Novel colloidal particles and natural small molecular surfactants co-stabilized Pickering emulsions with hierarchical interfacial structure: Enhanced stability and controllable lipolysis

Particle-stabilized Pickering emulsions pose several challenges to scientists researching food delivery systems. This study investigated Pickering emulsions co-stabilized by zein-propylene glycol alginate composite nanoparticles (size: 416.4 ± 8.5 nm) and rhamnolipid, quillaja saponin and tea saponin (0.01-1.00%, w/v). The results showed that different types and concentrations of natural small molecular surfactants (NSMS) had an important influence on the stability, microstructure and rheological properties of the Pickering emulsions. The surfactants were able to not only diffuse into the interfacial gaps but also adsorb onto the surface of particles to modulate the interfacial wettability, which was dependent on their types and concentrations. The negatively charged surfactants endowed the droplets with electrostatic repulsion and steric hinderance to prevent their flocculation and coalescence. In vitro digestion fate demonstrated that the presence of natural surfactants delayed the lipid digestion of the Pickering emulsions in the small intestine, particularly by decreasing the release rate of free fatty acids from 57.37% to 10.76% and 7.84% with the addition of quillaja saponin and tea saponin, respectively. The combination of nanoparticles and individual surfactants at the intermediate concentration (0.50%, w/v) exerted a synergistic effect on stabilizing the Pickering emulsions and inhibited lipolysis in the gastrointestinal tract, exhibiting potential applications as a fat replacer.