Reduction of Digestibility of Legume Proteins by Tannins

Abstract

The protein of certain legumes is known to be poorly digested. In this paper the effect of polyphenolic compounds present in the scedcoat of coloured varieties of common bean (Phaseolus vulgaris) is discussed. From human studies it was estimated that polyphcnols accounted for only 7 per cent of true protein digestibility, while other factors such as trypsin inhibitors and poorly-digested storage proteins may account for as much as 25 per cent. It was concluded that the effect of polyphenolic compounds on protein digestibility is relatively small and would be expected to be lower when beans were a part of a mixed diet. Therefore, other factors in cooked beans may be re sponsible for most of the low digestibility values reported.