How To Tell If A Sweet Potato Is Bad | What Are The White Spots?

Have you ever wondered how to tell if a sweet potato is bad? Here are a few things to look for:

Color: Fresh, or at least “not spoiled” sweet potatoes should be a bright, orange color (or light yellow, depending on the kind of yam or sweet potato) on the inside. The outside is a dull, dusky brown, with some spots. Large bruises, long sprouts, moldy areas, breaks in dry skin, bore holes, are all signs of bad sweet potatoes.
Texture: Sweet potatoes should be firm to the touch. If you feel any soft spots or mushy areas on a raw, whole sweet potato, it’s gone bad and needs to be thrown away and not eaten. If you see small sprouts or “eyes” but no other sign of a bad sweet potato, they can be removed.
Mold: Mold is a clear sign that a sweet potato is spoiled. If you see any mold on the sweet potato, it should be discarded immediately.
Smell: Sweet potatoes should have a mild, earthy, sometimes “dusty” odor. If your sweet potato has a strong rotten, sour, or unpleasant smell, it is bad.

Often you can see a couple of these signs at once, like a mushy texture and strong smell or a soft opening with mold in it, indicating a bad sweet potato.

If you’re not sure whether a sweet potato is bad, it’s best to err on the side of caution and throw it away. It’s not worth getting sick over a sweet potato!

In this article, let’s get into the details of a spoiled sweet potato with pictures of our unfortunate sweet potatoes giving it up for the cause. Plus, some storage tips, and a look at cooked and canned sweet potatoes, too.

Do sweet potatoes go bad?

Yes, whether raw or cooked, sweet potatoes will go bad. It can take weeks for whole raw sweet potatoes to go bad, so it depends on how they are stored. Right now, I’m keeping a whole ube in the crisper drawer of my fridge because the first two went bad after five days in my potato box, but I have some yellow yams in their unopened bag on the floor of my pantry that are still fine after a MONTH.

You can expect cooked sweet potatoes to stay good to eat for up to four days if kept cold and haven’t already been left out (like on the Thanksgiving table) for hours at room temperature.

How long do sweet potatoes last?

Raw sweet potatoes:
Whole and uncut: Best stored in dim light, loosely covered or kept in their original bags up to a month.
If you’ve bought them in “microwaveable” plastic wrap, probably good for a week.
Cut and/or peeled: Store in the refrigerator up to 7 days. Note: Don’t freeze raw sweet potatoes.

Cooked sweet potatoes:
Kept cold and hasn’t sat out, tightly covered, cooked sweet potatoes can probably still be good to eat in four or five days. They might “leak” syrup, but they should still be okay to eat in that timeframe.
Can be frozen for up to a year but six months is better. Press the air out of the packaging as much as possible before putting in the freezer.

Cans of sweet potatoes and yams

Unopened cans
Unopened, undamaged cans usually are still good to eat for a year. Keep in mind that the cans generally come with a use-by date. Bruce’s brand comments:

All of our Bruce’s Yams products have an expiration date stamped on either the top or the bottom of the can. We do not recommend consuming any product after the expiration date.

That said, the federal government encourages reduced food waste; your undented can of sweet potatoes might still be good years after the expiration date.

Opened cans
There’s less threat of opened cans causing illness these days, but generally, air gets to food left in cans. That said, opened cans of sweet potatoes that are chilled and kept covered should last about four days in the fridge. To best store canned sweet potatoes that have been opened, transfer them to shallow airtight containers and slide them right into the refrigerator.

How to tell if an uncooked sweet potato has spoiled

Sprouts: Sweet potatoes often sprout after they have been stored for a long time. Sprouts are not harmful, but they can make the sweet potato tough and fibrous. If you see sprouts on your sweet potato, cut them off and cook the sweet potato immediately.
Discoloration: Sweet potatoes should be a uniform orange color. If you see any dark spots or discoloration on the sweet potato, it may be spoiled.
Soft spots: Sweet potatoes should be firm to the touch. If you feel any soft spots on the sweet potato, it may be spoiled.
Mold: Mold is a sign of spoilage. If you see any mold on your sweet potato, it should be discarded.
Off-putting odor: Sweet potatoes should have a mild, earthy odor. If your sweet potato has a strong or unpleasant odor, it may be spoiled.

How to tell if a cooked sweet potato has spoiled

Mold. Mold is a sign of spoilage. If you see any mold on your cooked sweet potato, it should be discarded.
Unpleasant flavor or color: Cooked sweet potatoes should have a sweet, nutty flavor and a bright orange color. If your cooked sweet potato has an unpleasant, sour, or yeasty flavor, don’t continue eating it. If the color looks very brown, blue, purple or anything besides the gold or orange color, throw it away.

If you are unsure whether a sweet potato is spoiled, it is best to err on the side of caution and discard it.

What is the white inside a sweet potato?

The White Ooze: What Is It and Is It Safe to Eat?
If you’ve ever cut into a sweet potato and seen a white, milky substance ooze out, you’re not alone. It’s perfectly normal. This white substance is called sap, and it’s a mixture of sugar and starch. Sweet potatoes produce sap when they’re cut open because their cells are damaged. The more sugar and starch in the sweet potato, the more sap it will produce.

Organic sweet potatoes are more likely to have sap than non-organic sweet potatoes. This is because organic sweet potatoes are often grown in smaller quantities, which gives them more time to mature and develop more sugar and starch.

Fresh sweet potatoes are also more likely to have sap than older sweet potatoes. This is because fresh sweet potatoes have more moisture content.

So, if you see sap oozing out of a sweet potato, it’s a sign that the potato is fresh and sweet.

Why do some sweet potatoes leak sap while others don’t?
The amount of sap that a sweet potato produces depends on a number of factors, including:
– The sugar and starch content of the potato
– Whether the potato is organic or non-organic
– The freshness of the potato
Sweet potatoes with a higher sugar and starch content will produce more sap. Organic sweet potatoes are more likely to have a higher sugar and starch content than non-organic sweet potatoes. Fresh sweet potatoes are also more likely to have a higher sugar and starch content than older sweet potatoes.

Is it safe to eat sweet potato sap?
Yes, sweet potato sap is safe to eat. It’s a mixture of sugar and starch, both of which are essential nutrients. In fact, some people believe that the more sap a sweet potato produces, the sweeter it will be. So, if you see sap oozing out of a sweet potato, don’t be afraid to eat it! It’s a delicious and nutritious addition to your meal.

Black spots on sweet potatoes

Seeing black spots on your sweet potatoes after peeling them? The flesh will oxidize as it’s exposed to air for a while, a harmless reaction that is similar to how white potatoes turn brown after being peeled. But you may be seeing dark spots that happen when the sweet potatoes jostle against one another, and this can simply be cut away before or after cooking. There may even be a kind of opaque, all-over bruising called scurf, which is unseemly but also doesn’t affect eating.

Worrisome as any of these “black spots” may seem, sweet potatoes that show these signs are often still safe to eat.

Pinholes in your sweet potatoes

The tiny pinholes, bores, or tunnels that you might see in sweet potatoes are often caused by wireworms. Wireworms eat the potato and leave tunnels and holes behind. Since the wireworm itself is a larvae, it’s not laying eggs in the sweet potato but feeding on the flesh of the potato itself. While you aren’t likely to find a wireworm hanging out in the potato, the wounds it has left create openings for mold and bacteria to enter, so it’s not a good idea to eat a sweet potato that has these marks left in it.

The University of Delaware has good photo examples of sweet potatoes with wireworm holes.

Tips on storing sweet potatoes

1. Avoid storing most raw sweet potatoes in the fridge. This often produces a hard center.
2. You can store sweet potatoes in cool, dry, and well-ventilated containers instead out of the sun and away from heat.
3. For best results, keep them in a basement or a root cellar, as this will keep your sweet potatoes away from strong heat sources. (My store-bought sweets are either kept in the bag, or I remove them and add them to a tall stock pot with the lid off slightly and a clean kitchen towel on the bottom, which I keep in my pantry.)
4. If you are hoping for very long-term storage of your raw sweet potatoes, you can store them in sand. Maybe not practical for the typical suburban home, but not impossible.

Can you freeze sweet potatoes?

It is not recommended to freeze raw sweet potatoes, but you can freeze cooked sweet potatoes. While Michigan State University mentions “curing” sweet potatoes before cooking and freezing to bring out their utmost sweetness, it’s not always practical. Just cook and prepare them, then remove as much air as possible before putting them into the freezer. If wrapped tightly, they should be good to eat a year later.

The bottom line

Sweet potatoes are known for being shelf stable for a long time under the right conditions, but it’s important to know how to tell if they’re still good to eat. We had to set out our sweet potatoes for this article for over two months to get them to a “bad” state. Here are a few things to look for:

1. Soft or mushy texture. A good sweet potato should be firm to the touch. If it’s soft or mushy, it’s likely spoiled.
2. Discoloration. Look for any dark spots or patches on the skin. These could be a sign of rot. If the flesh inside the potato is discolored, it’s also best to discard it.
3. Mold. If you see any mold on the sweet potato, don’t eat it. 
4. Smell. A fresh sweet potato should have a mild, earthy smell. If it has a sour or off smell, it’s probably gone bad.