It's Still Not a Good Idea to Eat Raw Cookie Dough

By George Dvorsky on at

For some, sneaking a mouthful of raw cookie dough while baking is an indelible—and certainly delicious—part of the process. But while we’ve been told to avoid dough containing raw eggs, a new investigation confirms that tainted raw flour was responsible for an E. coli outbreak in 2016—a finding that will surely test our temptation to lick the bottom of the bowl.

Last year, US food company General Mills had to recall three of its flour products following an outbreak of Escherichia coli. That amounted to over 10 million pounds of flour. At the time, E. coli was fingered as a likely suspect, triggering an investigation. That investigation is now officially over, and the resulting study published in The New England Journal of Medicine confirms it. The dry, powdery substance that is flour can host foodborne pathogens, as unlikely as that sounds.

From December 2015 to September 2016, there were 56 cases of E. coli-related illnesses reported across 24 US states. No one died, but one patient came down with a severe form of kidney failure (haemolytic uraemic syndrome) brought on by an E. coli infection. Earlier in the year, experts with the US Centers for Disease Control identified the mysterious strain as belonging to serogroup O121, sparking an investigation that eventually linked the illness to the consumption of raw flour.

During the investigation, scientists interviewed the people who got sick, making sure they weren’t using ingredients that were past the “sell by” or “use by” dates. The patients said they remembered eating raw batter or dough while baking a few days before they came down with symptoms such as diarrhoea, vomiting, and fever. Importantly, 85 per cent of the patients baked with the same brand of flour, allowing the researchers to trace the outbreak to a single flour processing facility.

The authors of the new report warn that dangerous microorganisms on wheat or other ingredients in flour “can survive the drying process and remain viable in flour for months” in a dehydrated state. This is worrisome news because raw flour is traditionally not thought of as a vector for foodborne diseases.

It’s unlikely that your favourite brand of flour has E. coli lingering within, but as this new study shows, you may not want to take any chances. Last year, the US Food and Drug Administration put out an advisory warning people to avoid eating raw dough, while offering these tips:

  • Do not eat any raw cookie dough, cake mix, batter, or any other raw dough or batter product that is supposed to be cooked or baked.
  • Follow package directions for cooking products containing flour at proper temperatures and for specified times.
  • Wash hands, work surfaces, and utensils thoroughly after contact with flour and raw dough products.
  • Keep raw foods separate from other foods while preparing them to prevent any contamination that may be present from spreading. Be aware that flour may spread easily due to its powdery nature.
  • Follow label directions to chill products containing raw dough promptly after purchase until baked.

Each year in the United States, around 265,000 cases of E. coli-related illnesses are reported. In the UK, these numbers are lower but still considerable; in England alone, 38,132 cases of E. coli-related illnesses were reported between April 2015 and March 2016. As this new study shows, some of these could be avoided by not eating raw dough.

Mmmmm, delicious, tainted raw dough.... [New England Journal of Medicine]


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