Treatment of Plant Material, Extraction of Tannins, and an Overview of Tannin Assays Presented in the Manual

Abstract

Tannins are naturally occurring polyphenolic substances with various molecular weights and a variable complexity. These are chemically not well-defined substances but rather a group of substances with the ability to bind proteins in aqueous solution. Their multiple phenolic hydroxyl groups lead to the formation of complexes primarily with proteins and to a lesser extent with metal ions, amino acids and polysaccharides. Tannins are tentatively classified into two classes: hydrolysable and condensed tannins (although tannins are known which have components of both hydrolysable and condensed tannins), and are considered to have both adverse and beneficial effects depending on their concentration and nature besides other factors such as animal species, physiological state of the animal and composition of the diet.