Potential for growth from spores of Bacillus cereus and Clostridium botulinum and vegetative cells of Staphylococcus aureus, Listeria monocytogenes, and Salmonella serotypes in cooked ground beef during cooling

Abstract

The ability of 16 foodborne pathogens, representative of 5 different species, to grow during cooling or previously sterilized cooked beef was studied to determine a safe cooling rate. Auto-claved ground beef samples (3 g) were inoculated with heat-shocked spores of Bacillus cereus (strain BH 86) or Clostridium botulinum (nonproteolytic type B strains CBW 25, 17B, and KAP B5 and type E strains Whitefish, Saratoga, and Alaska) or vegetative cells of Listeria monocytogenes (strains HO-VJ-S, V-7, and Scott A). Staphylococcus aureus (strains 196E, B121, and B124), or Salmonella serotypes (S. dublin, S. enteritidis, and S. typhimurium), vacuum-packaged, and cooked in a stirred water bath to an internal temperature of 60°C in 1 h. In some experiments combinations of C. botulinum and B. cereus spores of S. aureus and salmonellae vegetative cell were used. Heated samples were cooled through the temperature range of 54.4 to 7.2°C at rates varying from 6 to 21 h. Samples were removed at various times during cooling to determine if growth of the pathogens had occurred. No growth was observed with cooling periods of up to 21 h. This study with the model meat system (3 g autoclaved ground beef inoculated with selected pathogens and then pasteurized) indicated that cooling from 52.4 to 7.2°C in up to 21 h would not pose a food safety hazard from growth of these pathogens.