Wine Analysis

Volatile Acidity (VA)

• Volatile acidity is often abbreviated to VA and refered to as "Vee Ay".
  
  
• Volatile acidity , as the name suggests, refers to the organic acids found in grape juice, musts and wine that are more volatile or more easily vaporized than the non-volatile or fixed acids (malic and tartaric acid).
  
  
• Volatile acids, because of their volatility, are able to be steam distilled over, collected and their concentration determined.
  
  
• The predominant volatile acid found in grape juice and wine is acetic acid, at about an average of 0.5 g/L
  
  Acetic acid is produced by acetic acid bacteria (acetobacter), which are introduced to damaged grapes, grape juice and wine by vinegar flies or contaminated equipment.
  
  
• Minor quantities of other volatile acids, formic, butyric and some fatty acids, are formed during fermentation, along with the less volatile acids lactic acid and succinic acid.
  
  
• Lactic, succinic, sorbic acids, are slightly steam-distillable, but are not considered part of the volatile acids and their contributions must be adjusted for.
  
  
• The presence of sulphur dioxide (SO₂) and dissolved carbon dioxide (CO₂) can exist as the volatile sulphurous acid and volatile carbonic acid respectively.
  
  These are not considered as part of VA and need to be neutralised or removed before VA determination.
  
  
• Ethyl acetate should not be confused for volatile acidity.
  
  Because ethyl acetate is formed from acetic acid and ethyl alcohol, ethyl acetate is often found to accompany the prescence of acetic acid.
  
  
• In Australia the maximum permitted levels of the total volatile acidity is 1.5 g/L.
  
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