The relationship between tannin content, enzyme inhibition, rat performance, and characteristics of sorghum grain

Abstract

Fifteen samples of sorghum grain representing various combinations of pericarp colour and the presence or absence of pigmented testa were analysed for protein, amino acid and tannin contents and alpha -amylase inhibition was estimated. Rat growth tests were done at a 10% protein intake (1% casein and 9% sorghum) with groups of 6 weanling male rats; control groups were given diets containing 5 or 10% protein derived from casein. Protein efficiency ratios (PER) were calculated at the end of the 21-day feeding period. Faeces were collected during the second week of the experiments for the estimation of DM disappearance (DMD). Values for lysine, the limiting acid, are quoted and there were small, but significant, differences between some samples. There was a highly significant positive correlation between lysine content and PER; all PER values were significantly lower than those for casein. Tannin content was significantly and negatively correlated with DMD but not with lysine concentration or PER. alpha -Amylase inhibition was high in brown grains but was absent in white or red grains or any grain without pigmented testa