ROASTING COFFEE

As far as we know coffee was first roasted towards the end of the 15th century. The oldest method consisted in roasting the green beans in a heavy frying pan over coals. By the end of the last century, a new process had been invented. The beans were spun in a hot air chamber heated by natural gas, and this is the process still used nowadays. 

Each type of coffee requires a different temperature and roasting time according to the bean size and origin. This process needs experienced staff since the diversity of aromas which can be captured in the coffee bean depends on the balance between temperature and roasting time. The chemical composition of the beans changes throughout the roasting process: the water dissipates in the bean and a series of chemical reactions turns sugars and starches into oils. 

These are responsible for the aroma and flavour of the coffee. As it is roasted, the bean doubles in size and becomes brown due to sugar's transformation into caramel. Dark roasted beans are less sour and contain less caffeine than the paler beans, although they need a shorter conservation period due to the amount of surface oil. A smoky, penetrating and burnt flavour pervades the darkest kinds of coffee, hiding the true flavour of the bean. Contrary to popular belief, a darker roasting does not necessarily give a richer or stronger cup of coffee. The roasting process does not determine whether a cup of coffee will be more or less strong. The fundamental factor is the amount of water in the coffee when preparing it. Light roasted beans have a more intense flavour. 

They have a higher sourness than in the darker types of roasted coffee. Because the coffee has been less exposed to heat, the qualities of the bean are better conserved. When roasting lighted coffee types, higher quality beans are used. In this case, the real flavour of the bean is revealed. The roasting process has several different levels, each one with its own characteristics, in turn reflecting different tastes or specific uses. These are:
 

Cinnamon roasting 
Clear cinnamon-coloured roasting.

Strong nut-like flavour, high sourness level in the coffee 
American roasting Medium roasting, brown shade

Caramel-like flavour City roasting Medium, brown roasting.
Average brown without surface oil

Absolute coffee flavour, with a little less sourness Urban roasting 
Brown chestnut, just darker than the City roasting

Absolute coffee flavour, with a good balance between sugar and sourness 
Vienna Dark brown, with signs of oil on the surface

Dark roasting flavour French roasting 
Dark brown, almost black, oily on the surface

IA bitter, smoky flavour and an intense aroma 
Italian Bitter brown chocolate, with surface oil

Burned flavour Espresso Dark roasting, specifically intended for espresso coffeemakers. 
Burned, strong and sweet flavour

There is a variant of dark-roasting which consists simply in adding sugar to the coffee while it is being roasted - this gives it a darker colour and a more bitter flavour. Once the coffee has been roasted at the required temperature, we need to extract the heat by cooling it as rapidly as possible. This is done by pouring the coffee on a cooling tray, where its temperature falls to ambient.