Physicochemical properties of edible oxidized gum arabic–polylysine crosslinked films and their effects on the postharvest preservation of litchi

To address the challenges of postharvest oxidation and microbial contamination in litchi fruit, this study utilized sodium periodate oxidation to synthesize oxidized gum arabic (OGA) with varying aldehyde contents as an eco-friendly crosslinking agent. Chitosan (CS) was used as the film-forming matrix, with ε-polylysine (ε-PL) and gallic acid (GAL) incorporated to construct a composite film exhibiting synergistic enhancement. FT-IR, XPS, and XRD analyses revealed that aldehyde groups in OGA covalently crosslinked with amino groups in CS/ε-PL via Schiff base reactions, forming C N bonds (accounting for 26.29 %, higher than the 21.55 % in the control group), while GAL interacted with the film materials via non-covalent hydrogen bonding. Crosslinking significantly enhanced the film’s compactness, UV-blocking ability, and stability. The maximum mechanical strength and elastic modulus of the films reached 19.25 MPa and 492.88 MPa, respectively, which were approximately two times higher than those of the control group. As the degree of crosslinking increased, the film’s water solubility, water vapor permeability, and oxygen permeability significantly decreased, while its thermal stability improved. The incorporation of GAL significantly enhanced the antioxidant capacity, with a maximum free radical scavenging rate of 56.82 % within 1 h, about 1.6 times higher than that of the control group. Antibacterial tests showed that the composite film exhibited 100 % inhibition against Escherichia coli , Staphylococcus aureus , and Pestalotiopsis litchii . Litchi preservation experiment demonstrated that the film significantly outperformed the traditional preservative prochloraz in delaying nutrient loss and inhibiting microbial growth. In conclusion, the edible crosslinked composite film developed in this study shows great potential for application in food preservation packaging.