How Do You Know If Potatoes Are Bad? Signs, Storage & Safety Tips

Potatoes are a kitchen staple found in households across America. These versatile tubers can last for weeks or even months when stored properly, but knowing when they’ve gone bad is crucial for your health and safety.

Whether you’re dealing with fresh potatoes from the farmers market or cooked leftovers in your fridge, understanding the signs of spoilage can help you avoid foodborne illness and reduce food waste. This comprehensive guide will teach you exactly how to identify bad potatoes and keep your family safe.

Clear Signs That Fresh Potatoes Have Gone Bad

Fresh, raw potatoes should be firm, smooth, and free from obvious damage. Here are the telltale signs that your potatoes have spoiled:

Texture Changes

The first thing to check is the potato’s firmness. Fresh potatoes should feel solid when you squeeze them gently. If a potato has become soft, mushy, or wrinkled, it’s past its prime and should be discarded. The flesh may feel squishy when pressed, indicating that decomposition has begun.

Shriveled potatoes have lost significant moisture and nutritional value. While slightly soft potatoes might still be edible after cutting away damaged portions, severely mushy ones should go straight to the compost bin.

Visual Indicators

Examine your potatoes carefully for these visual warning signs:

• Dark spots or bruises: Small blemishes can be cut away, but large black or brown spots indicate rot
• Green coloration: Green patches on the skin or flesh contain harmful toxins and should never be consumed
• Mold growth: Any fuzzy patches, white spots, or discoloration suggest mold contamination
• Excessive sprouting: While small sprouts can be removed, potatoes covered in long sprouts have lost quality
• Wrinkled skin: Deep wrinkles indicate dehydration and aging

Smell Test

Your nose is one of the best tools for detecting spoiled potatoes. Fresh potatoes have a mild, earthy aroma. If you notice any of these smells, throw the potato away:

• Musty or moldy odor
• Sour or fermented smell
• Rotten or putrid scent
• Any unusually strong or unpleasant odor

Sometimes a potato may look fine on the outside but smell bad when you pick it up. This indicates internal rot that isn’t visible from the exterior. Trust your sense of smell and discard any foul-smelling potatoes immediately.

What About Sprouted Potatoes?

Sprouting is one of the most common issues people encounter with stored potatoes. Those small shoots growing from the potato’s “eyes” are a natural process, but they come with important safety considerations.

Are Sprouted Potatoes Safe to Eat?

Potatoes with small, firm sprouts are generally safe to eat if you remove the sprouts completely. Simply snap or cut them off before cooking. However, you should never eat the sprouts themselves.

Sprouts contain high concentrations of glycoalkaloids, including solanine and chaconine. These toxic compounds can cause serious health problems, including:

• Nausea and vomiting
• Diarrhea and stomach cramps
• Headaches and dizziness
• Neurological symptoms in severe cases

When to Throw Away Sprouted Potatoes

While small sprouts can be removed, you should discard potatoes that are:

• Covered in long, thick sprouts
• Soft, wrinkled, or shriveled
• Have extensive green coloration
• Smell unusual or unpleasant

As sprouts grow, they draw nutrients and moisture from the potato, causing it to lose flavor, texture, and nutritional value. Heavily sprouted potatoes aren’t worth eating even if technically safe.

The Danger of Green Potatoes

Green potatoes are a serious food safety concern that should never be ignored. The green color indicates high levels of chlorophyll, which itself is harmless, but it also signals the presence of glycoalkaloid toxins.

Why Potatoes Turn Green

Potatoes develop green patches when exposed to light during storage. This triggers the production of chlorophyll and simultaneously increases glycoalkaloid levels to dangerous concentrations.

How to Handle Green Potatoes

If you notice small green areas, you can cut away the affected portions, removing at least 1/4 inch beyond the green part. However, if more than half the potato is green, or if it has a bitter taste, throw it away entirely. The potential health risks aren’t worth taking chances.

How to Tell If Cooked Potatoes Are Bad

Cooked potatoes spoil much faster than raw ones and present a higher risk of food poisoning. Unfortunately, harmful bacteria can multiply in cooked potatoes without obvious visual signs.

Visible Signs of Spoiled Cooked Potatoes

• Mold growth: Any fuzzy spots in white, green, black, or gray colors
• Sliminess: A sticky or slimy texture on the surface
• Discoloration: Unusual dark spots or color changes
• Separation: Liquid separating from mashed potatoes

Smell and Texture

Spoiled cooked potatoes often develop a sour, unpleasant odor. They may also feel overly wet, mushy, or have an off-putting texture. If your leftover potatoes smell or look questionable, don’t taste them—throw them out.

The Time Rule for Cooked Potatoes

Even without visible signs of spoilage, cooked potatoes should be discarded after 4 days in the refrigerator. This is because potatoes provide an ideal environment for bacterial growth due to their moisture content, slightly acidic pH, and protein content.

Dangerous bacteria like Clostridium botulinum, Staphylococcus aureus, Salmonella, and Listeria can multiply rapidly in cooked potatoes, especially if they weren’t cooled and stored properly.

Health Risks of Eating Bad Potatoes

Consuming spoiled potatoes can lead to two types of illness: glycoalkaloid poisoning from raw potatoes or foodborne illness from bacterial contamination in cooked potatoes.

Glycoalkaloid Poisoning

Eating green potatoes or potato sprouts can cause glycoalkaloid poisoning with symptoms appearing within hours:

• Burning sensation in the mouth and throat
• Severe nausea and vomiting
• Abdominal pain and diarrhea
• Headache and dizziness
• Fever and confusion

In severe cases, glycoalkaloid poisoning can affect the nervous system and become life-threatening, though this is rare with modern potato varieties.

Bacterial Food Poisoning

Spoiled cooked potatoes can harbor dangerous bacteria causing food poisoning with symptoms including:

• Stomach cramps and pain
• Nausea and vomiting
• Diarrhea (sometimes bloody)
• Fever and chills
• Muscle aches
• Weakness and fatigue

These symptoms typically appear within 6 to 48 hours after eating contaminated food and can last several days. In vulnerable populations—young children, elderly adults, pregnant women, and immunocompromised individuals—food poisoning can lead to severe dehydration, hospitalization, or even death.

How Long Do Potatoes Last?

Understanding potato shelf life helps you use them before they spoil. Storage conditions significantly impact how long potatoes remain fresh.

Raw Potatoes Storage Times

At cool temperatures (45-55°F / 7-13°C):

• Whole potatoes: 2-3 months
• Sweet potatoes: 1-2 months

At room temperature (68-72°F / 20-22°C):

• Whole potatoes: 1-2 weeks
• Sweet potatoes: 1 week

Cut raw potatoes in water:

• In refrigerator: 24 hours maximum

Cooked Potatoes Storage Times

Refrigerated (40°F / 4°C or below):

• Baked potatoes: 3-4 days
• Boiled potatoes: 3-4 days
• Mashed potatoes: 3-4 days
• Roasted potatoes: 3-4 days
• Potato salad: 3-5 days

Frozen (0°F / -18°C):

• Most cooked potatoes: 10-12 months
• Mashed potatoes: 10-12 months (quality may suffer)

Instant potatoes (uncooked, pantry):

• Unopened packages: Several years
• Opened packages: 6-12 months

Proper Storage Methods to Prevent Spoilage

Correct storage dramatically extends potato shelf life and prevents premature spoilage.

Storing Raw Potatoes

Best storage location: Keep raw potatoes in a cool, dark, dry place with good air circulation. Ideal locations include:

• Pantry or cupboard away from heat sources
• Root cellar or basement
• Cool garage or shed (above freezing)
• Dark corner of your kitchen (if cool enough)

Temperature considerations: The ideal temperature range is 45-55°F (7-13°C). Warmer temperatures accelerate sprouting and spoilage, while temperatures below 40°F (4°C) convert starches to sugars, affecting taste and cooking properties.

Container choices:

• Paper bags with holes for ventilation
• Cardboard boxes with openings
• Mesh bags that allow airflow
• Open bowls or baskets
• Perforated plastic bags

Never store potatoes in sealed plastic bags or airtight containers, as trapped moisture promotes mold growth and rot.

What NOT to Do with Raw Potatoes

Don’t refrigerate raw potatoes: Cold temperatures convert potato starch into sugar, resulting in an unpleasantly sweet taste and gritty texture. Refrigeration also increases acrylamide formation when potatoes are cooked at high temperatures.

Don’t expose to light: Light triggers greening and increases toxic glycoalkaloids. Always store potatoes in darkness.

Don’t wash before storing: Moisture promotes bacterial and fungal growth. Only wash potatoes right before cooking.

Don’t store with certain produce: Keep potatoes away from onions, apples, and bananas. These produce items release ethylene gas, which accelerates potato sprouting and spoilage.

Storing Cooked Potatoes Safely

Proper handling of cooked potatoes is critical for food safety:

Cooling: Refrigerate cooked potatoes within 2 hours of cooking (1 hour if room temperature exceeds 90°F / 32°C). Divide large batches into shallow containers for faster cooling.

Refrigeration: Store cooked potatoes in airtight containers at 40°F (4°C) or below. Use within 3-4 days.

Freezing: For longer storage, freeze cooked potatoes in freezer-safe containers or bags. Remove as much air as possible. Note that some potato dishes freeze better than others—mashed and roasted potatoes freeze well, while boiled potatoes may become grainy.

Reheating: Always reheat cooked potatoes to an internal temperature of 165°F (74°C) to kill any bacteria that may have developed during storage.

Special Cases: Different Potato Varieties

Sweet Potatoes

Sweet potatoes are more sensitive to cold and bruising than regular potatoes. They prefer warmer storage temperatures (55-60°F / 13-16°C) and don’t last quite as long. Signs of spoilage include soft spots, mold, shriveling, and an off smell.

New Potatoes

New potatoes have thin, delicate skins and higher moisture content. They spoil faster than mature potatoes and should be used within 1-2 weeks even with proper storage. Check frequently for soft spots and mold.

Fingerling and Small Specialty Potatoes

These varieties generally follow the same spoilage patterns as regular potatoes but may dry out faster due to their smaller size. Store them carefully and check regularly for wrinkles or soft spots.

Tips to Extend Potato Shelf Life

• Buy wisely: Purchase firm, unblemished potatoes without sprouts or green patches
• Inspect regularly: Check stored potatoes weekly and remove any showing signs of spoilage
• Separate damaged potatoes: One bad potato can accelerate spoilage in nearby tubers
• Don’t overbuy: Purchase only what you’ll use within the appropriate timeframe
• Cure properly: If you grow your own, cure potatoes at 50-60°F (10-16°C) with high humidity for 1-2 weeks before long-term storage
• Maintain consistent conditions: Avoid temperature fluctuations that stress potatoes and promote sprouting
• Keep dry: Ensure storage areas have low humidity to prevent rot

When in Doubt, Throw It Out

Food safety experts universally recommend erring on the side of caution with questionable food. If you’re unsure whether a potato is safe to eat, don’t risk it. The potential health consequences of food poisoning far outweigh the cost of a few potatoes.

Pay special attention to cooked potatoes, as they can harbor dangerous bacteria without obvious signs. Always follow the 4-day refrigerator rule and the 2-hour room temperature rule to minimize risk.

Frequently Asked Questions

Can you eat potatoes with small sprouts?

Yes, potatoes with small, firm sprouts are safe to eat after completely removing the sprouts and any green areas. However, don’t eat the sprouts themselves, as they contain toxic compounds.

Why did my potatoes turn green?

Potatoes turn green when exposed to light, which triggers chlorophyll production. Green areas also contain increased levels of toxic glycoalkaloids. Always store potatoes in complete darkness.

Can you cut off the bad parts of a potato?

Small blemishes, eyes, and minor green spots can be cut away, removing at least 1/4 inch beyond the affected area. However, if large portions are bad, or if the potato is soft, mushy, or foul-smelling, discard the entire potato.

How can you tell if mashed potatoes have gone bad?

Bad mashed potatoes may show mold, develop a sour smell, become slimy, or have liquid separation. Even without these signs, throw away mashed potatoes after 4 days in the refrigerator.

Is it safe to eat potatoes that have been left out overnight?

Cooked potatoes left at room temperature for more than 2 hours should be discarded due to bacterial growth risk. Raw potatoes can be left out but will spoil faster than those stored in cool conditions.

The Bottom Line

Knowing how to identify bad potatoes is an essential kitchen skill that protects your health and reduces food waste. Fresh potatoes should be firm, smooth, and smell earthy. Discard any that are soft, moldy, foul-smelling, heavily sprouted, or extensively green.

Cooked potatoes present a higher food poisoning risk and should be refrigerated within 2 hours, stored properly, and consumed within 4 days. When reheating, always reach an internal temperature of 165°F (74°C).

By following proper storage guidelines—keeping raw potatoes in cool, dark, dry places with good airflow, and refrigerating cooked potatoes promptly—you can maximize shelf life while maintaining safety. Remember: when in doubt about a potato’s freshness, it’s always better to throw it out than risk foodborne illness.

Sources:

• USDA Food Safety and Inspection Service
• FDA – What You Need to Know About Foodborne Illnesses
• CDC – Food Safety
• PubMed Central – National Institutes of Health
• FoodSafety.gov – FoodKeeper Storage Guide
• Mayo Clinic – Food Poisoning
• Poison Control – Are Green Potatoes Dangerous