How to Tell If a Potato Is Bad: 5 Clear Signs

A bad potato shows clear signs: soft or mushy spots, dark or black blemishes, a musty odor, visible mold, or excessive sprouting. Green discoloration indicates solanine buildup, making it unsafe to eat. When in doubt, discard the potato to avoid foodborne illness.

Spot Spoiled Potatoes Before They Make You Sick

Discovering spoiled potatoes after cooking wastes time, money, and risks food poisoning. Learning to identify bad potatoes takes seconds but protects your health and kitchen budget. This guide reveals exactly what to look for—no guesswork needed.

Step 1: Visual Inspection Checklist

Your eyes catch the first warning signs of potato spoilage. Examine potatoes under good lighting, checking all surfaces:

• Color changes - Green patches signal solanine (a toxic compound)
• Dark spots - Black or brown lesions that don't rub off
• Mold growth - Fuzzy white, green, or black patches
• Excessive sprouting - Long, thick sprouts (eyes)

Healthy Potato	Spoiled Potato
Uniform tan or yellow skin	Green patches anywhere on surface
Firm texture throughout	Soft, wrinkled, or mushy areas
Minimal small sprouts	Long, thick sprouts (1/2 inch+)
Crisp earthy smell	Musty, moldy, or sour odor

Step 2: Texture Test for Hidden Spoilage

Some spoilage hides beneath the surface. Gently squeeze the potato:

• Fresh potatoes feel solid with no give
• Spoiled potatoes develop soft spots that indent under light pressure
• Wrinkled skin indicates significant moisture loss and age
• Slippery or slimy surface means advanced decomposition

USDA food safety guidelines confirm that potatoes with soft spots exceeding 10% of the surface should be discarded immediately. Minor imperfections can be cut away, but extensive softness means bacteria has penetrated deeply.

Step 3: Smell Test for Safety

Your nose detects spoilage before eyes see it. Bring the potato close and sniff:

• Fresh potatoes have a clean, earthy aroma
• Spoiled potatoes emit musty, moldy, or sour odors
• Rotten potatoes smell distinctly unpleasant

According to Cornell University's Food Safety Lab, odor changes often precede visible spoilage by 24-48 hours. Trust your nose—if something seems off, don't risk it.

Special Cases: Green Spots and Sprouts Explained

Two common concerns require specific handling:

Green Spots: More Than Just Discoloration

Green areas develop when potatoes are exposed to light, triggering solanine production. This natural toxin causes:

• Nausea and vomiting
• Headaches and dizziness
• Neurological symptoms in severe cases

The FDA states that cooking doesn't destroy solanine. Cut away green areas generously (1/4 inch deep), but discard potatoes with extensive greening.

Sprouts: When Are They Safe?

Small sprouts (under 1/2 inch) on firm potatoes are generally safe to remove. But watch for:

• Sprouts longer than 1 inch
• Sprouts accompanied by soft spots
• Sprouts with visible root hairs

Michigan State University Extension confirms that sprouting drains nutrients and concentrates solanine in sprouts. Potatoes with heavy sprouting should be composted, not eaten.

When to Definitely Throw Out Potatoes

Follow these safety boundaries—no exceptions:

• Mold covering more than 5% of surface
• Multiple soft spots or mushy texture
• Strong unpleasant odor
• Extensive greening (over 25% of surface)
• Wrinkled, shrunken appearance

Food safety experts at the National Center for Home Food Preservation emphasize that potatoes showing multiple spoilage signs likely harbor harmful bacteria like Salmonella or E. coli that aren't visible to the naked eye.

Proper Storage to Extend Freshness

Prevent spoilage before it starts with these storage techniques:

• Store in cool, dark place (45-50°F / 7-10°C ideal)
• Use breathable containers like paper bags or baskets
• Never refrigerate raw potatoes (causes sweetness)
• Keep away from onions (they accelerate sprouting)
• Check stored potatoes weekly for early spoilage signs

University of California research shows proper storage extends potato shelf life by 3-4 weeks compared to room temperature storage. The ideal humidity level is 85-90%—too dry causes shriveling, too moist encourages mold.

Common Questions About Potato Safety

These frequently asked questions address critical safety concerns:

Can you eat potatoes with small sprouts?

Yes, if the potato remains firm. Remove sprouts completely using a vegetable peeler, cutting deeply around each sprout. Discard potatoes with long sprouts accompanied by soft spots or shriveling.

How long do potatoes last before going bad?

Properly stored potatoes last 2-3 months in cool, dark conditions. At room temperature, they typically spoil within 2-3 weeks. Refrigeration causes undesirable starch conversion and isn't recommended for raw storage.

Is it safe to eat potatoes with green spots?

Small green spots can be cut away (remove 1/4 inch around affected area). Discard potatoes with extensive greening as they contain solanine, a toxic compound that causes nausea, headaches, and neurological symptoms. Cooking doesn't destroy solanine.

What causes potatoes to turn black inside?

Internal blackening usually indicates blackheart disease from poor storage conditions. This occurs when potatoes experience temperature fluctuations or high humidity. Cut away affected areas if minimal, but discard potatoes with significant internal discoloration.

Can you get food poisoning from bad potatoes?

Yes. Spoiled potatoes can harbor harmful bacteria like Salmonella and E. coli. Green potatoes contain solanine which causes food poisoning symptoms. Never eat potatoes showing multiple spoilage signs including mold, soft spots, and unpleasant odors.