Traditional uses of Tannins include the transformation of
animal hides to leather (by the process of ‘tanning’) and beer
stabilisation. Introduction
The
term Tannin refers to a class of substances which are widely distributed in the
vegetable kingdom. They do not posses ‘primary functions’ in plants, (for
example biosynthesis and biodegradation), but they are rather classified as
‘secondary’ compounds with diverse biological activities including toxicity and
hormonal mimicry.
Traditional uses of Tannins include the transformation of
animal hides to leather (by the process of ‘tanning’) and beer
stabilisation.
Their chemical classification is still vague, and many definitions have been suggested by famous researchers in this field. Horvarth (1981) defined these substances as "Any phenolic compound of sufficiently high molecular weight containing sufficient hydroxyls and other suitable groups (i.e. carboxyls) to form effectively strong complexes with protein and other macromolecules under the particular environmental conditions being studied".
Nierenstein (1934) gave a definition including some of the most peculiar reactions of tannins:
“Amorphous, rarely crystalline substances….. remarkable for their astringent (austere, styptic, binding, zusammenziehend) taste, and for the ability to form coloured solutions and precipitates with iron and other metals. They are also precipitated from solution by albumin, gelatine and other proteins, as well as alkaloids”.
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