Preparation and characterization of photothermal-responsive CNC/chitosan composite films loaded with active ingredient nanoparticles from Ziziphus Spinosae Semen

Conventional passive packaging and petroleum-based materials face challenges of insufficient responsiveness and environmental pollution, while existing intelligent packaging lacks sufficient mechanical strength and inherent antibacterial and antioxidant functions. To address these issues and valorize agricultural waste, this study developed a photothermal-responsive composite packaging film. Ziziphi Spinosae Semen (ZSS) active extracts (flavonoids, saponins) were loaded into CaCO 3 -Polydopamine (PDA) Nanoparticles (NPs), and cellulose nanocrystals (CNC) were prepared from Ziziphi Spinosae pomace via acid hydrolysis. PDA/CNC/chitosan (CS) composite films were fabricated by solvent-casting with CS as the matrix. The optimal 4 % CNC loading enhanced CS film tensile strength by 145 % via hydrogen bonding. CaCO 3 -PDA NPs exhibited superior loading capacity (flavonoids:34.26 %, saponins:26.79 %) and pH-responsive sustained release. The 5 % CaCO 3 -PDA@ZSS-loaded film achieved a 77.0℃ temperature increase within 30 s under near-infrared irradiation, enabling 100 % antibacterial efficiency against Escherichia coli and Staphylococcus aureus. It also showed strong antioxidant activity (DPPH:72.88 %, ABTS:81.89 %) and improved water vapor barrier properties. Applied to strawberry preservation, the film extended shelf life from 2 to 10 days and exhibited good biodegradability. This work provides a sustainable strategy for multifunctional intelligent fresh food packaging.