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Why Do Potatoes Turn Black? (Explained)

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Potatoes are a type of vegetable that enhances the flavor of almost every cuisine, starting from French fries to grilled potatoes. It is one of the most popular vegetables, and it is widely available all over the world.

Let’s take a look at some of the reasons why potatoes turn black and learn about some potato storage hacks as well.

Why do potatoes turn black?

The principal cause of the potatoes turning black is direct air exposure. The oxygen in the air causes the oxidation of starch in potatoes. As a result, it turns black, brown, or grey. The blackening of potatoes is also caused by the oxidation of ferri-chlorogenic acid during boiling or frying.

A variety of factors might cause potatoes to become black. Let’s have a quick discussion on what happens to potatoes when they are exposed to certain stimuli. Those are as follows:

After cooking:

After cooking, potatoes have a tendency to darken. When you boil or fry potatoes, you’ll usually notice that they’ve darkened.

The oxidation of ferri-chlorogenic acid on the potato causes this. There is no need to be concerned because this is not harmful to the human body.


If potatoes are stored in a warm environment, they might begin to decay from the inside. A tuber pith cavity can form inside the potato, which is known as a “blackheart” or “black center”.

Therefore, when you cut the potato, you will discover a large pith-like hole inside it.

When exposed to air:

Potatoes have a good amount of starch in them. As a result, when peeled potatoes are exposed to air, the starch undergoes oxidation, turning the starch black, grey, or brown in color.

After cutting:

The oxidation process takes place if the raw potatoes are left exposed to air after chopping, causing the starch to turn brown quickly. Thus, if you don’t want your potatoes to brown, use them right after you’ve finished cutting them.

In saltwater:

When potatoes are kept in saltwater, they do not become black. If you keep them in the saltwater after chopping them, they become soft and floppy.

The water inside the potato begins to move out as the concentration of salt in the water exceeds that of the potato cells. Therefore, if the potatoes are stored in saltwater, they may shrink.

Furthermore, putting peeled and chopped potatoes in saltwater in the refrigerator is an excellent technique to protect them from turning black or brown.

After freezing:

Potatoes do not turn black after freezing. But they can turn black while thawing, as at that time they come into direct contact with oxygen.

Therefore, take a bowl of water and put your frozen potatoes in it so that even after thawing, they don’t turn black.

When boiled:

Boiled potatoes can also turn black if they sit around for a long after being peeled.

While boiling potatoes in a pot full of water, you will often notice that the water surprisingly turns black as well. This happens because the potatoes release their starchy molecules into the water while it is being boiled.

After peeling:

If the potatoes are left to sit for too long after being chopped, they will turn gray, brown, or black. This occurs as a result of the oxidation process, which turns the potato’s starch dark, grey, or black.

When baked:

Baked potatoes do not turn black. When potatoes are baked, the starch granules absorb all of the water, making the potatoes soft and fluffy. After you’ve finished baking the potatoes, you’ll notice that they’ve turned a gorgeous golden brown color.

Is black potato bad? Can you eat potatoes that turned black?

The black potatoes are not bad. They pose no harm to humans and are completely harmless. 

If the potatoes are stored at a high temperature, a tuber pith void known as a “blackheart” or “black core” may develop. Remove the black section of the potato while cutting it in this condition, and the rest of the undamaged flesh of the potato is perfectly safe to eat.

Black potatoes, on the other hand, should be avoided if you discover a greenish fungus-like element on them. As a result, before using potatoes, make sure to check for any green elents.

Potatoes turn black when they are exposed to oxygen, which causes the starch inside them to turn black, brown, or grey. It isn’t a disease at all. Therefore, even if the potatoes turn black, they will not harm our health.

How to tell if potatoes are bad?

It is essential to select the freshest and healthiest potatoes before using them in any recipe. There are a few methods for determining whether the potatoes are bad or not. Those are as follows: 

If the potatoes appear soft upon squeezing:

When you go to the vegetable to buy potatoes, make sure to squeeze them. If upon squeezing the potatoes turn out to be soft, it means that it is rotten and not suitable for eating.

If the potatoes have a foul odor:

The smell of a potato indicates its general condition and freshness. As a result, if the potato emits a stale odor, know that it is rotten and unhealthy.

If the potatoes have wrinkles:

Potatoes with wrinkles mean that they have lost their moisture from being exposed to too much heat. Therefore, wrinkled potatoes are indicative of bad quality potatoes.

If the potatoes have green skin:

Despite the fact that potatoes are produced underground, they can occasionally come into direct contact with sunlight that is exposed above ground. As a result, it creates a chemical called solanine to protect itself from predators.

Solanine causes the skin of potatoes to become greenish in color, making the potato unpalatable to eat. Thus, a green peel on potatoes is a sign of a rotten potato.

If the potatoes have dark spots and bruises:

Blight or fungal infection causes dark patches on potatoes. Mishandling is generally indicated by bruises. Thus, dark patches and bruises are regarded as bad conditions on a potato. 

How do you keep potatoes from turning black?

There are numerous ways of keeping potatoes from turning black. Let’s look at some methods for preventing the potatoes from turning black. Those are as follows:

Put the potatoes in the cold water:

It is essential to keep the potatoes away from direct air exposure, as this can cause them to turn black. To do so, fill a bowl halfway with cold water. The cold water will prevent the potatoes from turning brown and black by slowing down the oxidation process.

Use lemon juice:

Acids are quite beneficial in preventing the blackening of potatoes. Place the potatoes in½ gallon of water with a teaspoon of lemon juice squeezed in it. For the presence of citric acid in lemon, the potatoes will not turn black.

Use white vinegar:

Acetic acid is found in vinegar. Fill a bowl with ½ gallon water and a teaspoon of white vinegar. Place them in a bowl until used.

Should you put potatoes in the fridge?

No, potatoes should not be stored in the refrigerator. Because there are certain drawbacks to storing potatoes in the refrigerator. Firstly, raw potatoes should be stored in a cold, dry location. Thus, keeping potatoes in the fridge is not recommended at all.

Secondly, storing the potatoes in the refrigerator may result in a higher glycemic index. A chemical called acrylamide forms when the potatoes stored in the fridge are cooked, fried, or baked, which is responsible for the extra sweetness.

For the reasons stated above, it is preferable to avoid storing potatoes in the refrigerator.

How do farmers store potatoes?

After harvesting, farmers follow a set of steps in order to store their potatoes.

They begin by sorting the potatoes according to their condition. On some potatoes, dark stains, bruising, or green skin may appear. They separate the potatoes so that the rotting ones do not harm the healthy ones. Farmers usually discard potatoes that have been severely damaged.

Second, after they have finished sorting the potatoes, they cure the ones that are susceptible to rot. Curing is a method of halting the rotting process.

Finally, they keep their potatoes in a cool, dry, and dark location, such as a godown, root cellar, garage, or basement, where the temperature is normally between 38 and 40 degrees Fahrenheit.

The farmers do this mostly to keep the potatoes out of direct sunlight. They do, however, make sure the potatoes are stored in a well-ventilated area.

Farmers preserve their potatoes in this manner.

Final Thoughts

Potatoes can turn black due to a multitude of circumstances. It can be kept healthy and fresh for a long time if you pay attention and use suitable storage methods, such as keeping it away from the air. So, direct air exposure should be strictly avoided to keep your potatoes from turning black.

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