Valorizing agricultural waste into sustainable active food packaging: Preparation of chitosan-based film incorporating bioactive extract and lignin nanoparticles from green walnut husks

The extensive use of petroleum-based plastics in food packaging has contributed to escalating environmental pollution and the persistent accumulation of microplastics, driving the development of sustainable and biodegradable alternatives. In this study, an active chitosan (CS)-based film was developed by incorporating a polyphenol-rich extract (GWHE) and lignin nanoparticles (LNPs), both valorized from green walnut husk waste, into the CS matrix. The synergistic interaction between GWHE and LNP effectively densified the polymer network by enhancing intermolecular interactions, thereby significantly improving the structural integrity and physicochemical properties of CS films. The optimized composite film (CS/GWHE/LNPs-5 %) exhibited 100 % UV-shielding, a 159.13 % increase in tensile strength, and significant reductions in water vapor permeability (51.47 %), oxygen permeability (55.93 %), and water solubility (49.18 %) compared to pure CS. Additionally, the film displayed potent antioxidant activity (ABTS and DPPH radical scavenging >95 %) and strong antibacterial activity against S. aureus and E. coli (>90 % inhibition), while maintaining excellent biodegradability and biosafety. Practical application to fresh walnut kernels demonstrated that the film effectively mitigated moisture loss, suppressed lipid oxidation, and inhibited microbial spoilage during room-temperature storage, thereby prolonging shelf-life to 15 days. Overall, this work offers a sustainable strategy for developing active food packaging while promoting the high-value utilization of agricultural waste and advancing circular bioeconomy development.