HEAT-RESISTANCE OF LISTERIA-MONOCYTOGENES IN VACUUM-PACKAGED PASTEURIZED FISH FILLETS

The heat resistance of two strains of Listeria monocytogenes in sous-v ide cooked fillets of cod and salmon was investigated. Fish sticks of 5 g were inoculated, vacuum-packed and heated at different combination s of time and temperature (58-80 degrees C). Time-temperature combinat ions allowing survival and time-temperature combinations at which the bacteria were destroyed, were used to determine D-and z-values. D-valu es were in the range of what has been published for other food product s. D-60-values were between 1.95 and 4.48 min depending on the strain and the fish. Both strains were one-four-times more heat resistant in salmon than in cod, showing the importance of the heating menstruum. T his difference may be due to the higher fat content in salmon as compa red to cod. Z-values were calculated to be 5.65 and 6.4 degrees C, res pectively, for the two strains. The suitability of methods for heat re sistance experiments and the survival of L. monocytogenes in sous-vide cooked fish fillets are discussed.