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Roasting coffee beans - roasting process coffee beans

Roasting coffee beans

Only when the coffee beans are roasted, the beans get their taste, flavor, aroma and color!

The secret of a good coffee is in the roasting of the beans. In the coffee roaster the temperature is gradually increased. The coffee beans lose weight by evaporation of moisture and undergo a considerable increase in volume by the pressure of carbon dioxide. In the heating proces also hundreds of aromatic substances are created.

At a temperature between 170-200 oC the coffee beans caramelise and heat accumulates in the bean.

From about 205 oC the beans considerably increase in volue and lose more weight (this is called the first crack).

At a temperature of 220 oC carbon dioxide is released and the bean drops another 15% in weight.

At a temperature of approximately 230 oC the bean changes color and plops. This is called the second crack. This is a precise process and it is important not to increase the temperature to fast or keep it long on high temperature. A high level of combustion may occur leading to a dirty aromatic effect. Also the oils can react with the oxygen, which leads to a burnt taste.

The roaster follows the entire branding process closely and controls the proces by nose, ear and eyes. With color samples it can be determined when the right roasting level is reached.

With a lighter coffee roasting a more sweet, slightly sour flavor is created; with a higher roasting more bitter flavors are created.

If proper roasting level is reached, the freshly roasted coffee blends should be relatively quickly cooled. This is done with air or with water. Water cooling is most effective but air cooling is better. The beans will absorb no water or moisture.

The following descriptions are used for the various roasting gradations, the roasting kwalifications:

- Light Brown Roasting - high acid, low sweetness, medium aroma, weak body

- Medium light brown = U.S. branding - high acid, mild sweet, full aroma & body

- Full medium brown = high acid, mild sweet, strong aroma, full body

- Medium- dark brown = medium acid, sweet, strong aroma, very full body

- Dark brown (Italian Espresso) = low acid, full sweet, medium aroma, full body

- Very dark = very low acid, low sweet, mild aroma, weak body

Because roasting coffee is a precise process, it is important that the coffee beans in the roasting process as equal as possible. Small bean beans between large are roasted faster with the risk they burn before the big beans are ready. Having  coffee beans with different colors this may indicate a different drying process of the beans which again affects the roasting process.