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Wait, How Did Eggos Get Contaminated with Listeria?

The cinnamon ones are good, though.

Kellogg's has asked customer to l'eggo their Eggos after it detected listeria—an infectious bacteria—on some of its frozen waffles. We've heard of these kinds of recalls and contaminations before, but usually with foods like packaged vegetables or hot dogs. How in the world do frozen waffles get contaminated; isn't the whole point of preserved foods to prevent bacteria from growing?

On Monday, Kellogg's announced the recall of 10,000 boxes of its Nutri-Grain whole wheat waffles sold in 25 states. No one has reported getting sick, but the company said it discovered the possible contamination during routine tests and decided to do a full recall. It's also not the first time the company's waffles have been contaminated—the Georgia Department of Agriculture detected listeria on buttermilk Eggos back in 2009, prompting a similar recall.


Eating food contaminated with Listeria monocytogenes (its full name) can cause an infection called listeriosis that can cause fever and diarrhea. In older people it can be deadly, and for pregnant women, it can sometimes cause miscarriage, so it's no wonder companies try to move quickly to prevent an outbreak. But how did this happen?

Of course these are a thing. Image: Mike Mozart/Flickr

"This is sounding like a classic post-processing—or post-cooking—cross-contamination event," said Haley Oliver, an associate professor of food sciences at Purdue University who studies foodborne pathogens. "Listeria monocytogenes is a soil microorganism. We can find it out in nature, so it can be trafficked in on food products, like a fresh fruit or vegetable, or it can come in people's shoes, and it can set up residence in these processing facilities."

Oliver explained that the processing part of the waffle production, when the waffles are actually cooked, would be at a high enough temperature to kill off any bacteria. But if the Eggos get contaminated at any stage after that, such as during packaging, the listeria can stick around. And while cold temperatures, like in a freezer, can kill off the microbes that break food down and cause it to go rotten, it doesn't do much for infectious bacteria like listeria.

"Freezing never kills listeria, and neither does refrigeration," Oliver told me over the phone. "In fact, it's unique among foodborne pathogens in that it can grow in refrigeration temperatures. But freezing doesn't kill it, it just stops its growth temporarily."

The only way to rid the bug is to cook it at a high enough temperature. In fact, Oliver said if the waffles were cooked thoroughly enough in a toaster, they'd kill off the listeria. But since it's too hard to control—you could accidentally undercook it and not realize until you bit into a frozen, contaminated center—no company would ever recommend consumers just try to cook the bacteria away.

Kellogg's told me the contamination in this case was due to a "gap" in its sanitation process and that the company is "halting production on the line in question, conducting a deep sanitary clean of the area and reviewing our cleaning and sanitation protocols with the relevant plant employees." This is par for the course when these kinds of contaminations happen and helps to prevent them from recurring. But Oliver said it may be impossible to ever completely rid listeria from our food system, because it will always be a part of our environment.

"Listeria will always be with us," she said. "Death, taxes, and listeria."

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