A
good roaster must be part artist, and part scientist, to maintain quality
and consistency. It is during the roasting process that the sugars and other
carbohydrates within the bean become caramelized, creating a substance which
is known as the coffee oil. Technically, this fragile chemical is not actually
an oil, but it is what gives the coffee its flavor and aroma.
Speciality coffees are generally roasted in small
batches. The two most common roasting methods are drum-roasting and hot-air
roasting. Drum-type roasting machines roast the coffee beans as they tumble
in a rotating drum heated by gas or wood. When the desired roast is achieved,
the beans are poured into a cooling hopper to keep them from overcooking.
The
hot-air roaster, also known as a fluid-bed roaster, roasts the coffee beans
as they tumble on a current of hot air. Most green coffee is roasted at approximately
400 degrees. The roasting process causes the coffee beans to swell and increase
in size by over 50%, while at the same time greatly reducing their weight.
A lightly roasted bean may range in color from
cinnamon to a light chocolate tan. Lighter roasts are generally not used for
espresso since they produce a sharper, more acidic taste than do darker roasts.
Darker roasts, in contrast, have a fuller flavor approaching a bittersweet
tang. The amount of oil drawn to the surface of the bean increases proportionately
to the length of roasting time. As the roast darkens, caffeine and acidity
decrease proportionately. Dark roasts can range in color from a medium chocolate
brown with a satin-like luster, to an almost black bean with an oily appearance.
The darker the roast the more you will taste the char, rather than the flavor
of the bean. Extreme dark roasts will tend to have a smoky flavor, and are
better suited for brewed coffee rather than espresso.
Many roasters refer to the following terms concerning the degree of roast, from light to dark: Cinnamon, Medium High, City, Full City, French, and finally, Espresso or Italian roast. On the West coast of the U.S., French roast is the term generally used to describe the darkest roast. It is important for you to understand that these terms have no relationship to where the coffee is grown or roasted.
With more than 100 coffee-growing regions in the world, each producing beans with distinctive characteristics, we believe proper blending is essential to the balance of flavors necessary to create superior espresso. A single coffee bean will generally not possess the complexity necessary for great espresso. Many espresso blends will contain three to seven different types of beans.
The experienced roaster, with his knowledge of each bean, artfully combines them to create the desired blend of flavors. The roaster's blending knowledge is usually a closely guarded secret. In the United States, 100% Arabica beans are generally used for gourmet espresso blends. As we mentioned earlier, in Italy, some robusta beans will often times be added for the additional crema, caffeine, and complexity they contribute to the blend. The Italians possess generations of expertise in the art of blending coffees for espresso.
Argument still exists among roasters as to which should occur first--the roasting or the blending. Generally, roasting each varietal separately to maximize its flavor characteristics, and then blending, will produce the best result. Freshly roasted beans will release hundreds of chemical substances in the form of vapors. A day or two will generally be required for these gases to dissipate before the beans will reveal their optimal flavor characteristics.
Source: Coffee Universe
