NPR : News

Freezing Food Doesn't Kill E. Coli And Other Germs

Think that freezing food kills E. coli and other nasty microbes? Think again.

That's the lesson from the new E. coli outbreak caused by frozen chicken quesadillas and other snacks that has sickened 24 people in 15 states.

Freezing does slow down the microbes that cause food to spoil, but it's pretty much useless for killing dangerous bugs.

"It actually does a pretty good job of preserving many of the pathogens and microbes that will cause problems later if thawed out," says Trevor Suslow, an extension research specialist at the University of California, Davis, who studies food safety.

The strain of E. coli — shiga toxin-producing 0121 — involved in the current outbreak hasn't been seen in frozen food before, but other pathogens have caused illness through frozen foods like pot pies, says Martin Wiedmann, a professor of food science at Cornell University. He is working with Rich Products Corporation of Buffalo, N.Y., producer of the foods involved in the outbreak, to figure out the source of the contamination.

A product recall first issued last week was expanded Thursday to include all food produced at the company's Waycross, Ga., plant. Its frozen snacks, cheesesteak sandwiches, and the like are sold nationwide.

Weidmann also wasn't surprised to hear that frozen food could harbor E. coli. "We store a lot of microbes in the lab," he says. "The easiest way is at minus 80 degrees."

But while freezing doesn't defeat pathogens, heat will.

Bacteria die if they're heated to 165F. Cooking instructions on frozen food packages are designed to deliver a temperature of 165F to the coldest part of the product, according to the Grocery Manufacturers Association.

The foods involved in this outbreak are all meant to be cooked, not just warmed up, before they're eaten. Snacky foods like mini pizza slices and cheese steaks implicated in the outbreak are often heated in microwaves, and microwave ovens are notorious for heating food unevenly. Thus the sometimes-intricate package instructions involving turning, stirring, and waiting.

The median age of the people who have fallen ill is 17. It's easy to imagine a scenario where a hungry teenager briefly nukes the pizza dippers and dives in. That's not to say that's what happened in this outbreak. "I don't mean by any stretch to imply that the consumer is at fault here," Wiedmann says.

But safe equals piping hot when it comes to frozen foods. Wiedmann says the most foolproof way to do that is to give up the convenience of the microwave and put foods that require cooking in the oven for a good hot bake.

"With a frozen ready-to-cook food, I would always go with the stove, not the microwave," he says.

Copyright 2013 NPR. To see more, visit


Not My Job: We Ask The Choreographer Of 'The Lion King' About Lying Kings

We recorded the show in Rochester, N.Y., this week, which is home to the Garth Fagan Dance company. We'll ask acclaimed choreographer Garth Fagan three questions about really deceitful people.

Migrants Work To Hold Onto Latin Food History In Gentrifying D.C. Neighborhood

A restaurant in Washington D.C. that has long been a haven for Central American immigrants is adapting to gentrification in the neighborhood.

Sexism Is Out In The Open In The 2016 Campaign. That May Have Been Inevitable

With Hillary Clinton, the first woman to head a major party ticket on the ballot, it was always likely there'd be undercurrents of sexism. What surprising is just how out in the open it has been.

TIMELINE: AT&T's Merger With Time Warner Follows Decades Of Industry Deals

The $85.4-billion merger of a telecom and a media giants is the latest in the web of consolidation, spurned offers and spin-offs that are increasingly interlinking the two industries.

Leave a Comment

Help keep the conversation civil. Please refer to our Terms of Use and Code of Conduct before posting your comments.