Effects of refrigeration or freezing on survival of Listeria monocytogenes Scott A in under-cooked ground beef

Listeria monocytogenes Scott A, inoculated into ground beef, was heat-shocked at 46 °C for 60 min to enhance stress adaptations and simulate sublethal minimal cooking conditions. The effects of refrigeration at 4 °C or freezing at −20 °C were examined on pathogen survival prior to or following mild cooking at 60 °C. D10-values for heat-shocked samples were elevated as compared to nonheat-shocked controls. Refrigerated and frozen storage did not influence the observed effects. Cellular injury of survivors increased with timed exposure to 60 °C. The effects of refrigerated and frozen storage on heat-adapted L. monocytogenes in ground beef did not decrease the potential of the food-borne pathogen to survive additional low temperature cooking of food and raised concerns over the food safety of contaminated, temperature-abused foods