Ca2+-induced soy protein nanoparticles as pickering stabilizers: Fabrication and characterization

Abstract

The development of food-grade Pickering stabilizers has recently attracted fast increasing interest in the food science field. The work reports a novel non-thermal process to fabricate soy protein isolate (SPI) nanoparticles to perform as effective Pickering stabilizers. The nanoparticles were formed by Ca2+-induced aggregation and subsequent glutaraldehyde (GAD) crosslinking. At a protein concentration of 2% (w/v), increasing Ca2+ concentration (from 0 to 7.5 mM) led to a progressive increase in turbidity and particle size (60–130 nm), indicating aggregation and formation of nano-sized particles. The Ca2+-induced SPI nanoparticles, further treated with different concentrations of GAD (0–200% equivalents), were characterized in terms of particle size, surface hydrophobicity and charge, internal integrity, emulsification performance and interfacial packing, as well as emulsion stability. The results indicated that the crosslinking treatment resulted in larger particle sizes, lower surface hydrophobicity and higher surface charge, stronger internal integrity, lower emulsification performance and higher emulsion stability against coalescence, with the extent of changes increasing with the applied GAD concentration. The emulsions stabilized by these fabricated nanoparticles followed the rule of limited coalescence, and had a very low surface coverage (3.8–12.6%). The surface coverage is considerably lower than that of many Pickering emulsions previously reported in the literature. All the results confirmed that the fabricated SPI nanoparticles could perform as effective Pickering stabilizers. The findings would be of great importance for the development of food-grade Pickering stabilizers suitable for the formulations of functional foods and medicine.