Potatoes turn green when light exposure causes them to produce chlorophyll in the skin. Chlorophyll itself is not the main safety problem. Light exposure can also encourage the potato to produce more natural defense compounds called glycoalkaloids, including solanine. Heavy greening is a reason to discard the potato.
Why does sunlight make potato skin green?
Potatoes are underground stems called tubers. Once they are exposed to daylight or strong store lighting, their skin can make chlorophyll. At the same time, glycoalkaloid levels may increase, although the amount of visible green is not a precise measure of toxicity. Green color is an important warning sign, not a laboratory test.
Is it safe to eat a potato with a green spot?
For an otherwise firm adult-serving potato with only a very small superficial green patch, some university extension guidance permits completely cutting away the green tissue and eyes. Discard potatoes with extensive greening, a distinctly bitter taste, or heavy sprouting. If cooking for children, University of Maine Extension advises avoiding green potatoes altogether. When uncertain, throwing the potato away is the safer choice.
Does boiling or roasting make a green potato safe?
Do not count on cooking to remove the hazard. Glycoalkaloids are not reliably destroyed by ordinary home cooking. Trimming a tiny green area, where appropriate, removes tissue containing higher concentrations; it does not make an extensively green potato acceptable.
How to prevent potatoes from turning green
- Keep potatoes away from windows and bright kitchen lighting.
- Use a cool, dark, dry, ventilated pantry or other suitable storage location.
- Avoid clear bags or open countertop baskets under lights for long periods.
- Check stored potatoes regularly for major greening, sprouting, softness, and rot.
- Do not store washed potatoes damp; moisture encourages spoilage.
Frequently asked questions
Is green color itself poisonous? No; chlorophyll makes the color. The concern is glycoalkaloids that may rise with light exposure.
What if a potato tastes bitter? Stop eating it and discard it; bitterness can signal elevated glycoalkaloids.
Can potatoes turn green in a supermarket? Yes. Store display lights can contribute to greening, not just direct sun.
Related reading and sources
For more kitchen troubleshooting, see why stored onions sprout. Read University of Maine Cooperative Extension’s food safety guidance and University of Minnesota Extension on green tubers.
Leave a Reply