Red wine polyphenolic chemistry: mouthfeel, colour expression and stability

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4 Terms

1
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What are the two categories of grape and wine phenolics?

Non-flavonoid and flavonoid

may have one phenol ring or multiple phenol rings (polyphenol)

2
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What are the non-flavonoid phenols?

  • hydroxycinnamic acids - drives colour in white wine - found in pulp/stems

  • benzoic acids

  • hydrolysable tannins - oak derived

  • stilbenes

3
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What are the flavonoid phenols?

  • flavan-3-ols (monomeric and polymeric) - tannins! found in skins and seeds

    • catechin and epicatechin

    • procyanidins/proanthocyanidins

    • pigmented tannins

  • flavanols - found in skins - important one is quercetin (natural sunscreen in skins)

  • anthocyanins - colour - found in skins

4
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What occurs in the reactivity of flavonoids?

  • reactive due to electron density at various positions - high density regions = nucleophillic, will react with low density regions = electrophillic

  • electron density due to oxygenation pattern and double bonds

  • delta sign is used to indicate partial charge, so partial negative charge on the tannin (yellow) and partial positive charge on the anthocyanin (red)

<ul><li><p>reactive due to electron density at various positions - high density regions = nucleophillic, will react with low density regions = electrophillic </p></li><li><p>electron density due to oxygenation pattern and double bonds </p></li><li><p>delta sign is used to indicate partial charge, so partial negative charge on the tannin (yellow) and partial positive charge on the anthocyanin (red) </p></li></ul><p></p>