NCA 96th Annual Convention, Scottsdale, AZ, March 1-4, 2007
NCA 96th Annual Convention, Scottsdale, Scottsdale, AZ, March 1-4, 2007
Whats Your Profile? Presentation Topics 1. 2. 3. 4. 5. 6.
Profiling and Profi Profiling Profile le Roas Roasting ting Control Con trol Elem Elements ents and Compo Component nents s Variables Varia bles and Roas Roasting ting Losse Losses s Roast Bean Development and Spectrum of Quality Roastt Imper Roas Imperfect fections ions Glossa Glo ssary ry of Ter Terms ms
Preparation of Coffee
Cup of Green Coffee
Cup of Whole Roasted Beans
Cup of Expresso Gree Green n Co Coff ffee ee
Roas Roaste ted d Co Coff ffee ee
Grin Grindi ding ng and and Brew Brewin ing g
Schematic Representation Of The Roasting Process
Physical Changes Chemical Reaction
t u p n I at e H
V o l a t l M i o i e M s t a t u r e r e i a l /
Green Coffee Variables
Process Variables
Coffee Variety
Coffee Variety
Moisture Content
Moisture Content
Whole/Ground Beans Pretreatments: Decaffeination Mild Treatment
Whole/Ground Beans
Roasting Roasting Losses Losses
Roasted Coffee Properties Degree of Roast Color Value
Chemical/Physical Properties Acidity Extraction Yield Chlorgenic Acid Content Aroma Content Bulk Density, etc.
Quality Aspects Cup Quality
Appearance
Digestibility
Shelf Life
Heat Transfer And Motion Of Substances Inside The Bean
With higher temperatures, the pores or the cell structure will expand as internal pressure increases, resulting in a flow of gases. The velocity of the gases depends upon the cell density of the bean and is influenced by the air pressure surrounding the bean. In a vacuum, this velocity will increase and in higher than atmosphere pressure, it will decrease. Three forms of heat are always present, only their relative proportions are determined by the different types of roasters. Conductive Through contact with hot parts of the Heat container and other beans. Convection Heat
By hot air or other gases surrounding the beans.
Radiant Heat Through infra-red radiation. Whether by air quenching or water quenching, rapid cooling of the roasted coffee is crucial in bringing the overpressure inside the beans under control and preventing excessive loss of aroma.
Roast Development Roast Development
Time and temperature profile 1st Crack
Chemical Changes Physical Changes
2nd Crack
Chemical Changes Physical Changes
Physical Changes Water Content Before Roasting After Roasting
Color, Density, Shape, Weight 6-15% with avg. of 8-12% 4-5% depending on original content and degree of roast
The first crack is caused largely by the internal pressure on the bean of up to 8 atmosphere due to the evaporation of water found in the cell structure of the bean. The crack will be audibly louder with denser and fresher green beans. The second crack is due to further expansion from pressures generated by CO2 gases and coffee oil volatiles. The audible sound of the second crack differs because of change in the bean fiber due to the roast progress
Different Different Roast Roast Colors Colors
Weight Loss (aka Shrinkage) Light Roast
12-14%
Medium Roast 15-17% Dark Roast
18-21%
Of this, approx. 84% is water, the rest is gases and chaff Gases released from the roast and ground coffee are 87% carbon dioxide, 7.3% carbon monoxide, 5.3% nitrogen, .40% aromatic volatiles. Endothermic Reactions produced by absorption of heat Exothermic
Reactions from chemical changes inside the bean accompanied by the liberation of heat. Sugar Caramelization Condensation Polymerization
Flavor development occurs primarily in the exothermic stage. Pyrolysis
The development of organic products due to process of heat transfer.
PROBAT Control Engineering Profile Roasting
oC
600
%
100 oC
Supply air 90
500
% Supply air
400
Final roasting temperature
80
III
300
I
0
200
60
II
Reducing stages
70
Final roasting 120 180 240 300temperature 360 420 t
Product temperature 20 set values Required profile
100
60 50 40
0 0
60
120
180
240
300
360
Automatic supply air volume or temperature control according to a specific profile curve. Suitable for known coffees
420 t
3 Step Standard Roasting
Flexible Roasting
Reflex Roasting 1
20
3 2
PROBAT Control Engineering Profile Roasting. Profile roasting allows to follow a predesigned product temperaure graph for a single coffee or a blend of coffees.
Basic Values: PRESET-Values Roastingtime
Calculate timeslides
Producttemp.
Calculate difference
Machine factor
Supply-air temp.
Calculate PID Preset
Calculate Speed
PID Regulator Burner preset
Producttemp.
Supply-air temp.
PRODUCT-Values
Supply-air volume
Burner Oel or Gas
Speed regulator
Supply-air Fan
Machine
Roast Imperfections
Total Time/Temperature Scale Long Time/ Low Temp
Long Time/ High Temp
Baked
Burnt
Bland Flavor
Carbonized
Little Aroma
Charcoal
E M I T
Short Time/ Low Temp
Short Time/ High Temp
Under Developed
Scorched Outer
Greenish
Under Developed Inner Burnt/Grainy Tipped
Raw Nut/Grainy Sour/Thin
TEMPERATURE
Spectrum Of Quality Roasts
Baked
Burnt Dark
Medium
E M I T
Light Tipped
Under Developed
TEMPERATURE
Optimal Roasting
6 Minutes, RZ
Color 125 Color 130
Color 100
High Yield Roasting
1.5 Minutes
Color 110 Color 125
Color 100
Roasting Time Short roasting Increased
acidity Increased body Decreased bitterness
Increased
bulk volume Increased extraction yield Increased soluble solids
Roasting Time Long Roasting Decreased
acidity Decreased body Increased bitterness
Decreased
bulk volume Decreased extraction yield Decreased soluble solids
Glossary of Terms Temperature 1.
Heat transfer in the coffee bean progresses from the outside to the inside.
2.
The Transport of mass of volatile compounds inversely from the inside to the outside.
3.
Temperature Difference at the beginning of the roasting process between outer and inner bean layer is 50°C.
4.
Only if the bean core temperature is at about 150°C both temperatures inside and outside gradually become the same.
5.
The shorter the roast time, the greater the temperature difference.
6.
When roasting coffee, only a pseudo product temperature can be measured and controlled. The bean pile temperature consists of surface temperature of the beans and the air temperature within the roasting compartment. This temperature depends on coffee type, bean size, roaster type (design), batch size, and position and type of thermocouple.
7.
Specific heat requirements for Arabica coffee at a specific roast color and with a green coffee moisture of 11.5% is approximately 470kJ per kilogram of green coffee (theoretically).
Glossary of Terms, Contd.
Color 1.
When roasting high-altitude area cultivated and grown coffees, the sequence in color change runs from tender green to yellow, yellow-brown, light brown, dark brown to black brown.
2.
Coffees that grow in low lands first turn pale, quasicolorless, before turning to a yellow hue.
3.
Yellow color starts to develop at a temperature of approximately 130°C.
4.
A single Arabica coffee bean is composed of approximately 1,000,000 single cells.
5.
At a specific roast color or degree of roast an audible cracking (first crack) can be noticed.
6.
The weakest areas on the surface of the coffee bean can found on the flat side of the bean. Fine hairline cracks form in this area. The first crack is caused by the relief of the steam pressure from inside the beans. The second crack is caused by the formation of Carbon Dioxide.
Glossary of Terms, Contd.
Volume 1.
The volume of beans expands during roasting.
2.
Through the formation of steam and gas there is a high build up of pressure inside the cells of the bean causing coffee beans to swell.
3.
The permeability of the cell structure i.e., the porocities, does not allow for the gradual release of steam and the gas as it develops which causes the expansion of the beans. Depending on the coffee type, roasting time, and roast degree, the bean can grow in volume to be double its size.
4.
Hard beans, such as Kenya coffee, can be more resistant and will cause a slower increase in volume in comparison to a softer bean.
5.
There is a tendency in all coffees towards a decrease in volume for extended roasting times and an increase in volume at shorter roasting times.
Glossary of Terms, Contd.
Weight Loss 1.
Weight loss during roasting, also called shrinkage, is a loss in substance and can fluctuate depending on the degree of roast between 12 and 23 percent.
2.
The shrinkage is related to the loss of water and chaff, and also dry substance in form of carbon dioxide, carbon monoxide, nitrogen, volatile acids, and volatile aromatic compounds.
3.
Water loss makes up the greatest portion of weight loss.
4.
In reference to dry substance, the loss of carbon dioxide in comparison to other compounds is by far the highest.
Glossary of Terms, Contd.
Maillard Reaction 1.
It is a non-enzymatic browning process in which reducing sugars react with amino acids.
2.
Most of the aromatic compounds are formed by the Maillard reaction. The colorants, called melanoidins, arise from the non-enzymatic browning reaction.
3.
In the first phase of the Maillard reaction, the saccharides react with amino compounds, peptides or proteins for which reactive multifunctional intermediate products develop.
Glossary of Terms, Contd.
Pyrolysis 1.
It describes the thermal decomposition of complex substances.
2.
During pyrolysis, single compounds of coffee substances are developed as a result of decomposition.
3.
Trigonelline, for example, allows pyridine to form.
4.
The decomposition of chlorogenic acids leads to phenoles.
5.
Coffee oils allow for a slight amount of aldehydes and carbohydrates.
6.
During pyrolysis, carbon dioxide and carbon monoxide are released and water is formed.
7.
Chlorogenic acids in green coffee is destroyed during roasting.
8.
Chlorogenic acid is partly responsible for the stimulating effect and bitter taste of coffee.
9.
The decomposition substances formed from Trigonelline during pyrolysis, such as pyridine, contribute to the coffee aroma.
10.
Furfural is a leading substance for steam-volatile aromatic compounds of the roasted coffee. It produces a pleasant taste which is caramel-like to woody.
11.
The most important acids in raw coffee are quinic acid, malic acid, and citric acid.
Glossary of Terms, Contd.
Conversion into Caramel 1.
Through heating, some of the simple sugars present are caramelized into browning products.
2.
Browning products are created from the splitting of water which belongs to the furan group.
3.
A typical example of conversion into caramel is the formation of maltol from fructose.
4.
Maltol, which is larixinic acid, is a trypical, pleasantly caramel-smelling compound which incidentally, is easily soluble in water.
5.
The caramel products contribute, along with the melanoidins formed in the Maillard reaction, to the brown color of the coffee beans, i.e., the coffee beverage.
