Tannin Chemistry

The importance of tannin-protein interactions in leathermaking and in plant-animal interactions has long been recognized, but detailed knowledge of the chemistry of the interaction has only recently become available. Tannin-protein interactions are influenced by characteristics of the protein (including size, amino acid composition, pI, and extent of post translational modification), characteristics of the tannin (size, structure, heterogeneity of the preparation), and conditions of the reaction (pH, temperature, solvent composition, time). The most familiar tannin-protein interactions result in precipitation of the complex, but soluble complexes also form under certain conditions. Both soluble and insoluble complexes are stabilized by reversible, noncovalent bonds between tannin and protein.