Tannins, definition

Synonyms Gallotannicacid Gallotannin Glycerite Tannin Definition Mixt. of organic acids occurring in the bark and fruit of many plants, e.g., oak species, sumac Empirical Cj.gH52046... 

B Tannins consumed but there is definite selection against tannin-rich foliage some consumption may however be beneficial to avoid bloat. 

Dioscorides also notes that numerous plants or parts of plants, as the bark, leaves and roots of the oak, nutgalls, sumac, etc., contain a substance sour and astringent, which is used in medicine and for tanning leather, and for coloring and darkening the hair. The tannin, which is the essential constituent, was not, however, more definitely identified. It will be recalled that in the form of juices or... 

Definition. Some confusion exists even in the definition of tannin included under this name are many substances of varying structure, but having the common ability to transform fresh hides into rot-proof and barely permeable leather. The phenolic nature of these substances has often caused confusion between tannins and phenolic compounds of plants. 

Thus one arrives at a valid definition of tannins for plant chemistry, insofar as their characteristic properties are concerned, without reference to the leather industry. Such a definition has been given by Swain and Bate-Smith (28) ... 

It is obvious that such a definition will include molecules which are not tannins in the commercial sense of being economically important in the tanning of hides, but will exclude a large number of substances whose only relationship to the tannins is their capacity to reduce alkaline permanganate or give colors with ferric salts. 

This definition well demonstrates that to identify the tannins in a plant sample, it is not sufficient to know their amount. Their structures and particularly their molecular weights must also be known. 

For definite qualities of raw materials the specific gravities or degrees Baum of the solutions are sometimes used in industrial practice to deduce, from suitable tables compiled empirically, the approximate content in tannin and in total soluble matter. 

Among polyphenolic compounds, two types of flavonoids, the anthocyanins and flavanols (i.e., catechins, proanthocyanidins, condensed tannins), are particularly relevant to the quality of red wines, as they are key compounds for color definition and astringency. Other flavonoids such as flavonols may have some influence on color and bitterness, although they are present in red wines in much lower amounts. Phenolic acids and hydrolysable tannins, released from barrel wood, may also have an influence on wine taste and color, and hydroxycinnamoyl derivatives from grape must are involved in the oxidative browning of white wines together with flavanols. Besides, some of these perceptions may be modified by other sensory characteristics (e.g. sourness, sweetness) related to other wine components (Preys et al. 2006). 

Tannins are, by definition, substances capable of producing stable combinations with proteins and other plant polymers such as polysaccharides. The transformation of animal skins into rotproof leather results from this property, as does astringency, fining and enzyme inhibition. Tannins react with proteins in each instance collagen in tanning. 

The official definition of tannin (acidum tannicum) given by the Enological Codex is as follows ... 

Methods aimed at the determination of tannin material content in the extract. The classical method of this type still used is the hide-power and derived methods. These methods were devised to determine which percentage of the extract would participate in leather tanning. The main drawback for their use for adhesives in their inability to detect and determine the approximate 3 to 6% of monoflavo-noids and biflavonoids, or phenolic nontannins, present in the extract which do not contribute to tanning capacity but which do definitely react with formaldehyde and contribute to adhesive preparation. 

The potential of this development for the structural elucidation of the proanthocyanidin condensed tannins, especially the 5-deoxy analogues, from important commercial sources is clear. In addition, the method facilitates the ready definition of the absolute configuration of the chainterminating flavan-3-ol moiety in 5-deoxyoligoflavanoids, especially in... 

Definition From aq. extraction of fresh deseeded marc remaining after grapes are pressed to produce wine or juice contains anthocyanins, tartaric acid, tannins, sugars, minerals Properties Deep purple sol. in water Uses Colorant for beverages and pharmaceuticals... 

Definition Plant material derived from the dried bark of Quillaja saponaria contg. sapotoxin, tannin, and quillaja... 

Vauquelin, partly in collaboration with Fourcroy, discovered several important organic compounds. They distinguished a number of proximate constituents Yourcroy %principes immediats) in vegetables, such as acids, oils, camphor, gum, resin, tannin, starch, fibre, cork, caoutchouc, and extractive (a product of extraction with cold water and evaporation). Several definite compounds which had previously been obtained but the existence of which was in doubt were confirmed. Among these was malic acid and its salts. Sodium malate (with other salts of organic acids) was obtained by Donald Monro in 1767 and the acid from apples by Scheele in 1785 (see p. 232). The acid and its salts were studied by Fourcroy and Vauquelin. Vauquelin showed that the sorbic acid isolated from mountain-ash berries by Donovan is malic acid (the modern sorbic acid is a different substance) Vauquelin s elementary analysis of malic acid was inaccurate. 

Currently, understanding the biometabolism of HTs, especially ETs, can contribute to the definition of their bioavailability and potential biological properties on humans. Although there is little information on the absorption, distribution, metabolism and excretion (ADME) of HTs in humans, trials with rodents and pigs, in vitro studies and fecal batch fermentations have contributed to understanding tannins metabolism. This fact becomes even more relevant for GTs since, to the best of our knowledge, there is a lack of studies focused on the biometabolism of GTs or GT-rich foodstuffs. 

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