Coffee Roasting
Green Coffee Beans: The process starts with green coffee beans, which are seeds extracted from the cherries of coffee plants. These beans are dense, have a green colour, and lack the characteristic flavours and aromas associated with roasted coffee.
Preheating: The roasting machine is preheated to the desired temperature, typically ranging from 180°C to 230°C (356°F to 446°F). The specific temperature depends on various factors such as the desired roast level and the characteristics of the beans.
Drying Phase: The green coffee beans are introduced into the roasting chamber, and the heat causes them to lose moisture. This initial drying phase is crucial as it prepares the beans for subsequent chemical reactions.
Browning and Maillard Reaction: As the temperature rises, the beans undergo a series of complex chemical reactions. The sugars and amino acids present in the beans combine, leading to the Maillard reaction. This reaction produces a range of flavours, including nutty, caramel, and chocolate notes, and the beans start to develop a brown colour.
First Crack: As the roasting process progresses, the beans undergo physical changes. At a certain point, they reach a temperature of around 205°C to 220°C (401°F to 428°F), and they begin to emit a cracking sound known as the first crack. This cracking sound indicates that the internal structure of the bean is breaking down, and the beans are expanding in size.
Roast Development: Following the first crack, the beans continue to undergo further transformations. The roaster must monitor the colour, aroma, and temperature carefully to achieve the desired roast level, whether it be light, medium, or dark.
Second Crack (Optional): Some darker roast profiles, such as medium-dark or dark roasts, may undergo a second crack. This crack signifies that the beans have reached a higher temperature, resulting in deeper caramelization and a more pronounced flavour.
Cooling and Degassing: Once the desired roast level is achieved, the beans are rapidly cooled to halt the roasting process and prevent over-roasting. Cooling also helps the beans retain their flavour and aroma. After cooling, the beans require a period of degassing, during which they release carbon dioxide built up during the roasting process.
Resting and Packaging: After degassing, the roasted beans are typically allowed to rest for a few days to a week. This resting period allows the flavours to stabilize and develop further before the beans are packaged for sale or use.
Each step of the roasting process, from the initial drying phase to the final resting period, significantly influences the flavour, aroma, and characteristics of the coffee beans. Roasters employ their expertise and knowledge to achieve the perfect balance and bring out the desired qualities in the beans, creating the diverse range of coffee flavours and profiles that we enjoy.
