Synergistic Preservation of Chilled Pork Using Bilayer Films: Tea Tree Oil Pickering Emulsion as Active Core and Nano-ZnO Gelatin as Protective Barrier.

A novel bilayer active packaging film was designed for chilled pork preservation to overcome the limitations of single-layer matrices. The inner food-contact layer comprised a chitosan matrix incorporating a tea tree oil (TTEO) Pickering emulsion to achieve sustained release of active agents. The outer layer consisted of gelatin embedded with zinc oxide nanoparticles (ZnO NPs) to provide external barrier properties. This study systematically compared the structural and functional differences between the layer-by-layer casting method and traditional blending while optimizing the ZnO NP concentration. Results demonstrated that the layer-by-layer casting successfully generated a distinct structural interface, significantly improving the mechanical robustness and light-blocking capacity compared to blended films. The optimized bilayer film (loaded with 0.4% ZnO NPs) exhibited synergistic antibacterial and antioxidant effects. During chilled pork storage trials, this tailored bilayer structure effectively suppressed microbial proliferation and slowed lipid oxidation, reducing TBARS values by approximately 80% on Day 6 relative to the control. Consequently, the shelf life of chilled pork was safely extended to 6 days. This study offers a practical and structurally optimized biopolymer packaging strategy for the preservation of perishable meat products. PRACTICAL APPLICATIONS: This optimized bilayer active film provides an eco-friendly packaging alternative for chilled pork. The layer-by-layer construction achieves controlled release of tea tree oil Pickering emulsion combined with zinc oxide nanoparticles, suppressing microbial reproduction and lipid oxidation of chilled pork and extending its shelf life. The fabrication approach is easy to implement, and the developed biopolymer film is suitable for fresh meat retail packaging. This work facilitates the industrial development of sustainable active packaging to lower postharvest losses of perishable meat products.