How does fermentation work

fermentation or Fermentation (lat. fermentum: "Sourdough") describes in biotechnology the conversion of biological materials with the help of bacterial, fungal or cell cultures or by adding enzymes (ferments). The original terminology describes the biological reaction to the exclusion of air ("Fermentation c'est la vie sans l'air" (Pasteur)).

Term expansion

Nowadays, fermentation is understood to mean any technical bioreaction. Medically interesting products such as insulin, hyaluronic acid, streptokinase and a large number of antibiotics (e.g. penicillin) can be synthesized on an industrial scale in bioreactors with the help of microorganisms. Microorganisms are able to form substances that are very difficult or impossible to produce using a purely chemical route. The device that is used to ferment is called a fermenter.

Differentiation from fermentation

The fermentation takes place exclusively anaerobically. Fermentation is sometimes mistakenly used as a synonym for fermentation. The latter, however, includes both aerobic processes (see acetic acid fermentation) - also known as "oxidative fermentation" - as well as completely different microbial or autolytic enzymatic processes (e.g. herring ripening).

Areas of application

Food preservation

Outside of biotechnology, fermentation plays a central role in the preservation of food (e.g. sauerkraut or gimchi), the development of flavorings (e.g. soy sauce, Bionade) and the breakdown of tannins from tea, cocoa, coffee, marijuana and tobacco as well as the production of dairy products (cheese, yoghurt), tofu, raw sausage (e.g. salami) and alcoholic beverages such as whiskey, beer and wine. A borderline case is fermentation by a food's own enzymes, as occurs in matjes herring or tea.

"Fermentation" of tea

Under the Ferment A tea is understood to be the breaking down and oxidation of the tea leaves in a damp environment - so it is not a real fermentation, as this process takes place without microorganisms. The tea leaves are rolled for this purpose, whereby the plant cells are partially destroyed. This allows enzymes (especially phenol oxidases) and other ingredients of the tea plant (especially polyphenols), which are strictly separated from each other in the intact cell, to come together and react with oxygen to form dark-colored polyphenols and aromatic substances (e.g. essential oils). The process takes about three hours. In contrast to black tea, oolong tea is only short and green tea is not at all fermented.

"Fermentation" of raw tobacco

Fermentation of tobacco is understood to be the fermentation process that is required to produce a consumable tobacco from dried raw tobacco. The fermentation reduces the nicotine content and the leaf's own protein compounds are broken down. The latter would mask the characteristic aroma of the individual varieties when smoked.

After a larger amount of tobacco has been put together (at least 10 dt), the fermentation process starts by itself. However, it can also be set in motion by supplying heat without quantity limitation. The ideal fermentation temperature is between 50 and 60 ° C, higher temperatures should be avoided. With natural fermentation, the tobacco stacks are shifted 4-5 times - from the edge of the stack to the middle of the stack and vice versa - until all leaves are fermented evenly, it takes 4-6 months.

See also


  • Rainer Stürmer, Michael Breuer: Enzymes as catalysts. Chemistry and biology go hand in hand. In: Chemistry in our time. 2/40/2006, pp. 104-111, ISSN 0009-2851

Categories: Biochemical Reaction | Food chemistry