The study titled ‘A Novel Vehicle for Transmission of Escherichia coli O157:H7 to Humans’ was published in the journal Clinical Infectious Diseases.
The report’s authors, led by Karen Neil, warned consumers not to eat pre-packaged cookie dough before it was baked following a US e-coli outbreak in 2009.
The study also said that raw flour should be considered the prime suspect in future e-coli outbreaks.
The researchers analysed records of 35 patients taken ill during the 2009 outbreak. They found that 94% had consumed raw cookie dough.
The study said: “Despite instructions to bake cookie dough before eating, case patients consumed the product uncooked.”
It said that manufacturers should consider formulating ready-to-bake commercial pre-packaged cookie dough to be as safe as a ready-to-eat product.
“Food processors should consider the use of pasteurised flour in ready-to-cook or ready-to-bake foods that are likely to be consumed without cooking or baking, even though label statements may warn against consuming uncooked product.”
“More effective consumer education about the risks of eating unbaked cookie dough is needed,” it added.
The authors said eating the dough before it was cooked was popular among adolescent girls. Of the total 77 patients affected by the 2009 outbreak 71% were girls under the age of 19.
2009 e-coli outbreak
Between Match and July 2009, 77 people across 30 states in the US fell ill following an outbreak of Shiga toxin-producing Escherichia coli (STEC) that caused bacterial gastrointestinal illness.
There were no deaths, but 35 people were hospitalised and 3.6m packages of cookie dough were recalled.
US food authorities later discovered that the bacterium E.coli H7:157 had been detected in Nestle’s Toll House refrigerated cookie dough.
Toll House returned to stores in August the same year, but it wasn’t until Nestle detected e-coli in two dough samples at its Virginia plant in January 2010 that it realised a warning label may not do enough to deter consumers from eating the product raw.
Now Nestle uses heat treated flour to produce its refrigerated cookie dough.
Nestle was asked for its reaction to the present study, but was unable to reply before publication.
Flour ‘prime suspect’
For the 2009 outbreak, Neil and her colleagues suspect a contaminated ingredient used to produce the dough was to blame.
Their study did not conclusively implicate flour “but it remains the prime suspect”.
“Foods containing raw flour should be considered as possible vehicles of infection of future outbreaks of STEC," they said.
Study - Karen P. Neil, Gwen Biggerstaff, Kathryn MacDonald, et.al (2011) ‘Novel Vehicle for Transmission of Escherichia coli O157:H7 to Humans: Multistate Outbreak of E. coli O157:H7 Infections Associated With Consumption of Ready-to-Bake Commercial Prepackaged Cookie Dough—United States, 2009,‘ Clinical Infectious Diseases, DOI: 10.1093/cid/cir831 (available here)