How is coffee roasted?

Throughout history, there have been different methods of roasting coffee. From the most rudimentary to those that exist today, coffee has been roasted in many ways to improve the qualities and characteristics that this beverage can offer. Below you will learn all about the coffee roasting process.

History of coffee roasting

Africa and the Middle East are believed to be the cradles of coffee roasting. Before coffee spread worldwide, thin, perforated pans were used to roast coffee. Spoons were also used to stir the beans to achieve an even roast. However, only a small amount of beans could be roasted, so the process took more time and attention to prevent the beans from not roasting properly.

Later in the 17th century, cylindrical roasters were developed in Egypt. These devices enclosed the beans, and the heat was focused in this chamber, which rotated consistently over the fire thanks to the cranks on the device. This method also reduced smoke, promoting a more comfortable roasting process that spread throughout Europe and America.

With the advent of industrialisation in the 19th century, several patents for industrial coffee roasters were issued in the United States and Europe. However, the advent of gas meant that coffee roasting lost the smoky flavour it had with traditional roasting using wood or charcoal. After several attempts to obtain a safe and efficient roaster, the Probat company developed the drum roaster in 1880.

Electric motors made the coffee roasting process less laborious with electricity in the 20th century. By 1970, the revolution of the fluid-bed or hot-air roasters began devices that force hot air through a perforated base onto the coffee beans, which are lifted and heated by the movement of the machine.

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Why is coffee roasted?

Today, digital temperature gauges and profiling software allow coffee roasting to become more and more accurate. The importance of roasting coffee lies in the fact that it gains 100% of its volume, in addition to losing 20% of its weight and 10% of its caffeine. In addition, the acidic components of the coffee are reduced, and the fats are increased thanks to pyrolysis reactions that allow the sensory qualities of the coffee to be appreciated.

Coffee roasting

The coffee roasting process begins with drying the bean’s humidity, usually 12 %. Subsequently, the bean expands, and different chemical reactions are generated. When the beans are close to 170° centigrade, they begin to take on a cinnamon colour, and the first crackle or crackle occurs. At the same time, the sugars caramelise and take on a darker colour, and the skin of the beans peels off.

When the temperature reaches 190 degrees Celsius, the coffee crackles again, and its aromas and gases are released more strongly. The final temperature for roasting coffee can be between 200º and 240º centigrade. When the roasting is finished, the coffee is cooled and undergoes various cleaning processes to remove impurities.

Different compounds such as oxazole and pyrazine and gases are produced during roasting, continuously reducing after several hours. In the end, the humidity of the bean with the roast colour is between 12 and 20%. Roasting takes between 20 and 25 minutes, although this can vary depending on the type of machine and the variety of coffee.

Light roast

This type of roasting gives the coffee bean a cinnamon colour. It is the one that preserves most of the flavours of the coffee’s origin, which is why it is often used for origin or gourmet coffees, characterised by herbal and fruity nuances.

Dark roast

This type of roasting generates a dry distillation of the coffee, extracting its essential oils. It is used for coffees with low caffeine content, usually used in espresso machines to obtain smoky or spicy flavours.

Medium roast

This is an intermediate roast level that maintains a considerable level of caffeine but is sweeter. Because it requires more exposure to heat, the sugars caramelise, resulting in nuts, caramel, or chocolate notes. This type of roast is common for espresso or filter coffees.


Torrefacto is not a type of roasting, as it only requires the addition of sugar in the roasting process. In this way, the coffee takes on a blacker colour, with a slightly bitter taste and better preserves the aromas of the coffee. The amount of sugar allowed to be added to coffee is 15 kilograms per 100 kilos of green coffee.

As you can appreciate, roasting coffee is a process that allows exploiting the different flavours and aromas of coffee. Depending on the machine used and the variety of coffee, some characteristics are more evident than others.

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