A tannin (also known as vegetable tannin, natural organic tannins, or sometimes tannoid, i.e. a type of biomolecule, as opposed to modern synthetic tannin) is an astringent, plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids.

The term tannin (from tanna, an Old High German word for oak or fir tree, as in Tannenbaum) refers to the use of wood tannins from oak in tanning animal hides into leather; hence the words "tan" and "tanning" for the treatment of leather. However, the term "tannin" by extension is widely applied to any large polyphenolic compound containing sufficient hydroxyls and other suitable groups (such as carboxyls) to form strong complexes with various macromolecules.

The tannin compounds are widely distributed in many species of plants, where they play a role in protection from predation, and perhaps also as pesticides, and in plant growth regulation. The astringency from the tannins is what causes the dry and puckery feeling in the mouth following the consumption of unripened fruit or red wine. Likewise, the destruction or modification of tannins with time plays an important role in the ripening of fruit and the aging of wine.

The phenolic content in wine refers to the phenolic compounds—natural phenol and polyphenols—in wine, which include a large group of several hundred chemical compounds that affect the taste, color and mouthfeel of wine. These compounds include phenolic acids, stilbenoids, flavonols, dihydroflavonols, anthocyanins, flavanol monomers (catechins) and flavanol polymers (proanthocyanidins). This large group of natural phenols can be broadly separated into two categories, flavonoids and non-flavonoids. Flavonoids include the anthocyanins and tannins which contribute to the color and mouthfeel of the wine. The non-flavonoids include the stilbenoids such as resveratrol and phenolic acids such as benzoic, caffeic and cinnamic acids.

Origin of the phenolic compounds

The natural phenols are not evenly distributed within the fruit. Phenolic acids are largely present in the pulp, anthocyanins and stilbenoids in the skin, and other phenols (catechins, proanthocyanidins and flavonols) in the skin and the seeds. During the growth cycle of the grapevine, sunlight will increase the concentration of phenolics in the grape berries, their development being an important component of canopy management. The proportion of the different phenols in any one wine will therefore vary according to the type of vinification. Red wine will be richer in phenols abundant in the skin and seeds, such as anthocyanin, proanthocyanidins and flavonols, whereas the phenols in white wine will essentially originate from the pulp, and these will be the phenolic acids together with lower amounts of catechins and stilbenes. Red wines will also have the phenols found in white wines.

Tannin (Hebrew: תנין‎) or Tunannu (Ugaritic: Tnn) was a sea monster in Canaanite, Phoenician, and Hebrew mythology used as a symbol of chaos and evil.

Name

The name may derive from a root meaning "howling" or from coiling in a manner like smoke.

Canaanite mythology

Tannin appears in the Baal Cycle as one of the servants of Yammu (lit. "Sea") defeated by Baʿal (lit. "Lord") or bound by his sister ʿAnat. He is usually depicted as serpentine, possibly with a double tail.

Hebrew mythology

The tanninim (תַּנִּינִים) also appear in the Hebrew Scriptures' books of Genesis,Exodus,Deuteronomy,Psalms,Job,Ezekiel,Isaiah, and Jeremiah. They are explicitly listed among the creatures created by (the) Elohim on the fifth day of the Genesis creation narrative,translated in the King James Version as "great whales". The tannin is listed in the Apocalypse of Isaiah as among the sea beasts to be slain by Yahweh at the End of Days, translated in the King James Version as "the dragon". In Jewish mythology, Tannin is sometimes conflated with the related sea monsters Leviathan and Rahab. Along with Rahab, "Tannin" was a name applied to Egypt after the Israelite's Exodus to Canaan.