In 2009, Nestlé Toll House prepackaged cookie dough sickened 77 people in 30 states, and 35 of those people were admitted to the hospital, a few with severe illness. Nestlé recalled 3.6 million packages of its popular chocolate chip batter.
Last year, at an International Association of Food Protection meeting in Anaheim, a Nestlé food-safety specialist shared details of the extensive testing in the aftermath of the outbreak. And although he said the company never determined the root cause of the E. coli O157:H7 contamination, he acknowledged that flour was the only ingredient in the dough not cleared at the supplier level.
The flour in the cookie dough is also named as the prime suspect in a report on the outbreak investigation published Friday in Clinical Infectious Diseases and available online.
Led by Dr. Karen Neil, working with colleagues at the Centers for Disease Control and Prevention and state health departments, the study concluded that a single shipment of contaminated flour might have caused the problem.
Unlike the pasteurized eggs, molasses, sugar, baking soda and margarine in the cookie dough, flour was the only ingredient that did not undergo a kill step to eliminate pathogens, the authors noted. Chocolate was also ruled out as the culprit, in part because the chips in the prepackaged dough were the same as those Nestlé sells for home baking, and there were no reports of illness among people who made chocolate chip cookies from scratch.
“Although our investigation found no conclusive evidence that contaminated flour was the source of this outbreak, contaminated flour remains a prime suspect for introducing the pathogen to the product,” the authors wrote. They say raw flour has to be considered a potential hazard that could cause future E. coli outbreaks.
The authors suggest more effective consumer education is needed about the risks of eating dough before it’s baked, but concede that “despite label statements about the danger of such risky eating practices,” more information is not likely to persuade people to stop nibbling raw batter. In fact, some people who suffered E. coli infections in the 2009 outbreak said they didn’t plan to bake cookies; they bought the dough to eat it raw.
“Making the snacks safer may be the best outcome,” the public-health researchers suggest, adding that “manufacturers of cookie dough should consider reformulating their product to make it as safe as a ready-to-eat product.”
At the 2010 IAFP meeting in Anaheim, the Nestlé representative said his company is now using heat-treated flour for its cookie dough, which prompted a speaker from ConAgra to observe it’s not just cookie dough that consumers don’t bother to bake. He said ConAgra executives were surprised to learn from some of their own colleagues that they — and lots of other people — like to eat raw frozen pizza.