Thermal Death Times for Listeria monocytogenes (Scott A) in Crabmeat

Abstract

Thermal death times for Listeria monocytogenes (Scott A) in blue crabmeat were determined. Blue crabmeat was inoculated with 107 cells of L. monocytogenes strain Scott A/g prior to distributing 7.5g into sausage casings (1.6 cm × 4 cm). Ten to 12 sausages, one with a thermocouple connected to a recorder, were placed into a preheated, recirculating water bath at either 50, 55, or 60°C. At designated times, the L. monocytogenes populations was determined by plating serial dilutions onto both trypticase soy agar (TSA) and modified Vogel-Johnson agar. After incubation, presumptive L. monocytogenes colonies were counted. D-values based on enumeration of colonies from TSA were 40.43, 12.00, and 2.61 min at 50, 55, and 60°C, respectively. Heat resistance as demonstrated by using modified Vogel-Johnson agar as the plating medium was less with D-values of 34.48, 9.18, and 1.31 min at each of the same heating temperatures. Z-values of 8.40 and 6.99°C were derived from the TSA and modified Vogel-Johnson agar data, respectively. Based on these findings, the current parameters used to commercially pasteurize crabmeat are adequate to inactivate L. monocytogenes strain Scott A.