A year ago, US health officials sparked outrage warning Americans not to eat cookie dough for fear of E. coli infection from a rogue batch of flour.
Eventually, the issue appeared to be resolved, no more alerts went out, and the relieved public went back to sneaking a taste of mixture from the baking tin.
But yesterday, the day before Thanksgiving, researchers at the US Centers for Disease Control and Prevention issued a report telling sweet-toothers not to rest on their laurels: cookie dough remains a threat.
‘We’re not trying to ruin people’s holidays but we want them to be aware of the risks,’ lead author Dr Samuel Crowe, an epidemiologist at the CDC, insisted to the New York Times, after completing a years-long investigation of the 2015-2016 scandal.
‘The bacteria is not uniformly distributed in a two-and-a-half pound bag of flour.
‘A small amount could get you really sick. I’ve had E. coli and salmonella and it’s pretty darn unpleasant.’
Dr Crowe’s report, published in New England Journal of Medicine, is the result of more than a year of investigation into the outbreak which sickened 63 in 2015-2016.
They concluded that any flour can contain dormant bacteria – which is revived by the moisture of water, milk or eggs.
Normally, to reach a conclusion about an outbreak, the CDC would mine survey data.
However, flour is not tracked by all questionnaires. So the team tracked down as many of the men, women and children affected by dough as they could (10 people), and interviewed them for hours on end.
Dr Crowe said he asked as detailed and specific questions as possible, trying to get to the heart of what happened.
It was complicated, he admitted. Few remember what they had for breakfast today, let alone what they ate months ago.
But some people had some flickers of memories, and two people even remembered the specific dough, and produced pictures of the ingredients which sickened them.
Initially, Dr Crowe had suspected eggs could be to blame, since they are a classic source of salmonella. But his investigation changed when he saw that the two victims used the same flour.
Analyzing the flour, the researchers found that it contained a dormant strain of E. coli.
E. coli tends to fester in moisture, but Dr Crowe found that it can lie hidden in dry products, and is revived when it hits moisture like water or eggs or milk.
Experts say there are three main options for eliminating this risk.
First, the US could change the way it produces flour by heating it up before it’s packaged – but this would change the texture which customers seek out.
Second, manufacturers could blitz it with radiation, as they do to rid pests, but they would need much higher levels of radiation to hit the bacteria.
Third, home bakers could wait until the cookies are out the oven.