Acetic acid

Acetic acid is an organic acid best known as the main component of table vinegar. Its chemical formula is CH3COOH, and it is produced from ethanol (ethyl alcohol) and oxygen by acetic acid bacteria. This process is related to fermentation, and it is also relevant to sake brewing. When sake is made, yeast produces alcohol, but in an environment with a high alcohol concentration, acetic acid bacteria can become active, and as a result acetic acid may be produced. Acetic acid is one of the elements that influence the flavor of sake. In moderate amounts it can add complexity to the taste, but in excess it can spoil the flavor.