pH-Responsive Dual-Network PVA Films Integrating CNC-Stabilized Mosla chinensis Essential Oil Emulsions for Active Food Packaging

This study developed a pH-responsive dual-network polyvinyl alcohol (PVA) active packaging film by integrating cellulose nanocrystal (CNC)-stabilizedMosla chinensisessential oil (EO) emulsions with a tannic acid–Fe3+metal–phenolic network (MPN). The CNC-stabilized emulsion improved EO dispersion and retention in the PVA matrix and contributed to network reinforcement through hydrogen-bonding interactions, while the dynamic MPN further strengthened the film structure and acted as a pH-gated domain for regulating EO release. Composite film achieved high UVA and UVB blocking efficiencies of 90.06% and 99.60%, respectively, together with improved mechanical, barrier, antioxidant, and antibacterial properties. Compared with neutral conditions (pH = 7), EO release increased by 179.9% and 181.3% at pH = 4 and pH = 9, respectively, confirming the pH-gated release behavior of the film. In yam preservation, composite film effectively delayed browning, weight loss, firmness decline, and spoilage. Metabolomic analysis further indicated that the film treatment regulated phenylpropanoid metabolism and flavonoid biosynthesis, which may contribute to maintaining antioxidant-related metabolic homeostasis. This work offers a pH-responsive controlled-release active packaging strategy for browning-prone fresh produce.