The tannins are substances of organic origin which one finds in practically all the Végétaux, and in all their parts (bark S, roots, Feuille S, etc), characterized by their Astringence (feeling of drying in mouth). For example, the Pépin S of grapes are very charged in tannins.

The Bois of the barrel X also gives to the Vin stored these characteristics of astringency. They attenuate with time (it is said that tannins swell).

Tannin is also found in the Cidre, the apple-brandy and the pommel, if they were produced in barrels out of wooden (Chêne, Châtaignier…).

The barrels out of wooden of Châtaignier release much more tannins than those in Chêne.

History

Tannins are known since highest Antiquité. With the the Middle Ages, for the preparation of leather (Tannery), one extracted it from bark of oak which one crushed in mills with tan. Leather was soaked in pits with tan during at least a year before being worked. At the end of the XIXe century, industry substituted the Chrome for the tan.

Extraction

The extraction of tannins is made mainly starting from a Galle oak, well-known Excroissance which is caused by an insect, the Cynips of the oak ( Cynips quercusfolii ). There exist also synthetic tannins.

Chemistry

The tannins, derived from the Gallic acid and other acids polyphenolic, are not exactly Acide S, but they result from the Estérification, by these acids, of the alcoholic functions of the Glucose. Their chemical structure is very variable, but always comprises a polyphenolic part; one can thus classify them in: tannins hydrolysables, which give after Hydrolyze either of the Gallic acid , or of the ellagic Acide.

The tannic acid (or gallotannic) C₇₆H₅₂O₄₆, present in the Nipple S, is used for the clarification of the wine or the Bière and the denaturation of industrial alcohol.

Tannins have colors which go from the yellowish white to brown and sink with the light. They have a light characteristic odor, a bitter taste and are Astringent S. They dissolve in water, the Acétone and alcohol, but not in the Benzène, the ether or the Chloroforme. Heated with 210°C, they break up in particular to form Pyrogallol and Carbon dioxide.

Some, called condensed tannins , are containing phenol S, others are mixtures of Ester S, Glucose or others Sucres. Best tannins result from nut gall of the oak and the sheets of the Sumac. The maceration in water, or diluted alcohol, constitutes the first stage of the preparation. The precipitation, followed evaporation at low temperature, gives the commercial product then.

Orthography

Small orthographical characteristic, tannin (or tannin), is written with only one or two “N”, but all the derivatives are written with 2 “N”, tanning, Tannerie, to tan…

One rather says tannin, while speaking about the product usable (powder) and about the tannins when the generic organo-chemical substance is evoked, because there are very many tannins.

Use

One employs tannins to protect the Cuir, because they transform the Protéines contained in leather into insoluble products resisting the organic decomposition. The principal use of tannin is the Tannage (as its name indicates it) Peau X. Tannins confer on leathers their qualities of imputrescibility which made the richness of the Mégisserie to Mazamet in particular, but also on Graulhet or Millau.

Other uses:

• Ink S (by reaction with ferric salts),
• Dyeing of fabrics,
• gluing of paper or Silk,
• coagulation of the Rubber,
• clarification of the wines and beers,
• also required for their properties Antioxydant be (after coupling with other carbonaceous chains).

Pharmacopeia

At the biochemical level, they are ic compounds phenol making precipitate the Protéines. When they are those of the Salive, the lubrication of the mouth is then lacking, explaining the feeling of draining.

Certain tannins would have properties Antioxydant are, explaining certain beneficial effects of the Vin on health (cardiovascular protection with moderate amounts). They would also stop the development of the Microbe S. The phenol S intervene in the organoleptic characters of the wine (savor, astringency, hardness), in the problems of food hygiene (vitamin effect P and bactericidal effect) and in the transformations of the wine (treatments and ageing). In particular these substances, which come from the solid part of the bunch, are responsible for all the differences between the white wines and the red wines.

The tannic acid is used in external medicine like astringent antidiarrheic.

Simple: Tannin

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