The Fermentation of Coffee Beans

The Fermentation of Coffee Beans

On the way to an enjoyable cup of coffee

The cosmos of coffee from cultivation to harvest, from processing to roasting, is not only particularly multifaceted, but also extremely complex. Before you can enjoy the delicious hot drink, this high-quality natural product has gone through many processing steps. An important process in this context is fermentation. You will find out in a moment how coffee beans are fermented.

The different types of processing

First of all, the coffee cherries have to be harvested. The next step is the processing into green coffee, because the preparation of the coffee after the harvest has a decisive influence on the taste of the roasted coffee.

The specialist distinguishes between four causes that are responsible for the taste of the coffee:

  1. The growing conditions, i.e. the environment in which the coffee thrives
  2. The preparation
  3. The roast

There are three processes within processing:

1. The wet treatment
As the name suggests, this requires a lot of water. Bad and unripe coffee cherries are sorted out and the peel of the cherry and the pulp are removed so that only the layer of mucus and a parchment cover are left on the bean. This removal takes place with the help of a special machine, the “pulper”. The beans are then placed in large tanks for 12 to 36 hours, in which they are subjected to a fermentation process. The beans are then washed again so that any remaining pulp can be rinsed off. If the wet processing is particularly time-consuming, the effort will be rewarded with a higher quality.

2. Dry processing
This process is also called “unwashed” or “natural” processing. The coffee cherries are cleaned and then dried in the sun for two to three weeks. They have to be turned over constantly while drying. This procedure continues until the pulp with the parchment-like cover and the silver skin can be separated from the bean by machine. (There is no fermentation in this process.) The beans are then cleaned and then sorted.

3. Semi-dry
processing Professionals speak of “pulped natural” here. So the beans are de-pulped. This means that the pulp of the coffee cherry is removed from the coffee bean and then processed naturally. As a result, not the whole coffee cherry is dried here, but only the pulped core. In this process, too, there is no fermentation, as this process is also called.

What is fermentation related to coffee processing?

To put it simply, fermentation is the conversion of organic substances. These are often converted with the help of fungal, bacterial or cell cultures as well as by adding enzymes called “ferments”. Fermentation is very important for coffee production, as this process breaks down the tannins contained in the coffee beans. In coffee beans, bacteria are involved in fermentation. The duration depends on the temperature.


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Fermentation in coffee and its importance

This process is used in the wet processing of coffee beans. The coarsely peeled beans are fermented using water. To do this, the pulp is first removed from the coffee cherries so that the beans are only surrounded by the parchment and silver skin. Then they are placed in a water bath for about 12 to 16 hours. This will activate the fermentation process. The fermentation is responsible for the lively taste and the presence of acidity. However, the beans must not be fermented for too long, as the water in the tank can become bad due to the detached pulp residues.

In general, fermentation is very important for coffee. During the process, enzymes loosen the sticky residue that covers the parchment skin of the coffee beans. In addition, the process is necessary for the formation of the aromas, as this influences the taste properties and quality of the coffee. Given the importance of fermentation for taste, it is now often precisely controlled so that the process runs more smoothly and more slowly.