Fabrication of Soy Protein Nanoparticles via Partial Enzymatic Hydrolysis and Their Role in Controlling Lipid Digestion of Oil-in-Water Emulsions

In this study, a new type of soy protein nanoparticle (SPNP) was successfully fabricated through partial enzymatic hydrolysis by bromelain (SPIbro) or alcalase (SPIalc) to a DH (degree of hydrolysis) of 3%. SPNPs exhibited fast adsorption at the oil–water interface, and the resultant particle-laden interface with a high surface loading endowed the prepared oil-in-water emulsions with superior stability against droplet coalescence during long-term storage. Using a simulated gastrointestinal tract, the emulsions stabilized by SPIbro and SPIalc nanoparticles could remain stable during gastric digestion and showed a noticeably slower initial rate and a reduced degree of lipolysis in the intestinal phase, as compared to the characteristics of those prepared by native SPI, which may be closely related to the Pickering stabilization of the SPNP-laden interface thus offering greater resistance against bile salt displacement. On the contrary, further hydrolysis to a DH of 9% caused degradation of the SPI into amorphous peptides. Although delayed/reduced lipolysis was also observed for the emulsions stabilized by SPIbro and SPIalc at 9% DH due to the interfacial peptide aggregation in the gastric phase, these emulsions displayed poor stability with obvious flocculation and coalescence upon preparation and during storage, which is probably attributed to the lower desorption energies of thin interfacial layers formed by the peptides and/or peptide aggregates. These findings demonstrate that partial enzymatic hydrolysis can be a potential strategy for the fabrication of functional soy protein-based nanoparticles, which are used to design a particle-laden interface modulating lipid digestibility in emulsion-based functional foods.