Burgers Are Still Done at 71
Project Title
Assessing the Potential Implications of Heat Resistant Escherichia coli in Alberta Beef or Ground Meat Cooking Recommendations
Researchers
Mark Klassen klassenm@cattle.ca
Scientific Journals
| Status | Project Code |
|---|---|
| Completed September, 2018 | MISC.02.17 |
Background
Consumer confidence is crucial for the beef industry and can be shaken by E. coli outbreaks and other food bourne illnesses. During the 2012 XL Foods E. coli outbreak which infected at least 18 people and resulted in the recall of 1,800 tonnes of beef, media and the public became increasingly interested in the state of E. coli research and questioned whether Health Canada’s recommendation to cook hamburger to 71oC was enough to keep beef consumers safe. The cooking temperature recommendations faced scrutiny due to the understanding that more heat resistant strains of E. coli have emerged over the years. These concerns deserved serious investigation. In response, the Beef Cattle Research Council and Alberta Agriculture and Food supported a study led by Mark Klassen (Canadian Cattlemen’s Association) and Xianqin Yang (Agriculture and Agri-Food Canada’s Lacombe Research Station) to assess whether changes to Health Canada’s cooking recommendations were warranted. A panel of five additional scientists was assembled to review and approve the experimental design and methods before the research started.
Objectives
- Determine whether Health Canada’s recommendation to cook hamburger to 71oC is enough to kill food bourne pathogens including heat resistant strains of E. coli.
What They Did
Nine E. coli strains (both pathogenic and nonpathogenic strains) were tested for heat resistance under laboratory conditions. The most heat resistant strain was incorporated into beef patties by adding approximately 100 million E. coli bacteria per patty. The burgers were cooked to Health Canada’s recommended internal temperature of 71oC, allowed to cool for 3 to 5 minutes, then the number of viable E. coli were evaluated.
What They Learned
No E. coli survived after the burgers were cooked to the recommended internal temperature 71oC and cooled for 3 or 5 minutes, even though the beef had been artificially contaminated with very high levels of E. coli.
Burgers aren’t eaten straight off the grill; it takes a few minutes to carry them inside, gather the kids, melt the cheese, pass the relish, etc. The burgers continue to cook during the first part of this “cooling period”. In this study, internal temperatures continued to rise for 2 minutes after they came off the grill, sometimes reaching as high as 75oC, and maintained at least 71oC for another 2 minutes after that. This extended the length of time E. coli is exposed to lethal temperatures.
What It Means
Health Canada’s cooking recommendations are still valid. Your burger’s still done at 71. That means at least “medium”. Using a meat thermometer is highly recommended to ensure the proper temperature is attained.
This study found that cooking burgers to 71oC killed all the E. coli, even though it had been contaminated with extremely high levels of bacteria. Results may have been different if the burgers had been cooked to a lower internal temperature. Cooks and servers should never ask their families or guests “how” they would like their burgers cooked, even if they’re using a “source grind” burger or ground the beef themselves. Do them, yourselves, and our entire industry a favor – let them know that medium-rare or rare hamburger is not a risk worth taking. Medium to well-done is the only option for burgers.
Canada’s beef industry has made tremendous progress in combating E. coli in packing, further processing and retail sectors. However, beef is not the only potential source of E. coli. The Canadian Food Inspection Agency’s website reports that there have been 11 E. coli O157 related recalls since January 2014, but only one of those recalls involved beef. That means that cross-contamination from other foods in the same shopping cart, bag, refrigerator, kitchen or grill can also pose an E. coli risk to consumers. To reduce the risk posed by E. coli O157, cooks in homes or commercial kitchens need to keep it cold (refrigerate meat as soon as it arrives and refrigerate leftovers as soon as possible), keep it clean (wash hands, surfaces and utensils frequently when handling food – and always between handling meat and other food) and keep it covered (keep meat and meat products separate from other foods).