Influence of pH-shifting and transglutaminase on the freeze-thaw stability and thermal gel properties of mung bean protein-based liquid egg substitute prepared with two different oil phases

Abstract

The poor freeze-thaw stability and weak thermal gel properties of plant-based egg substitutes limit their opportunity for application. In the current study, the impact of modification by pH-shifting and transglutaminase (TG) cross-linking on the freeze-thaw stability and thermal gel properties of mung bean protein-based emulsions made by two different oil phases (canola oil and coconut oil) were studied. The pH-shifting induced improved emulsifying activity (up to 77.6% increased) and smaller droplets sizes (from 39.27 to 7.03 μm). After the freeze-thaw process, no matter with TG cross-linking or in different oil phase systems, all emulsion samples prepared with pH-shifting treated mung bean protein (BMBP) exhibited a superior freeze-thaw stability than that with native mung bean protein (NMBP). The apparent viscosity of BMBP emulsion was higher than that of NMBP, and the viscosity of BMBP-based CO-emulsion (222.50 mPa s) before freeze-thaw process was closest to that of real egg liquid (184.86 mPa s). In particular, BMBP was more sensitive to TG, resulting in a superior thermal gel hardness of BMBP-based emulsion. This study could serve as a feasible solution to enhance the freeze-thaw stability and thermal gel properties of plant-based emulsions by pH-shifting and TG cross-linking, providing some novel strategies for their applications as stabilized plant-based egg substitutes.