It's About Coffee - Coffee Roasting

All of the flavour and aroma that we enjoy in coffee is created by the roasting process.

Coffee is usually sold in a roasted state, and all coffee is roasted before being consumed. Coffee can be sold roasted by the supplier or it can be home roasted. The roasting process has a considerable degree of influence on the taste of the final product, creating the distinctive flavor of coffee from a bland bean, by changing the coffee bean both physically and chemically.                                                                                                                                     

Green coffee beans are heated to between 180ºC and 240ºC for 8 to 15  minutes,  depending on the degree of roast required. As moisture is lost, the bean "pops" audibly rather like popcorn and a chemical reaction called pyrolysis takes place: starches are converted into sugar, proteins are broken down and the entire cellular structure of the bean is altered. The heating process precipitates the release of caffeol, or coffee oil, the essence of coffee that we enjoy in the cup.  Since it is also volatile and water soluble, once the coffee beans have been roasted, the flavour can be damaged by moisture, light and especially by oxygen.

Roasting is one part art, one part science, and several parts judgment. Too much heat and the beans are roasted too dark and too much caffeol is burnt; not enough and the caffeol is not precipitated. 

Grades of coffee roasting are unroasted (or "green"), light, cinnamon, medium, high, city, full city, French and Italian. Depending on the color of the roasted beans, they will be labeled as light, cinnamon, medium, high, city, full city, French or Italian roast. Darker roasts are generally  less aroma but full bodied and smoother, because they have less fiber content and a more sugary flavor. Lighter roasts generally less bodied, stronger flavor from aromatic oils and acids which are destroyed by longer roasting times