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How To Tell If Potatoes Have Gone Bad (Plus Ways to Extend Their Freshness)

By Dan Scalco • Updated Leave A Comment

Potatoes are not only an incredibly versatile food in terms of cooking, they’re chock full of nutrients. It’s no wonder they’re a global staple food, ranked as the third most important food crop in the world (after rice and wheat).

You can boil ‘em, mash ‘em, stick ‘em in a stew—however, what’s most important is making sure your taters are good for eating and making sure that they will last long enough for your next meal.

Maybe you’ve got a big bag of potatoes that have been living in your pantry for a while and you’re not sure if they’re still edible. Maybe you found a potato from under the fridge that looks more like something from outer space; sprouts, mush, mold, and all.

While getting rid of a mushy, moldy potato is a no-brainer, how do you know whether the potatoes you’ve got have gone bad? And if they haven’t gone bad just yet, how can we make them last longer? In this article, we’re going to answer both.

Before we begin, we need to know some basics such as the average shelf life of a potato and how to pick out good produce.

Potato Shelf Life

The shelf life of potatoes varies by their environment. At room temperature, raw potatoes last for up to two weeks, while raw potatoes stored in a cool, dry place can last three months. After about five weeks in the pantry, uncooked potatoes start to lose their firmness.

Meanwhile, cooked potatoes can go up to four days in the fridge. Raw potatoes, on the other hand, do badly in the refrigerator and the freezer because the low temperature degrades their texture and taste, resulting in browning and softening.

Frozen cooked potatoes last up to a year in the freezer, but the quality of potatoes cooked with certain methods deteriorate once frozen. For example, mashed potatoes are going to have a completely different texture after being frozen due to the cooking process combined with what freezing does to potatoes.

Selecting Good Potatoes

Fresh Potatoes

The best way to keep your potatoes fresh and healthy is to select good potatoes in the first place. The potatoes that are going to have the longest shelf life will have the following characteristics upon inspection:

  • They’re firm to the touch
  • They have smooth skin
  • They don’t have bruises or any noticeable defects
  • They don’t have sprouts

Sometimes, potatoes are damaged during harvest or transport—these will have obvious injuries like shovel marks and cuts from machinery.

When picking potatoes, I always recommend going for the loose ones instead of the prepackaged ones, so you can check each tuber before buying them. Look for unblemished, whole potatoes, as they will last longer in your pantry.

Signs That Potatoes Have Gone Bad

Spoiled & Moldy Potato

So, how do we know whether our potatoes have gone bad? Like other produce, potatoes have specific signs that tell you whether they’re still good to eat.

When in doubt, I always use the “look, smell, and feel” test to find out whether your potatoes can be used. This test applies to both cooked and raw potatoes, but in different ways. Let’s start by looking at the signs that raw potatoes have gone bad.

Raw Potatoes

Sometimes, raw potatoes don’t show signs of spoilage on the outside—it’s always a good idea to peel and cut them into halves or quarters if you’re worried that the insides have started to rot.

Look Test

Good raw potatoes are firm to the touch, with smooth skin that doesn’t have any sprouts. From a glance, you can tell whether your potatoes have skin that is out of the ordinary—the skin on a potato ages with time, so if your potatoes have wrinkly, shriveled, soft, or mushy skin, that’s a sign that they’re just about ready to spoil.

Potatoes that are discolored or obviously decayed should go into the trash—black spots and soft spots indicate that the potato has started to rot. If there is mold on your potato, that also means that it’s time to throw it away. Even if you cut off the mold spots, there’s a chance that the mold spores have taken root elsewhere in the potato.

You can still eat potatoes that have wrinkly skin and dark spots, as they won’t affect the taste of the potato. However, if they’re already mushy or the skin is visibly sagging, it’s time to get rid of them.

Smell Test

Fresh potatoes have a distinctive earthy scent similar to other root vegetables. If your potatoes smell like mildew or mold, that’s a sure sign that they shouldn’t be eaten. On top of that, if the potato smells sour, bitter, or musty, it’s best to err on the side of caution and toss it.

When the potato isn’t showing any visible signs of spoilage on the outside but it smells funky, there’s a possibility that it’s already started to rot on the inside. If you’re buying potatoes at the store, you obviously won’t be able to cut them in half to tell whether they’re still good to eat, so take a sniff and see whether they still smell fine.

Feel Test

Soft potatoes are still alright to eat, but if it’s mushy, leaking liquid, or too soft that it can’t hold its shape, it’s better to discard it. After feeling your potato, check if it smells rotten—sometimes, the softness shows that the inside has decayed.

Cooked Potatoes

Once cooked, it’s a little trickier to tell whether potatoes have gone bad. Cooked potatoes show spoilage a bit differently than raw potatoes. However, the look, feel and smell test still applies.

Look Test

You can usually confirm whether your potato dish is still safe to eat by taking a look at it. If there’s mold growing on it, or if the appearance of the dish has changed significantly, you should throw it away. Mold on food looks like dark spots or fuzz growing on the dish. It can be brown, red, white, black, or blue-gray in color.

Clear liquid sometimes separates from mashed potatoes—you can mix it back into the mash only if it doesn’t smell offensive, but if the liquid or the solid has changed color, it’s better to be safe and toss it.

Smell Test

Spoiled cooked potatoes smell foul, especially if dairy has been mixed in during the cooking process. Once your cooked potatoes smell bad, sour, or moldy, that’s a clear sign that their next destination is the trash as they’re no longer safe to eat.

Feel Test

The feel of cooked potatoes varies according to the dish made. Since they can be prepared in a variety of ways, test for the appropriate texture using a toothpick or a fork. You can also cut into a piece of potato or scoop some mashed potatoes with a spoon to check whether the consistency of the food has changed. If the texture, smell, or look of the food is odd, it’s probably time to bin it.

Sprouting Potatoes

Potatoes Starting To Sprout

When it comes to raw potatoes, things get a little dicey once they start to sprout. Potatoes can still be eaten if they have small sprouts—just remove them with a vegetable peeler or a knife. However, if they have long or large sprouts that are greater than five inches in length, those potatoes are past their prime and you should toss them. Or, you can also plant them if you want to grow potatoes.

Part of why you shouldn’t wait too long to eat sprouted potatoes is because the sprouts take the nutrients out of the potato. This is the same reason why sprouted potatoes shrivel and shrink. Most store-bought potatoes are treated with a chemical that slows down sprouting, so you don’t have to worry too much if you’re getting your spuds from a grocery store. That being said, if your potatoes are organic, homegrown or you’ve gotten them from a farmer’s market, then the likelihood of them sprouting is higher.

Green Potatoes

Raw potatoes turn green as well. This is due to the development of chlorophyll under the skin, which is harmless on its own in other vegetables, but in potatoes, it also means that there is an increase in a toxin called solanine.

Solanine is one of a few toxic glycoalkaloids that develop in potatoes once they’ve started to sprout. If consumed in large amounts, solanine can cause symptoms like:

  • Diarrhea
  • Fever
  • Lower than normal body temperature (hypothermia)
  • Headaches
  • Slow pulse and/or difficulty breathing
  • Stomach or abdominal pain
  • Vomiting

In short, if you eat too many green potatoes, you’re in for a trip to the emergency room—in some rare cases, solanine poisoning can also be fatal. The good news is that mild solanine poisoning only lasts about 24 hours, and you’d have to eat more than a 16-ounce green potato to get really sick.

If your potato has turned green, you can remove the skin, shoots, and any other green parts since that’s where solanine is most concentrated. The green parts of a potato also taste bitter, so eating it won’t be a pleasant experience for your mouth (or your body). If you find yourself eating bitter potatoes at any point, stop immediately and get rid of them.

As potatoes are slightly acidic and hold a lot of moisture compared to other vegetables, cooked potatoes have a high risk of causing food poisoning if they’re not stored safely. But do not fret, we’re going to cover what you can do to ensure that your potatoes stay as fresh as possible with some simple tips below.

Ways to Extend Potato Freshness

Since we now know that raw potatoes have an average shelf life of two weeks to three months depending on how they’re stored, it’s clear that how and where you keep them will affect how long they last.

In short, here’s the best ways to store your raw potatoes:

  • In a cool, dry, dark place that is not the freezer or the fridge
  • In a storage container with good ventilation
  • Dry until you’re going to cook them
  • Away from onions and fruits

Like all plants, potatoes love heat and sunlight. If you keep them in a bright, warm place, they’re guaranteed to sprout and turn green ahead of time. This is good if you want to grow more potatoes, but bad if you want to eat it.

Once you’ve gotten your potatoes, they should be kept in a cool, dry place like a closet or tucked away in a corner of your pantry. If you got your potatoes from the store and they came wrapped in a plastic bag, transfer them to a breathable bag or a basket—this lets the air flow freely and reduces the chances of mold growth due to retained moisture.

When keeping potatoes in the pantry, store them away from onions, tomatoes, and fruits as they emit gases that make potatoes sprout. The worst fruit offenders are apples and bananas—as they ripen, they emit ethylene, an organic chemical that makes potatoes ripen quicker and sprout earlier. Going off of that, ethylene also ripens other fruits stored together.

Wash your potatoes only when you’re about to cook them. If you’d still like to have cleaner potatoes, try brushing them gently to get the dirt off instead. Once they come into contact with water, it’s hard to dry them off, and storing moist potatoes leads to mold growth and spoiled produce.

Storing Potatoes In The Fridge

In general, raw potatoes live their best and longest in cool temperatures between 45°F and 55°F. Keep them too cold and the starches present in your potatoes will start turning into sugar, making them taste sweet and turn brown when you cook them. On the flip side, keep them too hot, and the heat will speed up sprouting, greening, and dehydration in your potatoes.

Another reason why you shouldn’t keep your uncooked potatoes in the fridge where it’s too cold is that as the starches turn into sugar, the reducing sugars can turn into carcinogenic substances (acrylamides) when the potatoes are cooked at very high temperatures (such as in baking).

However, there’s one exception to not keeping raw potatoes in the fridge, and that’s when they’ve been prepared to be cooked. You can keep cut and peeled potato slices in the fridge for up to 24 hours, just make sure they’re protected from browning by covering them completely with water. Uncovered, the potatoes will react with the oxygen and their flesh will turn a grey or brownish color.

Make sure you use them within a day—potatoes left in water will absorb excess moisture and become tasteless and soggy, so this method is best for staggering meal preparation times when you’re planning to cook a big meal later or the next day.

You can also vacuum seal peeled and cut potatoes before keeping them in the fridge. I’ve found that they’ll last a week before they start to spoil.

As with most cooked food, cooked potatoes in any shape or form last up to four days in the fridge before they become unsafe to eat.

Storing Potatoes in the Freezer

Raw potatoes don’t do well in the freezer either. At very low temperatures, the water present in potatoes will expand, creating crystals that damage plant cell wall structures. As a result, frozen raw potatoes become brown and mushy when defrosted, rendering them unusable and inedible.

Potatoes contain enzymes that cause browning when they are left for too long—these enzymes remain active even when the potatoes are frozen. However, partially or completely cooking them helps deactivate the enzymes and prevent discoloration.

If you’re planning on keeping potatoes in the freezer, storing cooked potatoes is the way to go, as they’ll still be okay to eat but they may suffer a little in terms of texture and taste.

Potatoes freeze best when they’re processed into smaller pieces before blanching, so peel and cut them, then boil them for a few minutes before putting them into ice water to cool them down.

Keep your cooked potatoes in an airtight container or a vacuum-sealed plastic bag, then freeze—they’ll last up to a year in the freezer. You can also freeze other kinds of cooked potato dishes like mashed potatoes in the same manner.

To defrost cooked potatoes, leave them in the fridge overnight before you heat and serve them. In my experience, the texture will be better than defrosting using a microwave.

Canning Potatoes

If keeping potatoes in the fridge or freezer isn’t your thing and you’re looking for an alternative that will make them last a much longer time, you can consider canning them. If done properly, canning potatoes can make them last three to five years.

You’ll need:

  • Glass canning jars
  • A pressure canner
  • 10 to 12 pounds of potatoes
  • 1 whole lemon
  • 1 gallon of water
  • 7 teaspoons of salt

To can potatoes:

  1. Peel the skin and remove any blemished or injured parts of the tuber, including any eyes—this will reduce the amount of bacteria left on your spuds.
  2. Put the potatoes into small pint jars. Make sure you leave some space at the top for water and air.
  3. Squeeze the lemon juice into the water and mix thoroughly. Distribute the salt evenly among the jars, then fill the jars with the lemon water until there is half an inch left at the top.
  4. Begin the pressure canning process. Pressure canning steps differ depending on the manufacturer, so you should refer to the steps listed in the manual of your device.

Here’s a great potato canning tutorial that will walk you through the steps.

Final Thoughts

Packed full of vitamins and minerals while being versatile and forgiving to cook, potatoes are a great staple root vegetable to keep in your pantry. They have a relatively long shelf life that depends on how they are kept—store them in a cool, dry place away from sunlight and they’ll last for months.

Now that you know how to identify bad potatoes and how to make them last, you’ll be able to make the most of them. Between baking, mashing, roasting, and grilling, you’ve got plenty of options for making delicious potato dishes.

Have a question we didn’t answer in this article? Let us know in the comments below!

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