Black spots on sweet potatoes - What does it mean?

Delicious and nutritious, sweet potatoes are in kitchens around the world, and with good reason. From pies to chips, sweet potatoes are a colorful all-purpose vegetable.

Whether you bake, boil or roast them, black spots can be worrisome and unappetizing.

What do the black dots on sweet potatoes mean? If your sweet potatoes have little black dots, they can still be eaten. They can mean anything from bruising and oxidation to chemical reactions from cooking. However, if your sweet potato has deep black spots, it is a sign of rot and should be discarded.

If you want to get the most out of your spotted sweet potatoes without wasting the whole bunch, this article will explain why black spots appear on sweet potatoes, what to do when they occur, and how to prevent them wherever possible.

Black dots on sweet potato skin

Like almost all vegetables, sweet potatoes are not immune to bruising. Small black spots on the surface of sweet potatoes that are not nicked can be caused by harvesting and packing.

In general, they are not handled like delicate eggs, but are pulled out of the ground and dropped into containers for packing and shipping.

With all the toughness sweet potatoes go through to get to your kitchen, it’s not uncommon for them to have a few battle wounds.

Black spots may simply be a small bruise on the skin, or they may be caused by a wound that allowed bacteria to enter and a bit of mold to develop.

Luckily, small mold spots on the skin of the sweet potato are not a big problem. Most of the vegetable is still totally fine. You just have to trim the black spots when you are peeling the sweet potato and cook it as intended.

Black spots on peeled sweet potatoes

Even if you thoroughly check your sweet potatoes for black spots before peeling them, it’s not uncommon for them to turn black or gray after peeling. In fact, it’s almost guaranteed to happen.

Why do sweet potatoes turn black after peeling? Oxidation. Like other types of potatoes and some fruits like apples and bananas, when the flesh is exposed to air, it oxidizes and changes color.

It may look gross, but it does not affect the edibility or taste of the sweet potato.

To prevent sweet potatoes from changing color when you are peeling them, put them directly into a bowl or pot of cold water. You can further prevent browning after peeling by adding a bit of salt, vinegar, or lemon juice.

The acids stop the oxidation process, allowing them to retain their delicious color while you prepare the rest of the food.

Black spots on cooked sweet potatoes

Sometimes you can do all the preparations right and still the sweet potatoes change color and turn black in the cooking process.

Actually, sweet potatoes are a bit delicate. They don’t always show their bruises right away, so the color develops slowly as they cook and the structure of the sweet potato changes.

Sweet potatoes can have deep bruises just from being stored. If they are stacked too long, they can cause internal bruising that is not visible when the potato is raw.

Another reason sweet potatoes blacken during the cooking process is a chemical reaction that sometimes occurs when other ingredients are added before sweet potatoes are fully cooked.

You can avoid this by adding all the other ingredients to the sweet potatoes after you can easily stick a fork into the sweet potato.

The discolored sweet potatoes may not be as pretty as you imagined, but their flavor shouldn’t change noticeably.

Black spots on the inside of sweet potatoes

Spots in the center of a sweet potato can have a couple of different causes. Sweet potatoes are finicky about how they are stored.

They are the Goldilocks of the potato world, but if they get too hot or cold, they go bad. They prefer that the temperature is always adequate.

Ideally, store sweet potatoes in a cool (not cold) dark place, and in a single layer whenever possible, to prevent bruising.

Try to visually inspect each sweet potato before putting them away. If you notice visible damage or punctures, separate that sweet potato and use it as soon as possible, always watching for damage and removing any mold that may develop.

If you only find a couple of black dots inside the potatoes, you can cut them off and continue cooking.

If the concentration of black spots is about to cancel out the natural orange color of the potato, it is best to cut your losses and throw it away.

Brown spots inside sweet potatoes

If you come across a sweet potato that has brown spots on the inside, it could just be a bruise and you could leave or cut it.

To tell if the stain is a bruise and not something even less appetizing, take a look, feel, and smell the sweet potato in question.

If the discoloration is just a speck or two, the quality of the sweet potato is probably not compromised in any way. You can leave the spots or cut them, depending on your personal sensitivities and how you plan to prepare the sweet potatoes.

If your sweet potato smells bad, it is going bad and should be thrown away immediately. Any vegetables that smell rotten should never be eaten.

You can also squeeze the sweet potato a little. Sweet potatoes should always be firm. If you notice that the sweet potato is soft, mushy or spongy, it’s time to throw it away.

A sweet potato that isn’t nice and firm is on its way to spoiling, and any texture issues you detect with your hand will also be apparent when you eat the cooked version.

How to know if sweet potatoes are bad

Sweet potatoes aren’t shy about letting you know when they’ve gone bad. Sweet potatoes are usually firm. The soft parts of a sweet potato are the first sign that the vegetable is going bad.

Fully soft sweet potatoes are ready for composting, especially if they have gone from fluffy to soft and are starting to ooze.

However, this is not the same as a firm sweet potato leaking white liquid. We have a separate article if you are curious as to what this is.

Spoiled sweet potatoes also smell very bad. Even if you could bear the sight and the smell, you shouldn’t eat sweet potatoes that are this bad.

Sometimes the opposite happens, and the sweet potatoes become dehydrated. If you have a sweet potato that is wilting and wrinkling, it too is past its prime and likely tastes bad.

From time to time, given the right conditions, sweet potatoes will start to grow right in your cupboard.

If they only have a few eyes, you can easily cut or pluck them out. If you have a whole plant about to flower, it’s probably better to bury it than eat it.

Related questions

My sweet potato is growing roots, can I eat it?

Sometimes we leave the sweet potatoes in the pantry longer than expected. If we’re lucky and they don’t go bad, they can start to grow.

If your sweet potato starts to put out white roots, what do you do? These new roots can be easily pulled up, peeled, or cut. If you get to your sweet potato early enough, its flavor won’t be affected.

If the sweet potato has grown many roots and even leaves, it will have changed its flavor and texture. A ripe sweet potato that has grown to a plant will have a woodier texture and lose most of its sweetness and flavor.

Why do sweet potatoes discolor after peeling them?

Just like an apple, if you peel a sweet potato and leave it uncovered, it will start to turn greyish, black or brown.

This occurs because, when the sweet potato pulp is exposed to air, a chemical reaction occurs and it begins to oxidize.

Rust happens to many fruits and vegetables, but luckily, apart from looking less than perfect, it’s normal and safe and won’t alter the taste or texture of your food.