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Glycerol

• Glycerol, or glycerine, is a tri-alcohol or polyol in that it has three hydroxyl (OH) functional groups (see diagram).
  
  
• The word Glycerol is derived from the Greek word for sweet, and indeed glycerol does have a sweet taste.
  
  
• Glycerol has a taste threshold, for sweetness, at about 5.2 g/L in white wines.
  
  
• In wine, glycerol is only a minor alcohol and a by product of yeast fermentation along with ethanol and all the other alcohols.
  
  
• Glycerol is a colourless liquid found in insignificant quantities in wines (5 -12 g/L or ~ 0.5-1.2 %v/v) unless the grapes were considerably affected by botrytis (25 g/L or ~2.5% v/v)
  
  
• Glycerol, while having the greatest viscosity of all the alcohols found in wine, needs to be at concentrations of 28 g/L before a significant difference will be perceived.
  
  These levels of glycerol are rarely achieved and hence not a contributing factor to the viscosity of wine as is commonly believed.
  
  
• Glycerol has often been incorrectly associated with the so called, tears or legs, on the sides of wine glasses (see explanation).