Development of citric acid-crosslinked carboxymethyl cellulose /chitosan hydrogel films reinforced with ZnO nanoparticles for active broccoli packaging

A nanocomposite hydrogel film of carboxymethyl cellulose (CMC) and chitosan (CS), crosslinked by citric acid and reinforced with zinc oxide nanoparticles (ZnO NPs), was developed for the active packaging of fresh broccoli. ZnO was incorporated at 0.5–3 wt% to improve the performance of the film. CSA18GZ3 composition (3 wt% ZnO) exhibited enhanced properties, including 48 % reduction in water vapor permeability (4.01 × 10⁻⁹ g·m⁻¹·h⁻¹·Pa⁻¹), contact angle increase to 60.43°, and tensile strength and Young's modulus improvement. Crosslinking and ZnO dispersion were confirmed by FTIR and XRD, and homogeneous morphology by SEM. Antibacterial tests revealed considerable log reductions against E. coli (2.41) and Listeria monocytogenes (5.69) within 24 h. Shelf-life tests indicated that CSA18GZ3 preserved the freshness and visual appearance of broccoli for 7 days under ambient storage, performing better than traditional polypropylene (PP) cling film packaging. The combination of biodegradability, barrier, mechanical properties, and antimicrobial performance indicates the potential of this CMC/CS/ZnO system as a promising candidate for application in sustainable active food packaging technology.