A comparison of in vivo and in vitro estimates of protein digestibility of native and thermally processed vegetable proteins

Research was performed to determine the suitability of the rapid multienzymatic assay for in vitro protein digestibility estimation by using a group of native and thermally processed vegetable proteins which constitute the staple foods in developing countries. The in vitro digestibility was assessed by measuring the extent to which the pH of the protein suspension dropped when treated with a multienzyme system consisting of trypsin, chymotrypsin, and peptidase for 10 min, andStreptomyces griseus protease for 10 min more. The best correlation occurred between in vivo rat protein digestibility and the pH of the protein suspension after 15 min enzymatic treatment. The response of different types of proteins to the multienzyme assay was different, and thus distinct equations were derived for the in vitro digestibility estimation of the samples assayed. The first group included nonprocessed cereal grains and oilseeds, and cereal grain-leguminous seed mixtures. The second group was formed by leguminous seeds, and the third by thermally processed cereal and oilseed products. Although highly significant correlations between in vivo and in vitro estimates for the three groups were found, important differences occurred in the group of processed samples; therefore, more research is required with these types of samples.