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NCA 96th Annual Convention, Scottsdale, AZ, March 1-4, 2007


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Presentation TopicsPresentation Topics

1. Profiling and Profile Roasting

2. Control Elements and Components

3. Variables and Roasting Losses

4. Roast Bean Development and Spectrum of Quality

5. Roast Imperfections

6. Glossary of Terms

NCA 96th Annual Convention, Scottsdale, AZ, March 1-4, 2007

Whats Your Profile?


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Schematic Representation Of The Roasting ProcessSchematic Representation Of The Roasting Process

ChemicalReaction

HeatIn

put

Physical

Changes

VolatileMaterial/

Moisture


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Roasting LossesRoasting LossesRoasting LossesRoasting Losses

Coffee Variety

Green Coffee Variables Process Variables

Moisture Content

Whole/Ground BeansPretreatments:

Decaffeination

Mild Treatment

Coffee Variety

Moisture Content

Whole/Ground Beans

Roasted Coffee Properties

Degree of Roast

Color Value

Chemical/Physical Properties

Quality Aspects

Cup Quality Appearance Digestibility Shelf Life

Acidity Extraction Yield

Chlorgenic Acid Content Aroma Content Bulk Density, etc.


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Heat Transfer And Motion Of Substances Inside The BeanHeat Transfer And Motion Of Substances Inside The Bean

With higher temperatures, the pores or the cell structurewill expand as internal pressure increases, resulting in a

flow of gases. The velocity of the gases depends uponthe cell density of the bean and is influenced by the airpressure surrounding the bean.

In a vacuum, this velocity will increase and in higherthan atmosphere pressure, it will decrease.

Three forms of heat are always present, only their relativeproportions are determined by the different types ofroasters.ConductiveHeat

Through contact with hot parts of thecontainer 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, rapidcooling of the roasted coffee is crucial in bringing theoverpressure inside the beans under control and

preventing excessive loss of aroma.


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Roast DevelopmentRoast DevelopmentRoast DevelopmentRoast Development

Time and temperature profile

1st Crack Chemical Changes

Physical Changes

2nd Crack

Physical Changes Color, Density, Shape, Weight

The first crack is caused largely by the internal pressure on thebean of up to 8 atmosphere due to the evaporation of water found

in the cell structure of the bean. The crack will be audibly louderwith denser and fresher green beans.

Chemical Changes Physical Changes

Water ContentBefore RoastingAfter Roasting

6-15% with avg. of 8-12% 4-5% depending on original content

and degree of roast

The second crack is due to further expansion from pressuresgenerated by CO2 gases and coffee oil volatiles.

The audible sound of the second crack differs because ofchange in the bean fiber due to the roast progress


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Different Roast ColorsDifferent Roast ColorsDifferent Roast ColorsDifferent Roast Colors

Weight Loss (aka Shrinkage)

Light Roast 12-14%

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% aromaticvolatiles.

Flavor development occurs primarily in the exothermic stage.

Medium Roast 15-17%

Dark Roast 18-21%

Endothermic Reactions produced by absorption of heat

Exothermic Reactions from chemical changes inside the beanaccompanied by the liberation of heat.

Sugar Caramelization

CondensationPolymerization

Pyrolysis The development of organic products due toprocess of heat transfer.


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PROBATPROBAT ControlControl EngineeringEngineering

0 60 120 180 240 300 360 420

Reducing stages

I

II

III

Final roasting temperature

t

Product temperature

% Supply air

oC Supply air

0 60 120 180 240 300 360 420

600

500

400

300

200

100

0

oC

100

90

80

70

60

50

40

20 set values

Final roasting temperature

%

t

Required profile

Profile RoastingProfile Roasting

Automatic supply air volume or temperature control according to aspecific profile curve. Suitable for known coffees


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3 Step Standard

Roasting

1

Reflex Roasting

Flexible Roasting

2

3

20


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PROBATPROBAT ControlControl EngineeringEngineering

Profile Roasting.Profile roasting allows to follow a predesigned product temperaure

graph for a single coffee or a blend of coffees.

Calculatetimeslides

PRESET-Values

Roasting-time

Product-temp.

Supply-airtemp.

Supply-airvolume

Machinefactor

PRODUCT-Values

Product-temp.

Supply-airtemp.

Machine

BurnerOel or Gas

Supply-airFan

Calculatedifference

CalculateSpeed

CalculatePID Preset

PID RegulatorBurner preset

Speedregulator

Basic Values:


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Roast ImperfectionsRoast Imperfections

Baked

TEMPERATURE

TIME

Total Time/Temperature Scale

Bland Flavor

Little Aroma

Long Time/ Low Temp

Burnt

Carbonized

Charcoal

Long Time/ High Temp

Under Developed

Greenish

Raw Nut/Grainy

Short Time/ Low Temp

Scorched Outer

Under Developed Inner

Burnt/Grainy

Short Time/ High Temp

Sour/Thin Tipped


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Spectrum Of Quality RoastsSpectrum Of Quality Roasts

TEMPERATURE

TIME

Light

Medium

Dark

Baked

UnderDeveloped

Burnt

Tipped


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Optimal Roasting - 6 Minutes, RZ

Color 130

Color 125

Color 100


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Roasting TimeRoasting Time

Short roasting

Increased acidity

Increased body

Decreased bitterness

Increased bulk volume

Increased extraction yieldIncreased soluble solids


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Roasting TimeRoasting Time

Long Roasting

Decreased acidity

Decreased body

Increased bitterness

Decreased bulk volume

Decreased extraction yieldDecreased soluble solids

Glossary of Terms


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TemperatureTemperature

1. Heat transfer in the coffee bean progresses from the outside to theinside.

2. The Transport of mass of volatile compounds inversely from theinside to the outside.

3. Temperature Difference at the beginning of the roasting processbetween outer and inner bean layer is 50C.

4. Only if the bean core temperature is at about 150C bothtemperatures 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 bemeasured and controlled. The bean pile temperature consists ofsurface temperature of the beans and the air temperature within theroasting compartment. This temperature depends on coffee type,bean size, roaster type (design), batch size, and position and type ofthermocouple.

7. Specific heat requirements for Arabica coffee at a specific roastcolor and with a green coffee moisture of 11.5% is approximately470kJ per kilogram of green coffee (theoretically).

Glossary of Terms

Glossary of Terms Contd


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ColorColor

1. When roasting high-altitude area cultivated and growncoffees, the sequence in color change runs from tendergreen to yellow, yellow-brown, light brown, dark brown to

black brown.

2. Coffees that grow in low lands first turn pale, quasi-colorless, before turning to a yellow hue.

3. Yellow color starts to develop at a temperature of

approximately 130C.

4. A single Arabica coffee bean is composed ofapproximately 1,000,000 single cells.

5. At a specific roast color or degree of roast an audiblecracking (first crack) can be noticed.

6. The weakest areas on the surface of the coffee bean canfound on the flat side of the bean. Fine hairline cracksform in this area. The first crack is caused by the relief ofthe steam pressure from inside the beans. The secondcrack is caused by the formation of Carbon Dioxide.

Glossary of Terms, Cont d.

Glossary of Terms Contd


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VolumeVolume

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 causingcoffee 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 gasas it develops which causes the expansion of the beans.Depending on the coffee type, roasting time, and roastdegree, the bean can grow in volume to be double its size.

4. Hard beans, such as Kenya coffee, can be more resistantand will cause a slower increase in volume in comparisonto a softer bean.

5. There is a tendency in all coffees towards a decrease involume for extended roasting times and an increase in

volume at shorter roasting times.


Glossary of Terms, Contd.


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Weight LossWeight Loss

1. Weight loss during roasting, also called shrinkage, is aloss in substance and can fluctuate depending on thedegree of roast between 12 and 23 percent.

2. The shrinkage is related to the loss of water and chaff, andalso dry substance in form of carbon dioxide, carbonmonoxide, nitrogen, volatile acids, and volatile aromaticcompounds.

3. Water loss makes up the greatest portion of weight loss.

4. In reference to dry substance, the loss of carbon dioxide incomparison to other compounds is by far the highest.




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MaillardMaillard ReactionReaction

1. It is a non-enzymatic browning process in which reducingsugars react with amino acids.

2. Most of the aromatic compounds are formed by theMaillard reaction. The colorants, called melanoidins, arisefrom the non-enzymatic browning reaction.

3. In the first phase of the Maillard reaction, the saccharidesreact with amino compounds, peptides or proteins for

which reactive multifunctional intermediate productsdevelop.




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PyrolysisPyrolysis1. It describes the thermal decomposition of complex substances.

2. During pyrolysis, single compounds of coffee substances aredeveloped 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 andcarbohydrates.

6. During pyrolysis, carbon dioxide and carbon monoxide are releasedand water is formed.

7. Chlorogenic acids in green coffee is destroyed during roasting.

8. Chlorogenic acid is partly responsible for the stimulating effect andbitter taste of coffee.

9. The decomposition substances formed from Trigonelline duringpyrolysis, such as pyridine, contribute to the coffee aroma.

10. Furfural is a leading substance for steam-volatile aromaticcompounds of the roasted coffee. It produces a pleasant taste whichis caramel-like to woody.

11. The most important acids in raw coffee are quinic acid, malic acid,

and citric acid.




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Conversion into CaramelConversion into Caramel

1. Through heating, some of the simple sugars present arecaramelized into browning products.

2. Browning products are created from the splitting of waterwhich belongs to the furan group.

3. A typical example of conversion into caramel is theformation of maltol from fructose.

4. Maltol, which is larixinic acid, is a trypical, pleasantlycaramel-smelling compound which incidentally, is easilysoluble in water.

5. The caramel products contribute, along with themelanoidins formed in the Maillard reaction, to the browncolor of the coffee beans, i.e., the coffee beverage.




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Control Components/ElementsControl Components/Elements

1. A proportional integral derivative controller is an instrument to controlburner settings, fan speed, and bean temperature of the roasted coffee as itdevelops over time.

P or Proportionate Compensation determines how aggressively thecontroller or the system will approach a set point.

I or Integral determines the value by which the temperature is slightly raisedto attain a set point. I values work in an inverse relation to P values.

D or Derivative is the value which is used dampen oscillations above a setpoint. It is for super fine adjustments. It is less used when using a product

temperature to monitor the roast development.

2. A temperature sensor measures the bean temperature in the roaster. It is apseudo-temperature as a mix of product and air.

3. There are other temperature probes installed in the roasting system for airsupply temperature to the beans and exhaust air temperature from the roaster.

4. A program the feeds the PID loop the actual bean temperature profile data andcompares them with the target bean temperature profile data.

5. A profile is a temperature graph of coffee or batch monitoring thedevelopment of the roast process by following time and temperature set points.


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