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Coffee Roasting for Enthusiasts

Coffee roasting is a chemical process that changes aromatics, acids, and flavors in coffee beans. It involves slowly drying green beans until they smell toasted, then cracking and popping sounds occur as the beans expand and lose weight up to 13% at temperatures from 205 to 220 degrees Celsius, changing their chemical composition. Roasting is completed at 225-230 degrees when the beans take on an oily sheen, maximizing sweetness and aroma while minimizing bitterness and acidity for the best espresso. Color should be stopped between first and half of second crack at 205-215 degrees Celsius.

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921 views3 pages

Coffee Roasting for Enthusiasts

Coffee roasting is a chemical process that changes aromatics, acids, and flavors in coffee beans. It involves slowly drying green beans until they smell toasted, then cracking and popping sounds occur as the beans expand and lose weight up to 13% at temperatures from 205 to 220 degrees Celsius, changing their chemical composition. Roasting is completed at 225-230 degrees when the beans take on an oily sheen, maximizing sweetness and aroma while minimizing bitterness and acidity for the best espresso. Color should be stopped between first and half of second crack at 205-215 degrees Celsius.

Uploaded by

Anika
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Coffee Roasting

http://www.coffeeresearch.org/coffee/roasting.htm

Coffee roasting is a chemical process by which aromatics, acids,


and other flavor components are either created, balanced, or altered
in a way that should augment the flavor, acidity, aftertaste and
body of the coffee as desired by the roaster.

Roasting Coffee Beans

The first stage is endothermic. The green beans are slowly dried to
become a yellow color and the beans begin to smell like toast or
popcorn.

The second step, often called the first crack, occurs at approximately 205 °C (400 °F) in which the bean
doubles in size, becomes a light brown color, and experiences a weight loss of approximately 5%. The
corresponding Agtron number for this color is between 95-90 (Davids, 68-69).

In the next step the temperature rises from 205 °C to approximately 220 °C, the color changes from light
brown to medium brown (Agtron # 60-50), and a weight loss of approximately 13% occurs (Davids, 68-
69). The resulting chemical process is called pyrolysis and is characterized by a change in the chemical
composition of the bean as well as a release of CO2.

The second step is followed by a short endothermic period which is followed by another exothermic step
called the second crack. This second pyrolysis occurs between 225-230°C, and the roast color is defined
as medium-dark brown (Agtron #50-45) (Davids, 68-69). The second pop is much quicker sounding and
the beans take on an oily sheen.

Espresso potential is maximized in roasting when you


maximize the sweetness and aroma of the coffee while
minimizing the bitterness and acidity. Most people focus on
the latter and therefore roast extremely dark, yet without
sweetness and aroma the espresso will never be palatable.
This explains the unpopularity of straight espresso and the
popularity of espresso based drinks where either milk or
other flavors are used to replace the sweetness that was lost
by roasting darkly.

From 170-200°C the sugars in coffee begin to caramelize.


From tasting pure sugar versus its caramelized component it
is evident that uncaramelized sugar is much sweeter. The dark color of coffee is directly related to the
caramelization of the sucrose in coffee. Therefore, to maximize sweetness you want to minimize the
carmelization of sucrose, yet you do not want to roast too lightly or bitter tasting compounds will not
thermally degrade. Stop the roast somewhere between the end of the first crack and less than half way
through the second crack. Do not roast well into or past the second crack. We recommend a roasting
chamber temperature somewhere between 205-215°C. Realizing the danger of the following suggestion
we might recommend a color similar to the one below. Note: All monitors, computers, and internet
browsers will display the color slightly different. This is only a recommendation to point out that this
color is preferable to the almost black color you will frequently observe for espresso. To get a better idea
of roasting colors order the Agtron roasting classification kit from the SCAA.

One way to ensure the same roast degree is achieved each time it is necessary to purchase a set
of Agtron tiles from the SCAA or purchase an Agtron roast analyzer.

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