Heat-induced modifications in the functional and structural properties of vicilin-rich protein isolate from kidney (Phaseolus vulgaris L.) bean

Heat-induced changes in the physico-chemical (and/or functional) and structural properties of protein isolate from kidney beans (KPI) were characterised. The extent of protein denaturation, free sulphydryl contents, surface hydrophobicity, as well as structural characteristics of the proteins were evaluated. Analyses of size-exclusion chromatography combined with laser scattering showed that the heating at 95 °C led to transformation of 7S-form vicilin to its 11S-form, and even higher molar mass (MW) oligomers or polymers. Moderate heating (for 15–30 min) significantly improved protein solubility, emulsifying and foaming activities (at neutral pH), whilst extensive heating (for 60–120 min) on the contrary decreased these properties. Spectral analyses of fluorescence and/or Raman spectroscopy showed that tertiary and secondary conformations of protein in KPI were remarkably affected to a varying extent by the heating. The results suggested a close relationship between functional properties of the vicilin from kidney bean and its conformational characteristics.