Enhanced thermal destruction of Listeria monocytogenes and Staphylococcus aureus by the lactoperoxidase system

Abstract

The lactoperoxidase system (LPS) enhanced thermal destruction of Listeria monocytogenes and Staphylococcus aureus. After LPS activation, biphasic survival curves were observed for L. monocytogenes at 57.8°C and for S. aureus at 55.2°C. The data were consistent with a model that assumed two bacterial populations differing in heat sensitivity. The more heat-sensitive fractions (93% of the L. monocytogenes, 92% of the S. aureus) were killed almost instantly. For these biphasic survival curves, D values were based on the much smaller, less-heat-sensitive fractions. For L. ytogenes, the D(52.2°C) values were 30.2 min (untreated milk) and 10.7 min (LPS activated); corresponding D(55.2°C) values were 8.2 and 1.6 min; corresponding D(57.8°C) values were 2.3 and 0.5 min. For S aureus, the D(52.2°C) values were 33.3 min (untreated milk) and 2.2 min (LPS activated), and the corresponding D(55.2°C) values were 7.6 and 1.1 min, respectively. The most rapid killing of L. monocytogenes occurred when samples were heated soon after activation of the LPS. Activation of the LPS followed by heating can increase the margin of safety with respect to milkborne pathogens.