Proximate Composition of Two Varieties of African Yam Bean (sphenostylis sternocarpa) Seed Flour and Functional Properties of Their Protein Isolates

Abstract

Protein isolates were prepared from two varieties of African yam bean (sphenostylis sternocarpa I and sphenostylis sternocarpa II) by alkaline extraction followed by acid precipitation of the proteins at the isoelectric point (5.0). Proximate composition and functional properties of the see flours and protein isolates were determined. Protein isolates from S. sternocarpaI and S. sternocarpa II contain 90.84 and 92.43% of protein respectively. The proximate analysis show that S. sternocarpa II flour and protein isolate has a higher protein content of 24.78% and 92.45%. The result of the functional properties also revealed that S. sternocarpa II has a better water absorption capacity, oil absorption capacity, emulsion capacity and stability. The pH dependent protein solubility profile also shows that the highest solubility in both flours and isolate in the two varieties was at pH 10 while minimum solubility was obtained at pH 5.0 which corresponds to the isoelectric point.