Wine Analysis Home

Free SO₂ and Ascorbic acid use in red wine.

• Sulphur dioxide (SO₂) will loosely bind to red wine pigments and will not be free to participate in reducing oxidative reactions.
  
  
• When performing a free sulphur dioxide determination, the SO₂ bound to red pigments are included as free sulphur dioxide (FSO₂), giving false, high FSO₂ readings.
  
  Therefore the true FSO₂ can not be determined and therefore cannot be guaranteed in red wines.
  
  
• Large additions of SO₂, to ensure adequate FSO₂ concentration levels, could leave the wine unaccepatably decolourised.
  
  
• If ascorbic acid is used in red wines and no FSO₂ is available to mop up any H₂O₂ (hydrogen peroxide) present, excessive secondary oxidation will result. (see SO2 & ascorbic acid).
  
  
• Therefore the use of ascorbic acid in red wine production is not reccommended.