Abstract
This study compared the antimicrobial activity of several essential oils (EOs) vapor against food spoilage microbiota and further investigated the potential of EO vapor in extending the shelf life of leafy green vegetables. Oregano EO vapor showed stronger antimicrobial activities than basil and clove EO vapors against common spoilage-causing microorganisms in fresh produce, including Pantoea agglomerans, Pseudomonas cichorii, Pectobacterium carotovorum, Pantoea ananatis, Pseudomonas marginalis, Alterneria bassicicola, and Botrytis cinerea. When oregano EO vapor was applied to leafy greens, phytotoxic effects were observed on butter lettuce and iceberg lettuce but not on kai lan and kale. On the contrary, the green color and total chlorophylls of kai lan were preserved by oregano EO vapor. With the use of oregano EO vapor generated by 10 µL oregano EO in a 1.8-L container, the shelf life of kai lan extended from 3 days to at least 7 days when stored at 25°C and from 5 days to at least 14 days when stored at 7°C. The antimicrobial effect was studied with the plating counting method to reflect the dose-dependent amicrobial effect of oregano EO vapor on kai lan. High-throughput 16S/18S DNA sequencing method was applied to evaluate the microbial ecological changes of kai lan under oregano EO vapor treatment. Taken together, our results suggest that oregano EO vapor could be used to extend the shelf life of kai lan. However, the dose of usage must be optimized with care, and one must realize the effectiveness might vary essentially when applying the EO vapor on other types of leafy green vegetables.