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【English Name】Acetic Acid Fermentation

Acetic acid fermentation is a reaction in which ethanol is oxidized to produce acetic acid by the action of acetic acid bacteria (genus Acetobacter). It is classified as a type of oxidative fermentation.

In the course of the reaction, ethanol first changes to acetaldehyde, and as oxidation proceeds further it becomes acetic acid. In nature, acetic acid bacteria live alongside yeast in environments containing sugars and alcohol such as fruit, and the phenomenon of alcohol naturally turning to vinegar when exposed to air has been known since ancient times.

The one who scientifically elucidated the principle of acetic acid fermentation was Pasteur of France, who identified the existence of acetic acid bacteria in the 1860s.

Its connection with sushi is also deep. Sushi's prototype, narezushi, was originally a preserved food relying on lactic acid fermentation, but in the Edo period haya-zushi (quick sushi) using rice vinegar was born. What made the mass supply of vinegar possible was the development of kasuzu (lees vinegar) made from sake lees, which is said to have spread nigirizushi among the common people.

In modern vinegar production, in addition to the surface fermentation method, the submerged fermentation method, which conducts aeration and stirring within a tank, is used, making it possible to obtain highly acidic vinegar in a short time.