Name for a group of chemical substances found in leaves, wood, bark, fruit and roots of many plants. Tanned animal skin becomes leather due to the tanning substances, from which the term "tanning" is derived. Tannins belong to the group of polyphenols or phenolic compounds such as catechin as well as ellagtannins (ellagic acid) and gallotannins (gallic acid). In wine, these substances cause the tart, leathery and astringent taste impression. In grapes, the tannins are found in the skins (bellows), crests (lobes, stems) and in the berry seeds. The term tannin has a rather negative connotation, whereas tannin has a positive connotation, although they are at least partly the same substances. The wine defect woody is caused by undesirable tannins, the green t annins.
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