Antimicrobial biodegradable film based on corn starch/ <i>Satureja khuzestanica</i> essential oil/Ag–TiO ₂ nanocomposites

Abstract

Biosynthesis of nanoparticles (NPs) using plant extract is an eco-friendly method, in which natural materials are used and is a simple, non-toxic, and environmentally friendly green synthesis. In this study, corn starch (CS) film containing<i>Satureja khuzestanica</i>essential oil (SEO) and Ag-TiO₂nanocomposites (size: nearly 30-60 nm) were prepared and its antimicrobial, morphological, physical, and mechanical characteristics were investigated. Ag-TiO₂nanocomposites with different molar percentages were synthesized by<i>S. khuzestanica</i>extract and based on the best antibacterial results against Gram-negative bacteria (<i>Escherichia coli</i>ATCC 25922 and<i>Salmonella typhimurium</i>ATCC 14028) and Gram-positive bacteria (<i>Staphylococcus aureus</i>ATCC 25923), were chosen to prepare the films. Four types of biodegradable films were provided: simple CS film, the film incorporated with SEO (essence film), the film incorporated with Ag-TiO₂nanocomposites (nanofilm), and nano/essence film. The scanning electron microscopy (SEM) was employed for investigating the morphology of the films. The combined energy-dispersive x-ray spectroscopy with SEM was applied to analyze the near-surface elements. Physical characteristics of the films containing water vapor permeability (%) and their moisture content, mechanical tests, and antibacterial properties were examined. Antimicrobial evaluation of the films revealed a 3-4 log and 6-7 log (CFU ml^-1) reduction in<i>S. aureus</i>and<i>E. coli</i>species respectively, compared to the control group. The bio-polymer film incorporated with extracted essential oil of<i>S. khuzestanica</i>and Ag-TiO₂nanocomposites are effective to package foods and can delay chemical, physical, and microbial spoilage.