Pathogen Survival in Precooked Beef Products and Determination of Critical Control Points in Processing

Surfaces of precooked, roast beef slices were inoculated with Clostridium perfringens , Staphylococcus aureus , Escherichia coli , Salmonella typhimurium , or Listeria monocytogenes , vacuum packaged and then stored at 3°C for 70 d to determine survival of pathogens under extended refrigerated storage in the presence of a natural competing microflora. S. typhimurium and L. monocytogenes remained present on the slices for the duration of the experiment. Numbers of S. aureus did not decrease significantly (P>0.05), and counts of C. perfringens decreased steadily over the 70-d storage period. Numbers of E. coli also declined, but more rapidly than the other pathogens during initial storage of the product. Total bacterial numbers for both uninoculated (control) and inoculated slices were similar. Samples obtained at selected locations in the processing sequence of a commercial restructured beef product contained L. monocytogenes at most sampling locations prior to heat processing, but not after heating. Salmonella was occasionally isolated from the product prior to heating. Total bacterial numbers decreased as processing day progressed, as did counts for S. aureus , E. coli , and coliforms. Counts of S. aureus and total bacterial numbers increased after the cooked product was removed from the package and coated with a seasoning mix. Data collected in this study support the designation of the following locations as critical control points: initial bacterial levels on raw products, cooking temperature and time, proper cooling after cooking, sanitation after opening the package (rubbing with seasonings and rebagging), and temperature control of the final product.