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Flour Investigated as E. coli Source

ANAHEIM– If you test enough flour you can find some contaminated by the potentially deadly pathogen–E. coli O157:H7–but testing probably is not going to do much when it comes to making flour safe to eat.

So concluded three speakers–Cargill’s Joe Shebuski, Nestlé’s Tim Jackson, and ConAgra’s Ben Warren–who Monday addressed the International Association of Food Protection (IAFP) on flour food safety.

Flour, a food staple for at least the last 1,000 years, emerged as a “new” potential carrier of pathogens like E. coli and Salmonella last year when Nestlé’s raw cookie dough was blamed for infecting 72 people in 30 states with O157:H7.

With little previous research to go on, Nestle put five laboratories to work to find E. coli O157:H7 in flour.  It took 30 samples from each of 1,074 lots for a total of 32,220 batches that were all put to the test.

One sample for an incidence rate of 0.003 percent returned positive for E. coli O157:H7.  That was about one hundred times less than incidence rates for Salmonella found in previous studies.

“I think it is important that these kind of findings get shared around the industry,” said Shebuski.  He said Nestle deserves credit for disclosing their research findings with the conference.  The company is providing a technical briefing on the research on Wednesday.

A questioner asked Jackson how enough cookie dough could have become contaminated if E. coli O157:H7 was found so rarely and in such low levels.  Jackson said the research did not lead to a “root cause” for the 2009 outbreak.  He did say the flour was the only ingredient not cleared at the supplier level.

Since flour comes from milling wheat, Shebuski said it’s long been known growing something in an open environment carries with it risks from pests to pathogens.  He said past research showed the incidence of Salmonella in flour was 1.32 percent in 1957, and then it declined dramatically to 0.14 percent in 1989.

No comparable work had been done on E. coli until Nestle took on the project.

With the pathogens being found so rarely in flour, and with the bulk nature of the product, Shebuski said “test and hold” is not a realistic safety program for flour.  He said monitoring, HACCP plans, and perhaps looking at more controls on wheat growers and agricultural practices could make sense.

Pathogens in flour are usually rendered harmless by baking, frying, or boiling.

Consumer habits, however, are ever changing.  ConAgra’s Warren said the company was surprised to learn some people are eating raw frozen pizzas.  “We actually had somebody in the company who admitted to doing this,” he said.

It was the common consumer practice of eating bites of raw cookie dough that led to the Nestle E. coli outbreak. Warren is expecting more demand for “heat-treated” flour, the kind now used by Nestle.

A ConAgra analysis found potential demand for 25 million hundred weight of flour for uses that might require “heat treatment.”   Warren said there are a number of technologies for heat-treating, including hydrothermal, turbo, drum drying, and others.

He said E-beam radiation might work, but ConAgra found it left an “off-odor” that probably would not be acceptable to most.

The four-day IAFP annual meeting continues through Wednesday.

© Food Safety News
  • Carl Custer

    In addition to “growing in dirt”, wheat and corn in bumper years are often seen stacked in long high rows beside elevators awaiting transfer to railroad cars. In the meantime the rows of grain provide a feast for birds and rodents who are rarely “housebroken”. How fecal-borne pathogens end up in flour or corn meal should be no mystery.