Structural, physicochemical and interfacial stabilisation properties of ultrafiltered African yam bean (Sphenostylis stenocarpa) protein isolate compared with those of isoelectric protein isolate

• Secondary structure and physico-functional properties of African yam bean proteins were studied.
• African yam bean proteins contain highly ordered structure like β-sheet, α-helix and β-turn.
• African yam bean proteins' tryptophan were buried in the hydrophobic core.
• Membrane processed AYB protein had lower surface hydrophobicity than that of isoelectric isolate.
• Isoelectric AYB protein had higher interfacial stabilizing properties than those of Membrane.

Structural, Physicochemical and functional properties of ultrafiltered/diafiltered African yam bean (AYB) protein isolate (AYBUD) were determined. These were also compared with isoelectrically precipitated AYB protein isolate (AYBISO). Both AYBUD and AYBISO had the same X-ray diffraction (XRD peaks at 8.5° and 19.5°. The XRD profile for both AYBISO and AYBUD showed partial crystalinity. Emission maximum (λmax) of the intrinsic fluorescence spectra associated with tryptophan (Trp) residue in both AYBUD andAYBISO was observed at 330 nm, indicating a Trp residue that was deeply buried in hydrophobic core. Circular dichroism (CD) spectra showed that there were more highly ordered structure of α-helix, β and β-turns in AYBISO than AYBUD. The surface hydrophobicity (Ho), emulsifying and foaming abilities of AYBISO were significantly (p = 0.05) higher than those of AYBUD.