Impact of condensed tannin size as individual and mixed polymers on bovine serum albumin precipitation

Condensed tannins composed of epicatechin from monomer to octamer were isolated from cacao (Theobroma cacao, L) seeds and added to bovine serum albumin (BSA) individually and combined as mixtures. When added to excess BSA the amount of tannin precipitated increased with tannin size. The amount of tannin required to precipitate BSA varied among the polymers with the trimer requiring the most to precipitate BSA (1000 mu g) and octamer the least (50 mu g). The efficacy of condensed tannins for protein precipitation increased with increased degree of polymerisation (or size) from trimers to octamers (monomers and dimers did not precipitate BSA), while mixtures of two sizes primarily had an additive effect. This study demonstrates that astringent perception is likely to increase with increasing polymer size. Further research to expand our understanding of astringent perception and its correlation with protein precipitation would benefit from sensory analysis of condensed tannins across a range of polymer sizes. (C) 2014 Elsevier Ltd. All rights reserved.