Enhancement of food shelf life with polyvinyl alcohol-chitosan nanocomposite films from bioactive  Eucalyptus leaf extracts

Polyvinyl alcohol-chitosan (PVA–CH) films containing biogenic silver nanoparticles were prepared using solvent casting and particulate leaching. The films were characterized for structural, thermal, mechanical, and physical properties. Antimicrobial and antioxidant activities of the films were measured. The FTIR and XRD analysis showed that addition of Ag nanoparticles did not alter the structure of the PVA–CH films. Thermal analysis of the films showed that PVA–CH/Ag nanoparticles films were thermally stable. The thickness and contact angles showed significant difference after the addition of Ag nanoparticles (p < 0.05). Antimicrobial activity of PVA–CH/Ag nanoparticles (1:1) films showed bactericidal effects against important foodborne pathogenic bacteria ( Escherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus ), with >99.9% reduction. Antioxidant activities suggested an increased concentration–dependent free radical scavenging activity. In addition, PVA–CH/Ag nanoparticles showed first order release with Fickian diffusion and were non-toxic to Caco-2 cells at 1 mg/mL. The results suggested that addition of Ag nanoparticles did not alter the properties of the film, but rather increased its antimicrobial and antioxidant properties. Thus, this environmentally friendly packaging material may be able to be used to extend shelf life.