Evaluation of some Physicochemical and Functional Characteristics of Proteins from Mucuna pruriens Bean

Proteins isolated from Mucuna pruriens bean were characterized and the foaming properties of both the flour and protein isolates determined. The pH-dependent protein solubility profile of the flour and isolates indicated that the isoelectric point ranged between 4.0 and 5.0. At all concentrations, the foaming capacity of both the flour and protein isolates increased with concentration increase; increase in the ionic strength from 0.1 to 0.4 M and declined afterward as the ionic strength increase from 0.6 to 1.0 M. It reduced as the pH increased from 2 to 4 (or 5) after which it increased as pH increased to a maximum value at pH 10. The highest foam stability was observed at pH 4 or 5, following which it reduced as the pH increased. Incorporation of carbohydrates at a level of 0.25g/g of protein increased the foaming capacity and stability compared with the control sample. In the flours, the starch resulted in the highest improvement of the capacity and stability against protein isolates where lactose resulted in the highest increase. Two peaks were distinguished in Differential Scanning Calorimetry (DSC) thermograms: 7S-vicilin and 11S-legumins. In 7S-vicilin the stability of the proteins was highest in cochichinensis and least in rajada. The trend of stability of the 11S-legumins was highest in Veracruz mottle and least in rajada and deerigeana. Gel filtration chromatographic studies of the protein isolates show two major fractions with molecular masses of 40 and 15.3 kDa and minor components’ molecular weight 913.5, 35.8, 3.9 and 1.2 kDa. Polyacrylamide gel electrophoresis revealed a similar pattern of molecular weights. Finally, a major band consisting of a broad zone with molecular weights 36 ± 7 and 17 ± 3 kDa appeared in all the samples under both reducing and non-reducing conditions. _____________________________________________________________________________________________________________