Decontamination of Escherichia coli O157:H7 from the surface of leafy greens using copper and ascorbic acid alone or in combination with organic acids

Food safety issues and outbreaks of foodborne illness caused by E. coli O157:H7 in leafy greens have raised concerns among consumers. Consumers' demand for natural ingredients to control such pathogens is drawing attention to the food industry considering better alternatives. The objective of this study was to determine the efficacy of copper and ascorbic acid alone or in combination with organic acids in decontaminating leafy greens (cilantro, parsley, and dill) that were artificially contaminated with Escherichia coli O157:H7. Samples were individually submerged in an approximately 8 log CFU/mL cocktail suspension consisting of 3 E. coli O157:H7 strains. To allow attachment, inoculated samples were air dried under a biosafety hood for 2 hour before exposure to various treatment solutions. Samples were then kept in each treatment solution (Control, Copper (Cu) 50 ppm, Ascorbic acid (AA), Lactic acid (LA), and Acetic acid (AA) at 0.2%, or combination of Cu/LA, and Cu/AA solution). Our results indicated that a reduction of at least 2.0 CFU/g of E. coli O157:H7 was achieved when a combination 50 ppm copper with 0.2% lactic acid and 0.2% ascorbic with 0.2% acetic acid were applied. These results demonstrated that combination treatments could be useful in improving the microbial safety of leafy greens including cilantro, parsley, and dill.