Construction of egg white peptide assembly regulated by metal-phenolic networks: mechanistic insights into the stabilization of emulsion

Emulsion systems are of critical importance in the food industry, yet their thermodynamic instability leads to issues like coalescence, sedimentation, and lipid oxidation. While egg white peptides (EWP) possess potential as emulsifying agents, their inherent shortcomings, including a small molecular size and limited steric bulk, restrict their capacity for interfacial adsorption and functional performance. To overcome these limitations, this study constructed EWP assemblies regulated by a metal-phenolic network (MPN) formed from zinc ions (Zn2+) and quercetin (Que), and systematically investigated the emulsion stabilization mechanism. EWP (E1), Zn2+-EWP (E2), Que-EWP (E3), and Zn2+-Que-EWP (E4) assemblies were synthesized via anti-solvent co-precipitation. The introduction of the MPN profoundly modified their colloid properties, with E4 exhibiting an enlarged particle size (270 nm), a lower zeta potential (−12 mV), heightened surface hydrophobicity, and the formation of a β-sheet-dominated, ordered architecture. The E4 assembly exhibited the highest radical scavenging activity (DPPH, 74.2%; ABTS, 64.3%) and superior emulsifying performance (emulsifying activity index (EAI), emulsion stability index (ESI)). The E4-stabilized emulsion exhibited uniform droplets and exceptional stability (creaming index (CI) = 0) under various storage conditions, thermal treatment, freeze–thaw cycles, and a wide range of pH and ionic conditions. In vitro digestion revealed that the MPN interfacial film slowed pepsin hydrolysis, thereby modulating the release of amino acids. The study presents a systematic approach to creating peptide-based emulsions with enhanced stability and improved antioxidant properties.