Proteins of dehulled black beans: Digestibility in conventional and germ-free animals

Abstract

The bean (Phaseolus vulgaris, L.) is a legume of great importance in the Brazilian typical diet. Nevertheless, it presents a low protein quality due to its poor digestibility and low levels and bioavailability of its sulfur amino acids. The aim of this study was to evaluate the digestibility of albumin and globulin protein fractions of dehulled black beans in conventional and germ-free mice and also in weaning rats (Wistar) of 21 to 25 days of age. Protein Digestibility Corrected Amino Acid Score was also determined. True digestibility values in germ-free mice were 90.21 and 90.00%, in conventional mice were 85.53 and 86.73%, and in rats were 82.62 and 68.53%, for albumin and globulin respectively. Protein Digestibility Corrected Amino Acid Score was 61.00% for albumin and 51.00% for globulin. True digestibility values in germ-free mice were higher than those obtained with conventional animals. This fact suggests that intestinal flora is contributing to increase fecal nitrogen output in conventional animals, and, therefore, true digestibility of beans is being underestimated.