After obtaining high-quality coffee beans, the most important stage of coffee production begins, which is the roasting and blending of beans. A good coffee roaster needs to be both an artist and a scientist to keep the quality and consistency of the beans. By roasting, sugars and other carbohydrates in the coffee are caramelised, generating a substance known as coffee oil. Two of the most traditional coffee roasting methods are drum roasting and hot air roasting.
Machines with a drum roast coffee beans by rotating the beans in a drum heated with gas or logs. Once the beans are roasted, they are poured into a steaming container to avoid excessive burning of the beans. A hot air roaster roasts coffee beans by rotating them in hot air. Most of green coffee is roasted at about 200 degrees. Roasting swells the coffee beans up, making them more than 50% larger, but losing a lot of their weight. The colour of slightly roasted beans can vary from cinnamon to chocolate. Lighter roasts are usually not used for making espresso as these give a sharper and sourer taste than darker roasts. Darker roasts, however, have a richer taste and may even have a stronger sweet and sour aftertaste. The amount of oil gathering on the surface of the coffee bean increases the roasting time accordingly. As the roast gets darker, the sourness and caffeine amount decrease proportionally. As there are more than 100 coffee growing regions in the world, each growing beans of different characteristics, we think it is important to balance the taste properties by blending the beans correctly to get a high-quality espresso. One coffee variety usually does not have all the characteristics required to make a delicious espresso.
Many espresso blends contain three to seven types of beans. An experienced roaster who knows all of their coffee varieties is skilled at blending various types of beans to get the desired taste. Usually, the roaster is very secretive about their knowledge.