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Food Microbiol. 2015 May;47:69-73. doi: 10.1016/j.fm.2014.11.007. Epub 2014 Nov 26.

Application of an oregano oil nanoemulsion to the control of foodborne bacteria on fresh lettuce.

Author information

1
Department of Nutrition and Food Science, Wayne State University, Detroit, MI, USA; Department of Human Environmental Sciences, University of Central Oklahoma, Edmond, OK, USA.
2
Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, MI, USA.
3
Department of Nutrition and Food Science, Wayne State University, Detroit, MI, USA. Electronic address: yifanzhang@wayne.edu.

Abstract

Although antimicrobial activities of plant essential oils are well documented, challenges remain as to their application in fresh produce due to the hydrophobic nature of essential oils. Oregano oil nanoemulsions were formulated with a food-grade emulsifier and evaluated for their efficacy in inactivating the growth of foodborne bacteria on fresh lettuce. Lettuce was artificially inoculated with Listeria monocytogenes, Salmonella Typhimurium and Escherichia coli O157:H7, followed by a one-minute dipping in oregano oil nanoemulsions (0.05% or 0.1%). Samples were stored at 4 °C and enumerated for bacteria at fixed intervals (0 h, 3 h, 24 h, and 72 h). Compared to control, 0.05% nanoemulsion showed an up to 3.44, 2.31, and 3.05 log CFU/g reductions in L. monocytogenes, S. Typhimurium, and E. coli O157:H7, respectively. Up to 3.57, 3.26, and 3.35 log CFU/g reductions were observed on the same bacteria by the 0.1% treatment. Scanning Electron Microscopy (SEM) demonstrated disrupted bacterial membranes due to the oregano oil treatment. The data suggest that applying oregano oil nanoemulsions to fresh produce may be an effective antimicrobial control strategy.

KEYWORDS:

Foodborne bacteria; Lettuce; Nanoemulsion; Oregano

PMID:
25583339
DOI:
10.1016/j.fm.2014.11.007
[Indexed for MEDLINE]

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