29F-15

Microbial growth is predominant at the surface of many food products. Incorporation of essential oils (EOs) in chitosan coatings can protect ready-to-eat food form pathogen and spoilage microorganisms.

The objective of our research was to evaluate the antimicrobial effects of chitosan films enriched with essential oils against Escherichia coli O157:H7 and Listeria monocytogenes.

The films were prepared from solutions containing 1% chitosan, 1% acetic acid, 0.5% Tween20, and 1 to 4% EO (anise, basil, coriander, and oregano). The antibacterial efficiency of essential oils and chitosan-essential oil films was tested by disk diffusion method at 35°C.

L. monocytogenes was more sensitive to all essential oils, applied alone or incorporated in chitosan films, than E. coli. Inhibition activity toward both bacteria was strongest with oregano EO, followed by basil and coriander, and the weakest with anise EO. Inhibition zones of chitosan films with 40 mg EO/cm² against E. coli were 12.5, 12.9, 17.1, and 23.3 mm, and against L. monocytogenes 16.0, 16.6, 21.3, and 31.6 mm for anise, basil, coriander, and oregano EO, respectively. Inhibition activity of chitosan-essential-oil films was proportional to concentration of EO. Diameters of inhibition zones of chitosan-oregano films against L. monocytogenes were 19.1 mm and 31.6 mm for 10 and 40 mg EO/cm², respectively. Similarly, inhibition of E. coli growth increased from 15.9 mm to 23.3 mm with 10 and 40 mg oregano EO/cm² chitosan film, respectively.

Chitosan-essential oil films have potential in ensuring food safety due to local application of antimicrobials and reduced losses of active volatiles.