Over a 12-week period during the spring and summer of 2013, several thousand pounds of oat flour were processed at the IFSH BSL-3 pilot plant so that consumers could safely eat the cereals and snack foods they love.
The Centers for Disease Control and Prevention reports 10 food-borne illness outbreaks since 2006 associated with Salmonella or E. coli in low-moisture foods including seeds, nuts, spices, peanut butter, puffed cereals and snacks, pet food, and cookie dough. Many of these outbreaks have been directly linked to consumption of cereals and snacks made using an extruder and from consumer handling of extruded pet foods contaminated with Salmonella. These outbreaks sickened more than 1,000 people and lead to eight deaths. An extruder is a machine that mixes and heats raw materials as part of the cooking process, then forces the finished product through a die so that it forms a desired shape.
Several multinational food companies that manufacture these products are members of a collaborative Low-Moisture Food Safety Task Force based at ITT/IFSH and led by Nathan Anderson, a U.S. Food and Drug Administration (FDA) food process engineer. Low-moisture foods—dry pet food, cereals, puffed snacks, and the flours from which they are made—are normally considered low risk in terms of food safety, but food-borne illness outbreaks are occasionally associated with them. Anderson says the culprit is likely the raw materials such as flour that are contaminated with either E. coli or Salmonella. In low-moisture foods, the microorganisms survive for long periods and are very resistant to heat processes such as extrusion.
He and his team of IIT/IFSH and FDA researchers ran batches of oat flour inoculated with an outbreak strain of Salmonella through a pilot-scale Wanger X-85 single-screw extruder under worst-case process conditions.
“What we wanted to know was, if we run the contaminated flour through an extruder, would the extruder be an effective tool for inactivating the Salmonella?” says Anderson, who is preparing a manuscript of the team’s results for publication in a peer-reviewed journal.
“We clearly identified the boundary where we know the process is effective and where it isn’t,” he says. “We wanted to know if product processed at certain combinations of temperature and moisture content would be safe to eat without further cooking. I believe that we've done that.”
“The Laboratory That Infects Salad with Deadly Pathogens”: www.popsci.com/science/article/2012-06/infecting-salad-deadly-pathogens
American Biological Safety Association: www.absa.org/about.html
Abstract: “Method to Determine Differences in Thermal Tolerance of Salmonella Serotypes at Low Water Activity: https://iafp.confex.com/iafp/2013/webprogram/Paper4469.html