So, you left your cooked sweet potato out overnight. You ought to be ashamed of yourself. Just kidding—it happens to the best of us. But now you’re wondering: Is this sweet potato still safe to eat?
Cooked sweet potato left out for more than two hours (including overnight) should be thrown away according to USDA recommendations. Even if you heat up the sweet potato to kill any bacteria, there may be heat-resistant toxins made by certain bacteria like Staphylococcus aureus, which reheating can’t destroy.
Below, I’ll explain how to tell if sweet potatoes are bad and what happens if you eat bad sweet potatoes. I’ll discuss a specific situation in which potatoes are more likely to cause botulism. And I’ll also address sweet potato casserole, pie, and fries!
How Long Can Sweet Potatoes Be Left Out?
Here is the official answer, based on USDA recommendations: Cooked sweet potato should not be eaten if it was left out for more than two hours. And if it’s extra hot out (over 90°F or 32°C), the rule is one hour.
Temperatures between 40 and 140 °F are referred to as the “Danger Zone.” In this temperature range, bacteria double quickly, and these bacteria can make you sick. (source)
This also applies to baked sweet potatoes that you left in the oven overnight. Once the potatoes cool below 140°F, they’re the in “Danger Zone,” and bacteria can multiply for the rest of the night.
Leaving baked sweet potatoes in the oven overnight is especially dangerous if they are wrapped in tin foil. I’ll explain why below.
“But I Do It All the Time…”
If you ask your friends about this topic or read around on Internet forums, you will hear from people who say that it’s fine to eat sweet potatoes that were left out. Some will say they do it all the time and they’ve never gotten sick.
However, the FDA estimates there are 48 million cases of foodborne illness each year in the United States. Many people mistake food poisoning for something like the stomach flu. So common people may not be the best authorities to ask on this subject.
People may also tell you that if you heat up the sweet potato, it will kill any bacteria that had grown. But this is misleading.
Cooking food does not rid it of all possible toxins that were created by the bacteria—even if it kills the bacteria itself. Therefore, if you want to be on the safe side, you should just throw out the cooked or baked sweet potato.
What About Sweet Potato Casserole? Pie? Fries?
The same rule applies to sweet potato casserole, sweet potato pie, and sweet potato fries: If they’ve been left out at room temperature for more than two hours, they should be thrown out, according to the USDA.
Again, that’s the official answer, and it’s the safest thing to do. Many people feel that rule is overly strict—but it’s the government recommendation and the safest course of action.
What Happens If You Eat a Bad Sweet Potato?
It depends exactly how the sweet potato is “bad.” If you’ve left out your cooked sweet potato overnight, the risks are different than if your raw sweet potato has spoiled in the pantry before cooking.
Eating cooked sweet potatoes that have been left out can cause Staph food poisoning. This can cause nausea, vomiting, diarrhea, and stomach cramps. Although less common, other types of food poisoning are also possible.
If your baked sweet potato was left wrapped in aluminum foil, it has a higher chance of causing botulism. This is because the Clostridium botulinum bacteria thrives in a low-oxygen environment. When a potato is wrapped in tin foil, it is a low-oxygen environment.
So take extra caution with sweet potatoes wrapped in tin foil and left out. Botulism requires emergency medical attention, and it can be fatal.
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How to Tell If Cooked Sweet Potato Has Gone Bad
When it comes to cooked sweet potato that was left out, you shouldn’t try to judge if it’s bad by using your senses. Make the decision based on the number of hours that it has spent in the “danger zone” of 40 to 140 °F since being cooked.
If it was in the “Danger Zone” for more than 2 hours, it should be thrown it out, according to USDA recommendations. Additionally, if it’s been in the refrigerator for more than 5 days, it should also likely be thrown out.
Obviously, if you see visible mold on your sweet potato (or if it smells bad), that may be a sign to throw it out. But don’t expect that all “bad” sweet potatoes will necessarily look bad.
Unfortunately, you cannot rely on your sense of smell and taste to know for sure whether cooked sweet potatoes have gone bad. This is explained in a fact sheet from the FDA:
“You may be surprised to learn that food can make you very sick even when it doesn’t look, smell, or taste spoiled. That’s because foodborne illnesses are caused by pathogenic bacteria, which are different from the spoilage bacteria that make foods ‘go bad.'”
The document goes on to explain that many foods contain a small amount of pathogenic bacteria when you buy them from the store. So all it takes is a few hours of time in the “danger zone” (40 to 140 degree Fahrenheit), and those bacteria can multiply many times.
Here’s the takeaway: Don’t try to “figure out” if your cooked sweet potato went bad by looking at it, smelling it, or tasting it. You can’t accurately judge the levels of pathogenic bacteria that have multiplied by using your senses alone.
- Is a Sweet Potato Bad If It’s White Inside? Sweet potatoes can develop white spots inside if they’ve been refrigerated before being cooked. If that’s what happened, then the sweet potato is not necessarily bad. Read more about this below.
How to Store Cooked Sweet Potatoes
Cooked sweet potatoes should be stored in an air-tight container in the refrigerator or freezer. They can last about 3-5 days in the refrigerator or up to 6 months in the freezer. This applies to baked sweet potatoes, mashed sweet potatoes, and most variations.
Do Sweet Potatoes Need to Be Refrigerated?
Raw sweet potatoes should not be refrigerated. They should ideally be stored in a basket in the pantry, in the dark at room temperature. Cooked sweet potatoes should be refrigerated in an air-tight container, and they can last for about 3-5 days.
It might come as a surprise that, when it comes to raw sweet potatoes, you should ideally not refrigerate them. They should be stored, unwashed, in a “cool, dark, dry” place. But the refrigerator is a bit too cool. And they should have some air ventilation.
The ideal place to store raw sweet potatoes is in a bowl in the pantry, or in the basement. For shorter time periods, you could also just keep them in a bowl on your kitchen counter—but ideally, not right next to a window. (Remember: Cool, dark, and dry.)
If you do refrigerate raw sweet potatoes, they will still be safe—but they may be harder and less flavorful, with white spots in the middle. So it’s better to put them in the pantry, not the refrigerator. (source)
It’s also possible to freeze your raw sweet potatoes and store them for up to 1 year.
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