Synergistic multi-crosslinked networks in chitosan/Gallic acid/Fe3+ composite biofilms with high UV resistance and antioxidant properties

Food spoilage leads to plenty of food being wasted every year. Safe and multifunctional food preservation packaging is urgently required to prevent food from contamination. Chitosan/gallic acid/Fe³⁺ (CSGA-Fe³⁺) composite films were synthesized by incorporating gallic acid (GA) and Fe³⁺ into a chitosan solution. The integration of GA forms covalent and hydrogen bonds with chitosan, whereas Fe³⁺ addition establishes metal-ligand interactions with both chitosan and GA, resulting in a film characterized by a multi-crosslinked network structure. This multi-crosslinked system substantially enhanced the material's mechanical properties and increased resistance to oxidation and ultraviolet degradation. The data indicate that the mechanical strength of chitosan/gallic acid (CSGA) films, with an inclusion of 0.3 mmol of GA, improved by 37.5 % over pure chitosan (CS) films. Moreover, the mechanical strength of the CSGA-Fe³⁺ films saw a significant increase of 124.2 %, escalating from 1.32 MPa to 17.72 MPa. Additionally, the free radical scavenging capacities of the CSGA and CSGA-Fe³⁺ films rose by 279.4 % and 255.0 %, respectively, compared to the pure CS film. The UV-blocking efficacy of the CSGA-Fe³⁺ films, evaluated at 365 nm, reached 84.9 %. The water contact angle of the CSGA-1.5Fe³⁺ film increased by 18.08 % compared to the CS film. This study provides innovative ideas to promote the broader application of safe and multifunctional chitosan-based composite films in food preservation packaging.