🍷 Polyphenols

Polyphenols are a large group of natural compounds found in many fruits and vegetables, including grapes. In grapes their type and amount differ between the pulp, skin and seeds; flavan-3-ols, for example, are found mainly in skins and seeds. They include the anthocyanins, the red pigments of grapes and red wine, the tannins, and stilbenes such as resveratrol.

In wine, polyphenols are closely linked to quality: they shape colour, flavour and taste. Tannins (proanthocyanidins) help stabilize colour and sensory character, and the higher the concentration of condensed tannins, the more astringent the wine feels. Stilbene levels rise when grapes are under stress.

Red wine contains far more polyphenols than white, roughly 1–5 g/L against 0.2–0.5 g/L, because red wine is made in contact with all parts of the grape. A longer maceration increases catechin, epicatechin and tannin, although extraction slows after a point. During ageing, tannins increase and can form insoluble polymers, which changes astringency.

Polyphenols are not a reason to drink wine. The WHO states that alcohol is a Group 1 carcinogen, that no level of drinking is known to be safe, and that no studies show that benefits for heart disease or type 2 diabetes outweigh the cancer risk for individual drinkers.