"No coffee can be good in the mouth that does not first send a sweet offering of odor to the nostrils," said Henry Ward Beecher. This "sweet offering" is the aroma that is produced when coffee grounds come in contact with water. Before the water is added, coffee grounds exude a certain bouquet. Although technically the words aroma and bouquet are not interchangeable, they are often used synonymously. Aromas vary according to the bean; some are fruity, flowery, or spicy, and some coffees have more aroma than others.
Green coffee beans have about 7 percent chlorogenic acid, an acid that produces an astringent taste. To promote a palatable flavor, the beans are roasted. Roasting breaks down the raw components in the beans and causes chemical changes to occur, a process called pyrolysis. The chlorogenic acid disappears, and new acids with more flavorful tastes develop.
Acidity is the rich, tart taste in the mouth, a characteristic also called winyness. This flavor is affected by the elevation of the cultivation. Arabica raised in mountainous terrain is more acidic than robusta, which is cultivated at lower levels. Light roasts are more acidic than dark roasts.
A combination of taste, aroma, and acidity.
Coffee beans are naturally high in starch and sugar. When coffee beans are roasted for a long time, the sugar in the beans carmelizes and gives the beverage "body," or weight in the mouth. Professional tasters look for body that surrounds the mouth completely, a rich flavor that lingers on the back of the tongue a few seconds after it is swallowed. Dark-roasted coffees have more body than light roasts. Because light roasts undergo a short roasting period, the sugar in the beans does not carmelize and the brew is light-bodied.