Roasting turns green coffee beans a light white, and they lose their skin, or chaff. They next become yellow or orange, as they lose moisture. The beans begin to crack audibly -- a stage called, appropriately, "first crack" -- creating greater surface texture, then a darker brown skin.
A Range of Terms
While the coffee industry hasn't standardized the names of roasts, roasters roughly agree on some of the terminology. Coffee that undergoes additional roasting becomes less caffeinated, and its intrinsic flavors are replaced by a highly roasted taste.
- Light roast: Appropriate for milder varieties, and may also be called light city, half city or cinnamon, or even New England or blonde.
- City roast: A lighter roast, bright and lively. This is the preferred roast in the United States, and may also be called an American or breakfast roast.
- Full City roast: The beans continue to roast until they make a second audible crack. The surface becomes darker, and a rich, slightly bitter aftertaste develops. Also called a City Plus roast.
- Dark roast: After the second crack, the beans continue to a deeper stage of roasting, and parts of bean may be blown off. Oils surface within three days. Other terms include high, continental, Turkish, Italian, French, European, Viennese, New Orleans and espresso.
Retail coffee beans from the early years of Peet's and Starbucks tended to veer toward very dark roasts, although the companies are now adding medium and lighter roasts to their lines. This type prevails on the West Coast and in the American Southwest.
Commercial coffee roasters consist of horizontal rotating drums that handle a batch at a time or may roast a continuous production line of green beans. Home roasters may use a popcorn popper, skillet or home roasting machine, or even a convection oven. The length of time a bean spends in a roaster determines its internal temperature, and thus its degree of roasting.
The beans slowly change color from green to yellow, and then quickly go through the remaining shades of brown or blackish-brown. Experienced roasters caution that smell, the sound of the crack and appearance also need to be factored into determining when your roast is finished, as well as taste testing the resulting coffee.
- Light brown: Internal temperature, at least 370 degrees Fahrenheit.
- Brown stage: 393 F.
- First crack: 401 to 415 F, and attaining City roast at 426 F. City Plus roast occurs at 435 F and Full City roast at 444 F.
- Dark roast: 465 F or higher, but less than 482 F, when a tarry flavor like charcoal develops.
Expert roasters devote years of training to learning to read the beans and how to make a quick decision on when to pull them from the heat.
How to Use the Beans
Brew roasted coffee beans beginning three to five days after roasting. While the green beans can be stored indefinitely, roasted beans quickly lose their fresh flavor. But you want to allow them a brief interval to lose the carbon dioxide created by roasting before beginning to brew the beans.