Microbial contaminants in flour is not a new issue and continue to cause consternation for millers and suppliers of flour. A recent report from Germany will likely put this issue back in the spotlight and again illustrate the huge challenge of managing risks in a food that is inherently not ready-to-eat but is often treated as such.
So what is the issue? In response to the detection of Shiga toxin-producing Escherichia coli (STEC) in multiple flour samples in the Federal Monitoring Plan (BüP) of 2018, Germany’s Federal Ministry of Food and Agriculture (BMEL) asked its Federal Institute for Risk Assessment (BfR) to conduct a health assessment on the risks associated with the handling and the use of STEC-positive flour and consumption of food manufactured from that flour.
The nationwide monitoring plan, for which flour samples from mills were investigated for the occurrence of STEC, found 50 STEC-positive samples (15.2 %) in 328 wheat, spelt and rye flour samples.
Serotypes O157:H7, O103:H2 and O145:H28, which are considered highly virulent and often associated with hemolytic uremic syndrome (HUS), were isolated from various rye, wheat and other cereal flours. A total of 40 % of the isolates from rye flours (11 of 27) and wheat flours (25 of 62) belonged to clinically relevant STEC serotypes.
While both the U.S. and Canada have established a link between disease outbreaks and Shiga toxin-producing Escherichia coli (STEC) contamination in flour, Germany had seen no such direct linkage. However, the BfR’s assessment found a close genetic match between a STEC isolate in flour and the human isolate (EHEC O157:H7), leading the BfR to conclude that the occurrence of highly pathogenic EHEC variants in flour is also probable in Germany, but that the direct links have likely just not yet been discovered.
In relation to its task to determine which risks are associated with the handling and the use of STEC-positive flours as well as the consumption of food manufactured from STEC-positive flours, BfR stated that:
Included among the BfR recommendations for mitigation are:
BfR also recommends that the public be made aware of the possible presence of pathogens in flour and existing consumer guidance be amended to include recommendations such as storing and processing flour, baking mixes and raw dough separately from other foods; processing doughs as quickly as possible or storing them in the refrigerator; not eating raw doughs; cleaning utensils and surfaces thoroughly after contact with flour, baking mixtures, or raw dough; and washing and drying hands thoroughly after processing flour, baking mixes, or raw dough.
Additionally, BfR sees a need for further research before a final health risk assessment can be issued. As such, it is planning to meet with selected experts to discuss the open scientific question, such as:
So what does this mean to the food industry? Clearly this study is quite large and has found a level of STEC contamination that causes concern, especially as many of the STEC isolates were clinically relevant. While this is an issue that is well recognized by many flour suppliers, this new study could cause regulators to look more closely at the flour supply in the US, which could clearly create a nightmare for the flour supply in the US. I see this study as a need for continued dialogue between industry, regulators, and academia on how to solve this problem and to find ways to ensure an adequate level of public health protection without driving a massive disruption of the flour supply.