Acetic acid

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Acetic acid (commonly called vinegar) is a weak organic acid (pKa 4.76 at 25°C). Acetic acid has a pungent, tangy, sour flavor and aroma, characteristic of vinegar. It is produced in large amounts when making vinegar or kombucha. In most other beverages it is generally considered to be an off-flavor.

Acetic acid is produced by various microbes including acetic acid bacteria, Brettanomyces, lactic acid bacteria, and Saccharomyces under some circumstances.^{[citation needed]} Microbes can produce acetic acid ONLY when oxygen is available.^{[citation needed]} Therefore, good brewing and winemaking practices will prevent the formation of acetic acid despite the presence of any of these microbes. See Contamination.

Acetic acid is not particularly useful in brewing beer. However, it may be intentionally added to sour beer in order to add flavor dimension. See Adding acidic complexity to sour beer.

Certain microbes can metabolize acetic acid, although the practical significance of this is unknown.

See also

• Volatile acidity