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Binding of acetaldehyde with sulphur dioxide

• Acetaldehyde is one of the strongest binding compounds of SO₂ found in wine or fermenting must.
  
  
• At the onset of fermentation, the yeast involved produce acetaldehyde as an intermediate product, in the conversion of grape sugars (and introduced sugars) to alcohol.
  
  Practically all free sulphur dioxide (FSO₂) present, from earlier additions, will be bound to yeast produced acetaldehyde.
  
  No FSO₂ of any significance will be present after the completion of fermentation.
  
  Virtually all SO₂ will be present as bound SO₂ (BSO₂)