Structural and functional properties of fava bean legumin and vicilin protein fractions

In this study, we examined the physicochemical and functional properties of fava bean globulin fractions that are rich in legumin or vicilin proteins. The sulphur containing amino acids, branched chain amino acids, and arginine/lysine ratio obtained for legumin (1.89%, 18.32%, and 1.43%) are significantly (P < 0.05) higher than the 1.24%, 17.94%, and 1.05%, respectively, for the vicilin fraction. SDS-PAGE results show that the legumin fraction had a wider range of polypeptide sizes (approximately 14-140 kDa) when compared to the approximately 12-68 kDa for vicilin. The surface hydrophobicity (So) of legumin (86.07) was significantly (P < 0.05) lower compared with vicilin (118.19). The legumin had higher protein solubility (approximately 40-50%) than the vicilin (0%) at pH 3 and 4, but vicilin solubility was higher at pH 6-8. The vicilin had higher (83.58%) in vitro protein digestibility than the legumin (78.24%). However, the legumin had higher oil-holding capacity, lower least gelation concentration, and formed emulsions at pH 3, 7, and 9 with smaller mean oil droplet sizes than the vicilin. Foam formation was better with increased levels of alpha-helix secondary structure. We conclude that pH of the environment was a stronger determinant of protein functionality than the sample protein concentration.