pH-driven Zein-peanut protein isolate composite nanoparticles for stabilizing pickering emulsions and enhancing resveratrol delivery.

In this study, zein-peanut isolate protein (PPI) composite nanoparticles were fabricated by pH-driven self-assembly method and their potential applications in Pickering emulsion stabilization and resveratrol encapsulation were systematically explored. The results showed that the particle size, zeta potential, and dispersibility were significantly affected by the Zein:PPI mass ratio. Among them, the composite particles with a mass ratio of Zein:PPI of 1:2 showed the best performance, with an average particle size of approximately 389 nm, a low PDI value (0.32) and a high surface charge (-42 mV), indicating superior colloidal stability. Scanning electron microscopy results showed a porous lamellar structure, and contact angle analysis indicated that the surface wettability of the composite particles increased with increasing PPI ratio. Spectroscopic analyses (UV-vis, fluorescence, circular dichroism and FTIR) revealed significant changes in the protein secondary structure, with a decrease in α-helix and an increase in β-folding, reflecting stronger protein-protein interactions. Molecular docking and molecular dynamics simulations further verified the formation of a stable composite structure between zein and PPI mainly through hydrophobic interactions and hydrogen bonding. The Pickering emulsions stabilized by the composite particles were of the oil-in-water type and exhibited remarkable thermal and long-term storage stability. Meanwhile, they showed good colloidal stability under conditions of a wide pH range and high salt concentration. Rheological tests showed that the emulsions exhibited shear-thinning behavior and predominantly elastic gel properties, reflecting the dense interfacial structure. Furthermore, the composite particles significantly improved the encapsulation efficiency of resveratrol (86.5 %) and enhanced its antioxidant capacity. As a resveratrol-loaded emulsion system, the Pickering emulsion stabilized by Zein-PPI reduced the release rate of free fatty acid (FFA) in in vitro digestion to less than 6 %, and increased the bioaccessibility to more than 40 %. Moreover, the Pickering emulsion stabilized by Zein-PPI was superior to the emulsion stabilized by Zein and PPI in terms of sustained release, anti-ultraviolet stability and simulated gastrointestinal digestion. In summary, zein-PPI composite nanoparticles present a promising platform for the development of stable, lipid-soluble bioactive delivery systems in functional food applications.