tannin

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Related to tannic: tannic acid

tannin,

 

tannic acid,

or

gallotannic acid,

astringent vegetable product found in a wide variety of plants. Sources include the bark of oak, hemlock, chestnut, and mangrove; the leaves of certain sumacs; and plant galls. Tannin is also present in tea, coffee, and walnuts. A solution of tannic acid is obtained from one of these natural sources by extraction with hot water; in particular, gallotannic acid is obtained from plant gall. Tannin varies somewhat in composition, having the approximate empirical formula C76H52O46. Tannic acid is a colorless to pale yellow solid; it is believed to be a glucoside in which each of the five hydroxyl groups of the glucose molecule is esterified with a molecule of digallic acid. Tannin is used in tanning animal skins to make leather; it transforms certain proteins of animal tissue into compounds that resist decomposition. It is also used in manufacturing inks, as a mordant in dyeing, and in medicine as an astringent and for treatment of burns.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Tannin

 

any of a group of phenol compounds that are widespread in plants and are capable of forming strong bonds with proteins and certain other natural polymers, such as cellulose and pectins.

Originally (late 18th century), the term “tannin” was applied to a mixture of substances extracted by water from a number of plants that was capable of transforming animal hides into leather. In modern usage, the term includes all naturally occurring compounds having molecular weights from 500 to 3,000 and containing a large number of phenolic hydroxyl groups. (In the Soviet Union, tannins of plant origin are also called tannides.)

Tannins are divided into two classes. The first comprises the tannins formed by a polyhydric alcohol, such as glucose, in which the hydroxyl groups are partially or completely esterified by gallic acid or related compounds. These tannins are referred to as hydrolyzable; an example is seen in structural formula I. The second includes the tannins formed through the condensation of such phenol compounds as catechins. These tannins are described as condensed; an example is seen in structural formula II.

Tannins are contained in galls and in bark, wood, and leaves and/or fruits of tannin plants. They are used in tanning leather, and they also serve as mordants in dyeing cotton fabrics. In medicine they are used as astringents. When used on burns, aqueous solutions of tannins bind the toxic protein products of tissue decomposition and facilitate healing. In the body, tannins can bind bacterial toxins, as well as toxic salts of silver, mercury, and lead.

REFERENCES

Biokhimiia rastenii. Moscow, 1968. Chapter 22. (Translated from English.)
Zaprometov, M. N. Osnovy biokhimii fenol’nykh soedinenii. Moscow, 1974.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

tannin

[′tan·ən]
(organic chemistry)
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

tannin

any of a class of yellowish or brownish solid compounds found in many plants and used as tanning agents, mordants, medical astringents, etc. Tannins are derivatives of gallic acid with the approximate formula C76H52O46
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
According to their chemical properties, they can be divided into the hydrolysable tannins and condensed tannins, tannic acid (TA) is one of the most common material of hydrolysable tannins (Cork et al., 1993).
Tannic acid 3% was reported to exhibit high antimicrobial activity against Salmonella typhimurium CCM5445, E.
For the absorbance observed for sample (0.243) the concentration of tannic acid calculated from the calibration curve was 32mg/L.
Caption: FIGURE 1: HPLC profile of Punica granatum total extract and tannic acid analyzed.
Tannic acids belong to the hydrolyzable group of tannins [21-22].
Drinkers who are beginning to explore the drier end of the craft cider spectrum will enjoy Stone Dry for its full tannic mouth feel, perceived dryness and robust bittersweet aromatic notes, much like a very ripe apple."
What sets it apart from other wines in a similar way in France and Spain is that, after fermentation, the juice is left for a long time with the spent skins and picks up a slight but unmistakably tannic, bitter taste, which is just enough to offset the intense sweetness of the wine, allowing it to finish dry in the mouth.
By considering catalytical activity of tannic acid, we described an efficient method by employing tannic acid as an efficient catalyst for the synthesis of 12-aryl-8, 9, 10, 12-tetrahydrobenzo [a] xanthen-11-one derivatives by one pot cyclocondensation of aromatic aldehydes, [beta]-naphthol and dimedone under solvent free condition (Scheme 1).
The main parameters that influence the production of tannase are tannic acid concentration, humidity, type of substrate used, temperature, pH, incubation time and addition of different sources of carbon and nitrogen (LEKHA; LONSANE, 1997).
Processing acorns does take a decent amount of time because you have to remove the tannic acid, so do a bit of research about how to eat acorns before you dive in.