Thermal inactivation of Salmonella spp., Salmonella typhimurium DT104, andEscherichia coli O157 : H7 in ground beef

In 19.1% fat ground beef, Escherichia coli 0157:H7 was less heat-resistant at greater than or equal to 58 OC than the Salmonella typhimurium DT104 and Salmonella senftenberg, but at 55 degreesC the D value was similar to DT10 4 strains and higher than an eight-strain Salmonella cocktail. Inactivation of E. coli 0157:H7 was more temperature-dependent than the cocktail and DT 104 strains. E. coli and DT104 strains were more heat-resistant in beef con taining 19% fat than 4.8% fat. The cocktail was more thermally stable in st ationary as compared to log phase. Freezing of inoculated raw meat decrease d heat resistance of the cocktail. The pathogenic strain, growth phase of t he organism, state of the meat (fresh or frozen) and meat composition must be considered when designing protocols to verify thermal processes.