Coffee Roasting

All the characteristics that make a coffee an exquisite drink have an origin, a process and a secret, a fundamental part that a maximum connoisseur of coffee must identify and enjoy. Be an expert and know the coffee roasting ritual …

The coffee roasting process is essential, because without it and without the chemical transformations that it implies, the aroma of coffee, as we know it, could not be appreciated by the consumer. It is the roast that brings out that wonderful aroma that all coffee lovers are looking for and that captures the unsuspecting.

The roasting process

The roasting process can be divided into 3 stages:

The first is when the grain loses moisture, and begins to gain temperature; Then comes the roasting stage, in which the different chemical and physical reactions are carried out. And as a last stage, comes the one known as cooling, whose objective is to stop these reactions once the desired roast is obtained. In the first stage also known as dehydration because the grain reaches the boiling temperature of water.

In the first stage there are changes such as the color of the grains, from a bright green to a pale yellow due to dehydration, since the water content decreases from 90 to 70%, and sensually we perceive a bread and cereal-like aroma .

At 160 ° C the poriolysis reactions begin, its onset is indicated by a thunder, which is caused by the evaporation of water inside the grain, which increases its internal pressure. At that moment the grain cracks from its center; CO2 is produced, due to the oxidation of carbohydrates.

The grains change a pale yellow color and increase their size, which results in the shedding of the film.

Within the cells of the grain there is a hydrolysis of compounds, which produces water-soluble polysaccharides, which over time are caramelized, cause the grain to change color and contribute to the aromatic qualities of coffee. If the coffee is roasted at high speed, the astringency will be greater, since the reaction reactions of acids are not achieved, which contributes to increase the positive acidity.

Further along with this same process, a second thunder will be heard, caused by the breakdown of the grain structure giving a bright appearance. If the toast continues, the starches and sugars that were caramelized begin to carbonize causing the characteristic burning of dark toasts.

Once the desired degree of roasting is reached, this process should stop; either with cold air or with water. The amount of water used for this is critical, since coffee tends to gain weight because it absorbs water. The roasting process can take 7 to 30 minutes depending on the type of toaster.

The temperatures

During the roasting process, the temperatures reached by coffee beans are around 193 ° C for a light roast, about 200 ° C for a medium roast, and about 218 ° C for a dark roast. Once the roasting process is finished, the grains pass to coupling trays to cool quickly and thus stop the process when desired.

Toasted

The light roasts retain greater acidity and the subtle aroma of the lighter grains. A medium roast is general purpose, producing a stronger flavor while retaining its acidity. Dark roasting, also known as Italian, produces a stronger coffee, with a certain bitterness, but less acidic and with a soft body.

The mixtures can be of various varieties, some are preferred with different degrees of toast and different grain origins. The chemical transformations that occur then are indeed very complex and determine what types of coffee the cup will develop.

Factors that affect the roasting process

• Humidity and room temperature.
• Grain size and density.
• Grain Time
• Process of coffee cherry.
• Characteristics of the grain
• Toaster gas flow.
• Intensity of the toaster flame.
• Roasting time
• Roasting temperature
• Increase in temperature with respect to time.
• Time of day to be roasted.