Zein-EGCG‑sodium alginate conjugates with tunable interfacial properties for improved stability and antioxidant performance of walnut oil emulsions

Designing food-grade emulsifiers with enhanced interfacial properties and functional activities is key to improving walnut oil-in-water emulsion stability and oxidation resistance. This study used zein, epigallocatechin gallate (EGCG), and sodium alginate (SA) to construct binary/ternary emulsifiers with different compositions and bonding modes. An oil-to-water ratio of 2:8 was optimized for minimal droplet size. Emulsions stabilized by zein-EGCG-SA conjugates exhibited the greatest interfacial thickness (732 nm) and highest protein adsorption rate, resulting in superior stability against thermal treatment (85°C, 30 min), salt stress (200 mM NaCl), and freeze-thaw (-18°C and -80°C, 24 h) compared to other formulations. These improvements were attributed to the formation of a denser interfacial layer that provided enhanced steric and electrostatic stabilization. Moreover, the ternary conjugates significantly inhibited lipid oxidation through a synergistic mechanism involving inherent antioxidant activity, physical barrier formation, and metal ion chelation. This work shows multi-component emulsifier design modulates interfacial architecture and functionality for nutraceutical applications.