The green beans bagged on the plantation and purchased by importers have neither flavor nor aroma. But, between the freshly harvested green bean and the plump brown bean ready for the coffee mill a chemical and physical transformation takes place that makes the roaster's role in producing fine coffee as important as that of the grower. Coffee roasters have an immense responsibility. When properly roasted, good beans may turn into fabulous coffee; when improperly roasted, they might as well be thrown away. This is why the top firms always test-roast a sample from each lot of beans before deciding on the definitive roast.

Although coffee-roasting machines are equipped with portholes through which the roaster may evaluate progress and stop the roasting if necessary, and have probes for extracting samples, skilled roasters work mainly by ear. Coffee beans that have been roasted to a turn begin to "sing": they crackle and splutter. When experienced roasters hear this music, they know it is time to shut off the machine. After they have done so, they open a chute, and the sizzling coffee beans pour down it into a large vat with a ventilating system that cools them instantly.

The coffee roaster's art is infinitely subtle, reflecting individual tastes and preferences. Some roasters claim the beans should not be roasted all the way through, since this would kill their aroma. Differences of opinion abound especially when it comes to the degree of roasting appropriate for the world's great coffee varieties.

The range from very light to very dark is full of delicate nuances including all the colors of the official nomenclature: light, medium, light French (today the most common roast in France), European (deep brown), French (a very dark roast which, ironically is increasingly rare in France), and Italian (almost black). Light roasting highlights the aroma and diversity of the organic notes in mellow, mild varieties. This has long been popular in Germany, Scandinavia, and eastern France. Lightly roasted beans are also used in Turkey and Greece for making "Turkish /Greek coffee." Longer (i.e. darker) roasting, on the other hand, produces coffee that is black, strong, caramelized, and sometimes bitter, with more of the traditional "coffee" taste. Very dark roasts (which tend to create a better foam for espresso) are the rule in Italy, the north and south of France, and also-in a version that is even darker and oilier-in Lebanon and some countries of the Middle East, where the taste is for very strong Turkish coffee. The difference between light-roasted and dark-roasted coffee beans is almost as great as the difference between cooked and raw food, or black tea and green.
Incidentally, it is interesting to note the recent appearance in Italy and the United States of roasters who praise the qualities of their "wood-fire" roasting.
There are three ways of roasting

I. The light or golden roasting that gives coffee alight flavor. This way is more popular in Scandinavia and Greece.
II. The middle roasting that gives coffee a light brown color and stronger flavor. This coffee is popular in Central Europe and America.
III. The strong roasting gives coffee a very strong and bitter flavor and usually is drunk straight. Is most famous in countries of south Europe (Italy, Spain etc.)