You take a perfectly normal looking baked potato, cut it open, and BAM! — you see it. A dark, almost eerie black ring staring back at you from the inside of your potato like it is trying to tell you something. I’ve seen it myself and I am sure many others have. When you see that first time, you will probably think you have cooked a science experiment. But if you are curious about the black ring in your potato, then let us get to the bottom of it, all while we continue to enjoy eating.
What Is the Black Ring Inside My Potato?
That strange grayish-black ring in the center of your potato is called internal black spot or internal bruising. Although it may look scary, internal black spot is a very common problem, particularly in potatoes that have been stored improperly or mishandled.
Internal black spot appears as black or dark brown patches or rings in the interior of the potato. The patches or rings are usually a solid black color, occasionally with a purplish tint, but there is no fuzzy or slimy texture, simply solid potato with a somewhat bruised area inside.
Why Does My Potato Have a Black Ring Inside?
Now, let’s discuss the causes of why you might find this black spot inside your potato. There are several possible causes and most of them do not involve the potato rotting (at least, most of the time).
1. Pressure Damage from Handling or Storage
Pressure damage is the No. 1 reason you’ll find a black spot inside your potato. Potatoes are surprisingly fragile considering they spend their lives growing underground. If potatoes are stacked too tightly in containers or handled roughly during transportation, they can develop pressure damage on the inside of the potato without showing any evidence of damage on the outside. It is quite sneaky. You would never suspect it was damaged unless you sliced into it.
2. Lack of Oxygen Inside the Potato
Lack of oxygen inside the potato can lead to a condition that is commonly mistaken for something much worse called blackheart. While blackheart turns the central part of the potato completely black and is caused by a complete lack of oxygen, internal black spot is a more scattered and ring-shaped condition. Both are related to oxygen, but black spot is more of a pressure bruise situation.
3. Temperature Stress
Potatoes prefer cooler temperatures (not too cold) and warmer temperatures (not too warm). Storing potatoes in the refrigerator or allowing them to go through extreme temperature fluctuations can affect the internal chemistry of the potato and create dark spots even though the exterior of the potato appears to be unaffected.
4. Oxidation of Natural Vascular Tissue
In some cases, the black ring you’re seeing may not be a result of damage at all. It could be simply the natural vascular tissue of the potato oxidizing. The vascular tissues are vein-like structures that run throughout the potato. Over time, these vein-like structures can become darker, particularly after exposure to air during cutting or cooking.
How Do I Know That It’s Not Mold?
The last thing you want is to consume mold, so it is reasonable to be cautious. Here are some ways to determine whether you have internal bruising or mold.
Internal black spot is firm and smooth. There is no slimy, fuzzy, or patchy texture as you’d find with mold. Internal black spot does not have a strong smell such as a sour smell or a musty smell. Mold usually grows in uneven patterns and internal bruising tends to follow the internal structure of the potato.
Is It Safe to Eat a Potato with a Black Spot Inside?
Yes, most of the time. The internal black spot is not toxic or dangerous in any way. However, the areas where the internal black spot occurs tend to be slightly dry or have a slight bitterness. Most people choose to remove those areas and eat the remainder of the potato. I do the same. If the majority of the potato looks and smells normal, it is likely safe to eat.
However, you should discard the potato if:
It smells funny or sour
It feels soft or slimy
The skin is green (green indicates the presence of solanine, a natural toxin found in potatoes)
You actually see mold
How Can I Avoid Buying Potatoes with Black Rings Inside Them?
Although you cannot guarantee that you won’t end up with a potato that contains an internal black spot, there are a couple of things you can do to minimize the likelihood of getting a potato that will contain a black spot.
1. Check Your Potatoes for Softness Before Purchasing
Before purchasing potatoes, gently squeeze them to check for soft spots or dents. If you find any, pass on those potatoes. Those soft spots or dents indicate potential pressure damage that may later manifest internally.
2. Store Potatoes at Home Correctly
Store your potatoes in a cool, dark place with adequate ventilation. A pantry or paper bag works well. Store potatoes away from refrigerators because the low temperature disrupts the starches within the potatoes, which may increase the occurrence of internal black spot.
3. Shop at Grocery Stores That Sell Produce Frequently
Grocery stores that sell large volumes of produce generally restock their produce rapidly, which reduces the amount of time that any given potato sits under poor storage conditions, reducing the risk of developing internal black spots.
What’s the Difference Between a Black Spot, Blackheart and Rot?
Let’s clarify the differences between these three conditions.
Internal Black Spot: This is what you see, random black bruises or rings. The potato remains firm.
Blackheart: This is a lack of oxygen condition. The entire central part of the potato becomes dark, rather than just having a few spots. Typically this condition results from improper storage.
Mold or Rot: This is a soft, slimy, foul-smelling, fuzzy condition. Clearly, this is a definite “no” — toss it now.
So, if you’ve got a potato with a black ring inside, relax. It’s not a poisonous fungus or a cursed root vegetable. It’s just a weird bruise from the potato’s bumpy journey to your kitchen. Remove the affected portion, proceed, and perhaps you should give the next potato a gentle pat before baking it.
