Scientists urge caution despite flour test results

A study has found the prevalence of Salmonella and E. coli in flour in England is low, but researchers have highlighted the importance of consumer awareness in preventing infections.

Scientists looked at the possible contamination of raw flour and raw flour-based products, such as pancake/batter mixes, with Salmonella, generic E. coli and Shiga toxin-producing E. coli (STEC).

The samples included flour on sale in Britain from January to April 2020.

Of the 882 flours sampled, one was positive for Salmonella. This sample contained multiple ingredients, such as flour, dried egg and milk powder, and was milled in Great Britain.

A total of 68 samples contained generic E. coli in amounts above 20 colony-forming units per gram (CFU/g). Analysis of flour revealed the presence of the Shiga toxin (tx) gene in 10 samples, and STEC was isolated from seven samples. Five came from Britain and five were imported.

None of the STEC flour isolates matched previous human cases, while the Salmonella Newport isolate from the mixed ingredients product was similar to a human case from the United Kingdom in 2019.

Results published in the Journal of Applied Microbiology indicated that although the incidence was low, there is potential for Salmonella and STEC in flour. They will contribute to future risk assessments of the consumption of raw flour products.

Potential risks highlighted
Researchers say their findings demonstrate the importance of raising awareness among food companies and the public about the potential risks of consuming raw flour, dough and batter.

Previous European and North American studies have found Salmonella or STEC in flour products and outbreaks have been reported. The Centers for Disease Control and Prevention (CDC) is running a campaign to advise people not to consume unbaked dough or batter.

Cereal grains are raw agricultural products grown outdoors where they may be exposed to microbial pathogens in soil and irrigation water or directly from birds and animals. These pathogens can pose a threat if they persist during the processing steps into the final flour product.

The Food Standards Agency (FSA) says it is especially important for vulnerable people, such as children under five, people with compromised immune systems and the elderly, not to taste or eat raw dough or batter.

Flour samples were collected by local authorities from retailers, caterers, restaurants and manufacturers and examined by the UK Health Security Agency (UKHSA).

Of the 882 samples, 624 were produced in 40 different countries, including 476 from Great Britain, while 258 had no country of origin. Wheat was the most common grain, with 526 samples received, followed by rice with 53.

STEC types in flour were O26:H11, O36:H14, O155:H21, O156:H25, and O187:H28.

Regarding the Salmonella Newport positive result from the multi-ingredient Yorkshire pudding/pancake mix that corresponded to a 2019 case, no epidemiological data indicate that this product had been consumed.

Scientists say safety messages on packaging warning that flour and raw flour products, such as cake or pancake mixes, are considered raw ingredients and should not be consumed without cooking, could influence consumer behavior and reduce the potential risk of food poisoning.

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