Effects of Storage on Protein Nutritional Quality of Grain Legumes

The effect of storage under moderate conditions (12% relative humidity and 20°C) on protein nutritional quality of legumes grown in Canada (faba bean, lentil, seafarer, pinto and black beans and trapper and century peas) was determined. Little change in legume amino acid contents and only slight changes in relative net protein ratio (RNPR) and true crude protein digestibility occurred over the three years. No consistent changes were seen in plasma amino acids of rats fed the stored legumes, although plasma methionine and tryptophan were lower compared to casein-fed rats, reflecting dietary deficiencies in these amino acids. Amino acid scores indicated that tryptophan and sulfur amino acids were first and second limiting, respectively, in most of the legumes. Correction of amino acid scores for true digestibility of protein in the legumes greatly improved correlation coefficients between scores and RNPR.