🍷 Acetic acid bacteria

Acetic acid bacteria are bacteria that turn alcohol into acetic acid when air is present. They live everywhere: on berries, on equipment, in the air. They are dangerous to wine, because if air gets into it, the bacteria can spoil it and turn it to vinegar.

The process works like this: the bacterium takes oxygen and alcohol and produces acetic acid. The wine gets a sharp smell of vinegar and solvent, and the taste turns sour. To avoid this, the winemaker keeps containers closed and full, adds sulphites and watches cleanliness. Diseased berries are handled carefully: the bacteria often appear on rotten grapes, and then one speaks of sour rot.

But the same bacteria are useful when vinegar is wanted. Wine vinegar is made with their help: wine is left in the air and the bacteria gradually turn it to vinegar. So acetic acid bacteria are both a spoiler of wine and a helper in making vinegar.