The flavor of a bean is determined by many factors, but its flavor and aroma are brought to life by roasting, during which virtually odorless green coffee beans are exposed to temperatures of between 204-2600ºC (400-5000ºF) for a period of about five minutes. Dark roasts can be produced by holding the beans in the roaster for a longer time or by adjusting the temperature. The roasting process triggers chemical reactions that can continue for days or weeks after the roasting is completed. The chemical changes eventually lead to staleness unless the roasted beans are frozen or packed in an airtight container to prevent oxidation of the volatile chemicals created by the roasting process.
A darker-roasted bean tends to have an oily surface because the longer exposure to high temperatures forces oils within the bean to the outside. The darker color is the result of carbonization of cellulose and caramelization of starches and sugars in the bean.
A century ago, almost all roasts were dark. Coffee usually was roasted in the home or by the retail merchant who had his own small, batch roaster. Coffee roasting at home was something like popping corn in the fireplace. Green beans were placed either in a cylindrical drum attached to a long rod that was turned by hand, or in special heavy skillets that rested directly in the hot ashes. Some of the devices were known as coffee burners, which suggests the condition of the finished beans.
Commercial coffee roasting was done in a similar manner, an obvious difference being that the big processors used large-scale equipment and were somewhat more delicate about the degree of roasting. A large barrel holding up to 75 kilograms (175 pounds) of green beans was loaded by a husky man who also had to turn a crank while the beans roasted in the furnace for about 30 minutes. When the smoke coming from the barrel turned a certain shade of gray, the barrel was removed from the furnace and the beans, some of them burnt by the 1093ºC (2,000ºF) heat. were dumped on a stone floor to cool.
Modern roasters have made possible a variety of roasts, each of which can lend its particular flavor to any coffee.
The guide below lists the various kinds of coffee roasts offered by gourmet and specialty shops.
After-Dinner Roast - A coffee that has been roasted to a dark. but less than very dark, brown color. It has a somewhat oily surface. An after-dinner roast lends a bittersweet, tangy flavor to the beans.
American Roast - A coffee that has been roasted to a mediumbrown color, with a dry rather than oily surface. An American roast is acidy, but also noticeably sweet and rich in flavor. It may also be labelled as regular roast. but is usually labeled as American roast because it is particularly favored by American coffee drinkers, who are notorious middle-of-the-roaders.
Cinnamon Roast - The lightest of the standard coffee-roasting categories. The finished surface is light brown and dry. A cinnamon roast has a distinctively sour flavor. Because of its popularity in the northeastern United States, a cinnamon roast may also be identified as a New England roast. It does not contain cinnamon.
City Roast - A medium-dark roast, slightly darker than an American roast but not as dark as a full-city or light French roast. A city roast lends a neutral taste, lacking the acidy characteristics of American roast and the tang of darker roasts.
Continental Roast - A dark-brown roast with an oily surface. It has more tang than a city roast and definitely lacks the acidy taste of lighter roasts. It may also be listed as a dark roast. French roast, or Italian roast.
Dark Roast - See Continental Roast.
Dry Roast - Not a true roast, but a method whereby the freshly roasted beans are allowed to cool slowly in the surrounding air, as opposed to the usual method of quenching the hot beans with water. Air drying does not Significantly affect flavor.
Espresso Roast - A very dark roasted coffee that is preferred for the fine grind required for espresso coffee-making equipment. An espresso roast results in a very oily, black bean. The taste of the carbonized cellulose dominates any natural aroma or flavor that may have been in the bean. Robusta beans are sometimes used in very dark roasts: robusta beans can only be improved in flavor by the intense roasting, whereas the heat drives out the volatile flavor factors present in an arabica bean.
French Roast - See Continental Roast.
Full City Roast - A coffee roast found mainly in the New York City area where coffee drinkers prefer their beans roasted to a degree that is just noticeably darker than a regular city roast and with a bit more tang. It may also be called high roast.
Heavy Roast - A dark-brown to nearly black roast with a surface that is even oilier in appearance than espresso or continental roast. A heavy roast is completely devoid of acidity, and its tang is all but overwhelmed by the carbonization and caramelization of the carbohydrates in the bean.
High Roast - See Full City Roast.
Italian Roast - A coffee that has been roasted to a degree that is darker than a high roast. The surface of the bean is dark brown and oily but not as dark and oily as a continental roast. An Italian roast is the type most popular with consumers in the coffeeproducing countries. It has the rich coffee tang of a dark roast, unconcealed by the taste of carbon.
Light Roast - See Cinnamon Roast.
Light French Roast - A medium- to dark-brown roast marked by spots of oil on an otherwise dry surface. It is comparable to a regular city roast in aroma and flavor.
Medium Roast - See American Roast.
New England Roast - See Cinnamon Roast.
Summer Roast - Coffee roasted in a warm. humid atmosphere to reduce the bean’s sweating. Sweated coffee. as it is also called. has a darker brown color after roasting than it would if it had been roasted under low humidity. Green coffee beans may be given a steam bath before roasting in order to increase the degree of brown coloration. This procedure improves appearance. but has little effect on flavor.