Evaluation of Essential Plant Oils for Controlling Pathogens on Fresh Produce and Enhancing Human Health

NON-TECHNICAL SUMMARY: Although the public interest for nutraceuticals and natural antimicrobials derived from herbs and plants is growing around the world, the lack of scientific data on herbs and plants makes it difficult to determine both the validity of their effects and mechanisms of action. Due to limited data concerning the efficacy of herbs and plants, more detail antimicrobial and mechanistic studies are warranted. Of the medicinal plants widely used in the folk medicine around the world, Laurus nobilis, Pelargonium capitatum, Artimisia herba alba, and Rosa canina have been reported to have limited antibacterial, antifungal, antioxidant, anti-inflammatory, gastroprotective, hepatoprotective, cytotoxic, and anticarcinogenic activities. Although their chemical composition and activities against certain pathogens have been tested, there is limited information on their use as biopreservatives in fresh produce as well as their effects on select cancer cells. The use of antioxidant-rich essential oils as biopreservatives for produce safety and quality may also help boost intakes of antioxidants among consumers in the US. This approach is the exact opposite of the traditional use of chemical preservatives which leave harmful residues on produce and often linked to the onset of certain cancers and allergic reactions; hence, the novelty of the natural and doubly beneficial approach is used in this proposal.

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APPROACH: The essential oils of Pelargonium capitatum (PC), Laurus nobilis (LN), Artimisia herba-alba (AA) will be purchased from New Directions Aromatics. Total antioxidant capacities of the essential oils will be determined using reagent solutions (0.6M sulphuric acid, 28mM sodium phosphate and 4mM ammonium molybdate). The most effective concentration and combination of essential oils against foodborne bacteria will be determined in laboratory media. The following foodborne pathogens will be used in this study: E. coli O157:H7, L. monocytogenes, and Salmonella enterica which are commonly associated with fresh produce outbreaks in recent years. The antiproliferative activity of select essential oils will be tested against breast, colon, and liver cancer cells using the MTT assay. The mechanism of activity of essential oils against bacterial cells and cancer cells will be evaluated using the bacterial sensitization assay and human cancer pathway assay, respectively. The most effective essential oil combination will be further studied for its effectiveness against foodborne pathogens on select fresh produce (tomato, spinach, and cantaloupe). A sensory panel to test the acceptability of the most effective treatment combination/concentration of essential oils on tomato, spinach or cantaloupe will be performed by a group of 12 trained panelists. A 7-day trial to test the feasibility of using the most effective combination of essential oil to control the pathogens on fresh produce trial will be conducted with fogging/humidification of produce treated with 1) chlorinated water + UV light, 2) Chlorinated water - No UV (second level), 3) best combination of essential oil mixture + UV light (third level), and 4) best combination of essential oil mixture - No UV light (fourth level) at 8degrees C.