The Toxic Compounds: Solanine and Chaconine
Potatoes, belonging to the nightshade family, naturally produce glycoalkaloids, primarily solanine and chaconine. In healthy potatoes, these compounds are present in very low, non-harmful concentrations. However, when a potato is exposed to light or physical damage, or simply ages, the production of these toxins increases significantly as a natural defense mechanism.
The Dangers of Glycoalkaloids
Excessive ingestion of glycoalkaloids can lead to solanine poisoning, which manifests with several unpleasant and potentially severe symptoms. The signs can appear within a few hours to a full day after consumption. Mild symptoms include nausea, vomiting, abdominal pain, and diarrhea. More severe cases, though rare, can cause headaches, fever, confusion, and neurological problems. For children and individuals with a lower body weight, the risk of toxicity is higher, as they require a much smaller dose of the toxin to experience adverse effects.
The Parts of the Potato You Should Never Eat
To ensure safety, you must know and avoid the specific parts of the potato where these toxins concentrate.
- Green Skin and Flesh: The green color that appears on a potato's skin when exposed to light is caused by chlorophyll, which is harmless. However, its presence is a clear signal that the potato has also begun producing higher levels of solanine. This makes any green portion, whether on the surface or just beneath the peel, a significant risk. While you can trim small, isolated green spots, a potato with extensive greening should be discarded completely.
- Sprouts (Eyes): The sprouts, or "eyes," of a potato contain the highest concentration of glycoalkaloids. Even small sprouts signal that the toxin levels are rising. While you can remove small sprouts from an otherwise firm potato, if the potato has large, extensive sprouts or is shriveled, it's best to discard the entire thing.
- Potato Leaves, Stems, and Berries: The above-ground parts of the potato plant, including the leaves, stems, and any berries that form, are highly toxic and should never be consumed. Only the underground tuber is edible when handled correctly.
- Soft or Moldy Potatoes: A potato that is soft, mushy, or wrinkled is a sign of spoilage. If mold is present, it's a definite sign to throw it away. Mold on one part of the potato often means invisible spores are present throughout.
Comparison Table: Safe vs. Unsafe Potato Indicators
| Indicator | Safety Status | Action | Explanation |
|---|---|---|---|
| Firm texture | Safe | Proceed with cooking after washing. | Indicates a fresh, healthy potato with normal toxin levels. |
| Small sprouts | Borderline | Remove sprouts and eyes thoroughly. | Toxin levels are elevated but manageable if the potato is otherwise firm. |
| Extensive sprouts | Unsafe | Discard immediately. | Significant nutrient and moisture loss, with very high toxin levels. |
| Small green spots | Borderline | Cut out green spots and peel thoroughly. | Indicates localized toxin buildup from light exposure. |
| Deep greening | Unsafe | Discard immediately. | High toxin concentration makes the entire potato risky, as peeling won't be enough. |
| Soft or shriveled | Unsafe | Discard immediately. | A sign of severe dehydration and decay, often indicating high toxicity. |
| Bitter taste | Unsafe | Discard immediately. | The bitter flavor is a strong indicator of high solanine content. |
How to Prevent Potatoes from Turning Toxic
Proper storage is the best defense against glycoalkaloid accumulation. By controlling the environment, you can significantly prolong the shelf life of your potatoes and keep them safe for consumption.
- Store in a Cool, Dark Place: Keep potatoes in a dark location, such as a pantry or cellar, to prevent light exposure. Light is the primary catalyst for chlorophyll and solanine production.
- Ensure Good Ventilation: Use a breathable container like a mesh bag or basket, rather than a sealed plastic bag, to allow for air circulation. This helps prevent the buildup of moisture that encourages sprouting.
- Avoid Storing with Onions: Onions and other fruits emit ethylene gas, which can accelerate the ripening and sprouting of potatoes. Store them separately to maximize freshness.
- Use Within a Few Weeks: For best quality and lowest toxin levels, it is always recommended to use potatoes relatively quickly rather than storing them for months on end.
The Final Word on Potato Safety
While potatoes are a nutritious and staple food source worldwide, they must be handled with care to avoid the risks associated with glycoalkaloids. The toxic compounds are not destroyed by standard cooking methods like boiling or baking, so removing the affected parts is essential. If a potato shows significant signs of spoilage, greening, or extensive sprouting, the safest and most prudent choice is to discard it completely. When in doubt, always throw it out to protect your health.
For more information on food safety, you can visit the Centers for Disease Control and Prevention website.
Conclusion
Understanding which part of potato should not be eaten is a fundamental aspect of kitchen food safety. The sprouts, green skin, and other parts of the plant contain high levels of the natural toxins solanine and chaconine, which can cause illness. By inspecting your potatoes for signs of spoilage and storing them correctly, you can continue to enjoy this versatile vegetable with confidence and peace of mind.
