Novel protein-based nanoparticles from perilla oilseed residues as sole Pickering stabilizers for high internal phase emulsions

Pickering high internal phase emulsions (HIPEs) have attracted tremendous attention as solid fat substitutes due to their high stability. However, biocompatibility and biodegradability of inorganic and synthetic stabilizers limit their applications. In this study, a novel perilla protein isolate based nanoparticle was prepared by pH-cycling combined with homogenization. Homogenization resulted in breakdown of larger protein-based particles, and formation of spherical nanoparticles with size of 224 nm and wettability of 105.5 degrees. Stable Pickering HIPEs with an internal phase of 75% could be formed with nanoparticle concentration as low as 1.0% (m/v). The compressed polyhedral droplets of HIPEs formed a percolating network structure, which could not be disrupted by 6 mol.L-1 urea. Additionally, the elasticity of HIPEs could be slightly strengthened by increasing nanoparticle concentrations. All the HIPEs exhibited an interfacial protein adsorption around 50%, and the nanoparticles suffered greatly changes of secondary structure composition and tertiary conformation level when adsorbed at the biphase interface. The HIPEs at nanoparticle concentrations of 1.5-2.0% (m/v) were extremely stable against long-term storage, heating and ionic strength, but susceptible to freeze-thawing treatment. These findings will provide a theoretical reference for the development of novel food-grade Pickering HIPEs.