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Acetic Acid

• Acetic acid is an organic and carboxylic acid (see diagram).
  
  
• Acetic acid is the sharp tasting and main constituent of vinegar.
  
  
• Acetic acid is also the predominant acid of what is referred to as volatile acidity.
  
  
• Acetic acid is produced by acetic acid bacteria (acetobacter), which are introduced to grape juice and wine by vinegar flies or pre-contaminated equipment or cooperage.
  
  
• The loss of grape berry skin integrity, through disease or physical damage, exposes grape juice to bacterial attack with the production of acetic acid.
  
  
• Acetic acid bacteria can persist through to the wine, and in the presence of oxygen and low sulphur dioxide (SO₂) concentrations can degrade alcohol to acetic acid in wine.
  
  
• Acetic acid, at low levels can lift wine flavours.
  
  
• At high levels, Acetic acid can affect the taste of wine detrimentally leaving the wine tasting sour and thin.
  
  
• High levels may exceed maximum legal limits (1.5 g/L - Aust.).
  
  
• Acetic acid is often, but not necessarily, accompanied by the negative aromas and taste of ethyll acetate (nail polish remover odour).
  
  
• Expected levels of Acetic acid found in wine are 0.1-0.8 g/L.