Vanillin-modified hydroxyapatite enhanced chitosan film: Preparation, characterization, and application in beef preservation.

Traditional plastic packaging materials raise environmental concerns due to their poor degradability, motivating the development of sustainable alternatives for food packaging. In this study, chitosan (CS) was used as the polymer matrix, oyster shell-derived hydroxyapatite (HAP) served as the inorganic reinforcing phase, and vanillin (VAN) was loaded onto HAP to prepare a multifunctional composite film (CS/HAP(VAN)) via the solution casting method. FTIR confirmed the successful loading of VAN onto HAP and its strong interaction with the CS matrix. SEM observations showed that HAP(VAN) was uniformly dispersed in the film without obvious phase separation. Compared with the pure CS film, the CS/HAP(VAN) composite film exhibited enhanced mechanical properties, with the tensile strength increasing from 20.16 MPa to 24.69 MPa, as well as improved thermal stability, UV-blocking ability, and water resistance. Antibacterial assays showed that the CS/HAP(VAN) film exhibited inhibition-zone diameters of 18.40 ± 0.69 mm against E. coli and 22.11 ± 0.86 mm against S. aureus, which were significantly higher than those of the CS/VAN film. Furthermore, the CS/HAP(VAN) film provided sustained VAN release and effectively delayed the increase in pH, TVC, and TVB-N during refrigerated beef storage. Based on TVC and TVB-N freshness thresholds, the beef packaged with the CS/HAP(VAN) film maintained acceptable quality for up to 14 days, whereas the CK and PE groups exceeded the spoilage limit after approximately 6-8 days.