Coffee Fermentation – What Is It?

coffee fermentation

You’ve probably heard the word Fermentation many times, but it seems a little embarrassing to ask what it really means. Taste The coffee sheds light on fermentation and its crucial role in a coffee production.

Fermentation is a natural process of food processing. The process involves breaking down organic matter into either inorganic or other organic matter. In short, it is about microorganisms that can preserve and add raw materials to a specific taste and aroma. Fermentation is often combined with other preservation methods such as pasteurization, smoking, drying and subsequent cooling storage.

Fermentation has been used by our earliest ancestors who learned to process food to preserve and develop the taste. Yogurt, wine, cheese and sausages are also fermented today, without us thinking about it. It is well known that through different fermentation processes you can make many different kinds of wines from the same grapes, but the same also applies to coffee is less known.

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A look into the coffee bean

Diagram of coffee silverskin production from wet processing1

To understand the fermentation / processing of the coffee, we first have to go down to the detail level and gain insight into the coffee bean itself. A few facts:

  • Coffee beans are produced from red berries from the coffee bush, which originate from the coffee genus (coffea). Each berry usually contains two seeds or coffee beans.
  • When the berry contains only one seed it is called “peaberry” because of the pea form of the seed. Normally 5% of a coffee harvest will be “peaberry”.
  • Coffee beans, among other things, contain the active substance caffeine and various acids such as phosphoric acid.
  • Once the red berries are harvested from the coffee bush, the outer layer of peel and pulp is removed, leaving only the green coffee bean itself.
  • Microorganisms occur naturally on and in the coffee bean as the fruit matures. The natural microorganisms become active shortly after harvest, and if there is evidence of accidental fermentation, it can be measured right after harvest.

A wet and dry method

Coffee beans are fermented, among other things, to form the aromas of the coffee, but also to sort the pulp from the beans. The process takes place in the bean production countries. There are two well-known methods – a wet and a dry method. There are various ways in which the pulp is removed from the bean itself, and the methods are of great importance to the taste.

Dry method (natural): here the coffee is fermented without water. This means that the coffee is allowed to dry in its fruit peel before the bean itself is removed. That is, the bean is dried with the berry on, so the sweetness and fruit juice can really penetrate the bean. Only when the bean has dried is the pulp removed and the bean has a more yellowish character and can be more “dusty” in appearance. When you roast a “natural” coffee bean, you can expect it to be darker than a washed one, precisely because of the higher content of fruit juice and sugar. Traditionally, Africa has often resorted to this natural process.

The wet method: The wet variant is today the most widely used method, and it is more new in coffee contexts. The method was invented when coffee was imported to Latin America. Here we had problems using the dry method, which places certain demands on the climate. Instead, the solution was to wash the coffee carriers and then remove the pulp. When that happens, there is a slimy web that still sits on the stone. Just like eating a peach. To remove the hind, it is required that the coffee beans undergo a fermentation process in water.

The beans are therefore washed in large water tanks, which takes between 12 and 36 hours. Then the beans are washed and then dried in the sun for 4 to 7 days. Some plantations have drying drums to make the drying process more efficient.

How to taste the two methods?

This is the right answer to the coffee expert Asser Bøggild Christensen. He lives in Thailand, where he is very close to the coffee production. His taste apparatus is very well developed and he has no doubt that there are distinct taste differences:

“ Many consumers don’t think about it, but the difference between naturals and washed coffees is almost as significant as white and red wine. Washed coffees taste clean and have a balanced sweetness and acidity. You can call it the standard taste. The dried variant, on the other hand, has far more fruit, depth and sweetness. Typically, the acidity is lower and one can experience slightly fermented taste impressions. In recent years, the specialty coffee has taken on “naturals” in great style, as it is often here that you find the most unexpected notes, “explains Asser Bøggild Christensen.

A new trend: Honey processing

A new trend in fermentation has also begun to spread. It is called “honey processing”. Honey processed coffee is a kind of intermediate between washed and natural coffee.

The honey process preserves the fruit mucus on the bean during drying, giving it a more fruity taste in the end. It typically produces a sweet, mild and balanced cup. In this process one can expect the beans to look almost dark and dirty as this process leaves fragments of dried pulp (pulp) on the bean. This is perfectly normal and has no negative impact on the final result. The fruity shades are typically more subdued and the notes are sweeter. This method of taste is often a little more challenging than the other two methods.

Asser Bøggild Christensen believes that this process will become widespread over time. He elaborates:
“The honey process is an intermediary between the other two processing methods. It is called honey because there is a kind of mucus on the bean after the pulp is taken off, which may remind a hint of honey. The taste is less fermented, compared to a natural one, but it still has some crunch, sweetness and fruit flavor. Honey processed coffee has definitely come to stay. It gives manufacturers better conditions to experiment, compared to naturals. A coffee that does not grow on the world’s best farm at 1800 meters height can suddenly taste furiously, after being processed with the honey method. A similarly washed coffee can be a bit boring ”.

If you want to read more technical details about fermentation, go here .