Raw Cookie Dough Can Harbor E. coli

ATLANTAAn investigation by the Centers for Disease Control and Prevention determined ready-to-bake prepackaged cookie dough was the source of a 2009 multistate outbreak of Shiga toxin-producing Escherichia coli (STEC) that sickened 77 people and hospitalized 35 in 30 states.

The findings, published in the journal Clinical Infectious Diseases, discussed the 2009 investigation, which involved extensive traceback, laboratory and environmental analysis, and led to a recall of 3.6 million packages of all varieties of Nestlé Toll House refrigerated cookie dough.

The investigators suspected one of the ingredients used to produce the dough was contaminated. While the investigation didnt conclusively implicate flour, it remains the prime suspect. They said a single purchase of contaminated flour might have been used to manufacture multiple lots and varieties of dough over a period of time as suggested by the use-by dates on the contaminated product.

Flour does not ordinarily undergo a kill step" to kill pathogens that may be present, unlike the other ingredients in the cookie dough like the pasteurized eggs, molasses, sugar, baking soda and margarine. Chocolate also was not implicated in this outbreak since eating chocolate chip cookie dough was less strongly associated with the illnesses when compared with consuming other flavors of cookie dough.

The study authors concluded that foods containing raw flour should be considered as possible vehicles of infection of future outbreaks of STEC."

They suggested manufacturers consider using heat-treated or pasteurized flour, in ready-to-cook or ready-to-bake foods that may be consumed without cooking or baking, despite label statements about the danger of such risky eating practices. They also concluded manufacturers should consider formulating ready-to-bake prepackaged cookie dough to be as safe as a ready-to-eat food item.

Just a few months after the E. coli outbreak, Nestlé USA announced it would use heat-treated flour in its Toll House refrigerated cookie dough.