Chitosan-Based Composite Films Reinforced with Zein–Inulin–Thyme Essential Oil Pickering Emulsion for Enhanced Structural Integrity and Preservation Capacity

Herein, zein-inulin-stabilized thyme essential oil (TEO) Pickering emulsions were prepared via ultrasonication. The addition of inulin (0.12-0.5%) enhanced emulsion stability and antibacterial activity, with particle sizes ranging from 73.7 to 789.8 nm. Chitosan (CS) composite films were then fabricated using different TEO loading methods. Films incorporating Pickering emulsions exhibited denser and smoother structures due to hydrogen bonding between the emulsion and chitosan matrix, while electrostatic interactions between zein and inulin enabled effective TEO encapsulation. Compared to the pure CS film, the Pickering emulsion active films exhibited improved thermal stability, with a maximum decomposition temperature of 260 °C, blocked up to 82.22% of UV light in the UVA region (320-400 nm), displayed increased hydrophobicity (maximum water contact angle of 75.70°), and showed the strongest scavenging activity toward both DPPH (93.27%) and ABTS (98.42%). Moreover, these films effectively reduced weight loss, minimized firmness decline, suppressed pH increase, and inhibited microbial growth, thereby delaying blueberry spoilage. Based on the appearance and total soluble solids content of blueberries, the chitosan Pickering emulsion (containing 0.25% inulin) film (type VI) presented the best preservation performance among the eight tested films. This study highlights the potential of chitosan-based Pickering emulsion active films for food packaging applications.