Enhanced antibacterial effectiveness of essential oils vapors in low pressure environment

Due to their antimicrobial activity, essential oils (EOs) have potential to alternate conventional food preservatives. Relatively high doses of EOs necessary for microbial growth inhibition indicate that they should be used in combination with other preservation techniques rather than alone. Therefore, new combinations of preservative methods with EOs are still investigated. In our study, oregano, clove, cinnamon, and lemongrass EO vapors were tested in vitro in atmospheric and low pressure against Escherichia coli and Salmonella enteritidis at different times of treatment ranging from 5 min to 4 h. Combination of EO-low pressure shortened up to 48 times the time necessary for total inhibition of microorganism growth compared to the same treatment in atmospheric pressure. Minimal inhibitory times of EOs vapors ranged mostly from 15 to 60 min in low pressure and were equal to or more than 4 h in atmospheric pressure. Possible decrease of MICs of EOs in low pressure was also investigated. Microorganisms demonstrated increased susceptibility to oregano, lemongrass and cinnamon EOs in low pressure e.g. the MIC of cinnamon vapors for S. enteritidis decreased from 512 μL/L to 128 μL/L.