Preparation of soy protein-based microgel particles using a hydrogel homogenizing strategy and their interfacial properties

Abstract In this work, a two-step strategy for fabricating soy protein-based microgel particles was introduced. Gel preparation and homogenization made up the two steps. Microgel particles with nano-scale size were obtained by homogenizing the hydrogel made from soy protein isolate (SPI) with the addition of microbial transglutaminase (MTGase). Colloidal stability, surface hydrophobicity and interfacial properties of the microgel particles were systematically investigated. We confirmed that the microgels had a more rigid conformation when compared to that of SPI, which was attributed to the covalent cross-links inside the microgels formed during gel preparation. By comparison with SPI, the microgel particles with three-phase contact angles more close to 90° exhibited lower surface activity, weaker intermolecular interactions at the interface. We found that most of the microgels adsorbed at the interface and stabilize Pickering type oil-in-water (O/W) emulsion at the pH around the isoelectric point of SPI. The resulting emulsion had good storage stability for 8 weeks. This preparation method, which requires simple operation and common devices, provides a new perspective of fabricating edible functional particulates for food industry.