Fabrication and characterization of double-layer active intelligent film based on chitosan, polyvinyl alcohol, grape skin anthocyanin and selenium nanoparticle

This study involved the fabrication of double-layer intelligent films using chitosan (CS), polyvinyl alcohol (PVA), grape skin anthocyanin (GSA), gellan gum (GG) and selenium nanoparticles (SeNPs). The CS/PVA/GSA layer functioned as the internal indicator layer, and the GG/SeNPs layer acted as the external layer for antioxidant and antimicrobial purposes. SEM, FTIR, XRD, and TGA results confirmed the successful fabrication of double-layer films as well as the presence of hydrogen bonding interaction between the two layers. The tensile strength of double-layer films (8.06 MPa-9.61 MPa) fallen between that of single-layer CS/PVA/GSA film (12.51 MPa) and GG/SeNPs film (1.50 MPa-7.67 MPa). The double-layer films demonstrated good UV-blocking abilities, as well as outstanding antioxidant (ABTS scavenging rate can be up to ~80 %) and antimicrobial properties. Compared with single-layer CS/PVA/GSA film, the double-layer film incorporated with 6.6 wt% SeNPs (CPG/GS2 film) possessed a more rapid and stronger response towards NH₃/acetic acid as well as enhanced storage stability. Furthermore, the CPG/GS2 film can increase the shelf life of strawberries at 25 °C by 4 days, and its visible color change showed strong correlation with the weight loss rate (R² = 0.99) and hardness (R² = 0.98) of strawberries.