The Poisonous Compound: Solanine and Glycoalkaloids
All potatoes naturally produce small amounts of glycoalkaloids, including the toxic compound solanine. This is a natural defense mechanism used by the potato plant to protect itself from pests and pathogens. Under normal conditions, the levels of solanine in a healthy, ripe potato are very low and considered safe for consumption. The danger arises when these levels increase significantly due to specific environmental factors, causing certain parts of the potato to become toxic.
The nightshade family, to which the potato belongs, is known for producing these types of alkaloids. While the edible potato tuber is a staple food, other parts of the plant, such as the leaves, stems, and flowers, contain much higher concentrations of these toxins and should never be consumed.
The Toxic Parts to Avoid
Green Skins
When a potato is exposed to light—either in the field or in storage—it begins to produce chlorophyll, which causes the skin to turn green. While chlorophyll itself is harmless, its presence is a clear warning sign of increased solanine production. The green color is a visual indicator that the potato has been improperly stored, and the concentration of solanine directly under the skin is now significantly higher.
The amount of solanine that forms can depend on the intensity and duration of light exposure. If a potato has only a small, superficial green patch, it may be possible to cut it away. However, if the greening is widespread or extends deep into the flesh, the entire potato should be discarded. A bitter taste is another, more reliable indicator of high solanine levels, and any potato with a bitter flavor should not be eaten.
Sprouts and Eyes
The "eyes" of a potato are essentially buds from which new sprouts will grow. As a potato ages and begins to sprout, the concentration of solanine increases dramatically in these sprouts and the area surrounding the "eyes". This is part of the plant's strategy to protect new growth. It is therefore critical to remove all sprouts and the surrounding flesh completely before cooking. For heavily sprouted or soft, wrinkled potatoes, the safest course of action is to throw them away entirely, as the toxins may have permeated the entire tuber.
Damaged and Old Potatoes
Physical damage, such as cuts or bruises, can also trigger an increase in solanine production as a defensive response. Similarly, potatoes that have been stored for extended periods, especially in less-than-ideal conditions, will naturally accumulate more solanine over time. Therefore, it is best to use potatoes that are fresh, firm, and free of any visible damage.
Comparison of Toxic vs. Safe Potato Parts
| Feature | Toxic Parts (High Solanine) | Safe Parts (Low Solanine) |
|---|---|---|
| Appearance | Green skin, sprouts, soft/wrinkled texture | Firm, unblemished skin and white or yellow flesh |
| Storage | Exposed to light, warm temperatures, or for extended periods | Stored in a cool, dark, and dry place |
| Flavor | Bitter, with a burning sensation in the mouth or throat | Neutral or starchy, as expected for potatoes |
| Toxin Levels | Significantly increased concentration of solanine | Trace amounts of solanine, considered safe |
| Risk Level | Moderate to high, depending on amount consumed | Very low, under proper preparation |
Symptoms of Solanine Poisoning
Consumption of high levels of solanine can lead to a range of symptoms, primarily affecting the gastrointestinal and nervous systems. While severe poisoning is rare, it is a serious condition that requires immediate medical attention.
Typical symptoms include:
- Nausea and vomiting
- Abdominal pain and diarrhea
- Headaches and dizziness
- Fever
- A burning sensation in the throat
- Neurological symptoms in more severe cases, such as hallucinations or paralysis
How to Store Potatoes Safely
To prevent the build-up of solanine, proper storage is key. Always keep potatoes in a cool, dark, and dry place, such as a pantry or root cellar. Avoid storing them in direct sunlight or under artificial lights. Using a paper bag or basket is preferable to an airtight container, which can trap moisture and accelerate spoilage.
Can Cooking Remove Solanine?
It is a common misconception that cooking can destroy solanine. However, the heat required to break down this toxin is much higher than typical cooking temperatures. For instance, deep frying can reduce solanine content, but standard boiling or baking has only a minimal effect. The most effective method for minimizing solanine risk is to properly prepare the potato by peeling away the green skin and removing the sprouts.
Conclusion
The part of a potato that may be toxic is primarily the green skin and any sprouts that form, as these areas develop high concentrations of the natural toxin, solanine. While the green color is a sign of harmless chlorophyll, it serves as an important indicator that solanine levels may also be dangerously high. By storing potatoes correctly in a cool, dark place, carefully inspecting them for green patches or sprouts before use, and peeling or discarding affected areas, you can ensure that your meals remain safe and delicious.
Visit the official website for Poison Control for expert guidance on food safety concerns.
How to handle green potatoes safely:
- Proper Storage: Always store potatoes in a cool, dark place away from direct sunlight.
- Regular Inspection: Check potatoes for signs of greening, damage, or sprouting before cooking.
- Immediate Removal: Cut away any green skin and all sprouts, and discard them immediately.
- Taste Test: If a peeled and trimmed potato tastes bitter, it's a sign of high solanine levels and should be thrown out.
- Discard Entirely: For heavily green, soft, or shriveled potatoes, dispose of the whole tuber to avoid risk.
