Degradation investigation and active packaging performance of cross-linked chitosan film containing gallic acid†

We report the fabrication and analysis of a vanillin cross-linked chitosan film containing gallic acid as the active component. The active packaging material was found to successfully block 100% of UV light and had good water vapour barrier properties. Cross-linking via Schiff base formation reduced the water solubility and moisture content of the chitosan films and improved tensile properties, with a force at break measured as 29.4 ± 0.5 N. The material performed well in thermal testing, and we evaluated a glass transition temperature of 274.0 °C. We determined the successful controlled release of gallic acid from the composite film using UV-visible spectroscopy over 2 weeks. The material had strong antioxidant and antimicrobial capacities, reducing >98% of 2,2-diphenyl-1-picrylhydrazyl radicals and inhibiting the growth of both E. coli and S. aureus. We investigated the degradation of this biopolymer film in different environments including soil, compost, seawater, UV-light and water. The material reached over 90% degradation in soil within 12 weeks, rising to complete degradation after 24 weeks. We also investigated the potential mechanism for the degradation of the chitosan films, showing the effect of moisture and microbial availability in soil, and the related cleavage of the chitosan backbone via fragmentation. We determined improved degradation when the active components were released into solution before testing. Overall, the film has good physiochemical properties, strong antioxidant and antimicrobial activity and excellent degradation properties. Thus, the presented material is a strong candidate for future development of sustainable active packaging materials.