Effect of a combination of low level ozone and metal ions on reducing Escherichia coli O157:H7 and Listeria monocytogenes.

Ozonated water has been used as a strong antimicrobial agent against foodborne pathogens. In this study, the combined effect of low level ozonated water and different added components, including 0.2% starch and metal ions (1 mM CuCl2·2H2O and 0.1 mM AgNO3), on inactivation of Escherichia coli O157:H7 and Listeria monocytogenes was investigated. Treatment with 0.4 ppm ozonated water for 30 min resulted in a maximum log reduction in E. coli O157:H7 and L. monocytogenes compared to initial bacterial counts. The log reductions of bacteria in a starch solution containing ozonated water were slightly higher than those in ozonated water alone. Furthermore, the log reductions of E. coli O157:H7 (2.59 and 4.71 log cfu/mL) and L. monocytogenes (2.53 and 4.28 log cfu/mL) in a metal ion solution containing 0.2 and 0.4 ppm ozone for 30 min were significantly higher than those of the water and starch added groups (p < 0.05). These results indicate that a combination of ozonated water and metal ions may be useful as a antimicrobial agent.