The process of roasting coffee involves cooking the bean for about 15 to 30 minutes until the desired roast level is achieved. To properly roast coffee you need a good coffee roaster as well as the some knowledge of roastmaster skills.
Ideally a fine coffee bean won’t need excessive roasting and this will allow the coffee consumer to enjoy the bean’s origin flavors that reflect the climate of the growing region and the particular traits of the coffee bean including its genetics (e.g., Kona Typica, a variety of Arabica).
Darker roasts can mask many of these origin flavors, though in some cases a dark roast is appropriate because it brings out other flavors in the beans.
When coffee beans are roasted they grow in size as they lose moisture and begin to develop soluble oils. Darker roasts are created by using a higher roast temperature for a longer roasting time. Lighter roasts may be roasted just until the “first crack” when the beans crack or pop for the first time. In general, a lighter roast has a higher acidity than a darker roast, which will tend to have a fuller body and be sweeter.
A Full Roast, or Italian Espresso Roast is roasted until the “second crack” when the beans become a bit shiny and oily on the surface. The roast flavor is apparent and there may be spicy or chocolaty flavors.
A Dark Roast is roasted beyond the second crack until the sugars begin to carbonize creating smoky-sweet flavors.
The best roast for a particular coffee bean is best determined by taking into account the various factors including the type of bean, moisture content, how the beans have been stored, the age of the beans, bean quality, and other factors. Skilled roastmasters listen carefully to the beans as they are roasting to help determine the proper length of roasting time.
Most Kona coffee is only given a light or medium roast because the bean is naturally smooth and not overly acidic to begin with. About eight pounds of Kona coffee cherry (fruit) will roast to about one pound of roasted coffee due to the dissipation of moisture in the coffee beans.
If you are interested in roasting your own Kona coffee beans check out the Homeroasters Association.