If you need a quick meal that takes little to no maintenance, a baked potato might be your best option. They’re inexpensive, tasty, and a healthy alternative to French fries and hamburgers. However, if cooled improperly, this starchy vegetable can yield unsavory results.
Perhaps the most concerning consequence of cooling a baked potato improperly is the potential growth of Clostridium botulinum, which is a group of bacteria that can cause botulism. Botulism is a serious illness that can lead to paralysis and even death if left untreated. Symptoms include difficulty breathing and swallowing, vomiting, blurred or double vision, dry mouth, and baggy eyelids.
The good news is that botulinum bacteria need a low-oxygen environment to grow and thrive, which means that most food is safe from botulinum bacteria. The bad news is that when you wrap your potato in aluminum foil to bake, the potato is now in a low-oxygen environment.
Is aluminum foil dangerous?
So does that mean your potato is going to give you botulism if you cook it in tin foil? Not necessarily. Aluminum foil helps the skin on your potato stay nice and soft, and it is safe to use as long as you don’t allow your baked potato to cool down to a dangerous temperature while still in the foil after cooking.
What are dangerous temperatures?
Your potato is at a dangerous temperature when it is between 41–135 degrees Fahrenheit. Food experts call this range the temperature danger zone because within these temperatures, it is easiest for bacteria to multiply to unsafe levels on your food.
You need to be aware of the temperature your baked potato is at, but you also need to be conscious of the amount of time you leave it out of the oven too. These two factors are important because baked potatoes are considered to be a time/temperature control for safety (TCS) food. TCS foods, as they are commonly called, are foods that require attention to time and temperature, meaning that you need to be aware of how long you leave a food out at room temperature as well as how you cook and cool the food. It is important to be conscious of TCS foods because, if kept in the temperature danger zone for four hours or more, TCS foods can grow harmful amounts of bacteria on them, creating foodborne illnesses.
What makes a TCS food?
There are five questions you should ask yourself when identifying a TCS food.
- Does this food have a high or low acidity level?
Bacteria grows more readily on foods with lower acidity. For example, pineapple is highly acidic, so bacteria will be less likely to grow on it if you leave it out in the open for a long time. Cantaloupe, however, has lower acidity and will grow unsafe levels of bacteria if not refrigerated.
- How much moisture does this food contain?
The more moisture a food has, the more likely it is to grow harmful bacteria. Watermelon is one example of a food that contains high moisture.
- How do the acidity and moisture interact with each other?
You need to look at both the moisture content and acidity level together to determine if a food is considered a TCS food or not. For instance, although lemonade is high in moisture, it also has high acidity so it is not a TCS food. Tomato juice, however, has high moisture and low acidity—the perfect combination to create bacteria—making tomato juice a TCS food.
- Does it matter how this food is heated and cooled?
If it matters how you cook or cool the food, it may be considered a TCS item. For example, baked bread is not a TCS food. You don’t need to worry about how long you leave it at room temperature, how you warm it up, or how you cool it down. Chicken, on the other hand, is a TCS food. It is important how you cook it and cool it down, and it makes a big difference whether or not you leave it out on the counter overnight.
- Does this food need to be packaged or stored in a specific way?
Determine if there is a special way (such as refrigerating) that you need to store the food in order to prevent it from spoiling. If it requires a certain temperature with its packaging or storage, chances are it’s a TCS food.
If you ask these five questions about a potato, you will probably note that uncooked potatoes do not contain enough moisture to be a TCS food. When cooked, however, potatoes become a TCS food because their moisture level increases.
How can I make sure my baked potato is safe to eat?
You want to be able to eat your potato without worrying if you are going to get food poisoning or botulism. Here’s how you can ensure that your baked potatoes are safe to eat.
- DON’T let your potato sit out in the open at room temperature for over four hours regardless of whether or not it is wrapped in aluminum foil. Although botulinum bacteria cannot grow without the presence of aluminum foil, (or something that prevents the potato from being exposed to air) other bacteria can still grow on the potato if it is left out at room temperature.
- DO serve potatoes immediately after baking them or store them in the refrigerator to keep your potato at a safe temperature. If you use aluminum foil, remove the foil directly after baking to prevent botulinum bacteria from growing.
- DON’T place a baked potato in the refrigerator with the aluminum foil still on it. Your potato will have to pass through the temperature danger zone as it cools down, and if the aluminum foil is still on it, botulinum bacteria may have the potential to grow.
- DO remove the aluminum foil from your potato before storing it in the fridge.
By following these guidelines, you can feel confident that your next baked potato bar is a safe and scrumptious success. Don’t be afraid to use aluminum foil—just remember that your potato needs to breathe too.
Learn more food safety tips in the StateFoodSafety Food Handler Course.
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Editor’s note: This post was originally published in March 2016 and has been updated for freshness, accuracy, and comprehensiveness.