SURVIVAL OF BACTERIAL PATHOGENS IN PASTEURIZED PROCESS CHEESE SLICES STORED AT 30-DEGREES-C

Six lots of commercial pasteurized process cheese slices were evaluate d for the ability to support the growth of four foodborne pathogens, L isteria monocylogenes, Staphylococcus aureus, Salmonella serotypes, an d Escherichia coli O157:H7, during 4 days of storage at 30 degrees C. Individual cheese slices were inoculated separately with each pathogen to yield ca. 103 CFU/g. Slices were packaged in sterile plastic sampl e bags and stored at 30 degrees C for up to 96 h. Populations of Salmo nella serotypes and Escherichia coli O157:K7 decreased an average of 1 .3 and 2.1 log(10) CFLT/g, respectively, by 36 h and Salmonella seroty pes decreased an additional 0.6 log(10) CFU/g during the remaining 60 h. Populations of Listeria monocytogenes also decreased, although to a lesser extent, exhibiting approximately a 0.6-log(10) CFU/g reduction in 96 h. Staphylococcus aureus levels remained relatively constant du ring the testing period, and were below levels that support detectable enterotoxin production. The process cheese slices tested allowed surv ival but did not support rapid growth of S. aureus, whereas population s of L. Monocytogenes, E. coli O157:H7, and Salmonella serotypes decre ased during the 96-h storage at 30 degrees C.