Development of Gracilaria vermiculophylla extract films containing zinc oxide nanoparticles and their application in smoked salmon packaging

Films were prepared using extracts of Gracilaria vermiculophylla (GVE). Equal amounts of glycerol and sorbitol were added as plasticizers, and zinc oxide nanoparticles (ZnONPs) were added to prepare the antibacterial films. Physical and optical properties, ultraviolet (UV) light barrier, scanning electron microscopy (SEM) analysis, and antibacterial activity of the films were evaluated, and the films were then applied as a packaging material for smoked salmon. As the content of ZnONPs increased, the tensile strength increased, whereas the elongation at break decreased. The UV-visible light transmittance was decreased by the addition of ZnONPs. Viable cell counting indicated that the antimicrobial activity of the films increased with increasing ZnONPs content. After 9 h, the population of Listeria monocytogenes and Salmonella Typhimurium decreased by 4.99 and 5.08 log CFU/mL for the films containing 5% ZnONPs, respectively, compared to the films without ZnONPs. Smoked salmon packaged with the GVE films containing 3% ZnONPs resulted in increased antibacterial activity against L. monocytogenes and S. Typhimurium compared with the control during storage, as well as a low degree of lipid oxidation. Therefore, these results indicate that the GVE films containing ZnONPs have potential as an active food packaging material to maintain the quality of smoked salmon.