VALIDATION OF PREDICTIVE MATHEMATICAL-MODELS DESCRIBING THE GROWTH OFESCHERICHIA-COLI O157-H7 IN RAW GROUND-BEEF

The growth of Escherichia coli O157:H7 in raw ground beef was investig ated at 12 degrees C, 20 degrees C, and 35 degrees C at pH 5.7 (unadju sted) and adjusted to pH 6.3 to 6.4. These growth data were fitted to the Gompertz equation and the resulting growth kinetics were compared with predictions from the U.S. Department of Agriculture Patho en Mode ling Program. Close agreement with the model was obtained at pH 5.7, b ut at pH 6.4, growth was more rapid than predicted. The U.S. Departmen t of Agriculture Food Safety and Inspection Service has used this pred ictive model for developing proposed regulations on time-temperature r equirements for carcass cooling. As there may be considerable differen ces in the microenvironment of raw ground beef and a beef carcass, the validity of using predictive models for estimating growth rates on a carcass should be determined by performing growth studies on carcass s urfaces.