Dear Dot: Is it Safe to Eat from a Bulging Can? 



Dear Dot

When I was growing up, I was told that, as long as a food can isn’t bulging, it’s safe to eat. Is that true?


The Short Answer: A bulging can isn’t necessarily indicative of botulism, but it is a warning that the canning process was faulty. Better safe than six feet under. It is safe to eat food in a slightly dented can, but if the dent is deep enough that your finger can fit in it, toss it.

Dear Chris,

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It’s amazing to Dot that, among so many incredible stories on the Bluedot site, our story about expiration dates and food safety remains among the most widely read. 

But, while I hope readers will also take in the stories of folks around the world who are doing such interesting things in their communities to address climate change, the truth is that we all eat, we all hate wasting money, and none of us wants a raging case of diarrhea, botulism, or any of the myriad other illnesses caused by eating spoiled food. So I get why that story has had such traction. What’s more, increasingly, we know just how much food waste contributes to climate change. When it rots, food releases greenhouse gasses, most notably methane, which is far more potent than CO2. Food waste is blamed by Project Drawdown, which ranks both climate issues and solutions, as responsible for roughly eight percent of global emissions. 

What our story made clear was how arbitrary and largely misleading those dates stamped on food really are, and how little they actually have to do with food safety. But what it didn’t answer, Chris, was how to know when food is legitimately unsafe to eat.

So let’s open this particular can of worms — or peaches, or beans, or soup, as the case may be — shall we? 

That advice you received in your younger years to steer clear of bulging cans, Chris, was sound. The fear is of botulinum toxin, one of the most potent neurotoxins on earth. Just one gram is estimated to be enough to kill one million people

Botulism comes in different forms, including food-borne. Cans — moist, airtight, with a pH higher than 4.6 — provide top-notch conditions for Clostridium botulinum. “The botulinum toxin has been found in a variety of foods,” the World Health Organization explains on its site, “including low-acid preserved vegetables, such as green beans, spinach, mushrooms, and beets; fish, including canned tuna, fermented, salted and smoked fish; and meat products, such as ham and sausage.”

But, while a bulge in a can is an indicator that the canning process was faulty, it doesn’t necessarily mean the botulinum toxin is present. Given the risk, however, who wants to roll those particular dice? Not Dot, that’s for sure. Better to steer clear of the bulge and live to talk about it. 

What about cans that are dented? As long as the dent isn’t too deep, the USDA tells us that it’s safe to eat. “Deep” is defined as a dent that you can place your finger into. 

Home canners should be careful, too, following the National Center for Home Food Preservation’s guide



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