The roasting process

How coffee beans develop their aroma

Roasting coffee is crucial for the approximately 800 aromatic compounds that determine its flavor. From dark chocolate and roasted nuts to fruity berries – the roasting process creates the unique aroma profile of each bean.

Why is coffee roasted?

Only through roasting—that is, the dry heating of the clean coffee beans—do the aromas develop that make this stimulating beverage so unique. Anyone who has ever seen coffee cherries knows that they have little in common with the dark, aromatic beans that later go into the espresso machine. After the fruit is cut open, extracted, and dried, the small, light-colored seeds remain, the so-called green coffee. Many green coffees contain a relatively high proportion of chlorogenic acid and would be somewhere between unpalatable and unhealthy in their raw form. Depending on the condition of the green coffee and the requirements for the final product, there are numerous roasting methods and as many roasting recipes as there are coffee varieties. Today, coffee roasting is more of a craft than ever before and is becoming increasingly popular in Germany as well.

How does the roasting process work?

At The raw coffee beans are exposed to dry heat at 180°C to 230°C. They are constantly turned mechanically to ensure even roasting and prevent burning. The beans can go through various cycles in the roaster for between eight and twenty minutes; by carefully controlling the airflow, smokier aromas can also be produced. No additives are used. Several processes take place in the roaster:

• The water content drops from about 12% to around 2%, resulting in a Weight loss ("burn-in") occurs.
• The bean expands by up to 70% – its skin bursts open, and aromatic oils are released.
• The so-called Maillard reaction gives the beans their brown color; in this process, a few starting materials are converted into up to 1000 different flavor compounds, which give the coffee its unique aroma.
• The fructose contained in the bean caramelizes and influences sweetness and roasted notes.
• Caffeine is heat-resistant and remains intact, while pesticides are completely broken down. Therefore, even non-organic coffees are perfectly safe to drink.
• Slow, gentle roasting reduces the acidity, resulting in mild and easily digestible coffees.

Two main methods are used for roasting: the Drum roasting process and hot air roasting processDepending on the temperature, duration, and type of roasting, the many different roast levels we know by various names are created. Filter coffee, for example, is roasted relatively lightly and therefore develops fewer bitter substances; espresso blends, on the other hand, remain in the roaster longer and become somewhat darker.