Thermal-Death Times of Listeria monocytogenes in Green Shell Mussels (Perna canaliculus) Prepared for Hot Smoking

Abstract

Thermal-death times were determined for seven strains of Listeria monocytogenes in green shell mussels (Perna canaliculus) that had been soaked in brine in preparation for hot smoking. Subsamples (25 g) of blended mussels were aseptically transferred into plastic pouches and inoculated with 106 cells of L. monocytogenes g−1. The inoculated material was incubated at six different temperatures and L. monocytogenes numbers were determined at five time intervals for each temperature. Temperature trials were duplicated. A best-fit line, by least squares linear regression, was fitted to the data. The correlation value (R2) was 0.96. From the best-fit line, D values at 56, 58, 59, 60 and 62°C were calculated to be 48.09, 16.25, 9.45, 5.49 and 1.85 min respectively, with a z value of 4.25°C. This study demonstrates that small changes in the core temperature of a product during hot smoking can have a profound effect upon the rate at which contaminating L. monocytogenes cells are killed. Results from this study will help to ensure that thermal regimes designed to eliminate L. monocytogenes from hot-smoked mussels are based on adequate thermal-time information.