The white liquid of sweet potatoes - what is it?

Sweet potatoes are a fantastic staple that you should always have in your pantry. They’re delicious, versatile, and packed with nutrients—what’s not to like?

However, the sight of a white substance oozing from the potato may be enough to put you off considering this vegetable.

Hopefully, though, you’ll be willing to give them another chance, because not only is this normal, but it can even be a sign of an extra-sweet sweet potato.

What is the white exudate of sweet potatoes? The white stuff that sometimes seeps from cut sweet potatoes is completely normal sap, a mixture of sugar and starch. It is not harmful in any way and is completely safe to eat. 

If you want to know more about the common white sap in sweet potatoes, keep reading.

We’ll also share other common concerns about sweet potatoes and let you eat in peace, knowing what’s really worrying and what’s just nature being a little weird.

What is the white residue of sweet potatoes?

Many vegetables release a latex-like residue when cut. Pumpkin, chayote, and sweet potatoes are among the most common.

There are many speculations as to why some potatoes drip with sap and others do not. Some of the more common theories are

1. The sweeter the potato, the more likely it is to have white ooze because it is the sugars that leach out.
2. Organic sweet potatoes are more likely to have milky residue because something in the process of growing them in bulk reduces the milky starch. It is not clear if it is the genetic modification of the seeds, the use of different fertilizers and pesticides, or another factor.
3. The fresher the sweet potato, the more likely it is to lose the white ooze. This also makes sense because as sweet potatoes get older, they start to dry out. This makes it much less likely that they will lose any type of fluid.

So not only is white sap safe and not a cause for concern, it can also be a sign that your sweet potato is super sweet, organic, extra fresh, or all three!

Sweet potato white spots

Depending on how you prepare the sweet potato, you may never see white sap, or you may notice it in different ways.

A baked sweet potato that has been scrubbed but not cut in any way probably won’t have any sign of liquid starch.

However, if you peel a whole sweet potato, you may notice that some of the milkiness creates a fine sheen along the surface of the sweet potato. You can wash it before cooking, but it’s fine to eat.

If you cut a sweet potato in half and open it up, you may notice small white spots dotting the inside of the potato.

This, again, is simply the starch and sugar making its way into the flesh of the potato through whatever tiny hole it can escape.

Whether the white spots are small and spread all over the potato, or larger and concentrated in certain areas, the milky sap is not harmful and can be easily rinsed off, although it will be sticky to the touch.

Once cooked, the starch is not sticky and you won’t notice it on your potatoes in any way.

White flesh of the sweet potato

If you’ve bought a sweet potato that has white flesh inside, rather than vibrant orange flesh with white spots or a white ooze, you may have accidentally bought a sweet potato.

In most of North America, sweet potatoes are mislabeled. What is often called a yam is actually a type of soft sweet potato.

Proper sweet potatoes typically have brown skin and white or purple flesh, while sweet potatoes have orange flesh. If your sweet potato is white, you probably have a yam.

Yams and sweet potatoes are very similar in flavor and texture, although yams are slightly less sweet and have a drier texture.

How to know if a sweet potato is bad

Sweet potatoes last a long time under the right conditions, but even these root vegetables spoil over time. There are different types of spoilage to watch out for, each with unique signs that indicate the poor quality of your sweet potato.

The most obvious sign that your sweet potato has gone bad is shriveled, wrinkled skin. If your sweet potato has started to wrinkle, it’s best to throw it away and not eat it.

Other more common problems to deal with in connection with sweet potatoes are mold, pith or holes in the potatoes, and/or dry insides.

Mold

Sweet potatoes often develop dark spots, which doesn’t necessarily mean your potato has gone bad.

You only need to worry if, in addition to discoloration, you see visible mold.

Mold on sweet potatoes can be fuzzy and white, green, or blue around holes or cuts, or it can look and smell rotten under the skin of your sweet potatoes.

When potatoes of any variety rot, you will smell them. Do not eat potatoes that have signs of mold or you can get sick.

boneless

If you’ve ever picked up a sweet potato that you wanted to make for dinner and noticed that it looked spongy, you may have discovered a bone-in potato. If you were to open it up to discover holes inside, you would be safe.

Holes in sweet potatoes can appear when stored in a place that is too warm for your liking. Sweet potatoes are picky and do not do well in places that are too hot or too cold.

Sweet potatoes can be eaten without problems. However, the texture is compromised and the flavor is often less palatable than tubers that have been stored under more ideal conditions.

A few small holes can be eaten, but a very chopped potato should be thrown away simply because it doesn’t taste good.

dry

Dry spots on the inside or outside of your sweet potato are signs of an old potato that has lived past its prime.

Small dry spots on the surface can be removed and you shouldn’t notice much of a difference in taste or texture.

But if you cut into a raw sweet potato and see that it’s dry on the inside, that will affect the feel of the potato, mainly, but it can also affect the flavor.

If there is only a little dryness, you can boil and mash the potato without anyone knowing, but it’s best to throw out potatoes that have too many dry patches inside.

root growth

If you start to notice small sprouts or roots forming in the eyes of your sweet potato, take this as a sign that the quality is beginning to deteriorate.

They can still be eaten and will taste good, but the longer the roots grow, the less desirable the sweet potato will be.

When choosing from a large selection of sweet potatoes in your pantry, always use the ones that appear to be sprouting first. You just have to trim the roots that grow and peel or prepare them as usual.

Related questions

How long do sweet potatoes last?

Fresh, healthy sweet potatoes will last in your pantry for up to 3 weeks before they start to go bad, depending on storage conditions.

To keep sweet potatoes healthy for as long as possible, store them in a cool, but not cold, dry place, away from direct light.

Sweet potatoes do not like fluctuating temperatures or extremes of hot or cold. They are also much more likely to go bad if they are exposed to any kind of moisture, so make sure they are dry at all times.

Once you’ve cut the sweet potatoes, they should be used within a few days. Store them in water to prevent them from rusting, and make sure they are tightly closed, either in an airtight container or zip-top bag.

Cooked sweet potatoes can also be kept for a few days in the fridge. Try to finish them before 3 days.

You can also freeze the sweet potatoes and sweet potato chips and casserole. It is better to freeze them after they have been cooked. They will keep for 1-3 months if frozen carefully.

Why does my sweet potato taste like soap?

Humans have the ability to taste 5 different flavors: sweet, salty, sour, bitter, and umami.

Some people are especially sensitive to bitter tastes, known as supertasters, and many others simply dislike the taste of bitter foods. If sweet potatoes seem to you to taste like soap or perfume, the reality is that they are probably bitter.

Sweet potatoes are not meant to be bitter and this could be a sign that your sweet potatoes have started to rot or have been grown in poor conditions.

In any case, if your sweet potatoes are bitter, you may want to avoid eating them.

Is it safe to eat a potato with a hollow core?

Hollow heart in potatoes is similar to that in diced potatoes, but more severe. Rather than being caused by poor storage conditions, hollow hearts are often the result of poor growing conditions.

If you cut up a sweet potato and see that it is hollow in the center, or has a big brown, bruised area in the center, you have a hollow-hearted sweet potato.

Unfortunately, you will have a much smaller amount of potato than you expected. Fortunately, the flavor and texture shouldn’t be compromised, so you can safely eat the rest of the potato.