Composition and some functional properties of Bambara groundnuts vicilin fraction

Bambara groundnut is a drought tolerant pulse grain and an alternative source of protein. In this study, Bambara vicilin (7S) protein fraction was extracted and characterised in comparison to the storage protein. The proline content of vicilin fraction (4.3 g/100 g protein) was almost four times that of the storage protein. Fluorescence and hydrophobicity data suggested a less folded structure for the vicilin fraction when compared to the storage protein. Gel electrophoresis indicated three major polypeptides (50, 70 and 80 kDa) in the vicilin fraction with the presence of disulfide bond(s) in one of the strands. In contrast to the storage protein, which had < 40% protein solubility at pH 2-9, vicilin had a significantly (p < 0.05) higher solubility with a minimum of 50% at pH 5 and maximum of 82% at pH 3. Emulsifying stability of the proteins significantly differed (p < 0.05) at pH 7. Foaming capacity of the vicilin fraction was significantly (p < 0.05) higher than that of the storage protein at pH 3, 7, and 9. It could be concluded that Bambara vicilin fraction could serve as a potential ingredient in the formulation of food products at acidic pH.