Coffee roasting: how it works and which grade to choose

What is the process of roasting coffee beans?

The process of roasting coffee consists of roasting the beans in a special machine (roasting machine). The coffee is subjected to high temperatures that cause various effects, including dehydration of the product, oxidation and carbonisation.

Coffee roasting is an ancient practice, which can be traced back to the Ottoman Empire, as far as the 15th century. The first experiments were aimed at bringing out the best properties of the beans: the beans were placed in metal and ceramic pans and, just like in a rudimentary drum roaster, roasted until the desired result was obtained.

Since these early attempts, a host of technological innovations have made it possible not only to increase the roasting capacity, but also to control the degree of roasting of the beans very precisely.

What is the purpose of roasting coffee beans?

Coffee roasting is used to transform raw green coffee beans into brown beans. During coffee roasting, the beans lose weight and increase in volume, acquiring their characteristic aroma. This process takes place through a combination of heat and time, which allows the organoleptic qualities of the coffee to develop.

What happens to coffee beans when roasting?

In the roasting process, raw coffee is subjected to high temperatures, undergoing a series of physical and chemical transformations that make it suitable for the preparation of drinks and enhance certain properties and characteristics. As the transformations take place, it is the master roaster who chooses the ideal moment to interrupt this process of modification of the raw material, through careful observation and excellent training of the senses.

During coffee roasting, new aromatic compounds are formed and there is a reduction in the intrinsic acidity of the coffee bean. As the roasting process progresses, the oils within the beans begin to emerge on the surface, further contributing to the flavour and aroma of the coffee.

The major physical changes that coffee undergoes during roasting are:

• Dehydration: in the course of roasting, the water in the beans evaporates from around 10% to 1%, resulting in a decrease in the weight of the bean (around 15-20%);
• Increase in volume: due to the gas pressure formed inside the grain while it is being heated, the volume of the grain increases by 40-60% compared to the raw product. This effect is also indicated by the presence of one or more ‘cracks’ indicating the formation of some cracks and the escape of steam;
• Change in consistency: while raw coffee beans are hard and elastic, during cooking they become crumbly and porous;
• Change in colour: from the green of the Arabica variety and the yellow-brown of the Robusta variety, they turn a more or less intense brown depending on the roasting profile. This occurs due to caramelisation of the sugars and carbonisation of the cellulose contained in the bean;
• Loss (complete or partial) of the film covering the grain.

What are the roasting stages of a coffee bean?

The different stages of roasting greatly influence the final coffee profile, determining whether the taste will be mild and fruity, or rich and intense. The coffee roasting process can be divided into three stages:

• Drying or yellowing. Once the roaster has been brought to an ideal temperature to start the roasting process, the beans are placed in the roasting chamber. The drying phase has a variable overall duration depending on the moisture content of the beans and ends when 160° C is reached, once the beans have undergone a distinct yellowing;
• Caramelisation or browning. Starting at 160° C, the sugars and amino acids in the coffee undergo one of the most important reactions in coffee roasting: the Maillard reaction. During the browning phase, or ‘browning’, it is essential to adjust the time and temperature so that the right roasting profile is obtained, which enables the desired aromatic compounds to be obtained. This phase ends with the first ‘crack’, a crackling due to the escape of vapours inside the bean, which usually occurs between 190° and 200° C;
• Development. At this stage, the roasting process is gradually slowed down. Whether or not we reach the second ‘crack’, which is less loud than the first, once this phase is over it is important to proceed immediately to the cooling process: the beans must be brought to room temperature in order to interrupt the roasting process.

What are the degrees of coffee roasting?

Depending on the degree of roasting of the coffee, we can have light roast, medium roast and dark roast:

• The light or blond roast, also known as city roast, is the one that is completed at a temperature between 170° C and 190-200° C, when the ‘first crack’ occurs. The result is light brown beans, rich in caffeine and with a pronounced acidity. It is the preferred coffee in Northern Europe and North America, suitable for infusion extraction methods (such as filter coffee) and not very suitable for espresso preparation;
• Medium roast, known as full city roast, the degree of roasting practised by Caffè Roen, is obtained after the second ‘crack’, between 200°C and 220°C. The medium roast coffee is a more balanced coffee, has a less noticeable acidity and is of the typical ‘monk's brew’ colour. It is the ideal coffee for Italian espresso. Discover our premium blends and our single-origin coffees with medium roast.
• Finally, dark roasting is the one that involves beans with a more bitter taste and lower caffeine content. During this phase, the coffee beans take on a dark brown, almost black colour, while the natural oils of the coffee rise to the surface, giving the beverage an oily, shiny appearance.When carrying out this type of roasting, which takes place between 230° C and 240° C (sometimes exceeding this threshold), the roaster must be good at avoiding carbonisation of the coffee. This is the coffee preferred in Southern Italy, Spain and Portugal, where strong and very bitter coffee is preferred.
  
  

How to choose coffee roast?

Roasting is an incredible process that enhances the properties of a unique raw material. If you are a lover of quality espresso coffee, at Caffè Roen you will find the best coffee beans roasted to perfection for your moments of pleasure and sharing.

Discover the coffee from our artisan roastery and try our blends and single-origin coffees. Don't be satisfied with the usual coffee: with Caffè Roen discover a world of unique sensations!