The answer to why potatoes turn green is that chlorophyll production begins under the skin of potatoes exposed to light. Although this green color is a harmless pigment on its own, it is an important warning sign because it also indicates that a natural compound called solanine may be increasing in the potato under the same conditions.
When a potato is exposed to light, it starts producing chlorophyll, just like a plant's leaves, and its surface turns green. Chlorophyll itself does not pose a problem for consumption; however, greening shows that the potato has reacted to light and improper storage conditions. Under these conditions, the potato may also accumulate more glycoalkaloid compounds such as solanine, which can have a bitter taste. The areas where greening is most intense are usually the parts close to the skin and around sprouting eyes; these areas should therefore be given priority when assessing the potato.
Why Do Potatoes Turn Green, and How Can It Be Prevented?
Preventing potatoes from greening is largely possible by storing them away from light in a cool environment. When the precautions below are applied together, greening slows down noticeably.
- Potatoes should be stored in a dark cupboard or cellar that receives no light.
- A cool but non-freezing environment should be preferred, avoiding hot and humid corners.
- Potatoes should be kept in paper bags or perforated boxes rather than transparent bags.
- Storing them separately from ethylene-releasing products like onions delays sprouting and greening.
- They should not be kept for a long time; keeping a small stock and consuming them fresh should be a priority.
What Are Common Mistakes Made When Storing Potatoes?
Certain common mistakes made when storing potatoes speed up greening.
- Leaving potatoes on the kitchen counter in an open spot exposed to direct light triggers greening.
- Storing them in a transparent bag or glass jar does not stop light from reaching the potatoes.
- Keeping them in a hot and humid environment speeds up both greening and sprouting.
- Leaving greened areas unnoticed alongside other potatoes for a long time worsens the problem.
Can Greened Potatoes Be Eaten?
If only a small part of the skin has slightly greened, the rest of the potato can generally still be used once these areas are thickly peeled away and removed. However, if a large part of the potato has greened, sprouted, or has a noticeably bitter taste, it is recommended not to consume it, as the safer approach. A bitter taste should be taken as a practical sign that compounds like solanine may be high; the final assessment may vary depending on the person's sensitivity and the potato's condition.
Which Is a More Important Warning: Green Color or Sprouting?
Besides greening, a potato sprouting from its eyes is also a sign that storage conditions have deteriorated. If short sprouts are carefully removed and the area around them is peeled generously, the potato can often still be used; however, if greening and heavy sprouting occur together, it is safer to be cautious and set the potato aside. When these signs are considered together, it also becomes clear that the storage environment needs to be reviewed.
In summary, the answer to why potatoes turn green is that a potato exposed to light produces chlorophyll, which indicates improper storage. Storing potatoes in a dark, cool, and dry environment largely prevents greening. Thickly peeling lightly greened areas, and setting aside noticeably greened or bitter potatoes, is the most sensible approach for safe consumption.