What does coffee fermentation consist of?

Fermentation is a very old process applied in the coffee field to remove the mucilage of the grain. Today, producers can control the fermentation processes to improve the taste of coffee and give it a greater added value. Below, we explain this technique and its types to produce the best coffee.

Learn about the different types of coffee fermentation

Fermentation is a process by which producers create the ideal conditions to obtain new organic compounds and energy. This occurs when an environment has no oxygen, and the bacteria on the yeast break down a complex substance to transform it into a simpler one.  

Mucilage is the coffee substance obtained through different chemical reactions caused by fermentation, provoking an incredible variety of flavors in a cup.

The main mucilage components are water, sugars, lipids, proteins, and acids, which are decomposed by enzymes produced by bacteria and yeasts present in the substance. Chemical reactions that arise during the process produce other simpler substances, such as alcohols, acids, esters, and ketones.

These simple substances provide specific qualities to the coffee, such as smell, color, and flavor.

Types of coffee fermentation

The mucilage has a large number of yeasts and different bacteria. Among the yeasts generated during the process are Saccharomyces, Torulopsis, Candida, and Rhodotorula, which are very common in the mucilage of the coffee.

In terms of bacteria, Lactobacillus and Streptococcus are usually present. Each of them provides a different flavor to coffee and changes its characteristics. The substance resulting from fermentation is classified as follows:

• Alcoholic fermentation: the action of yeast produces ethanol and carbon dioxide.

• Lactic fermentation: lactic acid is obtained from sugars of the bacteria Lactobacillaceae and Enterobacteriaceae.

• Propionic fermentation: non-sporogenous bacteria transform acetic acid, propionic acid, carbon dioxide, and succinic acid into propionic acid.

• Butyric fermentation: it is carried out using the bacteria of the genus Clostridium to transform the glucose into butyric acid and gas.

• Acetic fermentation: this type of fermentation employs bacteria of the genus Acetobacter. It is an aerobic process in which ethyl alcohol is transformed into acetic acid. 

• Formic fermentation: it is a complex process involving bacteria of the genus Enterobacteriaceae. Escherichia coli produces ethanol, succinic acids, lactic, acetic, formic and gases, H2, and CO2 from glucose, while Aerobacter Aerogenes produces the mentioned acids (except succinic acid) alongside butylene glycol.

• Methane fermentation: it involves the methane bacteria and occurs when other microorganisms have fermented the soil and alcohols and fatty acids. H2 and CO2 have also been generated, and then these substances are converted into water and methane.
• Malolactic fermentation: it is performed when the bacteria Leuconostoc transforms malic acid into lactic acid.

To take advantage of all the natural benefits of coffee in the fermentation stage, the pulped grains are stored in containers without lids, with or without water, depending on the method desired, until washed or dried.

The coffee of every day is a work of art of nature and man. In the fermentation technique, microorganisms are subjected to processes controlled by producers to obtain a delicious final product.