In-vitro digestibility and microscopic appearance of germinated legume starches and their effect on dietary protein utilization

Abstract

The effect of germination on the in-vitro digestibility of some legume starches and their effect on dietary protein were studied. Starch was extracted from faba bean ( Vicia faba L.), kidney bean ( Phaseolus vulgaris L.) and chick pea ( Cicer artinum) before and after germination for 3 days. Germination increased the starch digestibility of the above three legumes (33.2%–32.3%, 39.5–47.2% and 44.71–49.4%, respectively). The microscopic appearance of the isolated starch was conducted using a scanning electron microscopic technique. The size of the starch granules increased with slight damage in the starch isolated from germinated seeds in comparison to the ungerminated. The effect of the isolated legume starches on the utilization of casein as the sole protein in rat diets was evaluated using protein efficiency ratio (PER), digestibility coefficient (DC) and net protein utilization (NPU) as parameters. The utilization of casein significantly increased when the diets were supplemented with isolated starches from germinated legume seeds compared to ungerminated legume starches. Cooked starch from germinated chick pea had PER, DC and NPU values similar to those of a corn starch diet, being 2.4, 93.4 and 74.1%, respectively. This study found a good correlation between the nature of the starch granules and their in-vitro digestibilities and the utilization of the protein in the rat diets.