Fate and Thermal Inactivation of Listeria monocytogenes in Beaker Sausage and Pepperoni

Abstract

Listeria monocytogenes may survive the typical process used to produce sausage such as pepperoni and hard salami that is made from uncooked meat. Studies were done to identify heat treatments that could be applied during sausage-making to inactivate the organism to undetectable levels. Initial studies with beaker sausage revealed that heat treatments of 51.7°C for 8 h or 57.2°C for 4 h reduced L. monocytogenes counts by >2 log10 CFU/g, but for each treatment the organism was detected by enrichment in one of two samples. Heating beaker sausage to an internal temperature of 62.8°C inactivated listeriae to undetectable levels. Studies with pepperoni revealed that heating sausage at 51.7°C for 4 h after fermentation but before the drying cycle killed most L. monocytogenes, but the organism was occasionally detected in samples during drying. Heating pepperoni at 51.7°C for 4 h after the drying cycle completely inactivated L. monocytogenes in all samples. An additional study done to determine the fate of L. monocytogenes in beaker sausage made with and without lactic starter culture revealed that the organism could grow at 32.2°C in sausage batter during the fermentation period if the lactic starter culture was not added. The organism did not grow, but was reduced by about 1 to 2 log10 CFU/g during fermentation, in sausage made with lactic starter culture.