Food Safety Implications of Deliberately Undercooked Hamburgers


(The views and opinions expressed in this blog are strictly those of the author.)


I’m at a point in life where there isn’t much that shocks me. I have to say however, that a story reported last week in Food Safety News took me completely by surprise.  


 An article by James Andrews reported that a 2014 outbreak of E. coli O157:H7 was linked to hamburgers that had been deliberately undercooked 


The outbreak involved at least 12 cases and resulted in the recall of 1.8 million pounds of ground beef produced by Wolverine Packing Company.  Food Safety News conducted an investigation of the events leading to the outbreak and determined that it was caused by ground beef burgers cooked to a rare or medium rare degree of doneness. During the recall, public health agencies reminded consumers that the recommended cooking temperature for ground beef is 160 degrees F.


OK – so far nothing that unusual. Sometimes things go wrong in restaurant kitchens and bad things result.


But that’s not what happened here – It wasn’t revealed at the time, but Food Safety News discovered that many of the cases were directly linked to a burger chain in Ohio that specializes in undercooked hamburgers. The name of the restaurants is Bar 145 – which refers to what they consider to be the perfect temperature for medium rare hamburgers – 145 degrees F.


 It’s like a car manufacturer that decides to make seat belts and air bags an option.  Not a great idea.


The whole thing raises a number of questions – How can this happen after 20+ years of public health warnings on the dangers of undercooked ground beef? Is this a common occurrence in restaurants and are large numbers of consumers ignoring warnings and ordering undercooked hamburgers? If this is the case, then a lot of thought needs to be given to developing alternate guidance for restaurants that prepare rare and medium rare burgers.


Just providing consumers with vaguely worded warnings about the risks of eating undercooked ground beef doesn’t cut it. If restaurants offer their customers the choice to order rare or medium rare hamburgers, they need to know exactly how they should be cooked to inactivate pathogenic strains of E. coli.


A journal article by Smith et al. that reported D-values  for lean and fat ground beef provides the inputs needed to design a safe cooking process for medium rare hamburgers .  (In microbiology, D-value refers to the decimal reduction time required at a certain temperature to kill 90% of the organisms being studied).  


Smith’s research makes it easy to determine the D-values for E. coli O157:H7 at the temperature preferred by Bar 145 (145 degrees F or 63 degrees C). They are 0.16 minute for lean ground beef (4.8% fat) and 0.18 minute for fat ground beef (19.1% fat). That translates to a holding time of 9.6 – 10.8 seconds at a temperature of 145 degrees F in order to achieve a one log reduction in E. coli O157:H7.


Since a minimum of a 5 log reduction is required to assure the safety of cooked ground beef, the required holding time at 145 degrees F would be almost a full minute.  This certainly wouldn’t be impossible to achieve, but restaurants would have to use calibrated thermometers and have a means to measure holding time when a target temperature is achieved.


It would also require that they understand the concept of integrated lethality and design their cooking procedures to assure they get it right every time.


Of course, this is the reason for the 160 degree F recommendation. When this temperature is achieved, the need for long holding times goes away. It makes cooking safe hamburgers easy for everyone.


However, if the 160 degree F recommendation is being largely ignored, maybe it’s time for FDA and FSIS to develop detailed guidance for restaurants like Bar 145.


Just two more thoughts– first, if you use a thermometer to measure a 160 degree cooking temperature for hamburgers, you may be surprised to see that they are not well done. They are still juicy and palatable. It really is a good practice and good advice for consumers and for restaurants.  It would have prevented the Wolverine outbreak and recall.


Finally, congratulations to James Andrews and Food Safety News on an excellent and thought provoking article!

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