Improving the emulsification of soy β-conglycinin by alcohol-induced aggregation

Abstract

Soy proteins have attracted fast increasing interests to be used in food emulsion formulations, due to their good emulsifying properties. Soy β-conglycinin (SC) and glycinin are the two major storage globulins in soy proteins, with the former generally recognized to exhibit much better emulsifying properties than the latter. The current work reported that the treatment of SC with ethanol at concentrations ([E]) of 20–80% (v/v) remarkably improved its emulsification performance and interfacial stabilization, in a [E]-dependent way. The influence of the ethanol treatment on the physicochemical and structural properties of SC was characterized. As expected, the treatment led to an [E]-dependent aggregation of SC, and formation of larger particles with more compact structure. Next, the emulsifying and interfacial properties of these ethanol-treated SC samples were evaluated in terms of emulsification performance and interfacial stabilization, at two oil volume fractions of 0.2 and 0.8. In both cases, the ethanol-treated SC showed greatly improved emulsification performance and interfacial stabilization. The improvements were largely due to the facilitated formation of bridged emulsions, via the strengthened Pickering stabilization by ethanol-induced aggregation. Even at a low concentration of 0.5 wt%, the ethanol-treated SC could still produce a kind of fine emulsions (produced by microfluidization), or high internal phase emulsions with a self-supporting gel network (that could resist the disruption of 6 M urea). The results demonstrated that the ethanol pretreatment can be applied as an effective modification to remarkably improve the emulsifying properties of SC, through the strengthening of its Pickering stabilization.