Basically, the process involves exposing the beans to heat, which causes the beans to expand, roast, and darken. Beans should not be roasted at low temperatures, which will cause them to bake. And beans should not be roasted at high temperatures, which will cause them to char. Beginners are recommended to purchase one of several home coffee roasters which have recently entered the kitchen specialty devices market. Some examples are the Alpenroast Drum Coffee Roaster, the Hearthware Home Coffee Roaster, and the Fresh Roast Coffee Bean Roaster.
Coffee roasting is an art.
Roasting times and temperatures vary, depending upon the method of roasting used and the roast desired. The bean expands, and chaff is formed on the surface. Here, the sound is sharper and sounds like rice cereal after adding milk. Many roasters use several senses during the roasting process. By listening for the cracks, smelling the changing fragrances during the roast, and observing the beans changing from green to cinnamon to various shades of brown, the roaster determines when to cut off the heat source.