Coffee Roasting - Wikipedia, The Free Encyclopedia

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Commercial drum type coffee roaster

Roa sting

Light roasted co ffee beans

Dark roasted coffee beans

Coffee roastingFrom Wikipedia, the free encyclopedia

Roasting coffee transforms the chemical and physical properties of green coffee beans into roasted c offee products. The roasting

process is what produces the characteristic flavor of coffee bycausing the green coffee beans to expand and to change in color,taste, smell, and density. Unroasted beans contain similar acids,

protein, and caffeine as those that have been roasted, but lack thetaste. Hea t must be appl ied for the Maillard and other chemicalreactions t o occur.

As green c offee is more stable than roasted, the roasting processtends to ta ke place close to w here it will be consumed. This reduc esthe time th at roasted coffee spends in distribution, giving it a long er shelf life. The vast majority of coffee is roasted commercially on alarge scale, but some coffee drinkers roast coffee at home in orde r to

have more control over the freshness and flavor profile of the bea ns.

Contents

1 Process

2 Equipment

3 Roasts

3.1 Roast flavors4 Home roasting

5 Packaging

6 Emissions and control

7 Gallery

8 See also

9 References

10 External links

Process

The coffee roasting process follows coffee processing and precedescoffee brewing. It consists essentially of sorting, roasting, cooling, and

packaging but can also include grinding in larger scale roasting houses.In larger operations, bags of green coffee beans are hand or machine-opened, dumped into a hopper, andscreened to remove debris. The green beans are then weighed and transferred by belt or pneumatic
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Window of a coffee-roaster shop inMontjoie (Germany)

conveyor to storage hoppers. From the storage hoppers, the green beans are conveyed to the roaster.Initially, the process is endothermic (absorbing heat), but at around 175 C (347 F) it becomes exothermic(giving off heat). [1] For the roaster, this means that the beans are heating themselves and an adjustment of the roaster's heat source might be required. At the end of the roasting cycle, the roasted beans are dumpedfrom the roasting chamber and cooled with forced air.

Equipment

The most common roasting machines are of two basic types: drum and hot-air, although there are othersincluding packed bed, tangential and centrifugal roasters. Roasters can operate in either batch or continuousmodes. Home roasters are available.

Drum machines consist of horizontal rotating drums that tumble the green coffee beans in a heatedenvironment. The heat source can be supplied by natural gas, liquefied petroleum gas (LPG), electricity, or even wood. The most common employ indirectly heated drums where the heat source is under the drum.Direct-fired roasters are roasters in which a flame contacts the beans inside the drum; very few of thesemachines are still in operation.

Hot-air roasters (http://www.coffeeroastersclub.com/content/21-video-of-javapro-crc-air-fluid-bed-roaster-in-operation) force heated air through a screen or perforated plate under the coffee beans with sufficientforce to lift the beans. Heat is transferred to the beans as they tumble and circulate within this fluidized bed.

Roasts

Coffee roasters use names for the various degrees of roast, such asCity Roast and French Roast, for the internal bean temperaturesfound during roasting. Roastmasters often prefer to follow a "recipe"or "roast profile" to highlight certain flavor characteristics. Anynumber of factors may help a person determine the best profile touse, such as the coffee's origin, variety, processing method, or desired flavor characteristics. A roast profile can be presented as agraph showing time on one axis and temperature on the other, whichcan be recorded manually or using computer software and dataloggers linked to temperature probes inside various parts of theroaster.

The most popular, but probably the least accurate, method of

determining the degree of roast is to judge the bean's color by eye(the exception to this is using a colorimeter to measure the groundcoffee reflectance under infrared light and comparing it to standardssuch as the Agtron scale). As the beans absorb heat, the color shiftsto yellow and then to increasingly darker shades of brown. Duringthe later stages of roasting, oils appear on the surface of the bean. The roast will continue to darken until itis removed from the heat source. Beans will also darken as they age, making color alone a poor roastdeterminant. Most roasters use a combination of bean mass temperature, smell, color, and sound to monitor the roasting process.
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Sound is a good indicator of bean temperature during roasting. There are two temperature thresholds called"cracks" that roasters listen for. At about 200202 C (392396 F), beans will emit a cracking sound muchlike popcorn does when it pops, only much quieter. This point is called "first crack," marking the beginningof light roasts. When the beans are at about 224226 C (435439 F), they emit a "second crack." Duringfirst and second "crack" pressure inside the bean has increased to the point where the structure of the beanfractures, rapidly releasing gases, thus an audible sound is emitted.

These images depict samples taken from the same batch of a typical Brazilian green coffee at various beantemperatures with their subjective roast names and descriptions. [2][3][4]

Unroasted

22 C (72 F) Green BeansGreen coffee beans as they arrive at

the dock. They can be stored for up totwo years.

165 C (329 F)Drying Phase

During the drying phase the beans are

undergoing anendothermic processuntil their moisture

content is evaporated,signifying first crack.

Light roast

196 C (385 F) Cinnamon RoastA very light roast level, immediately

at first crack. Light brown, toasted

grain flavors with sharp acidity,almost tea-like in character.

205 C (401 F) NewEngland Roast

Moderate light brown, but still mottled in

appearance. A preferred roast for

some specialtyroasters, highlightsorigin characteristicsas well as complex

acidity.

Medium roast

210 C (410 F) American RoastMedium light brown, developed

during first crack. Origin character isstill completely preserved.

219 C (426 F) CityRoast

Medium brown,common for most

specialty coffee. Goodfor tasting the varietalcharacter of a bean,

although roastcharacter is noticeable.

Dark or full roast

225 C (437 F) Full City Roast

230 C (446 F)Vienna Roast

Moderate dark brownwith light surface oil,
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Medium dark brown with occasionaloil sheen, roast character is

prominent. At the beginning of second crack.

more bittersweet,caramel flavor, aciditymuted. In the middle of

second crack. Anyorigin characteristicshave become eclipsed by roast at this level.

240 C (464 F) French RoastDark brown, shiny with oil, burnt

undertones, acidity diminished. At theend of second crack. Roast character

is dominant, none of the inherentaroma or flavors of the coffee

remain. [5]

245 C (473 F) ItalianRoast

Very dark brown andshiny, burnt tones

become more distinct,acidity almost gone,

thin body. [6]

| 250 C (482 F) Spanish RoastExtremely dark brown, nearly black and veryshiny, charcoal and tar tones dominate, flat,

with thin body.

Roast flavors

At lighter roasts, the bean will exhibit more of its "origin flavor"; the flavors created in the bean by itsvariety, the soil, altitude, and weather conditions in the location where it was grown. [7]

As the beans darken to a deep brown, the origin flavors of the bean are eclipsed by the flavors created bythe roasting process itself. At darker roasts, the "roast flavor" is so dominant that it can be difficult todistinguish the origin of the beans used in the roast.

Below, roast levels and their respective flavors are described. [8] These are qualitative descriptions, and thussubjective. As a rule of thumb, the "shinier" the bean is, the more dominant the roasting flavors are.
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CommonRoastNames

Notes Surface Flavor

Light

Cinnamon, American, Half City,

New England

After several minutes thebeans pop or "crack"

and visibly expand in size.This stage is called first

crack.

Dry

Lighter-bodied, higher acidity, noobvious roast flavor. This level of roast is ideal for tasting the full origin character of the coffee.

MediumCity,

City+, Full City

After being developed through first crack, the

coffee reaches these roast levels.

Dry

Sugars have been further caramelized, and acidity has beenmuted. This results in coffee with

higher body, but some roast flavor imposed.

Dark

Full City+,

Viennese, French,

Italian

After a few more minutesthe beans begin popping again, and oils rise to the

surface. This is called

second crack.

Shiny. The level of oil correlates to

how far the coffeeis taken past

second crack.

Bittersweet flavors are prominent,aromas and flavors of roast

become clearly evident. Little, if any, origin character remains.

Caffeine content varies by roast level. Caffeine diminishes with increased roasting level: light roast, 1.37%;medium roast, 1.31%; and dark roast, 1.31%. [9] However, this does not remain constant in coffee brewedfrom different grinds and brewing methods. Because the density of coffee changes as it is roasted, differentroast levels will contain respectively different caffeine levels when measured by volume or mass, thoughthe bean will still have the same caffeine.

Home roasting

Home roasting is the process of roasting small batches of green coffee beans for personal consumption.Even after the turn of the 20th century, it was more common for at-home coffee drinkers to roast their coffee in their residence than it was to buy pre-roasted coffee. Later, home roasting faded in popularity withthe rise of the commercial coffee roasting companies. In recent years home roasting of coffee has seen arevival. [10] In some cases there is an economic advantage, but primarily it is a means to achieve finer control over the quality and characteristics of the finished product.

Packaging

Extending the shelflife of roasted coffee relies on maintaining an optimum environment to protect it fromexposure to heat, oxygen, and light. Roasted coffee has an optimal typical shelf life of 2 weeks, and groundcoffee about 15 minutes. Without some sort of preservation method, coffee becomes stale. The first largescale preservation technique was vacuum packing in cans. However, because coffee emits CO 2 after

roasting, coffee to be vacuum packed must be allowed to de-gas for several days before it is sealed. Toallow more immediate packaging, pressurized canisters or foil-lined bags with pressure-relief valves can beused. Refrigeration and freezing retards the staling process. Roasted whole beans can be considered freshfor up to one month if kept cool. Once coffee is ground it is best used immediately.
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Emissions and control

Particulate matter (PM), volatile organic compounds (VOC), organic acids, and combustion products arethe principal emissions from coffee processing. [11] Several operations are sources of PM emissions,including the cleaning and destoning equipment, roaster, cooler, and instant coffee drying equipment. Theroaster is the main source of gaseous pollutants, including alcohols, aldehydes, organic acids, and nitrogenand sulfur compounds. Because roasters are typically natural gas-fired, carbon monoxide (CO) and carbon

dioxide (CO 2) emissions result from fuel combustion. Decaffeination and instant coffee extraction anddrying operations may also be sources of small amounts of VOC. Emissions from the grinding and

packaging operations typically are not vented to the atmosphere.

Particulate matter emissions from the roasting and cooling operations are typically ducted to cyclones before being emitted to the atmosphere. Gaseous emissions from roasting operations are typically ducted toa thermal oxidiser or thermal catalytic oxidiser following PM removal by a cyclone. Some facilities use the

burners that heat the roaster as thermal oxidisers. However, separate thermal oxidisers are more efficient because the desired operating temperature is typically between 650816 C (1,2021,501 F), which is 93 260 C (199500 F) more than the maximum temperature of most roasters. Some facilities use thermalcatalytic oxidizers, which require lower operating temperatures to achieve control efficiencies that areequivalent to standard thermal oxidisers. Catalysts are also used to improve the control efficiency of systems in which the roaster exhaust is ducted to the burners that heat the roaster. Emissions from spraydryers are typically controlled by a cyclone followed by a wet scrubber.

Gallery

Diedrich IR SeriesCoffee Roaster.

An old wood-firedcoffee roaster.

A two barrel coffeeroaster for roasting

coffee samples prior to

purchasing or roastinggreen coffee beans.

An antique "Mignon"five barrel test roasting

machine
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http://en.w ikipedia.org/wiki/Coffee_roasting 7/8

The roasting room at amidsize coffee

company.

See al so

Coff ee

Dry roasting

Ho me roasting coffee

Foo d grading

Fre nch press

Tor r efacto

Refer ences

1. ^ R aemy A, Lambelet P. A calorimetric study of self-heating in coffee and chicory. Int J Food Sci & Tech,

198 2;17(4):451460.

2. ^ Degree of Roast, by Dan Bollinger, http://www.homeroasters.org/index.htm

3. ^ "Using Sight to Determine Degree of Roast | Sweet Maria's Coffee Library"

(htt p://www.sweetmarias.com/roasting-VisualGuideV2.php). Sweetmarias.com. Retrieved 2012-07-28.

4. ^ "Glossary of Coffee and Espresso Terms" (http://www.coffeereview.com/glossary.cfm). Coffee Review.

Ret rieved 2012-07-28.

5. ^ "Glossary of Coffee and Espresso Terms" (http://www.coffeereview.com/glossary.cfm?alpha=F). Coffee

Rev iew. Retrieved 2012-07-28.

6. ^ "Glossary of Coffee and Espresso Terms" (http://www.coffeereview.com/glossary.cfm?alpha=I). Coffee

Rev iew. Retrieved 2012-07-28.

7. ^ S piller, Gene (9 October 1997). Caffeine . Los Altos, California, USA: SPHERA Foundation. p. 85. ISBN 978-

0-8 493-2647-9.

8. ^ Thompson, Tom (2009). "An Updated Pictorial Guide to the Roast Process"

(htt p://www.sweetmarias.com/roasting-VisualGuideV2.php). Retrieved 12 January 2010.

9. ^ Verlengia F, Rigitano A, Nery JP, Tosello A. Variations of the caffeine content in coffee beverages. ASIC, 2nd

Int Sci Colloq Green and Roasted Coffee Chem. 1965, 106-114.
http://www.sweetmarias.com/roasting-VisualGuideV2.phphttp://en.wikipedia.org/wiki/Special:BookSources/978-0-8493-2647-9http://en.wikipedia.org/wiki/International_Standard_Book_Numberhttp://www.coffeereview.com/glossary.cfm?alpha=Ihttp://www.coffeereview.com/glossary.cfm?alpha=Fhttp://www.coffeereview.com/glossary.cfmhttp://www.sweetmarias.com/roasting-VisualGuideV2.phphttp://www.homeroasters.org/index.htmhttp://en.wikipedia.org/wiki/Torrefactohttp://en.wikipedia.org/wiki/French_presshttp://en.wikipedia.org/wiki/Food_gradinghttp://en.wikipedia.org/wiki/Home_roasting_coffeehttp://en.wikipedia.org/wiki/Dry_roastinghttp://en.wikipedia.org/wiki/Coffee


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10. ^ Davids, Kenneth. Home Coffee Roasting: Romance and Revival . St. Martin's Griffin; revised edition,

No vember 2003. ISBN 978-0-312-31219-0

11. ^ htt p://www.epa.gov/ttn/chief/ap42/ch09/final/c9s13-2.pdf

Exter nal links

Ho meroasters.org (http://homeroasters.org)

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