Immerse yourself in the world of coffee roasting and discover how chemical processes and roasting levels shape the unique taste of your coffee.
Roasting coffee is a traditional craft and plays a crucial role in the flavor of your coffee. At Schön Kaffee, our roasting master creates a customized roast profile for each coffee to emphasize its unique character. In our roastery, we use the gentle drum roasting process to roast all coffees to perfection.
Very complex chemical reactions take place during the roasting of coffee. A coffee bean consists of approximately 300,000 to 400,000 cells and is one of the most aromatic foods. In fact, coffee contains more than twice as many natural aromatic compounds as wine. These aromatic compounds are strongly influenced by climatic conditions and the growing region. During roasting, sugars and amino acids recombine, creating an estimated 1,000 new aromas in each cell.
In our roastery, we use a traditional drum roaster to give our coffees their unique character. We roast in batches of 40 to 60 kg, and roasting times vary between 12 and 19 minutes, depending on the desired result. The final temperatures range from 200°C for light filter coffees to 220°C for our darkest espresso. After roasting, we quickly cool the beans on cooling screens using cold air, without using any water. We use a longer roasting time at a gentle heat to fully bring out the flavor nuances of our coffees. Especially with our espressos, we roast the beans a little longer to reduce unwanted acids and enhance the robust flavor.
The roasting process in detail
In the drum roasting process, the initially pale green, hay-scented green coffee beans are placed in the preheated roaster. The heat dries out any remaining moisture from the beans, and they gradually turn a yellow color. After about 7 to 10 minutes, the beans turn brown, giving off a spicy aroma reminiscent of popcorn or freshly baked bread. After around 12 to 15 minutes, the pressure in the beans is so great that the cell walls audibly burst—a moment known as the "first crack." From this point on, the coffee's full flavor spectrum unfolds. Fruit acids are broken down, sugar caramelizes, and the cell structure of the beans is weakened. Within a few minutes, the color of the beans changes from light brown to medium brown to dark brown. What makes drum roasting special is that the roasting drum is made of cast iron, which gives the coffee a distinctive flavor and a fuller body.
After roasting, the beans fall into a cooling sieve, where they are cooled by cold air and a stirrer. The beans then pass through a destoner, which removes any small stones from the green coffee. The roasted coffee is then packaged and allowed a few days to degas. Only after this resting period of approximately five to ten days can the coffee develop its full aroma.
The Maillard reaction and its significance
The most important chemical process during roasting is the Maillard reaction, in which amino acids and reducing sugars are converted into melanoidins. This process is responsible for the browning of coffee beans and the formation of their numerous aromas. Interestingly, coffees roasted using the gentle drum roasting process contain less acrylamide, a compound that forms at around 200°C.
The art of coffee roasting requires intuition, experience, and passion. The roasting masters at Schön Kaffee control the heat input of the roasting machine to achieve optimal aroma development. Even a few seconds or minimal temperature deviations can influence the taste of the coffee. The longer the coffee is roasted, the stronger and more bitter it becomes, with the bean's inherent flavor fading into the background.
Different roasting levels and their effects
When roasting espresso beans, the goal is often a strong flavor with a low acid content, which is why they are roasted for a longer time. Filter coffees, on the other hand, benefit from a slight acidity, which adds vibrancy to the flavor, and are therefore roasted for a shorter time. Especially with our light roasts, the roastmaster stops the roasting process shortly after the first crack. This roasting method is common in some countries, where the coffee is more reminiscent of tea than traditional coffee. In other countries, however, a dark roast is preferred, which produces strong roasted aromas and a bitter taste.
