Preparation of a novel nanoparticle with extruded soy protein isolate-oat β-glucan: Interfacial properties and mechanism of emulsion stability

A novel nanoparticle was prepared with soy protein isolate (SPI)-oat β-glucan (OG) conjugates obtained by extrusion (extruded SPI-OG) to stabilize the emulsion. Extruded SPI-OG nanoparticles exhibited a spherical and stable structure. The 90 °C and 110 °C extruded SPI-OG nanoparticles had higher absolute value of zeta potential (13.35 mV and 12.24 mV, respectively) and an average particle size of less than 200 nm. Moreover, interfacial tension of nanoparticles increased with increasing extrusion temperature, but diffusion rate and surface hydrophobicity were decreased, while penetration rate (Kp) and rearrangement rate (Kr) increased and then decreased. The 90 °C and 110 °C extruded SPI-OG nanoparticles had the highest Kp and Kr, and increased by 38.14% and 40.11%, 175.16% and 168.15%, respectively, compared with Kp and Kr of SPI nanoparticles. And emulsion stabilized by these two nanoparticles exhibited the extraordinary emulsion stability of 81.64% and 80.07%, respectively (p > 0.05). These results demonstrated that adsorption rate of extruded SPI-OG nanoparticles to the oil-water interface decreased, but could rapid unfold and rearrange at the interface to form interfacial layer for stabilizing emulsion. And adsorption capacity and microstructure of emulsion also proved that more extruded SPI-OG nanoparticles could adsorb onto the interface to form a dense interfacial layer. This may provide a theoretical basis for novel nanoparticles as interfacial stabilizer in emulsion.