Coffee fermentation

The fermentation process involves the breakdown of sugars into simpler substances by yeast and bacteria. Coffee production is impossible without fermentation, as is the production of yogurt, wine, bread, chocolate and sauerkraut. Fermentation in coffee is not only the taste of fermented berries in naturally processed coffee. There's a whole series of processes happening with coffee beans, each one that has its influence on their taste.

The processing of coffee, washed, is an important example of fermentation. During this process, the skin is removed from the berries and preserved in this form until the bacteria have destroyed the gluten and the pulp. After that, it will be easy to clean off the surface and processing can continue. Any method of coffee processing will result in fermentation.

At first, fermentation was intended to hasten the process of extraction of grain from berries. But over time, manufacturers realized: that as a result of fermentation, products of the breakdown of sugars and the activity of microorganisms are formed, which change the taste and aroma of coffee during roasting and can significantly improve the taste of coffee. Since different environmental conditions harbor different microorganisms, fermentation determines the flavor characteristics of the grain.

There are two major types of fermentation: aerobic and anaerobic. They are sometimes associated with the processing method: aerobic - with natural processing, anaerobic - with washed processing, but regardless of the processing method, coffee can be fermented in different ways. Moreover, there is a possibility of combining these two types of fermentation: for example, start with aerobic and then switch to anaerobic.

There's no guidance on how to make the right fermentation. The natural conditions, climate of the region, equipment, and varieties of coffee are essential for this complex process. During the fermentation process, however, several factors can be controlled: the sugar content of the grain, temperature, time, acid-base balance of the water, and washed processing, in addition to the presence or absence of oxygen. The higher the temperature is, the more vigorously the fermentation takes place and there will be a risk of overroasting coffee: it's going to get sharp acidity, and alcoholic or chemical characteristics in its flavor. So fermentation plays a crucial role in coffee production. Through trial and error, manufacturers determine the optimal conditions for fermenting their grains and try to maintain maximum stability of this process to obtain a quality product time after time.

For a long time, the taste of coffee was associated with its origin - terroir characteristics, for example, the height of growth. According to the principle of the wine industry. This is not entirely accurate. Growing conditions and the initial characteristics of the coffee variety play an important role in the development of flavor, but the real flavor transformation occurs during processing.

The major ingredients of fermentation are bacteria and yeast. Once berries have been harvested from the tree, an open space is formed at the spot of the break where the juice can be extracted. Once the sugar content of the juice is exposed to microorganisms on the surface, fermentation occurs.

• Dry processing

With notes of raisins, prunes, and caramel, the dry fermentation creates a sweet, fruity compote coffee. For 24 days, the berries are grown naturally on a patio.

• Washed processing

If there is a shortage of oxygen, bacteria will increase their activity. Therefore, fermentation occurs very intensively during washed processing in which the grain is placed into water tanks after depulping. A better profile, lighter drinking flavors, and an intense acidity will result from this treatment. The time of fermentation is shortened to 24 hours.

• Anaerobic fermentation

It is a process whereby coffee is fermented in sealed containers so that it does not have access to oxygen. The resulting flavor profile is expressed in characteristic scents of tropical fruits, yogurts, and spices.

• Carbonic maceration

A fermentation process that has been inspired by winemaking and is similar to anaerobic processes. The main difference is that in the case of carbonic maceration, carbon dioxide is added to sealed containers, completely removing oxygen, and the berries are not crushed.

The speed with which sugar in gluten breaks down is reduced, due to oxygen deprivation. It also takes a much shorter time for the pH level to drop. Carbon dioxide helps extend fermentation for three days, resulting in more flavors such as alcohol and flowers. A thick texture, strong acidity, and intense sweetness are present in the coffee. 

"By definition, a fermentation process that does not require oxygen is the decomposition of sugar by bacteria. It's not a good idea to call them anaerobic: every fermentation is an anaerobic one." 

The fermentation of the coffee berries is done using Lactic acid bacteria if you're going to make your coffee more acidic. The yeast tends to produce a more fruity flavor and less acidity. So if we're going for less acidic and more fruity coffee, it should be fermented by yeast as the main culture.

An experiment was carried out in Brazil 20 years ago, where DNA samples were taken from the pulp and skin of the berries that had been cut with a knife. Scientists have been able to identify more than one million species of bacteria, over 200 kinds of yeasts, and about a hundred types of fungi. It's fascinating that all this diversity has been discovered in a single gram of material. This brings us to this particular region, where there is a distinct imprint of genetics on coffee.

In terms of composition, the cultures that live on the skin of ripe berries are very different from the microbes that live on unripe berries. It usually takes longer for these crops to develop and they are more stable, thus surviving better in the high sugar environment. The quality of the water is another important factor that has an impact on fermentation reproducibility. It's important to know where the water comes from on the farm. There are different starting populations of microbes in all of them, whether it's the well, the sediment, or the river.

What material the fermentation containers are made of also plays an important role in their functioning. Tiles, plastic, stainless steel, concrete. In other words, it's not the material that matters, it's the quality of care. We introduce the bacteria when we stir coffee with our wooden tools because wood is a very porous material. The composition of microorganism culture, as well as the fermentation rate, is altered by temperature change.

 If we are talking about natural processing, larger open spaces will lead to quicker evaporation or absorption of moisture. The processing process can at first sight appear to be consistent: coffee, time, and temperature; but internal processes operate differently.