Food safety: Researchers seek kill-step to rid flour of pathogens

When you think of foods that present high food safety risks, flour isn’t generally top of the list. Flour’s dryness makes it less conducive to bacterial growth, and because it’s usually baked at a pathogen-killing temperature, it’s not very likely to cause foodborne illness once eaten.

That said, a few major recalls of flour have brought attention to the science surrounding flour contamination, and one team of researchers has dedicated itself to the challenge of improving flour food safety — and maybe devising a protective bacteria kill-step during processing, which doesn’t currently exist, protecting both commercial and home kitchen spheres.

“When I was trained as a food scientist, one of the things we were taught is that there were a few products that were generally safe,” said Kansas State University’s Gordon Smith, whose research team is studying flour-borne pathogens. “Maybe those products were not absolutely safe, but they were on a continuum of things that were much lower risk. Flour was one of those products.”

The public perspective on flour has shifted especially in the past four years, as improved reporting practices have made outbreaks and recalls associated with products containing raw flour more public.

Analyzing the process

We’re often told to resist the temptation to eat raw cookie dough because the raw eggs might infect us with a pathogen, but raw flour also poses this risk. Flour has been associated primarily with two pathogens: Salmonella spp. and E. coli, including the notorious shiga toxin-producing strains 0121 and O157:H7.

Contamination of flour can occur at multiple points in the flour processing chain; harvesting, milling, packing and storage are just some of the steps needed to bring flour to your pantry.

Each stage presents its own challenges. Colorado State University’s Food Source Information notes that wheat fields located near livestock feedlots may have a greater chance of being contaminated with E. coli during rainstorms or irrigation. Beyond the field, harvesting or processing equipment might not be easily sanitized, and it’s not feasible to heat-treat or wash flour to eliminate contaminants. The final step, cooking, is currently the only kill-step in eliminating pathogens in flour.

“We are curious about where the contamination comes from,” said Smith. “We can speculate and speculate, but no one knows the answer to that positively or if there’s a single source.”

The researchers are replicating the commercial milling and baking processes in their laboratories. The team introduces bacteria to the product at various stages and using what they observe to find ways to reduce contamination risks. Computerized models recreate the grain processing process, additionally.

“Computer modeling also provides insight into how these pathogens are transferred in the supply chain from farm to table and allows us to design a kill-step to inactivate these dangerous pathogens,” said Kansas State assistant professor Kaliramesh Siliveru.

While the team hopes to make discoveries with immediate commercial benefits, it also looks at the bigger picture of what its research means.

“It’s high-level research, but it’s also information that is part of teaching students,” said Kansas State food scientist Randy Phebus. “We may be training the first generation of food science, milling and baking science students who will be food safety experts concentrating on grain handling, flour milling, bakery products and even pet food.”