What Does It Mean If a Potato Is Green?
Green potatoes indicate the presence of solanine, a toxic glycoalkaloid, making them potentially unsafe to eat.
The Green Potato: A Cautionary Tale
The humble potato, a staple in diets worldwide, harbors a secret: it can turn green. This discoloration isn’t merely an aesthetic issue; it’s a visual warning signal indicating the presence of solanine, a naturally occurring toxin. Understanding why potatoes turn green and what to do about it is crucial for ensuring food safety and preventing unpleasant, even dangerous, reactions.
Understanding Solanine
Solanine is a glycoalkaloid, a naturally occurring toxic compound found in members of the nightshade family (Solanaceae), which includes potatoes, tomatoes, and eggplants. Plants produce solanine as a natural defense mechanism against insects, fungi, and diseases. While present in low levels throughout the potato, concentration increases significantly in the skin and sprouts.
Why Potatoes Turn Green
The green color is caused by chlorophyll, the pigment responsible for photosynthesis in plants. Chlorophyll itself is harmless. However, its presence indicates that the potato has been exposed to light. Light exposure stimulates the production of both chlorophyll and solanine. Therefore, a green potato almost always signals a higher concentration of solanine. This is why it’s best to store potatoes in a cool, dark, and dry place.
The Dangers of Solanine
Solanine is toxic to humans, even in relatively small amounts. Symptoms of solanine poisoning can include:
- Nausea
- Vomiting
- Diarrhea
- Stomach cramps
- Headache
- Dizziness
In severe cases, solanine poisoning can lead to:
- Neurological problems
- Paralysis
- Coma
While fatalities are rare, it’s important to avoid consuming high levels of solanine.
Factors Contributing to Greening
Several factors contribute to potatoes turning green:
- Light Exposure: As mentioned, light is the primary trigger.
- Storage Conditions: Storing potatoes in warm or humid environments can accelerate solanine production.
- Potato Variety: Some potato varieties are more prone to greening than others.
- Harvesting Practices: Improper harvesting or handling can damage potatoes, making them more susceptible to greening.
What to Do with Green Potatoes
The general recommendation is to avoid eating green potatoes. However, the extent of greening determines the appropriate action.
- Small Green Patches: If the greening is limited to small areas near the surface, you can carefully cut away the green parts, along with a substantial amount of the surrounding potato flesh. Peeling the potato entirely is also advised.
- Extensive Greening: If the potato is extensively green, especially with sprouts, it’s best to discard it entirely. Do not risk consuming it.
Storing Potatoes Properly
Proper storage is crucial for preventing potatoes from greening:
- Darkness: Store potatoes in a dark location, such as a pantry or cellar.
- Coolness: The ideal storage temperature is between 45°F and 50°F (7°C and 10°C).
- Dryness: Avoid storing potatoes in humid environments.
- Proper Containers: Use breathable containers, such as burlap sacks or perforated plastic bags.
- Avoid Storing with Onions: Onions release ethylene gas, which can cause potatoes to sprout and spoil faster.
Green Potatoes vs. Potato Sprouts
While often linked, greening and sprouting are distinct processes, though they frequently occur together. Sprouts, like greening, indicate that the potato is aging and potentially accumulating glycoalkaloids. Remove sprouts before cooking, and discard the potato if it’s extensively sprouted and green.
Solanine Levels in Different Potato Parts
| Potato Part | Solanine Concentration |
|---|---|
| Flesh | Low |
| Skin | Moderate |
| Sprouts | High |
| Green Patches | Very High |
Frequently Asked Questions
Is it safe to eat potato chips made from potatoes with slight greening?
Generally, it is not recommended to consume potato chips made from potatoes that had green patches, even if the patches were removed. Commercial potato chip manufacturers typically use potatoes free from greening. The risk, while potentially low with small quantities, is not worth taking.
Does cooking reduce solanine levels?
Cooking, including boiling, frying, or baking, can slightly reduce solanine levels, but it doesn’t eliminate them entirely. Therefore, cooking is not a reliable method for making green potatoes safe to eat.
Can I compost green potatoes?
Yes, you can compost green potatoes. The solanine will break down over time through microbial activity. However, it’s best to bury the potatoes deep in the compost pile to prevent pets or wildlife from consuming them.
Are all potato varieties equally prone to greening?
No. Some potato varieties are more susceptible to greening than others. Consult your local agricultural extension office or seed supplier for recommendations on varieties that are less prone to greening in your region.
If I peel a green potato, is it then safe to eat?
Peeling a potato with slight greening can reduce the solanine content, but it’s not a guarantee that it will be completely safe, especially if the greening is extensive or accompanied by sprouts. Discarding significantly green potatoes is always the safest option.
What is the safe level of solanine consumption?
The generally accepted safe level of solanine consumption is around 2-5 milligrams per kilogram of body weight. However, sensitivity to solanine varies among individuals.
How can I tell if I’ve been poisoned by solanine?
Symptoms of solanine poisoning typically appear within a few hours of consumption. Look for gastrointestinal distress (nausea, vomiting, diarrhea, stomach cramps), headache, and dizziness. If symptoms are severe, seek medical attention immediately.
Can solanine affect pets?
Yes, solanine can be toxic to pets, such as dogs and cats. Keep green potatoes and potato peelings away from your pets.
Is the green color always solanine?
While the green color is primarily due to chlorophyll and indicates the presence of light, it serves as a strong indicator that solanine levels are elevated. It is a useful visual cue even though the chlorophyll itself is not the problem.
What if my potatoes sprout but aren’t green?
Sprouts, even without greening, indicate that the potato is past its prime. While you can remove the sprouts and consume the potato, its nutritional value may be reduced, and solanine levels may be slightly elevated.
Are sweet potatoes susceptible to solanine?
Sweet potatoes are not part of the nightshade family (Solanaceae) and therefore do not produce solanine. While they can develop discoloration or other issues, they are not related to solanine toxicity.
Can I plant potatoes that have turned green?
It’s generally not recommended to plant potatoes that have turned green. These potatoes are likely stressed and may produce weak or diseased plants. It is always best to start with certified seed potatoes for the best results.