Never Eat Canned Food If You Notice This, Experts Warn
Its long shelf life doesn't negate this potential issue.

Do you have an extensive collection of canned foods in your kitchen you haven't sifted through in quite some time? It's a common scenario considering they have a long shelf-life and can contain the same essential nutrients found in fresh and frozen foods, without the added step of needing to be stored in a refrigerator or freezer. But when you finally decide to break out those black beans gathering dust in your pantry, the expiration date isn't the only thing you need to keep in mind. Canned food can go bad earlier than expected, even before the specified date. In fact, if you notice one thing in particular, you should never eat what's inside. Read on to find out what you should be looking out for when it comes to your canned goods.
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You should avoid eating canned foods that have been accidentally frozen.

If you've left can food out in your car or in your basement during extremely cold weather, it might end up accidentally freezing. Can goods that have been frozen "can be unsafe to eat" and potentially "present health problems," according to the U.S. Department of Agriculture (USDA). When canned food freezes, it can swell up and then burst, creating a broken seal.
"If the seams have rusted or burst, throw the cans out immediately, wrapping the burst can in plastic and disposing the food where no one, including animals, can get it," the USDA advises. Canned food should be stored somewhere in a temperature between 50 to 70 degrees Fahrenheit for best quality and safest preservation, according to the National Center for Home Food Preservation (NCHFP).
You might be able to save a frozen canned good by properly thawing it.

In some cases, however, you might be able to save a frozen canned good and have it still be safe to eat. "A frozen can that has not thawed and is not swollen, can be safely defrosted in the refrigerator and used," the USDA explains.
This trick might work even if the can is still swollen—so long as it hasn't rusted or burst. "If the cans are merely swollen—and you are sure the swelling was caused by freezing—the cans may still be usable," the USDA explains. "Let the can thaw in the refrigerator before opening."
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But if it wasn't thawed in the refrigerator, it isn't safe to eat.

If your canned food has been accidentally frozen but was left out and is no longer frozen, you should discard it. This is because it likely thawed at 40 degrees Fahrenheit or higher, which is also unsafe. According to the NCHFP, between 40 to 140 degrees Fahrenheit is considered the "danger zone," as thawing canned food at this temperature allows for "rapid growth of bacteria, yeasts, and molds."
But even if you follow all the right steps to preserve a frozen canned good, don't be too eager to eat or save it. "If the product doesn't look and/or smell normal, throw it out. Do not taste it," the USDA warns. "If the product does look and/or smell normal, thoroughly cook the contents right away by boiling for 10 to 20 minutes."
A deadly bacteria can grow inside of canned food.

A bacteria called Clostridium botulinum can grow inside and contaminate canned food. This bacteria causes botulism, which is a serious illness that "attacks the body's nerves and causes difficulty breathing, muscle paralysis, and even death," according to the Centers for Disease Control and Prevention (CDC).
"You cannot see, smell, or taste botulinum toxin–but taking even a small taste of food containing this toxin can be deadly," the CDC warns. "Before you open a store-bought or home-canned food, inspect it for contamination. Suspect contamination if the container is leaking, has bulges, or is swollen. If you think the food might be contaminated, do not open the container and throw it out."
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