You probably don’t realize it, but steaks and other cuts of beef that you buy in grocery stores or restaurants may have been run through a machine that punctures them with blades or needles to tenderize them. (Watch our video of beef being mechanically tenderized, above.)



Unfortunately, the process also can drive bacteria like the deadly pathogen E. coli O157:H7 from the surface deep into the center of the meat, where they are harder to kill. That can increase the risk of illness for people who eat that beef rare or medium rare.

Mechanically tenderized beef caused at least five E. coli O157:H7 outbreaks between 2003 and 2009, causing 174 illnesses, one of them fatal, according to the national Centers for Disease Control and Prevention.* The first documented outbreak in 2003 was traced to blade-tenderized, marinade-injected frozen filet mignon steaks consumers cooked at home, resulting in 13 illnesses that landed seven people in the hospital. (The process is also called "blading" or "needling." Costco, for instance, labels the mechanically tenderized beef it sells as "blade tenderized.")



A 2009 outbreak sickened 25 people, killing one and hospitalizing nine who had eaten mechanically tenderized sirloin served in restaurants. (Profiles of people who described the long-term health consequences of being sickened by E. coli in 2009 after having eaten at restaurants where they ordered medium-rare steaks that had been mechanically tenderized are included in an award-winning series published late last year by ­The Kansas City Star.)



These may not seem like large numbers, but cases reported as part of outbreaks represent only 10 to 25 percent of all lab-confirmed cases of E. coli O157:H7 that are reported annually by state and local health authorities, as is often the case with outbreaks. (Related: Read "Consumer Reports Investigation: Talking Turkey" for details on our tests of ground turkey, which show reasons for concern.)



“And for every lab-confirmed case reported, the national estimate is that there are 26 more out there that aren’t identified,” says Kirk Smith, an epidemiologist at the Minnesota Department of Health.

A report sponsored by the National Cattlemen’s Beef Association describing needling/blading and other techniques to tenderize beef noted that consumers are willing to pay a premium for cuts they perceive as more tender and that a 10 percent increase in the tenderness of U.S. beef would increase U.S. beef industry income by up to $170 million annually.



The Department of Agriculture estimates, based on 2008 data, that 37 percent of companies that slaughter or process beef use mechanical tenderization, producing more than 50 million pounds a month. Yet federal meat inspectors are not even testing this tenderized beef for E. coli. That’s despite the fact that “these products present some additional risk for E. coli contamination,” according to a recently released audit by the USDA’s Office of the Inspector General, which recommended that the agency reevaluate its testing policy.