Thermal Destruction of Listeria monocytogenes in a Meat Slurry and in Ground Beef

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Abstract
Thermal destruction of Listeria monocytogenes cells was determined in phosphate buffer, a meat slurry (20% ground beef/80% water) and in ground beef. D‐values at 60°C, 65°C and 70°C in phosphate buffer, and in the meat slurry were 0.63, 0.29 and 0.15, and 2.54, 0.75 and 0.23 min, respectively. Heating of ground beef (80% lean) in a 75°C water bath to 50°C, 60°C or 65°C required 6.2, 8.4 and 10.6 min, respectively, and resulted in 0.2‐0.9, 1.6‐3.4 and 4.4‐6.1 log reductions in L. monocytogenes cells, from the initial inoculation level of 8.08 log CFU/g. Viable cells were also detected after cold (21 days) or selective enrichment (24 hr) in eight out of nine samples of ground beef inoculated with 7.84‐8.08 log CFU/g and cooked to 70°C.