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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.