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Pot Pie Salmonella Case Raises Microwaving Concerns

By Pritzker | Ruohonen

Companies and regulators should consider studying whether microwave cooking is safe for certain not-ready-to-eat frozen foods, the U.S. Centers for Disease Control and Prevention (CDC) said this week in a report on the 2007 national Salmonella outbreak associated with Banquet pot pies.

CDC investigators, writing in the agency's Morbidity and Mortality Weekly Report, expressed concern that microwave cooking instructions on product labels aren't readily followed, especially because most consumers don't know the wattage of their microwave ovens, leading to incomplete cooking. The report also noted the propensity of consumers to deviate from label instructions for microwave cooking, a practice made risky by the inclusion of raw ingredients in some not-ready-to-eat products.

In the 2007 Salmonella outbreak associated with Banquet turkey pot pies and other pot pies from the same ConAgra Foods Inc. plant, the frozen meals contained pre-cooked meat and uncooked flour crusts, according to the report. Furthermore, the report said, the pot pies might have been cross-contaminated by raw poultry pastes that entered the plant. The pastes often harbor Salmonella. But investigators noted that the precise source of the Salmonella poisoning has not been found.

The outbreak was first detected June 6, 2007, when a cluster of four  Salmonella infections were identified by the Pennsylvania Department of Health as having the same genetic fingerprint according to pulsed-field gel electrophoresis. Eventually, 401 cases in 41 states were confirmed in subsequent investigations showing onsets of illness that carried through Dec. 11, 2007, with a peak in September.

Thirty-two percent of all ill persons were hospitalized. The report said: "Further investigation determined that 77 percent of patients who ate these pies cooked them in microwave ovens and that consumer confusion regarding microwaving instructions might have resulted in a failure to cook the product properly.''

The report said that microwave cooking instructions on the Banquet products may have been confusing because different parts of the package recommended different cooking times. ConAgra initiated a Salmonella-related product recall for all nine brands of pot pies made at the plant and then amended labeling of the products before resumption of production.

CDC investigators found that of the patients who said they cooked their pot pies in a microwave oven, only 23 knew their oven's wattage. Recommended cooking times vary by wattage. The report said consumer adherence to microwave cooking instructions on food packages could improve if output wattages were clearly and prominently listed on the appliances.

The report said a breakthrough in the investigation came on Oct. 4, 2007. That's when the Minnesota Department of Health determined that four case patients had consumed Banquet pot pies during the week before they got sick. From there, CDC's outbreak team started questioning patients about consumption of pot pies and confirmed the correlation. 

Full post as published by Food Poisoning Law Blog on November 27, 2008 (boomark / email).