321663948-CIP-Handbook-v1.pdf

Cleaning Handbook

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Cleaning Handbook Tetra Pa Pak Processing Processi ng Solut ol utio ions ns

Copyright 2008; Tetra Pak Processing Systems

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1. INTRODUCTION.......................................................................................4 1.1 CIP Validation Procedure ........................................... ................................................................. .......................................5 .................5 1.2 Glossary & Definitions ............................................ ................................................................... ...........................................5 ....................5

2. HYGIENIC HYGIENIC DESIGN OF L INES AND COMPONENT COMPONENTS S ....................... .............................6 ......6 2.1 Introduction..................... Introduction ............................................ ............................................. ............................................ .......................................6 .................6 2.2 Hygienic Design Prerequisites ........................................... .................................................................. ................................6 .........6 2.3 Hygienic design.......................................... design................................................................. ............................................. ...................................9 .............9 2.4 Hygienic Risk Ris k Assessment ........................................... ................................................................. .....................................25 ...............25 2.5 Hygienic Design Checklist – Machines and Peripheral Equipment.............26 2.6 Hygienic Design Checklist – Process Lines & Plants.....................................27

3. CIP TECHNOLOGY TECHNOLOGY ...................... ................................. ...................... ....................... ....................... ...................... .............29 ..29 3.1 Different Types of Soil ......................................... ................................................................ ............................................. ......................29 29 3.2 Water Chemistry and Quality ........................................... .................................................................. ..............................31 .......31 3.3 CIP Theory Theo ry ............................................. ................................................................... ............................................ .....................................33 ...............33 3.4 Detergent Chemistry................................. Chemistry........................................................ ............................................. .................................35 ...........35 Alkalis ............................................ ................................................................... ............................................. ............................................ ..........................36 ....36 Acids ........................................... ................................................................. ............................................ ............................................. ..............................37 .......37 Surfactants (wetting agents).................................. agents)........................................................ ............................................ ..........................37 ....37 Sequestering Agents (chelating (chela ting agents) .......................................... ................................................................ ......................38 38 Oxidation Agents .......................................... ................................................................. ............................................. .................................39 ...........39 Overview of Some Cleaners and Disinfectants ............................................. ....................................................40 .......40 3.5 Detergent Deterg ent Concentration Concentrati on ............................................. ................................................................... .....................................43 ...............43 Dosing of Cleaning Agents.................... Agents .......................................... ............................................. .........................................44 ..................44 3.6 Cleaning Temperature........................... Temperature................................................. ............................................ .....................................46 ...............46 3.7 Cleaning Time ........................................... .................................................................. ............................................. .................................48 ...........48 3.8 Cleaning Flow......................................... Flow............................................................... ............................................ .....................................49 ...............49 3.9 CIP Sequences for Certain Products...................... Products............................................ .........................................57 ...................57 Full CIP Sequences for Various Applications ........................................... ......................................................57 ...........57


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Aseptic Intermediate Cleaning.............................. Cleaning.................................................... ............................................ ..........................60 ....60 3.10 CIP of Specific Components in a Processing Line .......................................61 .......................................61 Separators...................................................... Separators................................ ............................................. ............................................. .................................61 ...........61 Homogenisers ............................................ .................................................................. ............................................ .....................................61 ...............61 Tank Cleaning..................... Cleaning ............................................ ............................................. ............................................ .....................................62 ...............62 3.11 Control Contro l of Cleaning Result..................... Result ............................................ ............................................. .................................65 ...........65 3.12 Disinfection/Sterilisation of Equipment........................................................66 Sterilisation ............................................ .................................................................. ............................................. .........................................66 ..................66 Disinfection.............................................................. Disinfection........................................ ............................................. ............................................. ......................66 66 3.13 Guidelines for Determining Cleaning Intervals for Sterilisers...................67 3.14 CIP Systems .......................................... ................................................................ ............................................ .....................................68 ...............68 Design of CIP Systems ............................................ ................................................................... ............................................. ......................69 69 Centralised CIP .......................................... ................................................................ ............................................ .....................................70 ...............70

FURTHER CIP READING...........................................................................72 Appendix..................... Appendix ........................................... ............................................. ............................................. ............................................ ..........................73 ....73 Extract from the t he EHEDG Glossary....................... Glossary............................................. ............................................ ..........................73 ....73


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1. Introd uction Cleaning, in this context, is the removal of deposited soil from processing equipment surfaces, and is an essential operation in food processing. The main reasons for cleaning are to satisfy food safety and regulatory standards, and to increase shelf-life and reduce spoilage rates. It is also compulsory for suppliers of food processing equipment to guarantee that the equipment can be cleaned. The purpose of cleaning is to ensure that processing equipment is physically clean, i.e. all visible soil is removed. The principle of cleaning is very easy: the forces that bind the soil to the surface of the equipment have to be overcome. This is achieved by mechanical and/or chemical effects, together with an increase in temperature. A term often used in cleaning is the Zinner circle, which defines the four main parameters governing the cleaning process: cleaning temperature, cleaning flow, detergent concentration and cleaning time. These are all closely related. Designing and implementing cleaning procedures are both extremely important, but before all else – processing equipment must be designed for hygiene. It must be possible to clean the equipment. A badly designed valve or processing unit will endanger good hygiene and can not be properly cleaned. Hygienic design is the basis for a good cleaning result, preventing the consumer’s health being put at risk due to hazards that can affect food safety and the quality of processed or packaged food. The aim of this document is to provide guidelines in hygienic design when integrating process equipment into a process line, and to provide a general overview of the importance of hygienic design. Furthermore, the document also describes the cleaning-in-place (CIP) state of the art. It briefly describes some of the different detergents used and the parameters of the Zinner circle. In the last section of Chapter 3 various CIP systems are described. The target groups for this Cleaning Handbook are pre-project leaders, field service engineers, designers, process engineers, development engineers and staff from market companies. However, all those who need to know more about CIP should hopefully find this a useful introduction.


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1.1 CIP Valid ation Proc edure A CIP validation procedure has been developed at Tetra Pak Processing Systems, which is owned by Tetra Pak Dairy & Beverage (document FCDPM 0706-001). The objective of this CIP validation procedure is to verify the effectiveness of the cleaning procedures in Tetra Pak’s processing equipment. The layout of the document is presented in Fig. 1. The following issues are discussed: • • • • •

Design qualification In-house validation Installation qualification Operational qualification and Performance qualification

For a more detailed description the reader is referred to the CIP validation document. The document also describes a method of assessing cleanliness. It is based on a method of determining the value of ATP on the cleaned surface. A limit is suggested defining clean processing equipment.

Fig. 1. The five steps in the CIP validation procedure.

1.2 Glos sary & Definiti ons The European Hygienic Engineering & Design Group (EHEDG) is an association working in the field of hygiene. They have developed a glossary including some of the most frequently used terms, phrases and expressions in cleaning and hygiene. The EHEDG Glossary is given in the appendix.


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2. Hygienic Design of Lines and Compo nents 2.1 Introduction Within Europe, the essential requirements of the Machinery Directive, 98/37/EC, should be met in respect of both safety risks to the operator of the equipment and hygiene risks (Annex 1, paragraph 2.1) to the food (i.e., the product processed by the equipment). The hygienic requirements of the directive can be met by using the Cstandard EN 1672-2:2005. The principles for performing a Hygienic Risk Assessment can also be also found in the same standard; see also Tetra Pak Corporate Standard B 2153.05. Hygienic requirements in the USA are to be found in Food & Drug Administration legislation, FDA CFR Title 21 Food and Drugs, in the Grade “A” Pasteurized Milk Ordinance (PMO) and the USDA Guidelines for the Sanitary Fabrication of Dairy Equipment. Equipment exported to the USA must have a TPV approval according to the 3A-SSI standard. Lubricants must have an NSF class H1 approval. Other countries have similar legislation, often corresponding to, or referring to, EU or US legislation and standards. However, questions concerning local legal demands and standards must be checked by each Tetra Pak market company.

2.2 Hygienic Design Prerequis ites The single most important issue in engineering is to consider food safety, i.e. a hygienic design. A design method that eliminates risks to both hygiene and safety should be adopted. If this is not possible, then options safeguarding both hygiene and safety should be employed. If this is not possible, either hygiene or safety should be safeguarded. Where no design or safeguarding options to adequately control both hygiene and safety risks are possible on the engineering level, one of the risks, or both, must be dealt with by other safety measures, including instructions to the user. The following affect the design and must be considered:; - Type of product - Materials in contact with food - Utilities in contact with food - Environment Type of product The following are presented for guidance and as examples of the range and type of factors that must be considered regarding the process line and the components/equipment in question when undertaking a risk assessment.

a) The intended use of the equipment: Will the equipment be used for one specific purpose only, for which the hygienic demands are readily identifiable, or could the


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equipment be used for a wide range of products in many industries (e.g. a pump)? Components are normally tested using water, or liquids with a similar viscosity. The component may therefore not be suitable for soups, sauces, or similar products. b) The type of product to be processed by the equipment: Will the product be contaminated (e.g. a raw material), or will it be pasteurised or aseptic? Are additives used? A product recipe may call for additives such as starch or stabilisers, or others to increase the fat or protein content, etc. This can cause problems during cleaning and may affect the choice of components and the flow engineering, etc., and must also be considered. c) The degree of further processing: Will the product processed by the equipment subsequently undergo a further process which acts as a hazard elimination step (e.g. heat treatment), or is the process for which the equipment is intended the final process? The method used for heat treatment, as well as the time/temperature combination differs depending on the type of product and its properties: such as viscosity, homogeneity, content of fibres or particles, whole berries, etc. d) Specific application of the product: 1. Is the product to be used by the consumer immediately after processing, or does the product have a shelf-life during which the food safety hazard could increase (e.g. microbial growth)? Use of hygienic zoning must be considered for ESL products, incubation areas, etc. 2. Will the product be used by a specific consumer group to whom the hazard may present a more serious risk (e.g. babies, the elderly or the infirm)? It may be necessary to fulfil specific demands, such as high quality welds, differentiation of production lines due to allergens in a product, etc. e) The degree of cleaning, disinfection, pasteurization, sterilization and/or inspection: Is the equipment to be cleaned, disinfected, pasteurized, sterilized and/or inspected after every batch, routinely during the day, every day, or every week, etc.? f) The use of the equipment: Is the equipment likely to be well maintained or used infrequently? Is it designed for high or continuous use, and is misuse foreseeable? This will affect the use of aseptic and non-aseptic equipment, as well as necessary barriers such as steam, sterile air, nitrogen, etc.


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Materials in contact with food The following are presented for guidance and as examples of the type of factors regarding materials in contact with food that must be considered for the process line and the components/equipment to be used in the various stages in risk assessment.

Under the intended conditions of use, the materials in contact with food shall be: • corrosion resistant • non-toxic • inert to the product, i.e. they must - not absorb material (except when technically or functionally unavoidable) - not transfer undesirable odours or colours, or taint t he food; - not contribute to the contamination of food, or have any adverse influence on the food. Detailed legal demands and directives are enforced for plastic, rubber, ceramics, etc. within the EU and the USA, as well as in several other countries, such as Japan. Glass should be avoided in equipment that comes into contact with food, and if used it must be splinter free, and it must be impossible for it to get into the food product. When necessary, filters are to be installed in the production line to avoid contamination from sacks, etc. Lubricants used in food production equipment must be of Food Grade, NSF approved, class H1. In the USA 10 mg/l is allowed in the product and in the EU the product must contain no oil. It is important to take into account the legal demands included in the design criteria in the purchase documentation sent to the suppliers. Utilities in contact with food The following examples of utilities are presented for guidance and as examples of the type of factors that must be considered regarding the process line and the components/equipment to be used. Steam must be of a specific quality when used in contact with food. Culinary or clean steam must be used as steam normally contains additives to prevent calcium deposits in the steam-generating system. These additives are toxic and must not come into contact with food. Water must be of a special quality when used in contact with food. Potable water according to the WHO recommendation must be used. Furthermore, Tetra Pak places specific demands on water quality, for technical reasons, to ensure correct functionality and to avoid corrosion of components/equipment. The water quality is naturally also of the utmost importance for the results of cleaning, for example, in avoiding re-contamination. Compressed air must be of a specific quality: dry, clean and oil free, when used in contact with food, for example in ice cream freezers. Additional active carbon filters,


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or corresponding equipment must be used when compressed air is used as sterile air in aseptic applications. Ventilation: the flow, temperature and humidity of incoming air must be controlled. Zoning may have to be considered to avoid contamination being spread from a lower zone to a higher one. Special HEPA filters then have to be installed to remove particles.

It is important to address the legal demands included in the design criteria in the purchase documentation sent to the suppliers.

2.3 Hygienic design General requirements Materials must be suitable for the intended use. Surfaces of materials and coatings shall be durable and cleanable and, where required, capable of being disinfected, unflawed, resistant to cracking, chipping, flaking and abrasion, and undesirable matter must not be able to penetrate the surface under the intended use. Surfaces 1. The surface finish shall be suitable for the intended use. 2. Surfaces shall be cleanable and, where required, it must be possible to disinfect them. For this purpose they must be smooth, unflawed or sealed. The surface design and finish shall be such that the product is prevented, as far as possible, from becoming accidentally separated from the food contact area and from returning to it, if that return could cause a hazard associated with the processed food. 3. Surfaces shall have a finish such that no product particle can become trapped in small crevices, thus becoming difficult to dislodge and so introduce a contamination hazard. The above requirements also apply to dismountable parts, which are removable for cleaning.

NOTE: Guidance for measurement of surface finish (roughness specification Rz and/or Ra) can be found in EN ISO 4288. Additional requirements for surface finish can be found in some equipment-specific type C standards.


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Joints Permanent joints

Joints shall be sealed and hygienic. Recesses, gaps, crevices, protruding ledges, inside shoulders and dead spaces shall be avoided. If technically impossible, adequate design solutions (e.g. cleaning or disinfection instructions, etc.) are to be given.


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Dismountable joints

Dismountable joints shall exhibit a true and hygienic fit. Gasket compression is to be limited by a mechanical stop. Fasteners Fasteners such as screws, bolts, rivets, etc., shall be avoided. If technically impossible, adequate solutions (e.g. cleaning or disinfection instructions, etc.) shall be given.


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Drainage

a) not drainable 1 concentric reducer 2 centric reducer The equipment should preferably be self-draining; if this is not possible, it must be easy to remove the residual liquid by other means. Note: In our applications piping should normally remain filled with water to prevent contamination and to avoid pitting corrosion which may occur when droplets evaporate.


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Internal angles and corners

Internal angles and corners shall be constructed such that they can be cleaned effectively and, where required, can be disinfected. Internal angles and corners are to comply with the technical requirements given in equipment-specific C standards.


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Dead spaces

Dead spaces are to be avoided unless technically impossible in the design, construction or installation of the equipment. Unavoidable dead spaces shall be constructed in such a way that they are drainable/cleanable and can be disinfected, when required.


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Bearings and shaft entry points

Bearings shall either be located outside the food area, except where this is technically unavoidable, or designed for and lubricated with food grade lubricant, cleanable and where required capable of being disinfected. Shaft seals and moving shafts in the food area shall be self- (or product-) lubricated, or should be designed for and lubricated with food grade lubricant, cleanable and, where required, capable of being disinfected.

Note: Requirements for equipment used in aseptic processing can be found in specific C standards.


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Instrumentation and sampling devices

Instrumentation and sampling devices shall comply with the relevant design parameters. Panels, covers, doors These parts shall be so designed such that they have no adverse influence (e.g. entrance and/or accumulation of soil) and shall be cleanable and, where required, capable of being disinfected. Control devices If there is no manual contact with the food, items or areas of equipment that are handled for control reasons by the operator, shall be considered as non-food areas. In the case of manual contact with the food, where cross-contamination can occur, these areas or items are to be covered by the definition of a food area.


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Splash area

Splash areas are to be designed and constructed following the same principles as those applicable to the food area. As the product does not return to the food area, the technical design criteria may be less stringent than in the food area in areas such as the following, provided that there is no adverse effect on the food: • technical requirements for surface finish may allow for higher Rz and/or Ra values; • internal angles and corners may be of smaller radius, provided they are still cleanable and, where required, capable of being disinfected • bearings, seals, moving shafts, etc., located in a splash area, may be lubricated by non-food grade lubricants, provided there is no adverse influence on the food. Non-food areas In addition to the general requirements, exposed surfaces in the non-food area are to be made of corrosion-resistant material or material that is treated (coated or painted) so as to be corrosion resistant. These surfaces shall be cleanable and, where required, capable of being disinfected, and shall not contaminate or have any adverse influence on the food.

Equipment shall be designed and constructed in such a manner as to prevent the retention of moisture, ingress and harbourage of vermin, and accumulation of soil, and to facilitate inspection, servicing, maintenance, cleaning and, where required, disinfection. Tubular framing shall be completely closed or effectively sealed.


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Welding The best welding method for hygienic welds is TIG, as this has the best performance when welding thin-walled stainless steel tubes. Orbital welding with inert gas ensures high repeatability, resulting in welds of high quality.

Weld defects, such as cracks, porosity, etc., must be avoided to prevent the build-up of residues, minimising the risk of microbiological contamination to the lowest possible level. The settings on the welding equipment (current, gas, etc.) are important, as well as preparation of the tubes. Misalignment, gaps, etc., should be avoided.

Steel quality: SS-2333, AISI 304 L Welding 2-pulse, O2 content shown in ppm It is important to visually inspect and check all welds. A fibroscope can be used to inspect welds inside tubes. Concavity, convexity, penetration, cracks, cavities, arc strikes and weld bead meandering must be considered in order to ensure a hygienic weld. It is also important to inspect the colour of the weld area as discolouration


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indicates the use of incorrect current or too high an oxygen content. Poor welds must be cut out and replaced by an approved weld. Hygienic zoning Zoning is understood as the physical segregation of different unit operations or activities including the use of physical barriers in regards to the hygiene level. Zoning is also used to control the movement of personnel, equipment and materials, as well as the circulation of ambient air.

Preventing the contamination of a product involves protecting the product, not only in the vicinity of, for example, a filling line, but also in the entire process area, or zone. Therefore, zones are defined according to the level of cleanliness and hygienic classification, to protect different types of products from, for example, various vectors carrying microorganisms (cross-contamination), pests and odours originating from the factory environment and its surroundings. Hygienic zones are normally defined in two or three levels of hygiene, such as the ‘Basic Hygiene Zone’, ‘Medium Hygiene Zone’ and ‘High Hygiene Zone’. Basic hygienic zones require Good Manufacturing Practice (GMP) and can be used to separate the area from outside areas. Typical basic hygiene zones are in the warehouse or incoming material reception areas. The milk reception area is also a basic hygiene zone. Personnel in this zone are not required to wear special clothing, but their clothing must be clean at all times. There should be no open product handling in this area. Medium hygiene zones also require GMP. Examples are process areas where products are made for consumer groups that are not especially sensitive, or products in which no further microbiological growth is possible in the final product. Areas in which closed equipment with much higher internal hygienic requirements is operated (e.g. most of Tetra Pak Processing and Filling equipment), are often defined as medium hygienic zones. Personnel clothing must be clean, and white coats and protective headwear (hairnets) must be worn. Changing of shoes for operators or shoe covers for visitors may be recommended, but are rarely essential. Filtered and conditioned air at an overpressure is recommended for certain applications. High hygiene zones are those in which processed products are exposed and are vulnerable to recontamination. This classification is typical for open processes or operations in which the highest level of hygienic precautions must be adopted. This zone should be limited in size, and the layout should be as simple as possible. Supplementary equipment such as fans, pumps, power supplies, etc., should be placed outside the area. Special rules are applied in such zones, for example, restricted movement of personnel and materials. Protective clothing, changing of shoes, etc., is


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essential before entering. Filtered (HEPA filter) and conditioned air at an overpressure is essential to minimise possible sources of contamination. Dry or controlled wet cleaning procedures are normally required for such areas. High hygiene zones are never subject to wet cleaning.

Note: Zoning should be used as a preventive measure, as part of the total hygiene concept. Zoning alone does not prevent contamination if the surfaces in contact with, or very close to, the product are not properly cleaned and maintained.


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Flow systems It is of the utmost importance to avoid the mixing of cleaning solution and product, or heat-treated and non-heat-treated product. In order to avoid this, different flow solutions can be used, such as swing bend plates, mix-proof valves or separation by valves and a drainable pipes. The three examples below show recommended flow solutions.

Examples of mix-proof arrangements Valve arrangements for tanks - Filling and emptying from the bottom of the tank When filling and emptying a tank with a single bottom connection, a valve arrangement such as that shown in Fig. 2 can be used.

Fig. 2. Valve arrangement V1 = Change-over valve, 3 gates for connection of CIP pressure V2 = Stop valve V3 = Change-over valve, 4 gates to separate tank cleaning, pipe cleaning V4 = Change over valve, 3 gates for connection of CIP return V5 = Change-over valve, 3 gates for bypass during pipe cleaning V6 = Change-over valve, 3 gates for bypass during pipe cleaning


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Cleaning of tank with mix-proof valves

Fig. 3. Cleaning of tank with mix-proof valves.

Cleaning of inlet/outlet backwards with pressure Note: It is possible to clean the inlet or outlet line with product in the tank.


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Common tank bottom inlet/outlet LKB/SBP

Fig. 4. Common tank bottom inlet/outlet LKB/SBP.

Application This design shows the arrangement of the connection of a tank to CIP and production using a swing bend panel. Functions during production When running the transport to the tank the swing bend must be in the horizontal position, as shown on the diagram. Cleaning the tank When cleaning the tank the swing bend must be in the vertical position. CIP return is on the right side of the swing bend panel. The valve in the bottom of the tank is to be flipped without pressure during certain steps in the CIP sequence. Cleaning the inlet/outlet pipe When cleaning the inlet/outlet pipe the swing bend must be in the vertical position. CIP return is on the left side of the swing bend panel.


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Instruction handbook An instruction handbook shall be provided by the manufacturer, which must meet several requirements including the requirement set out in EN ISO 12100-2:2003. Specific information related to the hygienic design is to be provided, in particular:

•

•

•

•

•

• •

Space required for operation and maintenance, for example, measures to be taken when installing equipment. Care shall be taken to ensure that there is adequate access for servicing the equipment and for cleaning service systems and their adjacent areas, so that the required level of hygiene can be maintained. Acceptable environmental operating conditions and, where required, measures to be taken to ensure that the food is not adversely influenced by, for example, air currents, dust or liquids derived from leakage, condensation or aerosols. Dismantling (if necessary), cleaning, disinfection, rinsing and inspection for control of cleanliness. The method and frequency of cleaning various surfaces, including dismountable parts, are, however, dependent on the food product being processed and the associated/relevant hazard(s). Recommended cleaning and disinfecting agents and instructions for dismantling (if necessary), cleaning, disinfection, rinsing and inspection to ensure cleanliness. The method and frequency of cleaning various surfaces, including dismountable parts, are dependent on the food product being processed and the associated/relevant hazard(s). A scheme describing the measures required to ensure that the necessary level of hygiene of food equipment is maintained within specified intervals. If food grade lubricants are required, this must be specified.

2.4 Hygienic Risk Ass essment Performing a hygienic risk assessment of the design will indicate the relative significance and the need for higher levels of protection (i.e. safeguarding). Hazards are to be eliminated, or the associated risks reduced by ensuring that the equipment is properly designed and constructed, and capable of being properly installed, operated, cleaned and maintained. The hygiene requirements of the different parts of the equipment depend on their function, the type of food to be processed, and the nature of the hazards to the food. The primary objective of applying design and construction criteria is to eliminate or reduce the risks to an acceptable level. The mandatory hygiene risk assessment at Tetra Pak follows the methodology described in Tetra Pak Corporate Standard, document No. KA 2153.05, which is based on the methodology described in EN 1672-2:2005.


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2.5 Hygienic Design Checkl ist – Machin es and Peripheral Equipment CE marking - hygienic design, possible to clean (MD 98/37/EC, Annex 1, paragraph 2.1) - HRA performed according to EN 1672-2:2005 - withstand product pressure/volume (PED 97/23/EC) Suitable materials for product contact surfaces - stainless steel (and other metals): quality suitable for the food to be processed - elastomers and plastics: quality suitable for the food to be processed - appropriate surface finish (USA & EHEDG 0.8 μm) Lubricants - NSF-approved food grade lubricant: zero content in food in the EU, in USA < 0.1 mg/l is permissible Joints - permanent joints shall be sealed; crevices, inside shoulders, dead spaces, etc. are to be avoided - dismountable joints shall exhibit a true and hygienic fit Drainage - the equipment should preferably be self-draining Internal angles and corners - shall be cleanable and, where required, capable of being disinfected, Rmin = 3 mm Dead ends - shall be avoided unless technically impossible in the design, max recommended length 1.5 x diameter - if unavoidable, they shall be drainable/cleanable and capable of being disinfected Fasteners - screws, bolts, rivet, etc., shall be avoided Hygienic welds - approved certified welder - suitable welding method with correct parameter settings - orbital welding preferred: tungsten electrodes and inert gas, recommended O 2 level 40 – 50 ppm - pipe alignment


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inspection and approval of welds (use appropriate method; visual, video scope, X-ray, etc.)

Bearing and shaft entry points - preferably located outside the food area, unless technically unavoidable - shaft seals and moving shafts in the food area shall be self- (or product-) lubricated - if technically impossible, they must be lubricated with food grade lubricant - shall be cleanable and, where required, capable of being disinfected Panels, covers, doors - must be designed to avoid any adverse effects, to be cleanable and, where required, capable of being disinfected - control devices can normally be considered as non-food areas Splash area - designed and constructed following the same principles as for the food area Non-food area - corrosion-resistant material or material that is inert (i.e. has no influence on food) and cleanable

2.6 Hygienic Design Checkl ist – Proc ess Lin es & Plants CE marking - hygienic design, possible to clean (MD 98/37/EC, Annex 1, paragraph 2.1) - HRA performed according to EN 1672-2:2005 or EN ISO 14159:2002 - withstand product pressure/volume (PED 97/23/EC) Suitable materials for surfaces in contact with food - stainless steel (and other metals): quality suitable for the food to be processed - elastomers and plastics: quality suitable for the food to be processed, EU reg. 1935/2004 or FDA - correct surface finish (USA & EHEDG 0.8 μm) Lubricants - NSF-approved food grade lubricant is to be used; in EU no presence in food, in USA < 0.1 mg/l Suitable components for the food to be processed - material approved for food contact - temperature resistance (process, hot water sterilisation, steam or other) - hygienic connection not causing dead ends or misalignment - installation direction not causing dead ends - need for steam barrier or hot condensate (correct temp. & flow) - T-pipes, correct CIP flow - drainable, no product residues in pockets Copyright 2008; Tetra Pak Processing Systems

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- positive pumps cleanable (by-pass valve) - masking of feedback signals, forced control, etc. (control system must not affect hygienic design) - instrumentation and sampling devices must comply with the relevant design parameters Hygienic welds - approved certified welder - suitable welding method with correct parameter settings - orbital welding preferred: tungsten electrodes and inert gas, recommended O 2 level 40 – 50 ppm - pipe alignment - inspection and approval of welds (visual, videoscope) Cleaning circuits - number of objects -fouling of cleaning solution - number of circulations (reuse) before reject - flow rate of cleaning solution >1.5 m/s - no mixing of product and cleaning solution possible, drainability - no simultaneous upper and lower flip on Unique valves Pipe support - pipe slope rec. 3% - expansion aid used to avoid risk of tension - valve clusters not used to support pipes, risk of tension – intercrystalline corrosion Positioning/layout - building and other premises acc. to Codex principles - hygiene zones with transfer barriers (air pressure, air filter quality, PPE, etc.) - possible to inspect and maintain equipment - possible to clean equipment externally (non-food area) - insulation properly mounted and suitably sealed Utilities - culinary steam quality in food contact - potable water quality in food contact and for cleaning purposes - sanitary compressed air in food contact (filter quality, oil- and condensationfree) - air used for ventilation (zoning, filter quality)


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3. CIP Techn ology The result of cleaning depends on a range of factors, including the type of product being processed, the quality of the raw material/product, the configuration of the equipment, running time before CIP, type of cleaning solution, detergent concentration, water quality, cleaning time, cleaning temperature, and flow rate of CIP solutions. Factor

Consequences

High quality of raw product Type and configuration of equipment Type of product Running time before cleaning Type of detergent

Improved protein stability Running time restriction Type of soil (mineral/fat/protein) Thickness of soil layer Alkali, acid and additives

Detergent concentration Water quality Cleaning time Cleaning temperature Flow rate

Cleaning result

3.1 Diff erent Types of Soil It is important to know the composition of the soil when designing a CIP sequence. The composition of soil will vary depending on the type of product being processed. Simply changing the fat content of milk can result in a change in the composition of the soil, which makes it more difficult to remove. Tetra Pak process equipment is used for different food applications, ranging from juices to prepared food such as rice pudding and Béchamel sauce. Table 1 shows a schematic overview of the different types of soil that need to be removed from equipment surfaces during CIP.


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Table 1. Different types of soil (according to Guthrie, 1972). From the Handbook of Hygiene Control in the Food Industry (Ed. Lelieveld, H. L. M., Mostert, M. A. & Holah, J., CRC Press, 2005) Type of soil Solubility Ease of removal Low/medium High pasteurisation pasteurisation/UHT Sugar Soluble in water Easy Caramelisation, more difficult to clean Fat Not soluble in Difficult Film formation, water, soluble in more difficult to alkali clean Protein Not soluble in Very difficult Very difficult water, soluble in alkali, slightly soluble in acid Mineral salts Solubility in water Varies Varies varies, most salts soluble in acid Starch Soluble in water Easy to moderate Glue-like and alkali formation, difficult to remove

Two examples are given below of the fouling that can be found in Tetra Pak processing equipment, originating from milk production and tomato paste production. Both products represent typical soil situations, but also serve to illustrate the differences in the CIP cycles. Milk fouling During the processing of milk, either pasteurised or UHT milk, the heating equipment is fouled. There are two main types of fouling (see Table 2). Lowtemperature pasteurisation (maximum temperature 72-75 °C) creates a kind of fouling with a high content of protein, mainly β-lactoglobulin. This type of fouling is denoted type A, and is dominant in the temperature range 70 to 105 °C. During the production of UHT milk, another type of fouling besides type A fouling, denoted type B, arises. Type B fouling is created in the high-temperature range starting at 110 °C. This type of fouling contains a higher level of minerals than type A fouling, mainly calcium phosphate. Table 2. Composition of soil in dairy applications. Type of fouling (Type A) %

Protein Minerals (calcium phosphate) Fat


50-60 30-50 4-8

(Type B) %

15-20 70-80 4-8

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Tomato paste fouling When cleaning a protein deposit, e.g. milk fouling, the detergent solution will cause swelling of the soil. Deposits resulting from the processing of tomato paste are cohesive, and can be removed in large chunks by hydration of the deposit–substrate interface. Fouling deposits form as a result of both adhesion of material to the equipment surface and cohesion between elements of the material.

3.2 Water Chemistry and Quality Two main issues are of importance regarding water quality, namely microbiological status and water hardness. The microbiological status is the more important one in food processing. The other issue, water hardness, concerns the amount of metal ions in the water. Water hardness and inadequate pre-rinsing are two major factors causing failure in CIP operations, apart from inadequate flow rates. Calcium and magnesium ions are considered in the context of water hardness, but other polyvalent cations may also be of importance. The European standard for water hardness is German degrees (°dH).

Three problems causing failure of CIP: • water hardness • inadequate pre-rinsing • too low flow rate (Sect. 3.8)

Water hardness can be discussed in terms of carbonate hardness (temporary hardness) or non-carbonate hardness (permanent hardness). The salts causing permanent hardness are Ca and Mg sulphates or chlorides. Temporary hardness is remedied by heating the water. The total water hardness is defined as the sum of the calcium and magnesium concentrations, expressed as equivalent calcium carbonate, according to: mg equivalent CaCO3/l = 2.4797 ⋅ [Ca, mg/l] + 4.118 ⋅ [Mg, mg/l]

When referring to water hardness, it is essential to make it clear whether one is referring to temporary, permanent or total hardness.

In Table 3 the limits for different degrees of hardness are given in terms of the concentration in mg/l (ppm), German degrees and milliequivalent/l. Several units are used to express water hardness, and Table 4 gives the conversion factors for those most frequently used.


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Table 3. Water hardness according to The Orange Book. Hardness CaCO3 German mg/l (ppm) dH

Milliequivalent/l meq/l

Very soft Soft Moderately hard Hard Very hard

1 1-2 2-4 4-8 >8

<50 50-100 100-200 200-400 >400

2.8 2.8-5.6 5.6-11 11-22 >22

Table 4. Conversion table for water hardness units (The Orange Book). = 17.9 mg CaCO3 / l 1 °dH 1 meq/l = 50.0 mg CaCO3 / l = 10.0 mg CaCO3 / l 1 °f = 14.3 mg CaCO3 / l 1 ° Clark 1 grain/US gal = 17.1 mg CaCO 3 / l

Water quality can vary depending not only on the source, but also the time of day. Some naturally soft water can cause corrosion due to its acidic pH. Mineral salts make water more basic (pH above 7) and corrosion increases, leading to a high risk of damage to pipelines, heat exchangers and boilers. Table 5. Water quality recommendations for minimum corrosion (ppm or mg/l). Hardness 4 – 7 °dH Alkalinity > 0.6 meq/l Chloride ions < 30 ppm Cl Chlorine < 0.2 ppm Cl2 pH 7.0 – 8.5 Sulphate ions < 100 ppm Aluminium < 0.1 ppm Iron < 0.2 ppm Manganese < 0.05 ppm KMnO4 consumption < 20 Aggressive carbon acid 0 ppm CO2


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3.3 CIP Theor y Cleaning of processing equipment is a necessity for all food producers. CIP should be planned in such way that it intrudes as little as possible on production time. In order to reduce CIP times it is important to consider the process as a whole. Cleaning is not an isolated event, and product recovery preceding CIP can be performed in an intelligent way. In many UHT applications, production starts immediately after cleaning, and thus the sterilisation of the process equipment must also be considered as part of the cleaning cycle. The factors influencing the cleaning of processing plants are mechanical design, process design and cleaning process. The interrelationships between these is illustrated in the figure below (Fig. 5). It can be seen how the process design is related to the cleaning process through the type and amount of fouling on the equipment surface. The type of detergent and concentration must be chosen so as to be appropriate for the type of fouling. The mechanical design then governs both the process design and the cleaning process. Designing and managing cleaning processes is extremely important, but before all else – processing equipment must be designed for hygiene . Mechanical design - materials, surface finish - equipment design and installation - geometry

Process design - quantity and type of soiling - age/moisture of soiling - composition of soiling

Cleaning process - detergent type and concentration - temperature - flow rate - water hardness

Fig. 5. The relations between the factors affecting the cleaning of a food processing plant.

Designing and managing cleaning processes is extremely important, but before all else – processing equipment must be designed for hygiene.


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The cleaning steps after pre-rinsing can be described in the following steps, which are illustrated schematically in Fig. 6. 1. The cleaning solution is transported to the fouling layer by the fluid flow (turbulence). 2. The detergent reacts with the surface of the fouling layer and the chemicals start to penetrate the layer. Proteinaceous fouling starts to swell. 3. The dissolved fouling layer is then transferred to the bulk solution. It is possible to prevent the soil from aggregating and re-attaching to the fouling layer by using additives.

Rinsing water

Alkaline cleaning solution



Fig. 6. Illustration of the cleaning mechanism. (from Jeurnink and Brinkman) .


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Fig. 7 illustrates Zinner’s circle consisting of the four main process parameters that can be controlled during CIP: the concentration of the cleaning agent, temperature, time and flow. Zinner’s circle is surrounded by a circle representing the production time. A longer production time usually results in a longer cleaning period. This in turn may result in a longer down time. Therefore, production time must be considered as well as the specific product being processed.

Time

Concentration

Flow

Temperature

Fig. 7. The parameters that affect the cleaning result.

It is important to know which of these four parameters is the most important. In order to reduce costs and energy consumption it is important to optimise the CIP sequence. The cost of the energy required to heat the CIP solutions, the energy needed to pump the CIP solutions and the price of the CIP solutions should thus be compared. In the broader perspective CIP must be included in the total production scenario. In the following sections the different aspects of cleaning will be considered in more detail, starting with the chemistry of cleaning.

3.4 Detergent Chemistry Many dairy producers today use lye (sodium hydroxide solution) and an acid as cleaning agents. This is sufficient for many applications and results in adequate cleaning. Commercial manufacturers offer a range of detergents for different applications and products. Various components are added to the alkaline or acid solutions, such as wetting agents and complex-forming agents. Cleaning components are usually described as alkalis, complex phosphates, surfactants,


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chelating agents and acids, and it is important to choose the most suitable component or components based on: • the kind of fouling to be removed • the detergent • the concentration, temperature and contact time • the quality of the water The function and effectiveness of various detergent compounds are summarised in Table 6, on a scale from 1 to 5, where 5 indicates excellent functionality. Table 6. The effectiveness of various cleaning compounds (from the Handbook of Hygiene Control in the Food Industry, Ed. Lelieveld, H. L. M., Mostert, M. A. & Holah, J., CRC Press, 2005) Cleaning Strong Mild Polyphosphates Weak Strong Surfactants function alkalis alkalis (sequestering acids acids agents) Chelation 1 2 5 1 1 1 Saponification 5 4 4 4 4 2 Wetting 2 3 2 2 1 5 Peptising 5 4 2 3 4 1 Emulsification 2 3 3 1 1 5 Dispersion 3 4 2 4 1 4 Rinsing 4 4 3 2 1 5 Corrosion 5 3 1 3 5 1

Alkalis If the fouling consists of proteins an alkali is the best cleaning agent. The most frequently used alkali detergents are sodium hydroxide (NaOH), potassium hydroxide (KOH) and sodium carbonate (Na 2CO3). Alkalis cause the proteins to swell, facilitating their removal. In order to reduce the cleaning time the pH of alkali solutions should be between 12 and 13 (Table 7). Fat is also removed by alkali. At high temperatures fat is saponified, i.e. soap is formed. Soaps also lower the surface tension of solutions thus improving the emulsification of fat and the wetting effect.


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Sodium hydroxide (NaOH) has excellent detergent properties but corrodes aluminium, galvanised metal and tin. Its rinsing and wetting properties are poor, and divalent metal ions (Ca2+ and Mg2+) are precipitated in alkaline solutions. If hard water is used for rinsing and/or preparation of the cleaning solutions, this will add to the mineral-based fouling of the equipment.

Table 7. pH as a function of concentration for two alkali detergents. Concentration 0.25 0.5 1.0 2.0 NaOH 12.5 12.8 13.0 13.3 Na2CO3 11.3 11.4 11.6 11.7

The use of NaOH with hard water will add to the mineral-based fouling of the processing equipment.

Acids The hydrogen ion (H +) in acids reacts with the fouling causing it to break down and dissolve. The most frequently used inorganic acids are nitric acid (HNO 3) and phosphoric acid (H3PO4). The former is most frequently used in Europe, while the latter is the first choice in the USA. Nitric acid is a stronger acid, having a higher coefficient of dissociation than phosphoric acid, and is thus more efficient, but it is also more corrosive to stainless steel. Among the organic acids, acetic acid, lactic acid, citric acid and gluconic acid are the most frequently used. These acids are weaker than, and not as corrosive as, nitric acid but expensive compared with the above mentioned inorganic acids. Hydrochloric acid (HCl) must not be used due to its corrosive properties on stainless steel. However, chlorine detergents are commonly used in membrane cleaning applications due to their high oxidising capability. In many applications alkali CIP is followed by acid CIP. However, inorganic acids have strong dissolving effects on protein fouling and can thus be used before alkali CIP in order to facilitate cleaning with an alkali detergent. Due to the passivating effect of acids on stainless steel, acid detergents are used after alkali CIP. In the cleaning of UHT milk processing equipment, especially in high-temperature parts of the steriliser, minerals and the white deposit called milk stone are removed by acid cleaners.

Surfactants (wetting agents) Surfactants, also called wetting agents, can be added to detergents to lower their surface tension, enabling them to wet the surface of equipment more effectively,


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thus making cleaning more efficient. They also prevent re-deposition of fouling material on the surface through electrostatic interactions or steric hindrance. As can be seen in Table 6, the function of these compounds in CIP detergents is to improve the physical dispersion, emulsification, foaming and wetting of the fouling layer. Surfactants may be ionic or non-ionic. The ionic surfactants are divided into three sub-classes: anionic (negatively charged in water), cationic (positively charged in water) and amphoteric (charge is pH dependent). Amphoteric surfactants are cationic under acidic conditions and anionic under alkaline conditions. The active components in these substances are tensides, which means they have a hydrophilic part (from the Greek for water-loving) and a hydrophobic part (from the Greek water-rejecting). This enables them to act as a binder between the hydrophilic water and the hydrophobic fat. Ionic surfactants Anionic wetting agents can be classified into five groups: sulphated alcohols, sulphated hydrocarbons, aryl alkyl polyether sulphates, sulphonated amides and alkyl aryl sulphonates, which have good to excellent detergency. Both the removed foulant and the equipment surface become negatively charged, thus preventing redeposition. However, in the presence of Ca 2+ or Mg2+ ions the effect will be the opposite, and therefore sequestering agents should be added to these detergent solutions.

Cationic wetting agents consist of quaternary ammonium compounds. This group of wetting agents exhibits lower cleaning efficiency than anionic and non-ionic wetting agents, and is not used for the cleaning of food processing equipment. Amphoteric wetting agents act by loosening and softening protein- and carbohydrate-rich soil, and are widely used in the food processing industry. Non-ionic surfactants These surfactants are best employed when removing soil consisting of oil, and are affected little by water hardness. The working principle is to sterically prevent the removed soil from returning to the equipment surface or aggregating in the bulk solution.

Sequestering Agents (chelating agents) The function of sequestering agents is to bind to calcium and magnesium ions in order to soften water. The ions are bound so securely that they can no longer react to form so-called milk stone or calcium soaps. Common sequestering agents are orthophosphate, orthosilicate and phosphates. It is important to bear in mind that the waste water evacuated to the drain contains phosphates, which can be an environmental problem. Complex-forming agents form a sub-group of sequestering agents. The difference between them is that sequestering agents act on a micro-crystalline level, unlike complex-forming agents. Complex-forming agents can only bind one metal ion per Copyright 2008; Tetra Pak Processing Systems

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molecule in contrast to sequestering agents, which can bind to a number of metal ions. The most common complex-forming agents are EDTA (ethylene diamine tetra acetic acid), NTA (nitrilo-tri acetic acid), IDS (imido-disuccinic acid) and gluconate.

Oxidation Agents Formulated alkaline detergents produced by detergent manufacturers can contain oxidation agents to boost their cleaning effects. Examples of such substances are oxygen-releasing agents, active chlorine or active-chlorine carriers. These may be in a liquid form, such as sodium hypochlorite, hydrogen peroxide or potassium hypochlorite, or in powder form, such as sodium perborate or sodium percarbonate. They are added in a stabilised form, and active oxygen is cleaved off over a certain period of time. They create new sites for detergents to act.

Summary of the different detergents used in food equipment cleaning: Alkalis - NaOH - KOH - Na2CO3 Acids - HNO3 - H3PO4 Wetting agents - Ionic (anionic, cationic and amphoteric) - Non-ionic Sequestering agents - EDTA - NTA - IDS - Gluconate Oxidation agents - Sodium hypochlorite - Hydrogen peroxide - Potassium hypochlorite - Sodium perborate


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Overview of Some Cleaners and Disinfectants Below follows an overview of acid descalers and cleaners, neutral cleaners, alkaline cleaners and disinfectants. Table 8. Acid descalers and cleaners (from the Handbook of Hygiene Control in the Food Industry). Ingredient Inorganic acids

Substance Nitric acid

Function Owing to its oxidising properties at high concentrations nitric acid cannot be used in complex formulations, e.g. with surfactants. Its use is limited to descalers for removing inorganic residues such as water scale and milk stone from surfaces.

Phosphoric acid Sulphonic acids Sulphuric acid

These acids can be combined with surfactants, defoamers and other components in cleaning agents, and may be used in formulations designed to simultaneously remove inorganic and organic residues from food contact surfaces .

Organic acids

Formic acid Citric acid Lactic acid Gluconic acid Sulphamic acid

See phosphoric acid

Inhibitors

Phosphonic acids

Protect materials against chemical attack.

Surfactants

Non-ionic and anionic surfactants

Improve cleaning efficacy regarding organic soil; enhance scale-removing properties and are the choice for removing fat residues.

Defoamers

Hydrophobic non-ionic substances Hydrotrophic substances

Suppress foam arising from formula components and/or removed soil.

Stabilisers

Stabilise liquid formulations at high and/or low temperatures.


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Table 9. Neutral cleaners (from the Handbook of Hygiene Control in the Food Industry). Ingredient Builders

Substance Phosphates Phosphonates Citrates

Function Enhance soil-removal and suspension properties as well as the effects of surfactants.

Surfactants


Allow soil penetration and emulsification, and provide better surface wetting.

Defoamers

Hydrophobic nonionic substances


Enzymes

Proteases

Improve protein removal at around neutral pH from sensitive surfaces.

Lipases

Improve fat removal without using surfactants.

Specific enzymes

Improve removal of recalcitrant substances from surfaces without using aggressive chemicals.

Hydrotrophic substances


Stabilisers


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Table 10. Alkaline cleaners (from the Handbook of Hygiene Control in the Food Industry). Ingredient Bases

Substance Sodium hydroxide Potassium hydroxide

Function Solve, peptise, soften or decompose organic soil.

Chelates

EDTA NTA IDS Gluconate

Chelates not only reduce the negative effect of water hardness on cleaning efficacy and provide scale prevention, they can also remove fresh, thin layers of inorganic deposits, attack inorganic soil and help in removing organic soil when combined with inorganic scale.

Builders

Phosphates Phosphonates Citrates Silicates

By chemical nature most of the builders are chelates. They enhance soil-removal and suspension properties as well as the effects of surfactants.

Surfactants

Non-ionic and anionic

Improve soil penetration and emulsification, as well as surface wetting.

Defoamers

Hydrophobic nonionic substances


Sequestering agents

Polyphosphates Phosphonates

Prevent scaling, especially in rinsing stages.

Corrosion inhibitors

Silicates

Protection of soft metals against chemical attack.

Oxidising cleaning boosters

Hypochlorites

Assist in removal of recalcitrant and insoluble soil. They can break down larger molecules into smaller fractions by means of oxidation, or render soil soluble by introducing functional groups.

Stabilisers

Hydrotrophic substances



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Table 11. Disinfectants (from the Handbook of Hygiene Control in the Food Industry). Ingredient Disinfectants

Substance Hypochlorites Peroxides Quaternary ammonium compounds Ampholytes

Function To kill microorganisms by complex reactions on either the outside or inside of the microbial cell.

pH-regulators, buffers

Bases Acids Salts

To provide optimum pH for the active biocide, stabilise the pH during application, e.g. to reduce the risk of corrosion with oxidising disinfectants, or to provide product stability in solution or in concentrated form.

Surfactants


To improve wetting, enhance biocidal efficacy and enable foam applications.

Defoamers

Hydrophobic nonionic substances Hydrotrophic substances

To control foaming during cleaning

Stabilisers

To stabilise liquid formulations at high and/or low temperatures.

3.5 Detergent Concentration When cleaning fails the natural reaction is to increase the concentration of the detergent. However, this may be counterproductive. A number of investigations into milk fouling in the pasteurisation temperature range have indicated an optimum NaOH concentration in the range 0.5-1% (w/w) (see Fig. 8). This can be explained by the fact that an increase in the NaOH concentration does not increase the cleaning rate, but instead results in a glassy surface on the soil, preventing the cleaning solution from penetrating it. The cleaning procedures used in the dairy industry involve a higher lye concentration than that mentioned above (0.5-1%). The reason for this is that these plants are more heavily soiled and lye is consumed during cleaning. However, it is important to bear in mind that increasing the detergent concentration may not solve cleaning problems. Many investigations have shown that there is an optimum detergent concentration and that increasing it will lead to less effective cleaning. The optimal concentration varies depending on the type of detergent, e.g. pure NaOH, NaOH with additives or formulated detergents from a detergent supplier.


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. u . a / e m i t g n i n a e l C

0

0,2

0,4

0,6

0,8

1

Lye concentr ation / %

Fig. 8. A number of investigations of milk fouling in the pasteurisation temperature range have indicated an optimum in NaOH concentration in the range 0.5-1% (w/w). The optimal concentration varies with the type of detergent.

The solution might not be to increase the detergent concentration when encountering cleaning problems. Consider other cleaning parameters, such as flow rate, temperature and cleaning time.

Dosing of Cleaning Agents The goal is to obtain an even distribution of the cleaning agent throughout the whole equipment. Cleaning agents can be dosed directly or in-line. The advantage of using in-line dosing is that the correct detergent concentration will be obtained for that particular piece of equipment or plant. To obtain the best effect with in-line dosing, both the flow and the dosing frequency should be high, making the distribution more even. The principle of in-line dosing is shown in Fig. 9. Three cases are shown.


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Fig. 9. The principle of in-line dosing. (From the Handbook of Hygiene Control in the Food Industry.) Top left: high flow velocity and low dosing frequency, resulting in a poor distribution of the detergent. Top right: changing the dosing volume will not result in a better distribution. Bottom: the best alternative is to maintain a high flow velocity and increase the dosing frequency.

When using in-line dosing high demands are placed on measuring and controlling the detergent concentration. This is normally achieved by measuring the conductivity in-line. Table 12 gives the conductivity for various solutions at 20 °C. It is important to remember that the conductivity is strongly dependent on temperature, as is shown in Fig. 10. The conductivity sensors used today are temperature calibrated. Table 12. Conductivity of different solutions at 20 °C (from the Handbook of Hygiene Control in the Food Industry). Solution Conductivity @ 20 C (mS/cm)

Tap water, soft Tap water, hard Tap water, saline Brackish water NaOH 1 % w/w NaOH 2 % w/w NaOH 3 % w/w


0.18 0.46 0.75 2 47.5 90.0 127.0

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350 1.0% w/w NaOH 300

2.0% w/w NaOH 3.0% w/w NaOH

) 250 m c / S m200 ( y t i v i t c 150 u d n o C 100

50

0 10

20

30

40

50

60

70

80

90

Temperature (C)

Fig. 10. Conductivity vs. temperature for three NaOH concentrations (from the Handbook of Hygiene Control in the Food Industry).

3.6 Cleanin Cleanin g Temperatu re Chemical reactions generally proceed faster at higher temperatures. This is also the case when cleaning solutions react with foulants. It is generally said that the effectiveness of an alkali solution will double for every 8 °C increase in temperature. This has been demonstrated for the removal of proteinaceous deposits at cleaning temperatures up to 80 °C, but is probably also true for higher temperatures. It can clearly be seen in Fig. 11 that increasing the cleaning temperature when removing protein fouling from a pasteuriser increases the cleaning rate. It is important to remember that the production temperature must not be exceeded when cleaning the processing equipment, especially when removing proteinaceous foulants. If this temperature is exceeded, the proteins may be denatured, making the deposit more difficult to remove.

Guideline Do not exceed the production temperature during CIP since proteins may be denatured, making the deposit more difficult to remove.


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. u . a / n a e l c o t

e m i T

60

70

80

90

Temperature / C

Fig. 11. The influence of temperature on cleaning time.

Table 13 gives some general guidelines for choosing CIP temperatures for some typical cleaning objects in a dairy process line. Table 13. Suitable cleaning temperatures for the cleaning of equipment in the dairy industry (from the Handbook of Hygiene Control in the Food Industry). Type of Temperature Equipment to be cleaned detergent ( C)

HNO3

NaOH

60-65

Tanks, pipes, milk pasteurisers

80-85

UHT plants

60-80

Milk collection tankers, milk tanks, cream tanks, quarg and yoghurt tanks, filling machines

70-90

Milk pasteurisers

90-130

UHT plants, sterilisers for puddings and desserts


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3.7 Cleaning Cleaning Time Cleaning time is the most interesting parameter from the production perspective. The cleaning time places the focus on the fact that cleaning is to a large extent an optimisation issue. The milk producer does not want to clean longer than necessary, but the soil must be removed to ensure food safety. The cleaning time is correlated to the specific equipment to be cleaned, thus it is of vital importance to characterise every piece of equipment when optimising the CIP sequence in order to identify the equipment that requires the longest cleaning time. Another factor that must be taken into consideration when designing CIP sequences is the length of production time preceding cleaning, which is illustrated in Fig. 7. A longer production time will probably result in the need for a longer cleaning period. The third factor that affects the cleaning time is the type of product that has been processed, chocolate milk being harder to remove than normal milk, for example. Several steps are included in the cleaning process that do not involve the use of cleaning solutions, such as pre-rinsing, inter-rinsing and final rinsing. The cleaning steps involving detergent require enough time for the solutions to dissolve the soil, swell it, saponificate it, disperse it and finally remove it. The detergent must be in contact with the foulant long enough to ensure that it is completely removed from the surface of the equipment.

Cleaning time depends on: - the kind of equipment to be cleaned - the production period prior to cleaning - type of product being processed


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3.8 Cleani Cleaning ng Flow The last parameter in Zinner’s circle, but perhaps the most important, is the flow. If the flow is too low, the efficiency of the other three parameters, detergent concentration, cleaning time and temperature, might decrease. Approximately 50% of all CIP-related problems are due to inadequate flow. The flow must be sufficient to ensure the satisfactory transport of detergent solution to the soiled surface. The soiled surface is also exposed to shear forces (mechanical forces) through the fluid flow, resulting in the removal of soil, which is then transported into the bulk solution.

The role of the flow in CIP is: - to transfer the detergent solution to the deposited soil and - to remove the dissolved soil.

In the CIP literature it is normally stated that the velocity in a pipe flow must exceed 1.5 m/s to obtain good cleaning results. For plate heat exchangers the CIP flow is normally 0.3-1.0 m/s. Table 14 gives the volume flows recommended for a range of pipe diameters to ensure a minimum CIP flow of 1.5 m/s. A common common recommendation for cleaning of tubular heat exchangers is to use a CIP flow 1.5 to 2 times higher than that during production.

Table 14. Recommended pumping capacities to ensure a flow of 1.5 m/s during CIP. Pipe outer diameter Pipe inner diameter Volume flow mm / inches mm l/h 38 /1.5 35.6 5 400 51 / 2 48.6 10 000 63.5 / 2.5 60.3 15 400 76 / 3 72.8 22 500


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Flow velocity in pipe flow: 3

=

Volume flow (m / s ) Area (m 2 )

where the volume flow and area are calculated from: Volume flow (m 3 / s) =

2

Volume flow (l / h)

Area (m ) = π ⋅

3.6 ⋅ 10 6

(d i.d . (m) )2 4

Figure 12 illustrates how the flow velocity in a pipe varies as a function of volumetric flow for a range of pipe diameters. It is important to bear this in mind when designing a process plant, so that pumps have the correct capacity to cope with pipe expansions and contractions. However, in some objects/components the flow does not reach this level, resulting in zones of low wall shear stress. The result of cleaning may be good despite this, due to the fact that the turbulence is high, ensuring that fresh detergent solution reaches the soil layer. However, a practical implication is that the CIP sequence takes longer than if a higher flow velocity had been used.


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Velocity v m/s

25 mm

38 mm

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51 mm

3.0

2.5

63.5 mm

2.0 76 mm

1.5 89 mm

1.0

0.5

5000 10000 15000 20000 25000 30000 35000 Flow rate Q l/h

Fig. 12. Illustration of the variation of fluid velocity in pipes with the volumetric flow rate for six different pipe diameters.

In Fig. 13 the Zinner circle is shown for three different cleaning situations: fully developed pipe flow, a dead end with poor fluid exchange, and zones with swirling flow. These examples should be regarded as guidelines, and not as exact ratios for the different cases. In the first case, with a fully developed pipe flow, all four cleaning parameters work well together to remove the soil from the surface. The contact time of the detergent solution will be long enough to weaken the chemical bonds between the soil and surface, and the soil will be removed by the flow. In Fig. 13b the principle of cleaning a dead end is shown. In this situation the cleaning time must be prolonged to ensure that the detergent solution reaches the soiled surface, and removes the dissolved soil. The lack of mechanical energy makes the removal of the soil much more difficult, and increasing the detergent concentration will have a limited effect. In the third case, when a swirling flow is dominating (Fig. 13c), the transport and exchange of cleaning solution is higher than in pipe flow. However, since the wall shear stresses are lower the cleaning time will be longer than in the case of fully developed pipe flow.


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Fig. 13. The influence of the different cleaning parameters on a) pipe flow, b) cleaning of a dead end and c) cleaning of zones with swirling flows.

In cases when the flow is not sufficiently high it is important not to compensate by increasing the detergent concentration, but instead prolonging the CIP sequence.

Three cases are described below, in which the role of the flow is crucial: flow in dead ends, flow in expansions and flow in 180° bends. It is important to be aware of cleaning problems related to these kinds of constructions which are caused by shortcomings in the design of processing lines.


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Dead ends The most difficult areas to clean are those exposed to low wall shear stress and low fluid exchange, e.g. dead ends resulting in recirculation zones. There should be no dead ends in a process line, but they are often encountered in processing lines that have been rebuilt, as well as in new constructions. When cleaning dead ends it is vital that the direction of flow is as illustrated in the left-hand diagram in Fig. 14, i.e. directly towards the dead end. In the right-hand diagram the flow direction results in a very low flow velocity in the dead end, leading to low wall shear stresses and little mechanical action on the deposited soil.

Fig. 14. Cleaning of dead ends. The diagram on the left shows the CIP solution reaching the bottom of the dead-end, while in the right-hand diagram it does not.

If the dead end is directed upwards, there is a risk that the cleaning solution will not reach to the top of the dead-end due to trapped air (Fig. 15). In the case of a dead end pointing downwards, there is a risk of debris being trapped.

Fig. 15. The direction of the dead end is important. If it points upwards there is a risk that air will trapped in the top. The opposite orientation also poses a threat to hygiene.

Tetra Pak employs a rule of thumb that the ratio L/d of a dead end must not exceed 1.5 in order to ensure a reasonable cleaning effect. EHEDG guidelines say a maximum of 0.5 and cGMP/ASME BPE a value of 2. Fig. 16 shows the fluid velocity in a dead end for a range of pipe velocities. The relative velocity (u/v m), where vm is the mean velocity of the pipe flow and u the velocity in the dead end, is plotted on the y-axis.


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For example, when L/d = 1.5 and the mean flow rate in the pipe is 1.5 m/s, the velocity in the dead end will be approximately 0.2 m/s (i.e. 12 % of the pipe velocity).

Fig. 16. Fluid velocity in a dead end (from The Federal Institute of Milk Research, Kiel, Germany).

Rule of thumb: The length of a dead end should not be more than 1.5 times its diameter:

L d


< 1.5

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Expansions Another flow situation is shown in Fig. 17, where the fluid is forced to flow through a constriction. Zones of recirculation of will arise as the pipe opens up. As a result, there will be little exchange of CIP solutions between the bulk flow and the soil on the surface. The wall shear stress acting on the surface in the expansion zone is also reduced.

Fig. 17. Fluid flow in a gradual expansion.

Is it possible to change the size of the recirculation zones by increasing or decreasing the flow velocity? Changing the flow rate does not have any effect on the location of areas where flow conditions are unfavourable for cleaning. Increasing the flow rate will of course result in a general increase in flow rate, but only very small increases will be seen in low-velocity areas. So the conclusion is:

Problem areas will remain where they are, regardless of whether the flow velocity is increased or not; however, the problem areas may be reduced.


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Bends The wall shear stress generated by the flow in a 180° bend is shown in Fig. 18a. The high wall shear stress zones are, not surprisingly, found on the outer side of the bend, whereas the inner side of the outlet of the bend is exposed to low wall shear stresses. Cleaning will be less effective in this zone due to the low mechanical energy, as can be seen in Fig. 18b.

High wall shear stresses

Flow separation Low wall shear stresses

Fig. 18a. Distribution of wall shear stress in a 180° bend.

Fig 18b. The results of cleaning, showing the dependency on wall shear stress.

Increasing the flow rate in a straight pipe will immediately give rise to a higher wall shear stress and thus more effective cleaning. Unfortunately, similar behaviour is not seen in a 180° bend. Increasing the flow rate will lead to a greater pressure drop, but will not result in a corresponding increase in the wall shear stress.


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3.9 CIP Sequences for Certain Products The cleaning procedure can generally be described as can be seen in Table 15: Table 15. Example of a typical cleaning sequence. Step Purpose

Pre-rinsing with water Cleaning with alkaline solution Intermediate rinsing with water Cleaning with acid solution Rinsing Disinfection/sterilisation Final rinse

To remove gross soil To remove attached soil (mainly proteins and fat) To remove cleaning chemicals and dissolved soil To remove attached soil (mainly minerals) To remove cleaning chemicals To reduce microbial load to a safe level To remove sanitiser

Full CIP Sequences for Various Applications Each step in an operation has an optimum operating temperature, depending on the kind of soil. The initial pre-rinse is usually carried out with cold water, but warmer water is sometimes used, 25 to 60 °C. In general, for cold surfaces, alkali and acid cleaning is performed at 60-80 °C. However, in UHT processing equipment, cleaning is performed at a higher temperature. Typically, alkali cleaning takes place at about 140 °C and acid cleaning at approximately 80-85 °C (temperature measured in the holding cell). The system is purged of product with warm water, followed by a 50-minute alkali cleaning step. The equipment is then rinsed with warm water, followed by a 30-minute acid cleaning step. The CIP sequence is then completed with a warm rinse and then a final rinse at room temperature. It is important to remember to flip the valves when cleaning a processing line in order to ensure that the surfaces in contact with the product are sufficiently cleaned.


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Table 16. An example of CIP of a dairy production plant for ambient white milk Cleaning step Duration, minutes Temperature, C Daily cleaning of non-heated surfaces (e.g. tanks and pipes) Water rinse >10 NaOH circulation (1.5 %) 60-80 Water rinse 50* Acid circulation (0.8 %) 60-65 Water rinse Cold

Daily cleaning of heated surfaces (steriliser) Water rinse >10 NaOH circulation (2-2.5 %) 140 Water rinse Cold or heated* Acid circulation (1-1.5 %) 80-85 / 105 Water rinse Cold

10-15 50 10-15 30 15

* Pre-heated water reduces cooling of the equipment during intermediate rinsing.

Table 17. An example of CIP of a dairy production plant for chilled white milk Cleaning step Duration, minutes Temperature, C Daily cleaning of non-heated surfaces (e.g. tanks and pipes) Water rinse >10 NaOH circulation (1.5 %) 60-80 Water rinse 50* Acid circulation (0.8 %) 60-65 Water rinse Cold

Daily cleaning of heated surfaces (pasteuriser) Water rinse >10 NaOH circulation (1.5-2 %) 75-95 Water rinse Cold or heated* Acid circulation (1-2 %) 65 Water rinse Cold

10 30 5-10 20 10



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Table 18. An example of CIP of a dairy production plant for chilled fermented milk Cleaning step Duration, minutes Temperature, C Daily cleaning of non-heated surfaces (e.g. tanks and pipes) Water rinse >10 NaOH circulation (1.5 %) 60-80 Water rinse 50* Acid circulation (0.8 %) 60-65 Water rinse Cold

Daily cleaning of heated surfaces (pasteuriser) Water rinse >10 NaOH circulation (1.5-2 %) 95 Water rinse Cold or heated* Acid circulation (1-2 %) 65 Water rinse Cold

10 30 5-10 20 10

* Pre-heated water reduces cooling of the equipment during intermediate rinsing. Table 19. An example of CIP of a production plant for orange juice: Cleaning step Duration, minutes Temperature, C Daily cleaning of non-heated surfaces (e.g. tanks and pipes) Water rinse >10 NaOH circulation (1.5 %) 70 Water rinse Cold

3-5 10 5

Daily cleaning of heated surfaces (e.g. plate heat exchangers) Water rinse >10 NaOH circulation (1.5 %) 70 Water rinse Cold

3-5 20 10

Weekly cleaning of heated surfaces (e.g. plate heat exchangers) Water rinse >10 NaOH circulation (1.5 %) 70 Water rinse Cold or heated* Acid circulation (1 %) 65 Water rinse Cold

5 20 5 10 10

* Pre-heated water reduces cooling of the equipment during intermediate rinsing. During processing of juices containing pulp, the pulp can clog the equipment. Therefore, the CIP flow is often reversed, so-called back-flushing, in order to remove the pulp.


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Aseptic Intermediate Cleaning Aseptic intermediate cleaning, AIC, is frequently used to prolong running times. The aim is to maintain the process equipment in an aseptic condition while performing CIP. When an acid flush is included it is of the utmost importance to check for possible deterioration of stainless steel equipment and rubber gaskets. Table 20. An example of an AIC procedure Cleaning step Temperature, C

Water rinse NaOH circulation (2-2.5 %) Water rinse

140* 140 140

Duration, minutes

15

Re-start of production * Production temperature.

Table 21. An example of an AIC procedure where acid is included Cleaning step Duration, minutes Temperature, C

Water rinse NaOH circulation (2-2.5 %) Water rinse Acid flush (1 %) Water rinse

140* 140 140 140 140

8-10 3-5

Re-start of production * Production temperature.


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3.10 CIP of Specific Components in a Processin g Li ne Separators In order to ensure the functionality of separators the parts of the separator in contact with the product must be completely clean before beginning a new production run. Normally, the separator is incorporated into a combined processing line together with heat exchangers and other peripheral equipment. The cleaning times and CIP solution concentrations must also meet the requirements of these parts. The following general CIP sequence is taken from the Tetra Pak guidelines for CIP of separators (Doc. No. AM-10002en3). Table 22 lists the usual steps. Disinfection is to take place immediately prior to separation. If chemical disinfectants containing chlorous components, such as sodium hypochlorite (NaOCl), are used, the temperature must not exceed 25 °C, as chlorine is highly corrosive at higher temperatures. It is also recommended in these cases that a maximum of 0.1 % NaOCl is used. The reader is referred to Doc. No. AM-10002en3 for further details.

Table 22. An example of CIP of a separator Cleaning step Temperature, C Daily cleaning Water rinse NaOH circulation (1.5 %) Water rinse Acid circulation (0.8-1 %) Water rinse

>10 75 Cold* 70 Cold

Duration, minutes

15-20 35-45 10-15 20-30 10-15


Homogenisers The homogeniser can be positioned either upstream of the aseptic side or downstream of the steriliser, i.e. on the aseptic side. The maximum lye concentration should be 2% at a maximum temperature of 85 °C. In the acid cleaning step, the concentration must not exceed 1.5%, and the temperature should be no higher than 85 °C (Table 23). The CIP inlet pressure must


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exceed 2 bar. The minimal required flow of cleaning agents must be equal to or exceed 100% of the maximal production flow. The CIP sequence should be the same as that for the process equipment. The maximum sterilisation temperature is 140 °C, for 30 minutes. The reader is referred to Tetra Pak guidelines for CIP of homogenisers (Doc. No. TeM-1245070-01) for further details.

Table 23. An example of CIP of a homogeniser Cleaning step Temperature, C Daily cleaning Water rinse NaOH circulation (2 %) Water rinse Acid circulation (1.5 %) Water rinse

Duration, minutes*

>10 85 Cold 85 Cold

* The duration of the different cleaning steps is the same as those in the cleaning procedure for the process equipment.

Tank Cleaning Tanks are used for a range of applications in a processing plant, such as reception, handling CIP solutions, BTD, storage and buffer storage prior to the filling machines. Depending on the application, different CIP sequences are required. Generally speaking, the cleaning of tanks differs from that of pipe cleaning. The main differences are: • CIP solutions are sprayed onto the walls and • there is no wall shear stress. Normally, a CIP tank flow of 300 l/m2 per hour is used for horizontal tanks and 200 l/m2 per hour for vertical tanks. Figure 19 illustrates some of the factors that should be kept in mind when cleaning tanks. A general recommendation for the cleaning of tanks is that vessels should be as empty as possible when sprayed with cleaning solutions to ensure complete washing of the walls and bottom. Puddles should be no more than 50 mm deep, and must be fully removed at some point during cleaning and at the end of the cleaning process. Spraying of the tank can be interrupted to do this. Two or more spray balls are often installed to ensure adequate cleaning. It is important to consider any


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equipment installed in the tank, e.g. baffles and sensors, that may prevent the cleaning solution from covering the whole surface. A centrifugal liquid ring pump should be used to ensure effective tank emptying because it can handle liquids with a high gas or air content. If a centrifugal pump is used as a CIP return pump, difficulties may rise due to pump cavitation.

Guidelines for tank cleaning • Complete drainage between CIP phases. • No mixing of water and detergent solution in the tank. • The tank must be completely drained during CIP to ensure adequate cleaning of the whole wall surface. • The pump used for CIP return flow should be a ring liquid pump to ensure complete drainage of the tank. • Flow for horizontal tanks: 300 l/m 2 per hour • Flow for vertical tanks: 200 l/m2 per hour

When applying the detergent solution it must be ensured that the whole surface area of the tank is covered. Among available tank cleaning devices are fixed spray balls, rotary spray heads and rotary jet heads. Alfa Laval tank cleaning devices are shown in Fig. 20. The simple fixed spray ball is cheap, but the flow pattern in the tank is not sufficiently effective, and cleaning is limited to a small surface area. In most tank cleaning applications the removal of biofilms, precipitate or sludge/ sediments is required. The CIP solution tanks must also be cleaned, so-called intrinsic cleaning, to prevent microbial growth.

The CIP tanks must be cleaned at certain time intervals to avoid microbial growth.


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The volume to each object is individually controlled

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Volume control guarantees cut-off point

CIP Pressure

Return flow from object are individually

No mixing of water/detergent in the tank

CIP Return

Complete drainage between CIP phases

Fig. 19. Illustration of tank cleaning to illustrate some important factors, i.e. no mixing of water/detergent in the tank and complete drainage between CIP phases.


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Fig. 20. Fixed spray ball Courtesy of Alfa Laval.

Rotary spray head

Table 24. An example of CIP of a Tetra Alsafe tank Cleaning step Temperature, C Daily cleaning Water rinse NaOH circulation (1-1.5 %) Water rinse Acid circulation (1-1.5 %) Water rinse

>10 65-80 Cold 65-80 Cold

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Rotary jet head

Duration, minutes

20 10

3.11 Contro l o f Cleaning Result It is imperative to check the results of cleaning. The document CIP Validation Procedure, mentioned in Chapter 1, describes how the cleaning results can be Copyright 2008; Tetra Pak Processing Systems

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controlled and validated. Chapter 5 of the CIP Validation Procedure document gives a checklist of critical control points for controlling the results of cleaning.

3.12 Disinfecti on/Sterili sation o f Equipment After CIP the plant is sterilised/disinfected if it is to be used directly. If the plant is not to be used for some time, a slightly acidic solution (pH around 5) is left in the processing equipment. The reason for this is to restrict microbial activity and growth.

Sterilisation Processing equipment is sterilised immediately before starting aseptic production by the circulation of hot water. After reaching the required temperature of 125 °C the water is circulated for 30 minutes to ensure aseptic status of the equipment. The temperature sensor is positioned in the return circuit to ensure correct temperature measurement.

Disinfection There are two types of disinfection: thermal and chemical. Thermal disinfection can be carried out with steam (< 1 bar) or hot water at 90-95 °C. Commonly used chemical disinfectants are chlorine, hydrogen peroxide, peracetic acid, and a combination of hydrogen peroxide and peracetic acid. Chemical disinfectants are usually used at ambient temperature. A comparison between thermal and chemical disinfection can be found in Table 25.


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Table 25. A comparison between thermal and chemical disinfection Properties Thermal disinfection Chemical disinfection

Bactericidal Sporicidal

Good None

Fungicidal

Good (except for extremely resistant mould spores) Leaving chemical residues No Rinsing with water No (pasteurised or filtered or eqv.) after disinfection Cooling of equipment Yes Penetration ability Good Corrosive No Energy consumption High

Good Certain effect but dependent on temperature, contact time and concentration Variable

Yes Yes

No Poor/None Yes Low

3.13 Guidelines for Determini ng Cleaning Intervals f or Sterilisers The QAM document FSQ-588012-101 provides hands-on instructions for determining the optimum ratio between production time and CIP for Tetra Therm Aseptic sterilisers. The reader is referred to this document for further information.


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3.14 CIP Systems There are two main types of CIP system: single-use systems, in which the CIP solutions are discarded after use, and re-use systems, where the CIP solutions are stored in tanks and chemicals are added as required (Table 26). Single-use systems are further divided into single-path CIP and single-use CIP systems. Re-use systems can be categorised as recovery CIP (centralised CIP) and satellite CIP (decentralised CIP) systems.

Table 26. The two types of CIP systems, single-use and re-use systems. Single use systems Re-use systems Single-path Single-use Recovery systems Satellite systems

•

Single-path CIP systems This type of CIP system is used for heavily soiled equipment or when crosscontamination must be avoided. The freshly prepared CIP solutions are used only once and then discarded. There is thus no recirculation of the cleaning solutions. This type of system is frequently used in the pharmaceutical industry. This type of system is associated with high operating costs.

•

Single-use CIP systems This system is also used for heavily soiled equipment or when crosscontamination must be avoided. Unlike the single-path CIP system, the solutions are recirculated before drainage. The volume of the cleaning solution is low.

• Recovery CIP systems (centralised CIP systems) The CIP solutions are used many times, and can be used for several CIP tasks. The solutions are stored in tanks between CIP sequences. Fig. 21 shows an example of a centralised CIP system. Centralised CIP systems are of primary interest in small dairy plants with short communication lines. This type of CIP system requires large volumes of cleaning solutions, which can be considered a drawback. •

Satellite CIP systems (decentralised CIP systems) This type of CIP system can be an advantage for large dairies. Instead of having a large central CIP station a number of smaller units are located close to the processing equipment. Another name for this type of system is the satellite CIP system. However, central storage tanks are needed to store the alkali and acid detergents. Supply of water is arranged at the cleaning object such as heating of water and detergent solutions.


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The main advantage of a small CIP unit is that the consumption of cleaning solutions and water is kept to a minimum. Steam consumption is also minimised. The white water produced during pre-rinsing is more concentrated and it is therefore cheaper and easier to handle and evaporate. As a result, the load on waste water systems is lower than with centralised CIP systems. Detergent solutions can be used once in decentralised CIP systems, which is not the case in centralised systems where CIP solutions are recycled.

2

1

Fig. 21. The principle of a centralised CIP system. The cleaning unit is shown in the shaded box. 1. Tank for alkaline detergent; 2. Tank for acid detergent; 3. Plate heat exchanger. Object to be cleaned: A. Milk treatment equipment; B. Tank gardens; C. Silo tanks; D. Filling machines.

Design of CIP Systems A number of important issues must be considered when designing CIP systems. • •

•

The recovery CIP system should be located centrally and as close as possible to the object to be cleaned. Pipes for the supply and return of CIP media should be as short as possible and of the correct diameter. Long pipes and small-diameter pipes result in a large pressure drop requiring greater pump capacities, which in turn will result in higher energy consumption. Conductivity meters should be positioned on the CIP return side to indicate the concentration of the CIP solutions. Conductivity measurements are also


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used to determine when rinsing periods can be stopped, and as a support tool for product recovery. Booster pumps must be considered in some cases in order to ensure the correct flow rate in the equipment being cleaned. Correct positioning of e.g. temperature sensors is crucial. The temperature sensor should be positioned at the outlet of the production equipment in order to measure the correct cleaning temperature.

For further information the reader is referred to the Plant & Production Requirement report PPR_CIP Buffer.

Centralised CIP The centralised CIP consists of various parts. 1. Tanks for CIP solutions 2. Tanks for holding water of different qualities - cold water (potable water quality) for the final rinse - rinsing water (re-cycled cold water and re-cycled hot water from disinfection) used for pre-rinsing and intermediate rinsing - potable water used for disinfection 3. Recovery tanks for: - product recovery - mixed phases 4. CIP stations - each consisting of a number of CIP circuits

Raw is raw and processed is processed, and never the twain shall meet. It is an absolute requirement that there should be separate centralised CIP for cleaning of equipment used to process non-heat-treated and heat-treated products. For cleaning objects containing both non-heat treated and heat treated product, CIP solutions from the CIP central working on the heat treated side must be used.

CIP stations A CIP station consists of the following components. - A CIP pump (normally a centrifugal pump) positioned below or on the same level as the outlet of the CIP solution tanks. A frequency converter is the best way to change the CIP flow and obtain an optimised flow for different cleaning situations. (The more old-fashioned approach of using throttling devices requires more energy.)


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Pipes on the CIP pressure side. A back-pressure valve ensures that no CIP solutions on the CIP pressure side can enter the CIP tanks. Pipes on the return side. These are equipped with temperature and conductivity sensors to control the status of the CIP solutions. A rule of thumb for reuse of CIP solutions is that if the concentration is higher than 50 % of its original concentration it should be collected in the CIP tank for reuse.

CIP circuits Each CIP station includes a number of CIP circuits. CIP circuits consist of different cleaning objects: tanks, pipes and heat treatment equipment. Each of these objects requires a different CIP sequence. - Tank cleaning requires breaks for draining of the tanks. - Cleaning of pipes is fairly easy, but can be complicated if the pipes are long. This requires booster pumps to compensate for pressure drops, and heat exchangers to correct the fall in temperature. - Heat treatment modules require longer CIP times than other objects.


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Further CIP Reading CIP: Cleaning in Place, Society of Dairy Technology, Ed. Romney, A. J. D., 1990. Cleaning-in-Place: Dairy, Food and Beverage Operations, Ed. Tamime, A. Y., Blackwell Publishing, 2008. EHEDG Glossary, Version 2004/04.G01, www.ehedg.org/guidelines/glossary.pdf Grasshoff, A., Cleaning of heat treatment equipment, Bulletin of the IDF, 328 (1997) 32-44. Handbook of Hygiene Control in the Food Industry, Ed. Lelieveld, H. L. M., Mostert, M. A. & Holah, J., CRC Press, 2005. Jensen, Stenby and Nielsen, Improving the Cleaning Effect by Changing Average Velocity, Trends in Food Science & Technology, 18 (2007) 58-63. Jensen, BBB and Friis, A., Fluid Flow in Cleaning of Closed Processes, New Food, 1 (2006) 64-67. Jeurnink, T.J.M. and Brinkman, D.W., The cleaning of heat exchangers and evaporators after processing milk or whey, Int. Dairy Journal, 4, (1994) 347-368.


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Appen dix Extract from the EHEDG Glossary

A Aseptic equipment Hygienically designed equipment that is sterilisable and is impermeable to microorganisms to maintain its aseptic status. Aseptic process A process using equipment sterilised before use, and which, in running conditions, is protected against recontamination by micro-organisms.

B Biofilms A microbial consortium adhering to a surface. Note: these are frequently but not in every case embedded in extra-cellular polymeric substances.

C CCP (critical control point) A step at which control can be applied and is essential to prevent or eliminate a food safety hazard or reduce it to an acceptable level. (Codex) CIP (cleaning-in-place) Automated wet cleaning system of a line and/or individual equipment in a closed circuit without dismantling. Note: CIP efficiency depends on 5T’s – time, temperature, titration, turbulence and technology. CIP can be done in a dry area, the aim being that the design precludes any water passing into the environment. Cleanability The suitability of equipment to be freed from soil easily. See also Comparative cleanability Cleaning The removal of soil, food residues, dirt, grease or other objectionable matter. (Codex)


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Coatings The result of a process where a different material is deposited to create a new surface. (3-A) Commercial sterilisation (see Sterilisation) Comparative cleanability The cleanability of equipment relative to a reference. Contaminant Any biological or chemical agent, foreign matter or other substance not intentionally added to food, which may compromise food safety or suitability. (Codex) Contamination The introduction or occurrence of a contaminant in food or food environment. Controlled environment (see Zoning) COP (cleaning-out-of-place) – (see also Wet cleaning) Manual cleaning of dismantled equipment. Note: The main part of the installation may remain fixed in a position but parts may be removed to another point for cleaning. Corrective action Any action to be taken when the results of monitoring at the CCP indicate a loss of control. (Codex) Note: Action taken to eliminate or reduce the causes of nonconformity, defect or other undesirable situation after a deviation has been detected, in order to minimise or prevent its recurrence. Every control point in a Quality Monitoring system must include the corrective action to be taken in case of deviation. Crevice A crack with an opening accessible to contaminants. For example, a narrow opening or fissure either in the bulk of a material or between two closely fitting components, such as a flange and its gasket. Typically, a crevice has a depth more than 20 times the width of its opening. Crevices may not only harbour soils and micro-organisms and be inaccessible to cleaning agents, but may also cause accelerated corrosion of the bulk material, rapidly increasing the size of the crevice.

D Disinfectant A chemical that is used after cleaning for killing a certain proportion/type of viable micro-organisms remaining on the surface. Note: A disinfectant is not expected to kill all micro-organisms of any type, including spores (see also Sterilisation). Nevertheless in the USA it is defined as an


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agent that will kill 100 % of infectious fungi and vegetative bacteria although it will not necessarily kill bacterial spores on inanimate surfaces. Disinfection The reduction, by means of chemical agents and/or physical methods, of the number of micro-organisms in the environment, to a level that does not compromise food safety or suitability. (Codex) Note: disinfection according to BSI 5283: the destruction of micro-organisms, but not usually bacterial spores. Disinfection does not necessarily kill all microorganisms, but reduces them to a level acceptable for a defined purpose e.g. a level which is harmful neither to health nor to the quality of perishable food. Specifically in USA, the terms sanitiser and sanitisation are more commonly used in the food industry (see Sanitiser/Sanitisation) Dry-cleaning Cleaning which does not involve any use of water, a technique which can be used as a preventive measure to reduce risks of microbial development in equipment and in the environment. It also reduces risk of contamination with e.g. residues of aged or modified product. Mostly done manually using brushes and/or vacuum cleaners.

E Easily or readily removable Quickly separated from the equipment with the use of simple hand tools if necessary. The latter are implements normally used by fitters, operating and cleaning personnel such as a screwdriver, a wrench or hammer. (3-A)

F Food hygiene All conditions and measures necessary to ensure the safety and suitability of food at all stages of the food chain. (Codex) Food safety Assurance that food will not cause harm to the consumer when it is prepared and/or eaten according to its intended use. (Codex)

G GHP (Good hygiene practice) Measures applicable throughout the food chain (including primary production through to the final consumer), to achieve the goal of ensuring that food is safe and suitable for human consumption. GHPs are a subset of GMPs.


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GMP (Good manufacturing practice) All procedures, processes, practices and activities aimed at ensuring that the quality and safety objectives are met consistently. GMPs should apply throughout the supply chain for food. Application of GMP is a prerequisite for any HACCP study. (see HACCP) Note that GHPs are a subset of GMPs.

H HACCP (Hazard Analysis Critical Control Point) A system which identifies, evaluates and controls hazards that are significant for food safety. (Codex) Note: A HACCP study must be performed during the development of new products and processes, covering thus new equipment, and when changes are made on existing lines or to products. All CCPs identified must be monitored and corrective action taken in case of deviation. Hazard A biological, chemical or physical agent in, or condition of, food with the potential to cause an adverse health effect. (Codex) Hygiene See Food Hygiene. Hygienic equipment class I Equipment that can be cleaned-in-place and can be freed from soil after reassembly. Hygienic equipment class II Equipment that is cleanable after dismantling and can be freed from soil after reassembly. Hygienic integration The process of combining or arranging two or more entities to work together for a hygienic purpose.

I In-place cleanability The suitability to be easily cleaned without dismantling.

M Manual cleaning Removal of soil when the equipment is partially or totally disassembled.


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Mechanical cleaning Shall denote cleaning, solely by circulation and/or flowing chemical detergent solutions and water rinses onto and over the surfaces to be cleaned, by mechanical means. Micro-organisms Micro-organisms that can cause disease/illness in humans and animals. Note: Distinguish from indicator micro-organisms, whose presence indicate a failure of a GHP. The number present is assumed to be related to the probability of contamination of a product with a pathogen. Monitoring The act of conducting a planned sequence of observations or measurements of control parameters to assess whether a CCP is under control.

N Non-absorbent materials Materials which, under the intended conditions of use, do not internally retain substances with which they come into contact. Non-product contact surfaces (See also Product contact surfaces) All exposed surfaces other than those in contact – or potential – contact with product. Non-toxic construction materials Materials which, under intended conditions of use, do not release toxic substances.

P Pasteurisation A microbiocidal heat treatment aimed at reducing the number of any harmful microorganisms, if present, to a level at which they do not constitute a significant health hazard. Note: pasteurisation applies to equipment as well as to food. Product contact surfaces All equipment surfaces that intentionally or unintentionally (e.g. due to splashing) come into contact with the product, or from which product or condensate may drain, drop or be drawn into the main product or container, including surfaces (e.g. unsterilised packaging) that may indirectly cross-contaminate product contact surfaces or containers. Note: A risk analysis can help to define areas of potential cross-contamination.


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R Relevant micro-organisms Micro-organisms able to contaminate, multiply or survive in the product and be harmful to the consumer or product quality. Removable (see Easily or readily removable) Risk A function of the probability of an adverse health effect and the severity of that effect, consequential to a hazard(s) in food. (Codex)

Risk is ‘the potential for the occurrence of unacceptable food safety deviations’ but may be extended to cover quality deviations. Note: In Codex terminology ‘risk’ pertains to public health issues. It relates to safety and not to quality related matters. Risk analysis A process consisting of three components: risk assessment, risk management and risk communication. (Codex) Note: Whereas Hazard analysis is under the responsibility of food manufacturers, Risk analysis is a public health matter. Risk assessment Risk assessment is the scientific part of the risk analysis process in which the hazards and risk factors are identified and the risk is calculated.

Apart from an end point calculation of risk, the risk model developed can be of value in determining the parts of the chain which contribute most to risk or to investigate the effect of changes in practices or processes throughout the chain on the risk level. Risk assessment contains four elements: - hazard identification which identifies particular hazards or contaminants in a product or process - exposure assessment which estimates the intake / exposure of the hazard by the consumer - hazard characterisation which relates exposure to the hazard with a public health effect (illness / death) frequently by assessing the dose-response relationship - risk characterisation which calculates the risk from the exposure (intake) and dose-response estimate (effect). Risk management Risk management is an evaluation of the acceptability of the risk posed and the implementation of measures to reduce this risk if necessary.


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Risk communication Risk communication involves transparent communication between the risk assessors (scientists) and the risk managers (regulators, industry, government agencies etc.). The results of risk assessment and risk management should be communicated more widely to the relevant stakeholders, including consumers. Risk zone (see Zoning)

S Sanitation (USA) Equivalent to hygiene in general terminology for the food industry. Sanitising or sanitisation (USA) A process applied to a cleaned surface capable of reducing the numbers of the most resistant human pathogens by at least 5 log10 reductions (99.999 %) to 7 log10 reductions (99.999999 %) by applying accumulated hot water, hot air, or steam, or by applying an EPA-registered sanitizer according to label directions. Sanitising may be effected by mechanical or manual methods using hot water, steam, or an approved sanitizer. See Disinfection. Sanitiser (USA) A substance that reduces the microbial contaminants on inanimate surfaces to levels that are considered safe for public health. According to the official food contact surface sanitizer test, a sanitizer is a chemical that reduces the microbial contamination of two standard organisms, Staphylococcus aureus and Escherichia coli, by 99.999 % or 5 logs in 30 seconds, at 25 °C. Non-food contact sanitisers must reduce contamination by 99.9 % or 3 logs in 5 minutes. Soil Any remaining, undesirable material in the equipment or process environment. It may or may not contain micro-organisms. Solutions Water and/or those homogeneous mixtures of cleaning agents and/or disinfectants and water used for flushing, cleaning, rinsing and disinfection. Splash contact surfaces Non-product contact surfaces that during normal use are subject to accumulation of soil and which require routine cleaning to avoid soil to drop or to be drawn into the main product or container.


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Sterilisation A process aimed at removing or killing all forms of micro-organisms, including bacterial spores. Note 1: In the USA, commercial sterilization refers to the inactivation of all organisms of significance to public health and the absence of spoilage under normal conditions of storage. Note 2: In the UK, still used to denote disinfection. Note 3: Sterilisation can equally apply to treatment of food. SIP (sterilisation in place) Sterilisation without dismantling. Surface rupture Breaking or tearing of a surface commonly the result of impact from a shot- or bead-blasting medium. Under magnification the damage to the surface will generally appear like fish scales, the openings under which face forwards the source of the shot or beads. These areas can harbour soils and micro-organisms and be difficult to clean. Surface treatment A process whereby chemical or mechanical properties of the existing surface are altered.

U Ultra-clean process A process using equipment disinfected before use, and which, in running conditions, is protected against recontamination by micro-organisms that may harm the safety and suitability of the specific product that is made. Note: Measures for initial reduction of microbial load and against recontamination can be less stringent than those applied for an aseptic process. Ultra clean or Aseptic refers more to the process line and not the environment.

V Validation Obtaining evidence that the elements of the HACCP plan are effective. (Codex) The obtaining of evidence that the food hygiene control measures selected to control a specific hazard(s) in a specific food(s) are capable of controlling the hazard to the level specified. (provisional Codex) Note: In the context of ISO 9000-2000, this process is named qualification. Validation is used in a much broader sense e.g. for validation of cleaning. Validation, in general, intends to establish documented evidence, that a specific process will consistently meet its predetermined objectives. In the case of cleaning process: the objective is that the next batch of product, which will be processed in the cleaned equipment, does not become contaminated from any microbiological Copyright 2008; Tetra Pak Processing Systems

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and chemical sources, foreign material or environmental residues, having potential affect on the food contact surfaces. Verification The application of methods, procedures, tests, and other evaluations, in addition to monitoring to determine compliance with the HACCP plan. (Codex) Note: In the context of ISO 9000-2000, this process is named validation, a situation that may lead to some confusion. In a wider sense can represent: Activities, including auditing, reviewing, inspecting, challenging, testing, checking etc., that demonstrate whether items, processes, services or documents conform to specified requirements for quality, especially food safety e.g. as seen in the HACCP plan.

W Wet-cleaning (Cleaning-out-of-place as opposed CIP – see specifically CIP) Can refer to cleaning of equipment or processing environment. Cleaning procedure carried out only when product is not exposed and using methods that limit the amount of water applied and its spread. The main aim of wet cleaning is to remove soil that may or may not contain micro-organisms. Note: The objectives are basically to use as little water as possible and to be as dry as possible rapidly after cleaning. This is a procedure specifically intended to reduce risks of build-up of environmental Listeria monocytogenes populations in ice cream, cheese and refrigerated products process areas. Also referred to as Controlled wet cleaning

Z Zoning The physical or visual division of the plant into sub-areas, leading to the segregation of different activities with different hygiene levels. Related terms and explanations. The following are proposals for use in EHEDG. Controlled environment refers to all zoning but may relate more to the high hygiene case.

Zoning cannot be defined for all plants and processes in black and white as there will always be local influences that play a role. Most important is that zoning fits into the overall plan of prevention with respect requirements of process and safety of consumers. High hygiene = high care or high risk


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IDF states: a critical hygienic area within the plant where products and ingredients vulnerable to contamination and/or microbial growth are processed, treated, handled or stored. An area within a plant’s zoning plan where the following products and ingredients are processed or stored – either those destined for a highly susceptible consumer group, being instant in nature or ready for consumption, or those which will be handled in a refrigerated supply chain and which are susceptible to growth of pathogenic micro-organisms such as Listeria monocytogenes . Note: The term “high risk area” could also be used for a zone where there is a high concentration of pathogens e.g. in fresh meat and chicken, raw cocoa bean, fresh raw milk and vegetable areas. These areas present a high risk for other process area and there should be adequate barriers to stop spread of pathogens. High hygiene is equivalent for food to clean room. Medium hygiene = medium care or medium risk

Can be a process area for products, susceptible to contamination but where the consumer group is not especially sensitive and where also no further growth is possible in the product in the supply chain. Can also be the intermediate area leading into the high hygiene zone but where access is only across certain barriers. Low (Basic) hygiene = Low care or low risk

Low (basic) relative to others but where minimal GHP must be applied. Low (basic) hygiene areas can be sub-divided as proposed in EHEDG Doc. 26 on dry materials. An area where products are not susceptible to contamination and are protected in their final packages. Can also be an area where raw materials are handled before being subjected e.g. to a thermal process step (a CCP). Examples: Related to cleaning for total zoning, some examples are given in the table below but these are certainly only guidelines. Each establishment must make its own zoning plans based on product and consumer group, local influences and legislation.


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