Physicochemical and structural properties of major protein fractions of two varieties of cowpea (Vigna unguiculata L.): A comparative study

Abstract

The polypeptide composition, structural and physicochemical properties of the major protein fractions from two cowpea (Vigna unguiculata L. walp) varieties (CU: Cuarentón; CO: Colorado) were determined. In both cowpea varieties, the globulin was the major protein fraction, followed by albumins, glutelins and prolamins with 48 ± 2 g/100 g, 33 ± 2 g/100 g, 8 ± 1 g/100 g and 2 ± 0.5 g/100 g of the total seed protein content, respectively. Under non-reducing conditions, the CU and CO globulin fractions, showed four major polypeptides with molecular masses of 80 ± 3, 65 ± 3, 56 ± 2 and 52 ± 2 kDa and some minor polypeptides with molecular masses distributed over a range of 45-25 kDa. The minor values of enthalpy (delta H) obtained for the major protein fractions of CU when compared to CO suggest that the former are partially denatured. The conformational studies performed on the globulin fraction of both varieties showed a higher content of aromatic amino acids than that of the albumin fraction and displayed a more hydrophobic behavior. Results provide useful data that will be supplemented with further studies on functional properties of these proteins fractions, followed by the development of legume protein products.