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Coffee Fermentation: What Is It & How Can It Improve Coffee Quality? -  Perfect Daily Grind
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Not so long ago, in an article on coffee processing, I mentioned fermentation. This process is very interesting, as it turned out to be important and requires a more detailed analysis. This concept refers to the production of coffee, tea, cocoa, wine and more. These are just the most famous examples. As you probably already understood, the article will be devoted to it, as well as its interaction with various processing methods. The topic is quite extensive and complex: after all, in order to fully reveal it, it is necessary to make sure of the effectiveness of this process through personal experience. As they say, see everything with your own eyes. Here we will consider fermentation in the context of the collection, processing and defect of the same name in the finished coffee. Unfortunately, only constructive theoretical information will be provided; I was not lucky enough to visit the processing stations yet, but everything is still ahead! Therefore, in the future, I will most likely continue and supplement this topic with interesting material.

Imagine a ripe, skinless coffee berry. You will see its pulp, and under it is a thin layer of gluten. It is these two layers that allow fermentation to take place both in natural and in man-made conditions.

In the natural (dry) way of processing, this coffee pulp is partially absorbed through gluten and parchment into the bean itself, and some is dried under the influence of sunlight and external temperatures. But gluten always remains on the surface of the parchment, inside the berry. Under such conditions, its fermentation, after the coffee pulp has been absorbed, is only a matter of time. Based on the drying conditions, fermentation occurs gradually due to the activity of exposure to sunlight and a certain level of humidity. Sunlight slows down natural fermentation during the day, and moisture ensures even fermentation at night. During fermentation, the temperature of the beans rises, and they have to be moved in order to achieve uniformity and prevent the temperature from exceeding 40 ° C. The process of such fermentation takes the same time as drying the coffee berry as a whole – up to 30 days, or until the humidity level drops to the required 11-12%. Everything worked out so perfectly because there is no direct contact with the air environment, where microorganisms necessary to accelerate the process live. Of course, if the grain has been damaged externally or infested with bugs during maturation, the likelihood of rapid and uncontrolled fermentation increases, which inevitably leads to a defect. But such things are usually tracked by farmers and by no means end up in the final batch of the crop, passing through careful sorting.

In the washed method, fermentation is the key process for the entire processing stage of the coffee beans. In an article about processing, I wrote that it can be of two types: anaerobic and aerobic (i.e. with and without water). The first type of fermentation is more controlled and widely used by coffee producers. It is controlled due to the fact that access to oxygen is limited and it is always possible to manually create conditions for coffee immersed in water. For coffee producers, this is good because there is always room for experimentation, which means the ability to create a more delicious cup based on market needs. Both types of fermentation take place in so-called tanks. They are either huge empty tanks, or a shallow pool, into which all the pulped and pre-washed coffee berries are dumped. In these tanks, the gluten is gradually separated by the action of yeast and bacteria. This can be achieved either by filling the tanks with water (anaerobic), or by combining two types of fermentation at once (first without water, and then with water). The gluten covering the outer parchment shell is destroyed in a short time under the action of its own peptic enzymes (i.e., the layer self-destructs using certain bacteria), while leaving each grain several complex aromatic compounds as a result. During fermentation, the acid-base balance drops from 6.7 – 6.8 to 4.3 – 4.5. This is due to an enzyme activity that increases the acetic acid content, which gives the washed coffee its characteristic aromatic acidity.

Fermentation is a necessary process involved in any of the coffee processing methods. Different countries producing coffee have characteristic, different taste (terroir) qualities, and thanks to fermentation they are always more pronounced. This is a kind of tool that helps to create explicit descriptors that we feel in the cup. The environment is home to millions of bacteria and yeasts that participate in fermentation processes. Accordingly, these microorganisms will be different everywhere, depending on the region or height of coffee growth. If the conditions are different, then the fermentation is different. Farmers always take this into account and achieve the desired result through trial and error. Fermentation is also one of the reasons why coffee tastes differently from around the world. It can be put on a par with genetics and terroir. Frankly, before writing this article, I did not think that this process is so significant in the world of coffee and beyond.