Solubilization and Electrophoretic Characterization of the Great Northern Bean (Phaseolus vulgaris L.) Proteins

Abstract

ABSTRACTProtein content of dry beans (Phaseiolus vulguris L.) cultivar Great Northern, was 26.10% (dry weight basis). The isoelectirc pH of the NaCl extractable proteins was about 4.4. Several salts, NaOH, and HCl were employed to solubilize the Great Northern bean proteins. Amongst all the protein solubilizing agents, Na2CO3, K2SO4, sodium dodecyl sulfate (SDS), and NaOH at respective concentrations of 0.5, 5, 5% (all w/v), and 0.02N were found to be better protein solubilizers than the rest; solubilizing 93.6g of Lowry protein per 100g of Kjeldahl protein. Albumins and globulins accounted for 21.18 and 73.40% respectively, of the total bean proteins. Protein content of albumins, globulins, protein concentrates, and protein isolates was 81.68, 92.26, 85.44, and 92.43% (dry weight basis) respectively. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) of the bean flour, albumins, globulins, protein concentrates, and protein isolates revealed the presence of 22, 14, 10, 14, and 11 subunits, respectively. The bean flour, albumin's, globulins, protein concentrates and protein isolates were characterized by the predominance of subunits with apparent molecular weights of 294,000, 266,000, 123,000, 146,000, and 135,000 daltons, respectively. Isoelectric focusing of the bean flour, albumins, globulins, protein concentrates, and protein isolates indicated 15, 13, 15, 16, and 11 subunits, respectively. Molecular sieve chromatography of the bean flour proteins, albumins, and globulins followed by SDS‐PAGE was also employed to study the complexities of these proteins.