Synergism of Mild Heat and High-Pressure Pasteurization Against Listeria monocytogenes and Natural Microflora in Phosphate-Buffered Saline and Raw Milk

As many as 99% of illnesses caused by Listeria monocytogenes are foodborne in nature, leading to 94% hospitalizations, and are responsible for the collective annual deaths of 266 American adults. The current study is a summary of microbiological hurdle validation studies to investigate synergism of mild heat (up to 55 degrees C) and elevated hydrostatic pressure (up to 380 MPa) for decontamination of Listeria monocytogenes and natural background microflora in raw milk and phosphate-buffered saline. At 380 MPa, for treatments of 0 to 12 min, d-values of 3.47, 3.15, and 2.94 were observed for inactivation of the pathogen at 4, 25, and 50 degrees C. Up to 3.73 and >4.26 log CFU/mL reductions (p < 0.05) of habituated Listeria monocytogenes were achieved using pressure at 380 MPa for 3 and 12 min, respectively. Similarly, background microflora counts were reduced (p < 0.05) by 1.3 and >2.4 log CFU/mL after treatments at 380 MPa for 3 and 12 min, respectively. Treatments below three min were less efficacious (p >= 0.05) against the pathogen and background microflora, in the vast majority of time and pressure combinations. Results of this study could be incorporated as part of a risk-based food safety management system and risk assessment analyses for mitigating the public health burden of listeriosis.