Inhibition of Listeria monocytogenes growth on fresh-cut produce with thyme essential oil and essential oil compound verbenone

• Thyme EO and verbenone are effective anti-listerial agents on melon and pineapple.
• Direct application of anti-listerial agents on fruits is more effective than dipping.
• Verbenone is maintaining a high product appearance for melon while thyme EO is not.
• EO and EO compounds on lettuce reduce product appearance beyond acceptance levels.
• Modified atmosphere packaging has limited effect on L. monocytogenes growth/survival.

The anti-listerial effectiveness of thyme essential oil (EO) and EO compounds camphor and verbenone was examined on fresh-cut lettuce, cantaloupe melon and pineapple with modified atmospheres and air in model packages at 4 and 8 °C. Listeria monocytogenes was found to be able to survive and grow in all atmospheres on melon and lettuce. However, on pineapple lowest survival was identified, presumably due to product pH. Thyme EO demonstrated the best anti-listerial effect, although direct application of the EO compromised product appearance. While camphor showed no anti-listerial effects, verbenone was found to have anti-listerial properties and maintained high sensory acceptance in fresh-cut fruit. The high growth rates of L. monocytogenes on melon were significantly reduced with the application of verbenone while being completely eliminated on pineapple. The use of thyme EO and verbenone as an antimicrobial dip was successfully applied to reduce growth of Listeria on fresh-cut melon and eliminate growth on pineapple; however growth-reduction was less pronounced in melon when compared to a conventional chlorine dip. Further research will be necessary to optimise conditions in fresh-cut produce treatments with natural products including verbenone and thyme EO to replace current chlorine treatments for improved food safety.

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