How to Tell If a Potato Is Bad: 7 Clear Indicators

Discard potatoes showing significant mold growth, deep soft spots, foul odors, or extensive greening. Potatoes with minor sprouting or small green patches can often be salvaged by removing affected areas. Properly stored potatoes typically remain fresh for 3-5 weeks at room temperature.

Ever pulled a potato from your pantry only to wonder if it's still safe to eat? You're not alone. Each year, American households waste over 130 pounds of food per person, with potatoes ranking among the most commonly discarded produce items due to uncertainty about spoilage. As a chef who's handled thousands of pounds of potatoes in professional kitchens, I've developed a foolproof system to determine potato freshness that balances food safety with waste reduction.

Immediate Red Flags: When to Toss Potatoes Immediately

These visual and sensory cues indicate your potato has crossed into unsafe territory:

• Foul or musty odor - Fresh potatoes have an earthy smell; sour or moldy scents signal bacterial growth
• Extensive mold growth - Any visible fuzz, especially in multiple colors (white, green, black)
• Deep soft spots - Areas that feel mushy when gently pressed, particularly if they leave indentations
• Significant greening - More than 25% of the surface turned green (explained in detail later)
• Liquid seepage - Moisture leaking from the potato indicates advanced decomposition

Condition	Safe to Eat?	Action Required
Minor sprouting (<1 inch)	Yes	Remove sprouts and eyes before cooking
Small green patches	Yes (after treatment)	Peel deeply to remove all green areas
Surface mold in one spot	Possibly	Cut away mold plus 1-inch margin around it
Multiple soft spots	No	Discard entire potato
Foul odor	No	Immediately discard

Understanding the Potato Spoilage Timeline

According to USDA food safety guidelines, potatoes follow a predictable deterioration pattern when stored at room temperature:

1. Days 1-7: Optimal freshness - firm texture, earthy aroma, no sprouts
2. Days 8-21: Early changes - slight softening, possible small sprouts emerging
3. Days 22-35: Advanced changes - noticeable sprouting, possible minor greening
4. Day 36+: High risk - significant soft spots, potential mold development

This timeline assumes proper storage conditions. Refrigeration extends freshness but can convert starches to sugars, affecting flavor. The FDA recommends storing potatoes in a cool, dark place between 45-50°F (7-10°C) for maximum shelf life without quality degradation.

The Green Potato Conundrum: Solanine Risk Explained

When potatoes turn green, they're producing solanine - a natural toxin that protects against sunlight. Research from Cornell University's Food Science Department shows that solanine concentrations increase dramatically with greening:

• Normal levels: 0.004-0.022% of potato weight
• Green areas: Can reach 0.1-0.2% (up to 10x normal)
• Danger threshold: 0.2% or higher requires immediate discard

The National Capital Poison Center warns that consuming high-solanine potatoes can cause nausea, headaches, and in severe cases, neurological symptoms. When you see green patches, peel deeply (at least 1/4 inch below the green area) or discard if greening is extensive.

When Sprouted Potatoes Are Still Safe

Contrary to popular belief, sprouted potatoes aren't automatically dangerous. The European Food Safety Authority confirms that sprouts themselves aren't toxic, but they indicate the potato is aging and converting starch to sugar. Here's my professional assessment protocol:

1. Check firmness - squeeze gently; discard if soft anywhere
2. Examine sprout length - discard if sprouts exceed 1 inch
3. Inspect for secondary issues - no accompanying soft spots or mold
4. Remove sprouts completely using a knife (don't just pull them)

Potatoes with minor sprouting often have enhanced flavor due to sugar development, making them excellent for roasting. Just avoid using sprouted potatoes for dishes requiring firm texture like potato salad.

Proper Potato Storage: Extending Freshness

Based on my experience in professional kitchens and research from the University of California's Agricultural Extension, these storage practices maximize potato shelf life:

• Never refrigerate - Cold temperatures increase sugar content and cause blackening when cooked
• Avoid plastic bags - Use breathable containers like paper bags or wicker baskets
• Keep away from onions - Both release gases that accelerate each other's spoilage
• Store in complete darkness - Even brief light exposure triggers greening
• Maintain humidity around 90% - Too dry causes shriveling; too moist encourages mold

For long-term storage (beyond 4 weeks), consider placing an apple in your potato storage container. The ethylene gas from the apple inhibits sprouting, as verified by multiple university extension studies.

Reducing Food Waste: Creative Uses for Aging Potatoes

Before discarding slightly imperfect potatoes, consider these professional chef techniques:

• Sprouted potatoes - Make twice-baked potatoes; the hollowed centers accommodate fillings that mask texture changes
• Slightly soft potatoes - Ideal for mashed potatoes or soups where texture matters less
• Minor green patches - Peel deeply and use in dishes with strong flavors like curry or chili
• Beginning to shrivel - Soak in cold water for 30 minutes to temporarily restore firmness

Remember: When in doubt, throw it out. The USDA's FoodSafety.gov emphasizes that no cooking method eliminates solanine once it's formed in green areas.

When Potato Imperfections Are Actually Beneficial

Not all changes indicate spoilage. Some characteristics actually enhance cooking potential:

• Sprouting - Increases sugar content, creating better caramelization for roasting
• Slight softening - Makes potatoes easier to mash without becoming gluey
• Developing eyes - Indicates starch conversion that improves texture in baked dishes

The key distinction is whether changes are uniform and moderate versus localized and extreme. A uniformly slightly soft potato may be perfect for mashing, while one with isolated soft spots has begun to rot.

Can you eat potatoes with small sprouts?

Yes, potatoes with small sprouts (under 1 inch) are safe to eat if you completely remove the sprouts and any soft areas around the eyes. The sprouts themselves aren't toxic but indicate the potato is aging. After removing sprouts, the potato should feel firm when squeezed and show no other signs of spoilage.

How much green on a potato is dangerous?

Any visible greening indicates solanine formation. Small green patches (less than 25% of surface) can be safely removed by peeling at least 1/4 inch below the green area. Potatoes with more than 25% greening should be discarded entirely, as solanine concentrations become potentially harmful. The National Capital Poison Center recommends discarding potatoes where greening extends beyond surface level.

Why do potatoes get soft spots?

Soft spots develop when moisture accumulates in certain areas, creating ideal conditions for bacterial growth. This often starts at the eyes or damaged areas. Surface softness might be reversible by drying, but deep soft spots that leave indentations indicate advanced decomposition and mean the potato should be discarded. Proper storage in a cool, dark place with good air circulation prevents most soft spot development.

How long do potatoes last in the pantry?

Properly stored potatoes typically remain fresh for 3-5 weeks at room temperature (50-60°F). The FDA recommends storing them in a cool, dark place with good ventilation. Warmer temperatures accelerate sprouting, while refrigeration converts starches to sugars. Check potatoes weekly for signs of spoilage, and remove any showing early deterioration to prevent spread to others.

Can cooking destroy potato toxins?

No, cooking does not eliminate solanine, the natural toxin that forms in green potatoes. Boiling, baking, or frying only reduces solanine levels by about 40%, according to research from Cornell University. The only safe approach is to physically remove all green areas by peeling deeply (at least 1/4 inch below discoloration) or discarding heavily affected potatoes.