When Is a Potato Bad to Eat: Safety Guide & Warning Signs

A potato is bad to eat when it shows significant greening (indicating solanine toxin), has become soft or mushy, developed extensive mold, or has sprouted excessively with shriveled skin. Potatoes with minor sprouting or small green spots can often be safely eaten after properly removing the affected areas, but severely spoiled potatoes pose real health risks including nausea, vomiting, and neurological symptoms from solanine poisoning.

How to Identify When a Potato Has Gone Bad: Your Complete Safety Guide

Knowing exactly when a potato has spoiled isn't just about preventing food waste—it's a critical food safety issue. Potatoes contain natural compounds that become dangerous when the tuber begins to deteriorate. This guide provides clear, science-backed criteria to help you make safe decisions about your potatoes.

The Critical Danger Signs You Must Recognize

When examining potatoes, focus on these four key indicators that signal a potato is bad to eat:

1. Significant Green Discoloration

Green patches on potato skin aren't just unsightly—they're your first warning sign of solanine buildup. This natural toxin develops when potatoes are exposed to light. According to the FDA Food Code, green potatoes should be handled with caution as solanine isn't destroyed by cooking and can cause foodborne illness.

2. Texture Changes

Fresh potatoes should feel firm and solid. If your potato yields to gentle pressure, feels mushy, or has wet, slimy spots, it's entered the danger zone. The USDA recommends discarding potatoes that have lost their firm texture as these conditions indicate advanced spoilage and potential bacterial growth.

3. Mold Development

Visible mold—whether fuzzy white, green, or black patches—means immediate disposal. Unlike some foods where you can cut away mold, potatoes' high moisture content allows mold to penetrate deep below the surface. The Centers for Disease Control and Prevention (CDC) warns that consuming moldy potatoes can lead to mycotoxin exposure with serious health consequences.

4. Excessive Sprouting with Shriveling

While small sprouts are common, potatoes with long sprouts accompanied by shriveled, wrinkled skin have passed their safe consumption window. These potatoes have converted most of their starch to sugar and may contain elevated toxin levels.

Condition	Safety Status	Action Required
Minor sprouting (small buds)	Generally safe	Remove sprouts and eyes before cooking
Small green spots (less than 10% surface)	Conditionally safe	Cut away green areas deeply (1/8 inch minimum)
Significant greening (more than 10% surface)	Unsafe	Discard entire potato
Soft/mushy texture	Unsafe	Discard entire potato
Visible mold	Unsafe	Discard entire potato
Excessive sprouting with shriveling	Unsafe	Discard entire potato

Understanding the Solanine Risk: When Potatoes Become Dangerous

Solanine is a glycoalkaloid toxin naturally produced by potatoes as a defense mechanism. While present in small amounts in healthy potatoes, concentrations increase dramatically when potatoes green or sprout extensively.

The CDC reports that solanine poisoning symptoms typically appear 8-12 hours after consumption and may include:

• Nausea and vomiting
• Stomach cramps and diarrhea
• Headache and dizziness
• In severe cases: fever, confusion, and neurological symptoms

What many home cooks don't realize is that solanine isn't neutralized by cooking. Boiling, baking, or frying won't make green potatoes safe to eat. The toxin remains stable through normal cooking temperatures, making proper identification before preparation essential.

Storage Mistakes That Accelerate Spoilage

How you store potatoes directly impacts how quickly they become bad to eat. Common storage errors include:

• Refrigeration - Cold temperatures convert potato starch to sugar, affecting flavor and creating potentially harmful compounds when fried
• Exposure to light - Even indirect light triggers chlorophyll and solanine production
• Sealed plastic bags - Traps moisture and accelerates rot
• Storing near onions - Onions release gases that speed potato sprouting

The USDA recommends storing potatoes in a cool (45-50°F), dark, well-ventilated place like a pantry or cellar. Under these conditions, most potatoes remain safe to eat for 2-3 months.

The Sprout Dilemma: When Are Sprouted Potatoes Still Safe?

Not all sprouted potatoes need immediate disposal. The key is assessing the extent of sprouting and accompanying changes:

• Minor sprouting - Small buds (¼ inch or less) with firm texture: safe after removing sprouts
• Moderate sprouting - Longer sprouts with some firmness remaining: use immediately after thorough preparation
• Advanced sprouting - Long sprouts with shriveled skin: discard entirely

When preparing sprouted potatoes, use a deep-cutting paring knife to remove not just the sprouts but also the 'eyes' and surrounding tissue. The FDA advises cutting at least 1/8 inch below visible sprout points to ensure complete removal of potentially concentrated toxins.

Special Considerations for Vulnerable Populations

Certain groups face higher risks from consuming borderline potatoes:

• Pregnant women should avoid even mildly green potatoes due to potential developmental effects
• Young children have lower body mass, making them more susceptible to toxin effects
• Individuals with compromised immune systems should exercise extra caution

When in doubt about whether a potato is bad to eat, follow the food safety maxim: "When uncertain, throw it out." The minor cost of replacing a questionable potato pales in comparison to potential medical expenses from foodborne illness.

Practical Potato Safety Checklist

Before using any potato, run through this quick safety assessment:

1. Examine for significant greening (more than small spots)
2. Check firmness by squeezing gently
3. Inspect for mold or unusual odors
4. Assess sprout length and skin condition
5. Consider storage duration (discard after 3+ months)

By following these guidelines, you'll significantly reduce your risk of consuming potatoes that are bad to eat while minimizing unnecessary food waste. Remember that food safety isn't about perfection—it's about making informed decisions based on clear, observable criteria.

Can you eat potatoes that have turned green?

Potatoes with minor green spots (less than 10% of surface) can be eaten after cutting away the green areas with at least 1/8 inch of surrounding tissue. Potatoes with significant greening (more than 10% surface) should be discarded entirely as they contain unsafe levels of solanine toxin that cannot be removed by cooking.

How long after eating a bad potato do symptoms appear?

Symptoms of solanine poisoning typically appear 8-12 hours after consumption, though they can sometimes manifest within 10 minutes to 24 hours depending on the amount consumed and individual sensitivity. Common symptoms include nausea, vomiting, stomach cramps, and headache.

Are sprouted potatoes safe to eat if I remove the sprouts?

Potatoes with minor sprouting (small buds) are generally safe after removing sprouts and the surrounding tissue with a deep cut. However, potatoes with long sprouts accompanied by shriveled, wrinkled skin should be discarded as they've likely developed elevated toxin levels and lost nutritional value.

Does cooking destroy the toxins in bad potatoes?

No, cooking does not destroy solanine or other toxins that develop in spoiled potatoes. Boiling, baking, or frying will not make green or moldy potatoes safe to eat. The only safe approach is to properly identify and discard potatoes showing significant spoilage indicators before cooking.

How can I store potatoes to prevent them from going bad quickly?

Store potatoes in a cool (45-50°F), dark, well-ventilated place like a pantry or cellar. Keep them in a paper bag or breathable container, never in plastic. Avoid refrigeration as cold temperatures convert starch to sugar. Don't store potatoes near onions, as onions release gases that accelerate sprouting.