Evaluating lethality of beef roast cooking treatments against Escherichia coli O157:H7.
Added salt, seasonings, and phosphates, along with slow- and/or low-temperature cooking impart desirable characteristics to whole-muscle beef, but might enhance Escherichia coli O157:H7 survival. We investigated the effects of added salt, seasoning, and phosphates on E. coli  O157:H7 thermotolerance in ground beef, compared E. coli O157:H7 thermotolerance in seasoned roasts and ground beef, and evaluated ground beef-derived D- and z-values for predicting destruction of E. coli O157:H7 in whole-muscle beef cooking. Inoculated seasoned  and unseasoned ground beef was heated at constant temperatures of 54.4, 60.0, and 65.5°C to determine D- and z-values, and E. coli O157:H7 survival was monitored in seasoned ground beef during simulated slow cooking. Inoculated, seasoned whole-muscle beef roasts were  slow cooked in a commercial smokehouse, and experimentally determined lethality was compared with predicted process lethality. Adding 5% seasoning significantly decreased E. coli O157:H7 thermotolerance in ground beef at 54.4°C, but not at 60 or 65.5°C. Under nonisothermal conditions,  E. coli O157:H7 thermotolerance was greater in seasoned whole-muscle beef than in seasoned ground beef. Meeting U.S. Government (U.S. Department of Agriculture, Food Safety and Inspection Service, 1999, Appendix A) whole-muscle beef cooking guidance, which targets Salmonella  destruction, would not ensure ≥6.5-log CFU/g reduction of E. coli O157:H7 in ground beef systems, but generally ensured $ 6.5-log CFU/g reduction of this pathogen in seasoned whole-muscle beef. Calculations based on D- and z-values obtained from isothermal ground  beef studies increasingly overestimated destruction of E. coli O157:H7 in commercially cooked whole-muscle beef as process severity increased, with a regression line equation of observed reduction = 0.299 (predicted reduction) + 1.4373.
Department of Food Science, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Kimberly M
KM
Wiegand
Steven C
SC
Ingham
Barbara H
BH
Ingham
D000818:Animals; D002417:Cattle; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D003296:Cooking / Q000379:methods*; D019453:Escherichia coli O157 / Q000254:growth & development*; D005516:Food Microbiology; D006358:Hot Temperature; D006801:Humans; D008460:Meat / Q000382:microbiology*; D008461:Meat Products / Q000382:microbiology; D010710:Phosphates / Q000494:pharmacology; D012492:Salts / Q000494:pharmacology; D013997:Time Factors
D010710:Phosphates; D012492:Salts