Coffee beans are usually roasted in large batch dryers, which spin and heat them evenly at temperature that reaches 550 ° F. During roasting process, about 20 percent of the water content of the green beans evaporates and gases are released. In addition, the beans’ starch content is converted to sugar.
Roasting releases the oils and acids that give each coffee its unique flavor. The volatile oils and acids that give coffee is tempting aroma and delicious flavor are developed during the roasting process.
The flavor of roasted coffee, to a large extent depends upon the manner and extent of roasting. The flavor and aroma of coffee are best when it is freshly roasted and deteriorate on standing.
Sucrose which is the most abundant simple carbohydrate present in green coffee, acts as an aroma precursor during roasting, generating several classes of compound, such as carboxylic acids furans, and aldehydes, which will affect the flavor of coffee. Sucrose is found to be destroyed quickly at the early stages of roasting.
Coffee bean roasting
