At 212° F the coffee beans turn yellow and lose water, from 248° F to 302 ° F the color changes from yellow to light brown and russet, folds in the beans open and release an essential oils, cafeone. At 392° F pyrogenation is reached.
The loss in weight by roasting depended on the kind of the coffee and the manner in which the roasting was done.
During roasting, vapors formed and cell fragments are removed by suction of an exhauster and in larger plants, incinerated.
Until coffee is roasted, its taste remains unknown. The end product is discharged rapidly to cooling sifters or is sprinkled with water in order to avoid over-roasting or burning and aroma loss.
The cooling was then followed by an air suction operation called ‘stoning’ which removed any stones or other hard material that would damage a grinding mill.
By the time coffee finishes roasting, more than 700 identified compounds cumulatively called coffee flavor – exist.
The most obvious change was production of a fragrance, attributed to a mixture do several substance. It was partly due to the volatile oil called caffeol, which was produced at the expense of other substances and partly to the sugars which were caramelized.
Coffee roasting
