Extractability of African yam bean (Sphenostylis stenocarpa) protein in acid, salt and alkaline aqueous media

Protein extractability from defatted Africa yam been (Sphenostylis stenocarpa) was studied under various conditions: solid/solvent ratio, time, pH, and salt. Extractable protein from S. stenocarpa was strongly dependent on all these factors. Maximum extractable protein was obtained after 2 h extraction time; the solid to solvent ratio in the range of 1:20–1:50 gave maximum protein extractability. The pH corresponding to maximum and minimum extractable proteins were 10 and 5, respectively, but addition of NaCl changed this slightly. Extractable protein of 92%, 88% and 84% were obtained in aqueous concentration of 0.01 MNa2SO4, 1.5 MNaCl and 0.01 MNaOH, respectively while other concentrations gave lower extractability. These salt concentrations, i.e. 0.01 MNa2SO4 and 1.5 MNaCl gave slightly lower extractable protein under alkaline condition. S. stenocarpa flour has a higher buffer capacity in acid medium than in alkaline medium.