The Processing
Roasting coffee involves heating the coffee beans to a very high temperature. Thanks to this process, the green beans turn brown and become crumbly, delicate and highly fragrant.
The most common way to describe the different roasting levels is to use the colour of the roasted beans. Indeed, it is the process of roasting green coffee at high temperatures that causes it to turn its characteristic shade of brown.
During roasting, the coffee is heated to a temperature of between 190˚ and 230˚, the former giving a light roast and the latter a dark roast. Generally, the coffee blends used for everyday espresso are heated to a maximum of 227˚, which is considered a medium roast, being neither light nor dark.
The level of roasting determines the colour of the coffee, and also plays a crucial role in defining the so-called organoleptic qualities of the drink produced. The roasting process also brings out the distinctive factors of a given blend – i.e. acidity and body, which increase or decrease depending on the extent to which the beans have been roasted.
During the roasting phases, the green bean undergoes substantial chemical changes: the first phase consists of the heat exchange whereby it starts to take on a golden colour and the roasting aroma begins to be released; in the second phase, following the increase in the temperature of the bean, as well as shedding some of its weight it turns slightly darker. At this point, its density is reduced, and it starts to release carbon dioxide – a phenomenon that, if allowed to keep on going for days, sees the bean also increase in volume.
Having obtained the ideal level of roasting, and to stop combustion from continuing, the coffee is immediately cooled. After roasting, the coffee is left to rest for several days before being packaged.