Comparative physico-chemical, functional and structural characteristics of winged bean [Psophocarpus tetragonolobus DC] and Soybean [Glycine max.] Protein isolates

The physicochemical (colour, bulk density, thermal properties, molecular sizes), functional (water and oil absorption, solubility, emulsifying and gelation properties) and secondary structural properties of winged bean isolate (W-ISO) were studied and compared with those of soybean isolate(S-ISO) as reference. Results showed that W-ISO and S-ISO had extraction rates of 32.23 and 37.52 g/100 g, respectively, with corresponding protein content of 81.68 and 85.69% (dry weight basis). W-ISO and S-ISO had denaturation temperature and enthalpy of 105.53 & 111.61 °C, and 3.77 & 3.30 J g-1, respectively. Both isolates showed comparable functional properties, but W-ISO had higher foaming and oil absorption properties whereas S-ISO had higher water absorption and surface hydrophobicity. FTIR spectroscopy showed that W-ISO is composed of 15.38% α-helices, 37.46% β-sheets, 31.67% turns and 15.38% disordered secondary structures whereas S-ISO had 15.46% α-helices, 46.15% β-sheets, 30.78% turns and 7.69% unordered components. In addition to being a potential food ingredient comparable to soybean isolate, winged bean isolate can also be employed in foods where high foam volume is essential.