Preparation of citric acid cross-linked chitosan quaternary phosphonium/polyvinyl alcohol composite film and its application in strawberry preservation

Chitosan quaternary phosphine salts (NPCS) were synthesized with enhanced antimicrobial properties using a two-step method. Composite films (CNSP) were prepared by incorporating NPCS and polyvinyl alcohol (PVA) as the base material, citric acid as the crosslinker and functional additive, exhibiting antibacterial and UV-blocking properties. The composite film showed a maximum tensile strength of 20.4 MPa, an elongation at break of 677%, and a UV light barrier transmittance of 70%. Application of these composite membranes in preserving strawberries demonstrated effectiveness in maintaining freshness by preventing water loss, inhibiting microbial growth , and extending shelf life. In addition, the composite film demonstrated biosafety. These results indicate that CNSP composite films holds significant promise for safe and sustainable food packaging applications.