Extraction, partial characterization and nutritional aspects of proteins from Carioca 80 bean (Phaseolus vulgaris L.)

Extraction, fractionation and characterization by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis of proteins from Carioca 80 beans (Phaseolus vulgaris) were performed at three pH values (2.5, 8.0 and 9.0). Extraction at pH 7.0 proved to be more efficient and, after dialysis, produced a better separation of the albumin and globulin fractions. Relative mobility of the main protein in the globulin fractions occurred between 0.30 and 0.40, and dissociation was observed when the pH was increased. The two most representative bands gave molecular weights of 35,400 and 76,900, while in regard to the trypsin inhibitor, three bands gave 28,800, 22,500 and 18,300. Pepsin and pancreatin in vitro digestibility rendered values of 33.43% and 62.63% for whole flour and for protein precipitated at pH 4.5, respectively. The content of available methionine found, of 1.36 g/16 g N, appears to be high in relation to that of other bean varieties.