Are Potatoes That Are Green Safe To Eat? | What the Green Means

Seeing a potato with a green tint can spark a moment of hesitation in the kitchen. This color change isn’t just cosmetic; it signals important chemical shifts within the potato that are worth understanding for your well-being. Let’s understand what causes this greening and what it means for your meal.

The Green Hue: What It Signals

The green color on a potato’s skin is primarily due to chlorophyll production. Chlorophyll is the same pigment that makes leaves green, and its presence in potatoes is a direct response to light exposure. Potatoes naturally grow underground, away from sunlight. When they are exposed to light, even ambient kitchen light, they begin to photosynthesize.

While chlorophyll itself is harmless, its appearance serves as a visual indicator. The processes that trigger chlorophyll formation, particularly light exposure, also stimulate the potato to produce glycoalkaloids, with solanine being the most prominent one. This concurrent production is why greening is a significant warning sign.

Chlorophyll vs. Solanine

• Chlorophyll: This pigment is responsible for the green color. It is not toxic and is found in many edible plants. Its presence simply shows the potato has been exposed to light.
• Solanine: This is a natural plant toxin, a glycoalkaloid, produced by potatoes as a defense mechanism against pests and diseases. Unlike chlorophyll, solanine can be harmful to humans in sufficient concentrations.

Solanine: The Hidden Concern

Solanine is a naturally occurring compound found in all members of the nightshade family, which includes potatoes, tomatoes, and eggplants. In potatoes, solanine is concentrated just under the skin, in sprouts, and in “eyes.” Healthy, properly stored potatoes contain very low, generally harmless levels of solanine, typically less than 10 milligrams per 100 grams of potato.

When potatoes are exposed to light, damaged, or stored improperly, their solanine content can rise significantly. This increase is a protective response, but it also makes the potato less suitable for consumption. The greening of the skin often coincides with this increase, though the green color itself is not solanine.

Factors Increasing Solanine Levels

1. Light Exposure: Direct or indirect light, including fluorescent light, triggers both chlorophyll and solanine production.
2. Physical Damage: Bruises, cuts, or other injuries to the potato can stimulate localized solanine formation as a wound response.
3. Improper Storage Temperature: Storing potatoes in warm conditions (above 70°F or 21°C) can accelerate solanine development.
4. Age and Sprouting: Older potatoes, especially those with sprouts, tend to have higher solanine concentrations. Sprouts themselves are particularly rich in solanine.

The U.S. Food and Drug Administration (FDA) monitors food safety, and while specific thresholds for solanine are complex, general guidance emphasizes avoiding potatoes with high levels.

FDA

How Solanine Affects Health

Consuming potatoes with elevated solanine levels can lead to adverse health effects. The severity of these effects depends on the amount of solanine ingested and an individual’s sensitivity. Symptoms typically appear within a few hours of consumption.

Solanine acts as a neurotoxin and gastrointestinal irritant. It disrupts nerve function and can cause discomfort in the digestive system. Young children, older adults, and individuals with compromised immune systems may be more susceptible to its effects.

Common Symptoms of Solanine Toxicity

Spotting the Signs of Solanine

Beyond the visible greening, there are other indicators that a potato might have high solanine levels. Recognizing these signs is crucial for making safe choices in the kitchen.

• Green Skin: This is the most obvious visual cue. The greener the potato, the higher the likelihood of elevated solanine.
• Sprouting: Potatoes with sprouts, especially long or numerous ones, indicate increased solanine. The sprouts themselves are particularly high in the compound.
• Soft Spots or Wrinkles: These can indicate an older potato, which may have accumulated more solanine over time, even without significant greening.
• Bitter Taste: A distinctly bitter or acrid taste in raw or cooked potato is a strong indicator of high solanine content. This bitterness is not typical of a fresh potato.

Safe Preparation: Peeling and Trimming

If you encounter a potato with minor greening or small sprouts, it’s often possible to salvage it safely by removing the affected parts. Solanine is concentrated near the surface and in the sprouts.

1. Peeling Thoroughly: Always peel green potatoes generously. Since solanine is mostly just under the skin, removing a thicker layer than usual can reduce its concentration.
2. Trimming Green Spots: Cut away any visibly green areas, sprouts, or “eyes” with a knife. Ensure you remove not just the green color but also a bit of the underlying flesh to account for solanine that may have diffused deeper.
3. Removing Sprouts: Snap off or cut out any sprouts and the surrounding “eye” tissue. These are hotbeds for solanine.

Cooking methods like boiling, baking, or frying do not significantly reduce solanine levels. The compound is heat-stable, meaning it will persist even after thorough cooking. This underscores the importance of physical removal before cooking.

USDA

When to Discard a Potato Entirely

While minor greening or small sprouts can be addressed, there are situations where it’s safer to discard the entire potato. Prioritizing health means recognizing when a potato has crossed the line from salvageable to unsafe.

• Extensive Greening: If a significant portion of the potato’s surface is green, or if the greening extends deep into the flesh, it’s best to discard it. The solanine concentration is likely too high to be safely removed.
• Multiple or Large Sprouts: Potatoes with numerous or very long sprouts (over half an inch) often have substantially elevated solanine throughout the potato, not just in the sprouts themselves.
• Soft, Wrinkled, or Shriveled Texture: These are signs of an old potato that may have accumulated high solanine levels, even without prominent greening.
• Bitter Taste: If, after peeling and trimming, you taste a small piece and it’s bitter, discard the entire potato immediately. This is a definitive sign of high solanine.
• Unpleasant Odor: Any unusual or strong odor, beyond the earthy smell of a fresh potato, can indicate spoilage and potential toxin accumulation.

When in doubt, it’s always prudent to err on the side of caution. A single potato is not worth risking your well-being.

Green Potato Action Guide

Proper Storage to Prevent Greening

Preventing potatoes from turning green and developing high solanine levels is straightforward with proper storage. A few simple practices can help maintain their quality and safety for longer.

1. Darkness is Key: Store potatoes in a cool, dark place. A pantry, cellar, or cupboard away from direct light sources is ideal. Light exposure is the primary trigger for greening and solanine production.
2. Cool, Not Cold: An ideal storage temperature is between 45-55°F (7-13°C). Avoid storing potatoes in the refrigerator, as cold temperatures can convert their starch to sugar, affecting taste and texture, and potentially increasing solanine in some varieties over time.
3. Good Air Circulation: Store potatoes in a breathable container, like a mesh bag, paper bag, or an open bowl. Avoid airtight containers, which can trap moisture and promote spoilage.
4. Separate from Onions and Fruits: Do not store potatoes near onions, apples, or other fruits that release ethylene gas. Ethylene can accelerate sprouting and spoilage in potatoes.
5. Inspect Regularly: Before storage and periodically thereafter, inspect your potatoes for any signs of damage, greening, or sprouting. Remove any compromised potatoes to prevent them from affecting others.

By following these storage guidelines, you can significantly extend the shelf life of your potatoes and ensure they remain safe and delicious for your meals.

Founder & Lead Editor

Mo Maruf

I created WellFizz to bridge the gap between vague wellness advice and actionable solutions. My mission is simple: to decode the research and give you practical tools you can actually use.

Beyond the data, I am a passionate traveler. I believe that stepping away from the screen to explore new environments is essential for mental clarity and physical vitality.

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