Types of fermentation in coffee

Updated: Nov 28

To begin with, it is of sufficient knowledge that humanity has used the fermentation process to reach flavors, aromas, modify textures and transform the quality of food and beverages; the exploration of fermentation reaches new standards in the quality of coffee and is the new preference for the processing of coffee.

Currently, we know that fermentation is produced by microorganisms that activate the process spontaneously, where different chemical reactions take place. Similarly, fermentation can be defined as those methods of preservation in which microorganisms act by generating anaerobic biochemical reactions, that is to say, that air and oxygen are subtracted.

In a simpler way, fermentation is the natural transformation that occurs when sugars and water are combined. These two elements are not exempt in coffee cherries, which allow for different methods of coffee fermentation.

Actually in fact fermentation improves the coffee flavors; at this point, it is common knowledge that after the coffee harvest fermentation is a fundamental and essential part of the coffee process.

Thus, fermentation is a key part of coffee processing and can occur in three ways:

This fermentation process through spores of the filamentous fungus A. Oryzae has shown outstanding results, improving the complexity and body of coffee, and also provides a worldwide opportunity for farmers to improve their coffees.

This new method can potentially generate new opportunities for coffee farms since koji has a unique property to take advantage of the remaining 30% of the sugar. Another great advantage of koji is that it can be grown on practically any starch, which is amazing because it can be grown on previously unused coffee bean starches such as skin, mucilage, and pulp.

In this process, the coffee cherries are taken to the first stage of fermentation lasting 3 days; subsequently, the A. Oryzae spores are applied to the surface of the cherries themselves and left for another 60 hours of fermentation. At this point, the drying process is continued to achieve a final moisture content, followed by hulling and finally packaging and transport to the roasters.

Depending on the roasting level of the beans, the flavor varied widely from tropical fruits such as pineapple and mango to chocolate and gingerbread. The mouthfeel will be surprisingly silky and luxurious like butter. The rounded and full-bodied texture made in these flavors will last a long time.

This is a process that consists of fermentation without oxygen, where they are left in different ranges of hours depending on the results you are looking for.

The anaerobic fermentation of coffee is a process that tries to create and control a flavor profile that enriches its original qualities. In this case, the coffee cherries are placed in tanks, before or after pulping, and covered with water allowing the different microorganisms to act.

In the case of anaerobic fermentation, as we have seen above, effervescence must be carried out in the absence of oxygen. In this process, whole cherries with the peel or pulped cherries are used. For anaerobic fermentation conditions, its time can vary from different hours, which the process is considered to be finished depending on the results that are been look for. It is of utmost importance to control the pH to be maintained at approximately above 3.8, without allowing this value to become lower.

In hermetic stainless steel tanks where an anaerobic environment is created by pumping carbon dioxide to automatically eliminate oxygen particles and have an anaerobic environment with higher pressure.

Namely, carbonic maceration is similar to anaerobic fermentation, but it has a fundamental difference: the use of carbon dioxide. CO2 is introduced into sealed, airtight tanks filled with cherries in order to eliminate residual oxygen. The microorganisms in the tank break down the sugars in the cherries more slowly, resulting in coffees with complex flavors that are often described as bright and vinous.

Granted that carbonic maceration is an anaerobic fermentation technique in an atmosphere dominated by carbon dioxide, the procedure is as follows:

  • Sterilization of the cherries in order to prevent undesirable microbial agents in the fermentation.

  • Add in the tank the coffee mass with the additive of bacteria, yeast, and leachates.

  • Inject CO2 according to the pressure (PSI) allowed by the tank capacity.

  • Periodically monitor the declining pH curve.

  • Control the temperature of the mass (at 23ºC) so that it is neither too hot nor too cold, in such a way that it favors and prolongs the action of the yeasts throughout the coffee mass.

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