Ion-shielded emulsions enabling salt stability and synergistic pH-responsive release for high-salinity food preservation

The proliferation of halophilic bacteria severely shortens the shelf life of high-salt foods. However, in emulsion-based active packaging systems, abundant salt ions can readily destabilize the emulsion structure through ionic complexation, resulting in the burst release of active agents and ultimately weakening preservation efficiency. Here we reported an ion-shielding strategy for salt-resistant emulsions in which tea polyphenol-grafted sodium polyacrylate (PNa@TP) forms robust interfacial stabilizing shell, while curcumin (Cur) serves as an active model. Molecular dynamics simulations showed that hydrophobic aromatic rings of tea polyphenol (TP) assemble into continuous hydrophobic domains at the oil–water interface, effectively preventing hydrated ions from approaching and disrupting interfacial structure. Consequently, PNa@TP–Cur emulsions maintain a unimodal size distribution and excellent macroscopic stability for over 30 days under high-salinity conditions up to 2.0 M in NaCl, KCl, and CaCl 2 solutions, whereas pristine PNa emulsions undergo rapid phase separation within 24 h. Moreover, reversible interactions between ammonia and sodium carboxylate groups dynamically modulate polymer interchain associations, enabling synergistic pH-responsive release of the encapsulated agent. As proof of concept, composite films containing these emulsions effectively extended the refrigerated shelf life of salted pork and sea shrimp during storage. This work establishes a general ion-shielding design paradigm for emulsion-based smart materials operating in high-ionic-strength environments.