Polyphenols

The polyphenols found in grapes are highly diverse compounds and can be broadly classified into four groups:

• Phenolic acids (eg gallic acid)
• Anthocyanins (pigments, eg malvidin 3-glucoside)
• Simple flavonoids
• Complex flavonoids (proanthocyanidins)
  

Around 90% of polyphenols are not extracted from the wine making process.  The majority remains naturally within the grape skins and seeds and lost from the winery with the marc.

• Grape seed
  • 60% of extractable grape polyphenols
  • Mainly proanthocyanidins (monomeric flavan-3-ols, especially (+)-catechin, (-)-epicatechin, (+/-) gallocatechin, (-)-epicatechin 3-0-gallate; and their oligomers and polymers)
    
    
• Grape skin
  • 30% of extractable grape polyphenols
  • Mainly pigmented tannins (flavonoids)
    
    
• Grape pulp
  • Less than 10% of total extractable grape polyphenols