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Wine oxidation

Causes

Consequences

Minimisation





















Causes


• Oxidation of wine involves the bonding of of oxygen molecules to oxidisable compounds present in wine.
  
  
• Wine oxidation occurs much more slowly then juice oxidation, but will occur over time when in contact with oxygen.
  
  
• Oxygen can be introduced into wine through partially filled storage vessels, leaks and transfers.
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
• Oxidation of wine results in -
  
  
  • The production of brown compounds and browning of red piments with loss of colour.
    
    
  • The destruction of both desirable grape (primary), fermentation (secondary) and aging (tertiary) derived flavours.
    
    
  • The production of new undesirable flavour compounds which can mask the desirable flavour compounds. These include different compounds to those produced in the oxidation of juice.
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  Wine oxidation minimization -
  
  
  • Oxidation is reduced in the presence of sulphur dioxide (SO₂), hence judicious and calculated additions.
    
    
  • Oxidation is reduced in the combined presence of ascorbic acid and FSO₂ (free sulphur dioxide).
    
    The use of ascorbic acid in conjuction with Sulphur dioxide should be used in white wines only where free sulphur dioxide (FSO₂) can be guaranteed. See ascorbic acid use in red wines.
    
    
  • Preventing contact of oxygen through leaks in tanks, barrels, pumps etc
    
    
  • Minimise wine handling (e.g. plan logistics to minimise rackings)
    
    
  • Avoiding metal contamination. (see catalysts in wine chemistry)
    
    
  • Storage at reduced temperatures.
    
    
  • The overriding element in wine oxidation is the amount of oxygen present and time exposed.
    
    
  • The slow, insidous oxidation of wine means that the effects are not noticed until the damage is done.