Roasting

Roasting is a heat process that turns coffee into the fragrant, dark brown beans with which we are most familiar.

Before being roasted, the beans were stored green, a state in which they can be kept for approximately two years without loss of quality or taste. Once roasted and rested, however, they should be used as quickly as possible before the fresh roast flavour begins to diminish.

When beans are roasted, they store up CO2. While fresh, the beans give off this CO2, which is the reason for storage in special coffee bags that have a one-way valve. This valve allows the CO2 gas to escape, but not allow oxygen in. “Resting” the beans refers to the time of storage after roasting where the beans give off the most CO2.

Roasting is a technical skill which approaches an art form. It takes years of training to become an expert roaster with the ability to ‘read’ the beans and make decisions with split second timing. The difference between perfectly roasted coffee and a ruined batch can be a matter of seconds.

Roasting brings out the aroma and flavor that is locked inside the green coffee beans. A green bean has none of the characteristics of a roasted bean. It is soft and spongy to the bite and smells green, almost ‘grassy.’ Roasting causes numerous chemical changes to take place as the beans are rapidly brought to very high temperatures. When they reach the peak of perfection, they are quickly cooled to stop the process. Roasted beans smell like coffee, and weigh less because the moisture has been roasted out. They are crunchy to the bite, ready to be ground and brewed.

Most roasters have specialized names for their favored roasts and there is very little industry standardization. This can cause a great deal of confusion for the buyer. But in general, roasts fall into one of four color categories—light, medium, medium-dark or dark. The perfect roast is a subjective choice that is sometimes determined by national preference or geographic location.
[Source: National Coffee Association, USA]