Nutritional evaluation and metabolic effects in rats of protein isolates obtained from seeds of three legume species

Three legume seeds, peas (Pisum sativum L), faba bean (Vicia faba L) and soybean (Glycine max L) and their respective protein isolates, were assayed for their nutritional value and metabolic effects. Feeding rats with either the legume seeds or the protein isolates resulted in an impairment in growth and significantly lower nutritional indices as compared to the control group. Protein apparent digestibility improved in the protein isolate fed rats, with similar digestibility data to those observed in the casein fed group. Liver, gastrocnemius muscle and spleen weights were decreased by legume consumption, and the enlargement detected in the small intestine weight in the animals fed on the legume seeds, was partially reversed in the animals receiving the protein isolate. This reversal was significant in rats offered faba bean protein isolate. Biochemical parameters were consistent in the legume groups, and hypoglycaemic and hypotriacylglycaemic responses were observed for the legume meals. Lower uric acid levels were found in some of the legume fed animals. Serum free amino acid profiles were affected by the legume intake, as compared with casein. Methionine and taurine concentrations decreased, whereas serine concentrations were augmented. Other amino acids, particularly glycine and valine, also showed modified plasma concentrations. These results suggest that the preparation of protein isolates, following an easy protocol, yield products with better digestibility, which keep the positive effects on glucose and triacylglyceride plasma levels, and partially reduce some other undesiderable consequences related to legume consumption. (C) 1998 Society of Chemical Industry.