Amino Acid Scores of Dry Bean Proteins Fractionated by Deae Cellulose1

Abstract

AbstractDry bean (Phaseolus vulgaris L.) are an additional source of protein for human consumption, but the crop has never been exploited as a protein source. The objective of this study was to determine if dry beans exhibit a wide range of sulfur amino acids in proteins fractionated by DEAE chromatography. Protein was extracted from two cultivars (‘Sanilac’ and ‘Bush Blue Lake 290’) and one genotype (P.I. 136‐691) of dry beans with phosphate buffer and fractionated. The amino acid scores of each protein fraction were calculated, based upon the estimated amounts for human needs. The sulfur amino acid scores varied from 19 to 184. Three protein fractions from P.I. 136‐691 had sulfur amino acid scores greater than 100. Lysine scores ranged from 101 to 187 with most being 140 or greater. Threonine scored below 99 in three fractions. Valine and leucine scored below 100 in one of 15 protein fractions analyzed. Isoleucine, tyrosine, and phenylalanine were never limiting in these isolated proteins. Although the phosphate extract contained about 50% of the total bean N, the protein fractions from the DEAE cellulose columns represented too small a fraction of total bean protein, (−0.5 to 7 mg/g dry wt. of bean) to be useful for screening potential genotypes for breeding.