Abstract: In order to develop a new biodegradable antimicrobial packaging material, four typical essential oils including oregano oil, thyme oil, rosemary oil and cinnamon oil were screened for antimicrobial activity, and we investigated the effect of incorporating different concentrations of cinnamon oil on mechanical, optical and antimicrobial properties and water vapor permeability of composite films prepared using corn starch, chitosan and konjac glucomannan (KGM) as film forming materials, glycerol as a plasticizer and Tween-80 as a surfactant. The antibacterial activity against Staphylococcus aureus, Escherichia coli and Salmonella enterica of the essential oils was in the descending order of cinnamon oil > oregano oil > thyme oil > rosemary oil. Tensile strength (TS) and water vapor permeability of composite films decreased, while elongation at break (EAB) and opacity increased with the increase of cinnamon oil. The color parameter a* value did not vary significantly (P > 0.05), whereas L* value significantly decreased and b* and ΔE values significantly increased with increasing cinnamon oil concentration from 15.0 to 20.0 g/L (P < 0.05). The antimicrobial properties of composite films were improved significantly with the incorporation of cinnamon oil (P < 0.05). The combination of Tween-80 and cinnamon oil demonstrated synergistic antimicrobial activity against Gram-negative E. coli, while an antagonistic effect against Gram-positive S. aureus was observed. The film with 20.0 g/L cinnamon oil had good physical and antimicrobial properties. However, further studies are needed to optimize the preparation of biodegradable antimicrobial cinnamon oil/corn starch-based films.

Key words: composite film, corn starch, cinnamon essential oil, physical properties, antibacterial activity