Pickering emulsions stabilized by zein–gallic acid composite nanoparticles: Impact of covalent or non-covalent interactions on storage stability, lipid oxidation and digestibility

Studies have shown that covalent and non-covalent zein-polyphenol complexes exhibit significant differences in structure and properties, but their effects on the characteristics of Pickering emulsions are still unclear. In this study, zein nanoparticles (ZNPs), non-covalent (N-ZGANPs) and covalent (C-ZGANPs) zein-gallic acid nanoparticles were fabricated to investigate the influence of complexation types on the properties of an algal oil-in-water Pickering emulsion. Results indicated that the addition of gallic acid was associated with the decrease of interfacial tension of particles. C-ZGANPs possessed the strongest interfacial adsorption capacity, which contributed to the optimum physical stability of the covalent emulsion during storage. The rheological experiment demonstrated that C-ZGANPs decreased the viscoelasticity of the emulsion, while N-ZGANPs showed the opposite effect. Moreover, the emulsions stabilized by C-ZGANPs significantly delayed the oxidation of the encapsulated algal oil, protected astaxanthin (AST) from heat, as well as increased the bioaccessibility of AST in simulated digestion.