Studies on physical, mechanical, antibacterial and microstructural properties of chitosan edible films containing thyme and cinnamon essential oils

Combining antimicrobial agents directly into a food packaging is a form of active packaging. In this study chitosan-based edible films containing thyme and cinnamon essential oils at 0.5%, 1%, and 1.5% v/v were prepared to examine their antibacterial, physical and mechanical properties. Scanning electron microscopy was carried out to explain structure-property relationships. Films were more effective against gram-positive bacteria than gram-negatives. Films containing thyme essential oil revealed larger inhibition zones than those of containing cinnamon essential oil against bacteria tested. Incorporating thyme essential oil into chitosan-based films increased moisture content, solubility in water, water vapor transmission rate and elongation at break of edible films. Cinnamon-enriched films had opposite changes such as increase in tensile strength and decrease in moisture content and solubility in water. It is postulated that the unique properties of the cinnamon essential oil added films could suggest the cross-linking effect of cinnamon essential oil within the chitosan matrix. Electron microscopy images confirmed the results obtained in this study. The results of this study showed that thyme and cinnamon essential oils have a good potential for using with chitosan to make antimicrobial films and coatings for various food applications.