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Acetaldehyde

• Acetaldehyde is an intermediate product of yeast fermentation.
  
  
  Some residual acetaldehyde is to be expected after fermentation.
  
  The residual amount depends predominantly on yeast strain and to a lesser extent on fermentation conditions
  
  
• Acetaldehyde is also produced on the oxidation of alcohol in wine
  
  
• Acetaldehyde can also be introduced through fortification, from the fortifying spirit.
  
  
• Acetaldehyde is strongly bound to sulphur dioxide (SO₂) with important implications for wine production.
  
  
• Acetaldehyde at low concentrations, can add to flavour complexity in full flavoured wines, especially red wines.
  
  
• High concentrations of acetaldehyde can leave the wine tasting flat with flor sherry characteristics.
  
  
• Other descriptors for acetaldehyde are green apple, sour and metallic.
  
  
• Acetaldehyde is a two (2) carbon aldehyde with the chemical formula C₂H₆O and structure as per this diagram
  
  It is the end carbon (C) with the double bonded oxygen (O) and single bonded hydrogen that forms the aldehyde functional group.
  
  
• Other aldehydes are also produced by yeast in smaller quantities, but with significant flavour contributions.