Date Available


Year of Publication


Degree Name

Master of Science (MS)

Document Type

Master's Thesis




Animal Science

First Advisor

Dr. Gregg Rentfrow


This study explored the in vitro and in situ antilisterial inhibitory activity of 16 essential oils during indirect exposure: Spanish Basil oil (Ocimum basilicum), Bay oil (Pimenta racemosa), Italian Bergamot oil (Citrus bergamia), Roman Chamomile oil (Anthemis nobilis), Sir Lanka Cinnamon oil (Cinnamomum zeylanicum), Citral, Clove Bud oil (Syzygium aromaticum), Cumin Seed oil (cuminum cyminum), Eucalyptus oil (Eucalyptus globulus), Eugenol, Geranium extract (Pelargonium graveolens), Marjoram oil (Origanum majorana), Neroli extract (Citrus aurantium), Peppermint oil (Mentha piperita L.), Rosemary oil (Rosmarinus officinalis L.),and Spanish Sage oil (Salvia officinalis L.). All essential oils were tested against Listeria monocytogenes (ATCC 4644). In vitro inhibitory activity was determined using the microatmosphere method at three temperatures (37°C, 24°C, 4°C) and six possible volumes (0, 10µl, 25µl, 50µl, 100µl, 150µl, or 200µl). In situ inhibitory activity was determined using inoculated bologna slices packaged in Modified Atmosphere Packaging (80% O2, 20% CO2). Essential oils (0, 0.13ml, 1.35ml, or 2.70ml) were injected into the sample packages adjacent, but not touching, the bologna slices and stored at 24°C for 24h. Basil oil displayed the least antilisterial activity across the three temperature applications in vitro. Peppermint, Cumin Seed, and Citral consistently exhibited the greatest antilisterial activity among the temperature applications in vitro. However, only Eugenol applied at 1.35ml achieved a mean one log10 CFU/ml reduction in LM in situ, which could not be replicated. Peppermint (P < 0.048) displayed significant differences between application volumes (0.13ml, 1.35ml) but did not attain a mean one log10 CFU/ml reduction in LM. This study suggests that while various essential oils can display antilisterial activity in vitro, transitioning into a MAP food system warrants further research in mode of actions and application volumes.