Researchers at Wayne State University in the USA have been investigating the use of nanoemulsions of antimicrobial essential oils from plants as an alternative to chlorinated water for decontaminating fresh produce.
The research team looked at essential oils from plants such thyme, oregano and clove as natural antimicrobials that could potentially reduce levels of bacterial contamination on the surface of fruits and vegetables. However practical applications for these oils are limited by their low solubility and immiscibility in water.
They therefore examined the possibility of formulating nanoemulsions as a more effective delivery system for antimicrobial oils. Experiments to evaluate the idea were carried out by dipping fresh lettuce inoculated with Listeria monocytogenes, Salmonella Typhimurium and E. coli O157:H7 in 0.05% and 0.1% oregano oil nanoemulsions for one minute.
The results showed significant reductions (2.31 – 3.57 log CFU/g) of all three pathogens even at the lower concentration and examination by scanning electron microscopy revealed disrupted bacterial membranes after treatment with the nanoemulsion.
The Wayne State researchers suggest that their study shows that essential oil nanoemulsions are a possible alternative to traditional chemical decontaminants for fresh produce. They now plan to investigate combinations of different oils and determine the minimum quantities that would be needed for effective treatment.
A report of this work is published in the journal Food Microbiology and an abstract can be found here.