The principal molecules in the family of polyphenols are:
non flavonoids:
- phenolic acids (and their derivatives), benzoid acids and cinnamic acids,
- hydrolysable tannins,
- phenolic aldehydes,
- volatile phenols.
flavonoids:
- flavonols, yellow-colored pigments that are not significant in tasting,
- anthocyanins (cyanidin, peonidin, delphinidin, petunidin and malvidin), coloring substances responsible for the purplish-ruby shades of red wines,
- tannins, phenolic compounds with a molecular weight of between 500 and 3000.
In turn, tannins can be divided up into:
· condensed or catechic tannins (natural tannins from the grapes, which are to be found in wine in polymerized form – catechin complexes)
1. proanthocyanidin
2. catechin and epicatechin
3. polymers
· hydrolysable (hydrosoluble or ellagic) tannins (which derive from wood)
1. gallotannins
2. ellagitannins.
Both catechic (from the grapes) and gallic tannins (from the barrels) determine the wine’s sensations of structure and, in particular, of astringency. This manifests itself in different ways and more or less intensely: it ranges from a slight dryness of the gums, through a mouth-puckering sensation to a bothersome impression of “leatheriness”.
Thanks to oxygenation, to a spell in barriques or to the wine’s evolution in bottle, the tannins tend to polymerize, giving:
1) greater intensity of color (copigmentation);
2) greater stability of the wine over time;
3) greater softness and volume in the mouth;
4) more fruitiness, less vegetal and “reduced” sensations (because of the alteration in the wine’s oxidation-reduction potential);
5) less dryness.
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