Biopolymeric chitosan/ZnO-nanocomposite films from pomegranate peels for sustainable and functional food packaging

Abstract

Chitosan (CS), a biopolymer derived from chitin, is well known for its biodegradability and significant antimicrobial, photocatalytic, and UV-protective properties, making it an intriguing candidate for sustainable and active food packaging solutions. In response to rising environmental concerns and the demand for sustainable food packaging, this study investigates the eco-friendly synthesis of CS-conjugated Punica granatum (PG)-derived zinc oxide nanocomposites (PG-ZnONCs) for use in food packaging applications. A quality-by-design approach was employed to identify optimal conditions that maximize the desired properties of the nanocomposite films, ensuring a robust and efficient formulation process. Nanoparticle and nanocomposite preparation was confirmed by monitoring colour change and validated by UV-visible spectroscopy. X-ray diffraction, SEM, and TEM analyses confirmed the crystallite structures of the particles, with particle sizes of 112.3 nm and 160.8 nm, polydispersity indices of 0.182 and 0.215, and zeta potentials of -21.98 mV and - 10.6 mV, indicating stability. The successful application of DOE (Design of Experiments) ensured a robust and efficient formulation process, contributing to the high-quality characteristics of the final product. PG-ZnONPs and PG-CS/ZnONCs demonstrated strong antioxidant activity, effectively scavenging radicals in DPPH and ABTS assays, and exhibited potent antibacterial effects against foodborne pathogens. The PG-CS/ZnONC films (2.5 percent, 5 percent, and 7.5 percent) exhibit excellent mechanical, thermal, and barrier properties, thereby extending the shelf life of fresh foods. Incorporating Alizarin (AZ) as a pH-responsive indicator enabled real-time freshness monitoring. The PG-7.5 percent NC film preserved Solanum lycopersicum (cherry tomatoes) for 16 days and Stolephorus indicus (Indian anchovy) for 9 days, compared to 4 days for uncoated samples. Overall, PG-CS/ZnONC films, particularly with AZ for smart monitoring, present a promising solution for sustainable food packaging, enhancing food preservation while reducing waste.