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Susceptibility of Escherichia Coli O157:h7, Salmonella Enterica Sp., and Listeria Monocytogenes to Antimicrobial Mixed Micelle Delivery Systems

Within the food industry, there is an ever increasing demand to improve the quality of food and ensure safety from pathogenic/spoilage microorganisms. Globalization of the food industry in the 1990’s, in conjunction with the worldwide shipment of food created a need for the extension of shelf-life and enhanced maintenance of food quality (12). In the United States alone, the Centers for Disease Control and Prevention report that each year, roughly 1 in 6 Americans (or 48 million people) gets sick, 128,000 are hospitalized, and 3,000 die of foodborne diseases; this correlates to approximately $77.7 billion in economic loss annually (17). Thus the demand for innovative techniques to reduce or eliminate the unintentional presence of microorganisms in food products has increased. Na-Lauroyl-L-arginine ethyl ester monohydrochloride (lauric arginate (LAE)) is a cationic surfactant possessing antimicrobial ability against the proliferation of several microorganisms including bacteria, fungi, and yeasts (58). Composed of lauric acid, Larginine, and ethanol, LAE is active over a wide pH range (3-7), and the antimicrobial properties have been reported to be derived from its action on the cytoplasmic membranes of microorganisms (58). Although LAE is an ideal antimicrobial its usage in the food industry is limited due to its instability. LAE tends to precipitate from solutions at non-acid pH (pH >4.5) as well as in the presence of solutions with high ionic strength (4). Previous research has shown that the tendency for LAE to precipitate in aqueous solutions can be overcome by combining LAE with a non-ionic surfactant (Tween 20) to form mixed micelles (5). The antimicrobial effectiveness of the cationic surfactant Na-Lauroyl-L-arginine ethyl ester monohydrochloride (lauric arginate (LAE)) applied singly or in combination with the anionic surfactant Tween-80, and oil-in-water emulsions were studied to compare inhibition of three foodborne pathogens (Salmonella sp., Escherichia coli O157:H7, and Listeria monocytogenes). The influences of both exposure time and the amount of oil upon the minimum inhibitory concentrations (MIC) were evaluated and are presented here.