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Why Do Sweet Potatoes Turn Black? (And How to Prevent It)

Why Do Sweet Potatoes Turn Black? (And How to Prevent It)

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Root vegetables have been used as comfort foods for thousands of years. In fact, they have been a staple of our diet since kingdom come. The earthy flavor that they add to any meal makes them an excellent choice, and they can also be paired with other food items.

Sweet potatoes, as you might know, are an incredibly popular choice for people all over the globe. They can be cooked in a myriad of different ways, and can really compliment your dishes.

While they are relatively resilient vegetables that can be stored quite easily, you should know that the sweet potato might start showing black spots now and then.

For people who are used to cooking sweet potatoes, this is a common occurrence. Sweet potatoes turn black before or after cooking, but have you ever wondered why?

Thankfully, you don’t need to worry about the edibility of the vegetable even after these black spots appear. However, you might want to know why these spots generally appear, and once you know, you can resolve that problem to ensure that these spots do not appear.

Now, let’s talk about some of the reasons why the sweet potatoes usually turn black.

Physical Damage or Mold Spots

Spoiled Red Potato

From time to time, you might notice these black spots appearing on the sweet potatoes before they have been cooked. This can happen if you have kept the sweet potatoes in storage for a long while. In some cases, this might happen because the potato might have sustained damage during the harvesting or storage phase.

When the potato sustains damage, it could expose a wound, allowing mold and bacteria to enter the vegetable. This will cause black spots to appear on the vegetable. They will also become visible from the outside. The best thing that you can do is cut out these parts before you begin cooking.

If you somehow miss these parts and boil the sweet potatoes, you should remove them as soon as the temperature drops a bit, which will allow you to handle the potato again. Keep in mind that the mold will add an unpleasant flavor to the vegetable, and it’s not something that you want.

It should be common practice to check the sweet potato from all angles and to make sure that it is clean from all sides before you decide to cook it.

Again, it’s important to note that it doesn’t really matter if you cook the sweet potato with spots on it; you just have to make sure that you remove the black spots before eating it, otherwise it’s going to leave a weird taste in your mouth.

Mysterious Black Spots

Baked Sweet Potatoes With Toppings

It is relatively easy to spot external damage on the sweet potatoes; you just have to look at it closely to understand what it means. In certain cases, the sweet potato might be completely fine before you put it in the pot or the oven, but when you take it out, it might have black spots.

These large, blackened areas are known as “mystery spots.” However, while the reason for this discoloration is given below, you should know that this doesn’t make the sweet potatoes unsafe to eat.

They are only going to affect the appearance of the dish in general, and you won’t have to worry at all about the taste.

So, What’s the Issue?

Assorted Potatoes on Wood Background

Understanding why these spots appear is important, and if you have been confused about why they appear, you’ve come to the right place!

Basically, you should know that the amount of phenolic compounds in sweet potatoes is considerably high. These are complex organic molecules that are responsible for the color, the aroma, and the nutritional value of the vegetable.

Chlorogenic acid is one of these molecules, and is basically the prime reason for which these spots appear. This acid is found in both sweet and regular potatoes, and affects them both equally when they are cooked.

The chlorogenic acid basically combines with the iron ions found in the potatoes and the oxygen that is absorbed from the surroundings as well as the cooking water, thus creating a dark color.

Of course, it doesn’t look very good, and you would probably want to avoid keeping these sweet potatoes up front in a big dish that you are making.

How to Make Things Better

Cut Sweet Potatoes in Pot

If you are about to make a meal and the sweet potatoes are going to be featured prominently, you might want to check on your chemistry concepts, as they can help you minimize the chances of discoloration on the potatoes.

If there are other acids present within the mixture, they are going to compete for the combination of the chlorogenic acid and the iron ions, and this might prevent your sweet potatoes from turning black.

To prevent that from happening, you might want to consider waiting until your sweet potatoes have been cooked at least halfway through. You have to check to ensure that they have begun to soften, but make sure that you do not add the acid ingredient before the potatoes start softening.

This is going to improve the bonding between the cell walls and will create a very firm texture. You simply don’t want that.

You should only add the lemon juice or any other acid after it has softened to at least 50%. This is a simple trick that is going to reduce the probability of black marks appearing on your sweet potatoes. Again, there’s really no way to reduce the chances of this completely.

Also, when you go shopping for sweet potatoes, you should be a bit careful. Selecting the right potatoes could reduce the chances of black spots occurring.

Always choose firm and dark sweet potatoes that don’t have any bruises, sprouts, or wrinkles on them. You might spot some sweet potatoes that have black spots on them already, so you should avoid those altogether.

These are just a few things that you should know about why sweet potatoes turn black.

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