Term for mostly aromatic and fragrant compounds similar to alcohols. They belong to the group of organic acids with low acidity. Besides simple phenols, there are also many phenolic compounds which are also contained in oak wood, such as lignin. They are also found as a component of the skins, seeds and stems of grapes, although the content in red wine grapes is significantly higher than in white wine grapes. However, the finest, most aromatic and desirable phenolic compounds are found in the skins of berries, while those from grape seeds are rather undesirable. The phenols are responsible for the characteristic astringent taste impression in red wines.
The most important phenolic compounds in wine are the groups of flavonoids (with anthocyanins, catechin, fisetin, quercetin) and tannins, phenolic compounds such as eugenol, resveratrol, salicylic acid, tyrosol and vanillin, as well as other flavourings. The phenols are formed in the berry skins to a greater extent in the case of higher solar radiation(exposure), especially in southern wine-growing regions, but the opposite effect for the anthocyanins occurs when the limit values are exceeded. All substances can polymerize and form new compounds. Such processes also take place during bottle ripening or aging.
Certain phenols play a very important role in the taste of wine and also contribute to the ageing of the wine for a long shelf life. For some phenolic substances, such as fisetin and especially resveratrol, an extremely positive health effect is postulated due to their antioxidant properties. A too high proportion in white wine is negatively described as phenolic in terms of taste. See also a complete list of all wine ingredients under total extract.
From Yelkrokoyade - author, CC BY-SA 3.0, Link