Purpose: The objective of this study was to evaluate thermal cook cycle parameters in achieving a 7-log CFU/g reduction of Salmonella strains on whole muscle sliced beef or pork pieces.
Methods: Raw, whole muscle sliced beef or pork pieces were fully submersed into a Salmonella cocktail (Salmonella Heidelberg, Salmonella Typhimurium, Salmonella Enteritidis) for 60 sec, then placed onto racks for 30 min to allow attachment. Experimental cook cycle parameters were programmed into an Enviropak™ Minipak series commercial oven. One sample was pulled to determine concentration on pre-treated slices. Slices were put into the pre-heated oven. One sample was pulled for analysis at the end of each cook cycle step, then each hour past “Step 3” until the target water activity was met. The experiment was performed in duplicate. A 10 g sample was taken, serial dilutions were made, then plated on XLD with a thin TSA overlay. The plates were incubated for 37°C for 24 h and counted to determine surviving populations. Counts were converted to log CFU/g prior to statistical analysis. Samples with an inconclusive count were analyzed through culture confirmation and agglutination.
Results: The cook cycle showed a (P < 0.05) reduction of Salmonella by approximately 7.2 log CFU/g for beef slices and 7.3 log CFU/g for pork slices. However, viable Salmonella cells were detected after enrichment for most time points.
Significance: This study demonstrates a reduction of 7.0 log CFU/g Salmonella is achieved during the cook cycle, but that viable survivors remain. An increase in the relative humidity at the beginning of the cycle should be evaluated as a means to further reduce survivability.