Cookie Dough Blues: How E. Coli Is Sneaking Into Our Forbidden Snack

Flour seems innocuous. We've long been warned to wash our hands after handling chicken, and to cook our hamburgers well. We wash lettuce that came straight from the field. But really, flour?

This week, the Centers for Disease Control and Prevention reminded everyone that flour is, in fact, a raw, uncooked food, just like those fresh greens. Yes, it can make you sick.

The agency announced that 46 people, so far, have been sickened by E. coli that apparently contaminated flour sold by General Mills. The first case was reported seven months ago, and the outbreak continues. Tests haven't actually detected disease-causing E. coli in the company's products, but General Mills has recalled the batches of flour that included packages sold to people who got sick.

But how does flour become contaminated in the first place?

A researcher at AIB International inserts thermometers into cookie dough to monitor the baking temperature. The goal is to make sure the dough reaches the temperature needed to kill any bacteria inside. (Courtesy of AIB International)

Charlene Wolf-Hall, a food microbiologist who is currently vice provost at North Dakota State University, says it could happen almost anywhere from wheat field to flour mill. The prime suspects are wild creatures that carry E. coli or salmonella. "It could be bugs, it could be birds, it could be rodents, it could be people with their hands — you just don't really know what the source is," she says.

Scientists have found that the wind can carry disease-causing bacteria from cattle feedlots to fields nearby.

Frank Manthey, a specialist on wheat at North Dakota State University, says wheat is especially vulnerable after harvest. "All animals want to eat it. It's good food," he says. Wheat is usually stored in animal-proof bins, but during busy harvest times, it may end up sitting outside for a while, where animals can more easily get to it.

Wheat is cleaned before milling, but that doesn't kill bacteria. In fact, according to Wolf-Hall, bacteria that might have been on just a few contaminated kernels of grain can spread more widely when they're ground up into flour. And "the wheat bran is actually going to have a lot more than the flour," Wolf-Hall says, because the outer surface of the wheat kernels are more likely to be contaminated.

Applying heat could kill the bacteria, but doing so would be "challenging and expensive," says Wolf-Hall. According to Stephanie Lopez, vice president of Food Safety Services for AIB International, using heat also can "impact the functionality of the flour, which affects end-product quality for baked goods." Irradiation would also eliminate bacteria, but companies have been unwilling to adopt it for fear of consumer resistance.

One small flour producer, Ardent Mills, sells a special version of flour that's been treated using a "proprietary, all-natural" process to get rid of bacteria, but the company isn't revealing how that process works. In a statement, Ardent Mills told The Salt that its "SafeGuard" flour is only a small part of its business. It's primarily intended for companies that use flour in ready-to-use products such as cookie dough ice cream or refrigerated cookie dough.

All of which means that you should think of raw flour more like unwashed raw vegetables than, say, pasteurized milk. It needs to be cooked before you eat it.

That's how we normally consume flour, of course. Which is why disease outbreaks linked to flour are relatively uncommon. The one that attracted the most attention occurred in 2009, when raw, prepackaged cookie dough sickened 72 people. Most of the people who got sick were teenagers or children and 71 percent were female, perhaps reflecting the demographic composition of America's cookie-makers — or cookie dough tasters.