Emulsions co-stabilized by Polygonatum sibiricum saponin and soy protein isolate: Physical stability, interaction mechanism, interface behavior

This study investigates the interaction mechanism between Polygonatum sibiricum saponin (PSS) and soy protein isolate (SPI) to enhance the stability of oil-in-water emulsions, laying the foundation for an efficient PSS delivery system. Initially, we evaluated the stability of oil-in-water emulsions with various PSS concentrations (0.1%, 0.2%, 0.3%, 0.5%, and 1% w/w). Results indicated that PSS enhances emulsion stability by increasing absolute zeta potential, reducing average particle size, and improving resistance to external factors. Notably, concentrations of 0.3%, 0.5%, and 1% (w/w) PSS show significant improvements in emulsion stability (p < 0.05). Subsequently, we elucidated the mechanism by which PSS enhances stability. Our findings reveal that PSS interacts with SPI, inducing structural modifications in SPI and expanding its hydrophobic regions. Additionally, PSS forms SPI-PSS complexes through hydrogen bonding with aromatic amino acid residues in SPI, thereby reducing interfacial tension and maintaining stable viscoelasticity. Comparative analysis of Lissajous plots identifies the optimal PSS to SPI ratio as 0.3% (w/w) each, resulting in a resilient interface film formed by numerous SPI-PSS complexes capable of withstanding compression or extension. Overall, our study underscores the efficacy of PSS in navigating the emulsion system and collaborating with SPI to stabilize emulsions. • PSS and SPI demonstrated a synergistic effect in enhancing emulsion stability. • SPI-PSS reduced interfacial tension and maintain interface viscoelasticity. • The SPI-PSS interface film showed strong resistance to deformation.