

Fig 2: A typical brand profile produced by FlavorActiV. A narrative describes the main brand attributes, it shows the beer descriptors that are present, those which should be absent. A 12-parameter spider diagram is supported by an ‘origins’plot which details the contributions from grain, yeast and hops. Each origin is split further into specific flavour characteristics altogether giving a very comprehensive finger print for the brand.

28



Lovely Ale Profiles FLAVOUR DESCRIPTION

Best

Special

B it te r

Bi tte r

Ale

Body / Fullness

3

4

2.5

Alcohol

3

3.5

2.5

Fruity/Estery

3

4

2.5

Hoppy/Floral

2.5

3.5

2.5

3

4

3

1.5

1.5

3.5

Sweet

2

2 .5

3.5

Bitter

3

4

2

Condition

3

3

3

Malty Burnt /Roast

Dark

Flavour intensity scores

0 1 2 3 4 5

no taste very slight s li h t evident strong very strong

Fig 3 above: The key brand attributes for the Lovely ale range in tabular and spider diagram formats. Fig 4 below right: A completed trueness to type form for Lovely Bitter in cask showing there is a way to go before matching is complete. not be in a beer. The company also supply flavour ‘spikes’ in the form of capsules which are specifically made to be used in taste training and brand comparisons. There are currently about 40 flavours available, which are constantly being added to. BRi is another organisation which is often used by companies for flavour analysis and training. These services, sit alongside its other activities which include brewing research, information services, and consultancy services to member companies and other customers.

TRUENESS TO TYPE ASSESSMENT

Cask Lovely Special Bitter Tasted by DATE TASTED WHERE TASTED APPEARANCE

A Taster CODE PACK

4/1/07 Lovely Brewery

On freshly poured beer, assess and add totals for clarity,head/foam and lacing/cling Score 3 2 1 0

CLARITY

Brill

Clear

Hazy

Cloudy

Thin

Poor

Fair

None

3

Triangular taste test This is the classic method to assess whether tasters can tell the difference between two beers. A number of tasters are asked to pick out a different beer from three glasses, two contain the same beer, and the third a different one. Statistical analysis is used to say whether there is a difference between the two beers. Brewers use a 1*, 2* and 3* difference which relates to a 5%, 1% and 0.1% probability of the result being due to random variation. For this test 7 or 8 tasters may be used, but greater than 15 is ideal. The test can also go on to ascertain why the beers are different and which is preferred. However, as only a small sip is taken, results must be guarded and only used in conjunction with tests involving larger volumes. These tests do not require any special training and can be undertaken by people other than the breweries’ trained tasters. Trueness to Type In this test, beer is tasted against an agreed brand profile. Each brand has a basic description and a list of flavour characteristics with a known intensity. There can be a list of flavours but from experience, it is easier to introduce if there are only about ten of the more easily recognised flavours. The process

TOTAL

7

Clarity, head,cling =

HEAD/FOAM

V.good

Good

LACING/CLING

V.good

Good

2 2

Is there a difference?

2/28/07 9 gal cask

Very good = 7- 9 Good = 5 - 6 Fai r = 4

U nac ce pt abl e = <4

A - Standard Flavours Please taste the beer & score the following flavours. Put a mark in the appropriate column. If you thing the beer is a little too bitter, mark the ’1 - A little too much column’ If you think the beer is ’just right’ for bitterness, mark the ’0 - just right column’

Less Intense

Weighting Description

More intense

Standard

-3

-2

-1

0

-1

-2

-3

Much

Clearly

A little

JUST

A little

Clearly

Much

too little

too little

too little

RIGHT

too much

too much

too much

x

Body / Fullness Alcohol Fruity/Estery Hoppy/Floral Malty Burnt /Roast Sweet Bitter Condition

-1

x x

-2

x x x x

-1 -1

x x

-5 B - ’Off’ and non-standard flavours OFF/other flavours you have noticed that you think changes the overall beer flavour - these are to be deducted from the score These flavours are normally something extra to the flavour of the beer and must score 1 to 5 according to intensity

Slightly sulphury nose TOTAL B - ’Off’ flavours & non-standard flavours

-1

HOW TO WORK OUT THE % TRUENESS TO TYPE 3. LOOK UP THE SCORE ON THE ATTACHED LIST TO GET THE % TTT SCORE TOTAL OF A and B TRUENESS TO TYPE % TOTAL OF A and B TRUENESS TO TYPE %

0 100 -7 74

-1 96 -8 70

-2 92 -9 66

-3 89 -10 63

-4 85 -11 59

-6 78%

= =

1. ADD UP THE TOTAL STANDARD FLAVOURS (A) and TOTAL OFF FLAVOURS (B)

-5 81 -12 55

-6 78

A score of 80% is considered as True to Type,a score of > 85% is considered a very good example of this brand



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MATCHING BEERS

OVERALL OPINION A score of 6 and over is acceptable, A score of 5 is borderline A score of < 5 is not acceptable Score 10 9 8 7 6 5 4 3 2 1

Description - how much do I like this beer ? The best beer An excellent beer A very good beer A good beer Satisfactory beer Acceptable Poor Not good - some "off" flavours Very poor Undrinkable

The best beer I’ve ever tasted An excellent beer A very good beer A good beer - typical of the style Some minor defects A few noticeable defects A poor example of this beer - but style is recognisable Some significant "off" flavours - style just recognisable Very poor - style not recognisable Very poor/undrinkable

Fig 5: Scoring guidance for a simple numerical beer assessment. involves comparing a beer with the standard profile and saying whether it has more or less of each attribute. Although a ‘brewing scientist ’ may disagree, it is also possible to include other characteristics of the beer like ‘condition’ for a cask beer, or maybe ‘smoothness’ for a nitrogenated ale. Since trueness to type tasting is set against a brand profile, results can be handled to produce a ‘spider’ diagram where key differences are easily identified (Fig 3). A simple calculation can also be used to give a Trueness to Type score, often quoted as a percentage. The test can also include appearance (colour, clarity and foam) and aroma. Many people would separate aroma from taste, but they are very much linked – especially when tastes such as hoppiness and sulphury are present (Fig 4) If there are any undesirable or ‘off’ flavours, these can be noted and will count against a beer and reduce the overall Trueness to Type score. Overall Opinion Another useful assessment is an ‘overall opinion’, normally set on a 1–10 scale where 1

is a very poor beer, 10 is superb. Scores and descriptions vary but a beer with a score of 7 could be considered a good beer. If the beers are tasted by a team of regular tasters, it is surprising how consistent they become in assessing their beers (Fig 5). In my opinion tasters don’t have to be ‘brewers’, but I think they do have to have a good palate and enjoy tasting beer. Again, ‘brewing scientists’ may disagree, and say that tasters do not necessarily have to enjoy the product. I think we ought to have more passion about beer – we are not tasting dog food! Preference Testing – the ‘ two glass test’ Sometimes there is a requirement to see if one beer is preferred to another. Two glasses of beer are tasted alongside each other, and the taster says which beer they like most and then goes on to say which characteristics are preferred. Statistical analysis can be carried out, but just collating results can be very informative. In this test it is preferable to have larger volumes (say half a pint) to sample. ‘Sip tests’ such as triangular taste tests are fine for testing to see if there is a difference between

the beers, but sweeter beers are often preferred. Drinkability Testing This should be the most definitive test, after all, the aim of a brewing company is to be profitable by selling beers that people are willing to pay for. A perfectly-brewed beer is no good if it does not have drinkability – that is ‘moreishness’ or ‘balance’. I firmly believe that balance is a characteristic of most successful beers. Bitterness and fruity hoppiness, balanced off against maltiness and subtle sweetness is a characteristic of many of Britain’s finest ales. Similarly character and balance is also is evident in many of the world’s best appreciated lagers. Drinkability testing in its true sense can be an interesting exercise. In one test – nearly ten years ago now, I was involved in some hopping changes in Boddingtons Bitter. The test involved 300 regular Boddingtons drinkers having: a triangular test, a two glass preference test and a four pint drinkability test which involved the participants giving their opinions after each pint to a lady armed with a clipboard. Half the participants tasted the original beer, the others the trial beer. They were asked how they rated each beer against the previous one they had tasted. Participants were sent home in a taxi and as the incumbent Head Brewer I was obliged to attend over all three nights of the test – life can be very hard can’t it? The same young lady rang participants the following morning to check for any ill effects and the answers were collated and a graph showed that the dr inkability of the new hopping regime was equal to the previous one (Fig 6)

The value of Market Hall tests

Fig 6: The results from a drinkability test where one beer was initially preferred but after one than one glass that preference changed.

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In an ideal world, consumer or ‘market hall testing’ would be carried out whenever a significant brand change is made. They are normally carried out by the larger companies, where the outlay for the test (£10– 30,000 is not unusual) can be justified by the value of

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