Effect of structuring emulsion gels by whey or soy protein isolate on the structure, mechanical properties, and in-vitro digestion of alginate-based emulsion gel beads

Whey protein isolate (WPI) and soy protein isolate (SPI) were used as emulsifiers and structure-modifying agents to produce alginate-based emulsion gel beads. The purpose of this study was to compare the effects of WPI and SPI on the structural and mechanical properties of alginate-based emulsion gel beads and the in-vitro release of encapsulated lycopene from emulsion gel beads. The results of microscopy and light scattering indicated that WPI had better emulsifying properties than SPI, resulting in emulsions with smaller and more even droplet size distribution. The rheological properties of protein/alginate mixtures and emulsions indicated strong interactions between WPI and alginate and weak interactions between SPI and alginate, resulting in increased Young's modulus of WPI-stabilized emulsion gel beads and decreased Young's modulus of SPI-stabilized emulsion gel beads, compared to gel beads without proteins. The presence of WPI and SPI increased changes of Young's modulus and shrinkage during simulated gastric digestion and delayed the release of lycopene from gel beads. Findings in this study are important for structuring emulsion gels with naturally occurring polymers to achieve controlled release of encapsulated compounds.