Potatoes are a staple in many diets, but a green hue on their skin often raises questions about their safety. This discoloration prompts consumers to wonder if the potato is still suitable for consumption. Understanding the science behind this change clarifies concerns regarding their edibility and how to handle them safely.
The Science Behind Green Potatoes
Potatoes turn green primarily due to light exposure. This triggers the production of chlorophyll, the green pigment found in leaves that allows plants to perform photosynthesis. The green color itself, from chlorophyll, is harmless and tasteless. However, chlorophyll formation in potatoes indicates another, more concerning compound may also be present.
The conditions encouraging chlorophyll production also stimulate the potato to increase its levels of glycoalkaloids, particularly solanine. Potatoes are tubers, modified stems that naturally grow underground, shielded from light. When exposed to light, the potato’s metabolic activity in its skin increases, leading to both greening and heightened solanine synthesis. This dual response is a natural defense mechanism.
Solanine: The Hidden Danger
Solanine is a natural glycoalkaloid found in potatoes, serving as the plant’s defense mechanism against pests and diseases. While naturally present at low, safe levels, its concentration significantly increases when potatoes are exposed to light, damaged, or begin to sprout. The highest concentrations of solanine are found in the potato’s skin, just beneath it, and in any sprouts or “eyes.”
Ingesting potatoes with elevated solanine levels can lead to symptoms primarily affecting the gastrointestinal and neurological systems. Common symptoms include nausea, vomiting, diarrhea, stomach cramps, and headaches. In more severe, though rare, cases, individuals might experience fever, a burning sensation in the throat, a slow pulse, or even hallucinations and paralysis. A bitter taste in the potato is a reliable indicator of high solanine content, as solanine itself is colorless and has a bitter flavor.
A toxic dose of solanine is 2 to 5 milligrams per kilogram of body weight, with fatal outcomes possible at 3 to 6 milligrams per kilogram. For instance, a potato with visible greening might contain around 250 to 280 milligrams of solanine per kilogram. This means even a small amount of a heavily greened potato could pose a risk, particularly for children, who are more susceptible due to their lower body mass. Cooking methods like boiling or frying do not effectively destroy solanine, as it is heat-stable.
Safe Practices for Potato Consumption and Storage
When potatoes show signs of greening, appropriate handling can mitigate risks. If only small areas are green or have minor sprouts, these portions can be carefully removed. Peeling the potato and cutting away any green flesh and sprouts significantly reduces the solanine content, as most of it concentrates in these areas. However, if a potato is extensively green, feels soft, or tastes noticeably bitter even after trimming, it is advisable to discard it entirely.
Proper storage is key to preventing potatoes from turning green and accumulating solanine. Potatoes should be stored in a cool, dark, and dry place with good air circulation. Ideal temperatures for long-term storage range from 45 to 50 degrees Fahrenheit. Keeping potatoes away from all light is paramount.
It is beneficial to store potatoes in opaque containers, such as paper bags or cardboard boxes, to block light exposure. Avoiding storage near heat-emitting appliances or certain fruits and vegetables, like onions, is also recommended. Onions and some other produce release ethylene gas, which can accelerate the sprouting and aging process in potatoes, potentially increasing solanine levels.