ANTIMICROBIAL, PHYSICAL AND MECHANICAL PROPERTIES OF CHITOSAN-BASED FILMS INCORPORATED WITH THYME, CLOVE AND CINNAMON ESSENTIAL OILS

Chitosan-based films containing thyme, clove 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 containing thyme essential oil revealed larger inhibition zones than those containing clove and cinnamon essential oils against gram-positive and gram-negative bacteria tested. Films were more effective against gram-positive bacteria than gram-negative. Incorporating thyme and clove essential oils into chitosan-based films increased moisture content (from 17.80-28.38%), solubility in water (25.97-30.62%), water vapor transmission rate (0.00233-0.00571 g/s/m2) and elongation at break (25.31-42.70%) of films. Cinnamon-enriched films had opposite changes such as increase in tensile strength (from 12.2-21.35 MPa) and decrease in moisture content (17.80-9.36%) and solubility in water (25.9-14.21%) of films. PRACTICAL APPLICATIONS Microbial growth on food surfaces is a major cause of food spoilage. Combining antimicrobial agents such as plant essential oils directly into a food packaging polymer is a form of active packaging. These films possess the potential for improving microbial stability of foods by acting on the food surface upon contact. Because of the effect of direct addition of plant essential oils to food on sensory characteristics of packaged food, incorporation of essential oils into films may have additional applications in food packaging.