UKHSA Conducts First Investigation of Salmonella, STEC Risks Associated With UK Raw Flour Products
Image credit: Cloud1902 via Pixabay
A recent survey of raw flour and flour-based foods conducted by researchers at the UK Health Security Agency (UKHSA) found a low incidence rate of Salmonella and Shiga toxin-producing Escherichia coli (STEC) among sampled products; however, the finding does not negate the food safety risk posed by these pathogens in this food category, as whole genome sequencing (WGS) revealed a link between a Salmonella isolate from a flour-based food and a human case of salmonellosis.
In the UK, the Bread and Flour Regulations of 1998 define which ingredients are permitted in flour and bread, but do not require regular monitoring of the microbiological quality of flour and flour-based products. At the same time, previous studies carried out in Europe and North America have linked human Salmonella and STEC infections to flour products, and several foodborne illness outbreaks caused by these pathogens have been potentially linked to flour and flour-based foods in the U.S. and Canada within the last decade.
Additionally, in the UK, flour has not traditionally been regarded as a significant risk for exposure to STEC or Salmonella. However, outbreaks of STEC and Salmonella, as well as sporadic cases of illness, linked to the consumption of raw flour have been reported. In this context, UKHSA carried out the present study to determine the level of Salmonella and STEC contamination of raw flour and raw flour-based products available for sale in the UK.
The researchers collected 882 samples of flour and flour-based products (comprising barley, buckwheat, chickpea, corn, mixed grain, oat, pulses, rice, rye, spelt, wheat and other varieties of flour) from retailers, caterers, restaurants, and manufacturers between January and April 2020. Wheat was the most common grain sampled with 526 (59.6 percent) samples received, followed by rice with 53 (6 percent).
UKHSA detected STEC in only ten of the 882 samples (1.1 percent), although 68 samples (7.7 percent) tested positive for generic E. coli.
Salmonella Newport was detected in just one flour sample (0.1 percent), from a wheat grain product with multiple ingredients, including dried egg and dried milk. WGS linked the S. Newport found in the flour-based product to a human clinical isolate of S. Newport from 2019, although no epidemiological data exists to suggest that this specific product had been consumed to cause the illness.
Overall, UKHSA concludes that eating raw flour and dough has the potential to cause illness, and that efforts are required to educate consumers that flour-based products should not be consumed as a ready-to-eat (RTE) product. UKHSA suggests including safety messages on commercially available packages warning that flour and raw flour products, such as cake or pancake mixes, are considered a raw ingredient and should not be consumed without cooking.
To the researchers’ knowledge, the present study is the first to investigate the Salmonella and STEC risks associated with flour and flour-based products sold in the UK.
Looking for quick answers on food safety topics?
Try Ask FSM, our new smart AI search tool.
Ask FSM →
