ANTIBACTERIAL ACTIVITY OF THE LACTOPEROXIDASE SYSTEM AGAINST LISTERIA-MONOCYTOGENES AND STAPHYLOCOCCUS-AUREUS IN MILK

The lactoperoxidase system (LPS) was activated by addition of thiocyanate (SCN) and hydrogen peroxide (H2O,) and utilizing the inherent milk lactoperoxidase (LP). For Listeria monocytogenes studies, initial concentrations of 2.4 mM SCN- and 0.6 mM H2O2 were added. The corresponding concentrations were 1.2 mM SCN- and 0.3 mM H2O2 for Staphylococcus aureus studies. The LPS increased the predicted time to reach half the maximum attainable CFU/ml by 326 h for L. monocytogenes at 10°C and by 6.3 h at 35°C. For S. aureus, the corresponding increases were 36 h at 10°C and 2.4 h at 37°C. During the initial period after activation of the LPS, bactericidal effects against L. monocytogenes at 35°C and S. aureus at 37°C were observed. After recovery from the effects of the LPS, growth rate of each pathogen was of similar magnitude as in the H2O2-treated and untreated milk, with the exception of L. monocytogenes at 10°C. Copyright © International Association of Milk, Food and Environmental Sanitarians.