Development of Chitosan Nanocomposite Films Reinforced with Metal Oxides and Lignin Derivatives for Sustainable Food Packaging

The development of sustainable packaging materials with advanced functional properties is a key priority for the food industry. In this study, chitosan (CS)-based nanocomposite films incorporating titanium dioxide (TiO2), zinc oxide (ZnO), hybrid ZnO_TiO2 nanoparticles, lignin (LG), and nanolignin (nLG) were synthesized and comprehensively characterized. Structural analyses (FTIR, XRD, SEM) confirmed strong intermolecular interactions and homogeneous nanoparticle dispersion, particularly for TiO2 and low ZnO concentrations. Mechanical testing showed that TiO2 and ZnO significantly enhanced tensile strength (up to fourfold) and elongation at break. Among the prepared nanocomposite films, CS-TiO2 films at 2 wt% exhibited the best balance of mechanical performance and antioxidant activity. Subsequent incorporation of LG and especially nLG into the CS-TiO2 matrix further enhanced flexibility and toughness, antioxidant efficiency, and radical-scavenging activity above 90%, and improved UV-shielding capacity by reducing light transmittance. Moreover, antibacterial testing against Escherichia coli demonstrated that CS/TiO2/nLG films achieved the highest reduction (~46%), attributed to synergistic electrostatic, oxidative, and phenolic mechanisms. Overall, CS/TiO2/nLG nanocomposites emerge as multifunctional, biodegradable films with significant potential for next-generation active food packaging applications.