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

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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 7.5 g 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.