Sweet potatoes are a nutritious root vegetable that can begin to spoil quickly if not handled properly after harvesting. Knowing how to identify signs of fresh versus bad sweet potatoes can help avoid foodborne illness from consuming rotten ones. This article covers indicators of fresh and spoiled sweet potatoes, causes of spoilage, proper storage methods, whether moldy sweet potatoes can be safely eaten, and how long sweet potatoes last when refrigerated or frozen. Using these guidelines can ensure you are able to fully enjoy sweet potatoes while they are still fresh and flavorful.
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Signs of a Fresh Sweet Potato
Here are some signs that indicate a sweet potato is fresh and suitable for eating:
- Firm and heavy. Feels solid with no squishy spots and weighs substantial in the hand.
- Smooth, taut skin. Skin appears smooth and tight, not wrinkled or shriveled.
- Intact skin. No cracks, bruises, breaks, or soft spots on the skin.
- Strong, earthy odor. Has a distinct sweet potato smell when raw.
- Bright color. Vibrant, rich orange-yellow flesh inside.
- Moist flesh. The raw interior looks moist, not dried out.
Sweet potatoes that are lightweight, show skin damage, or have dull flesh may be past prime or spoiled.
What Causes Sweet Potatoes to Go Bad?
There are a few reasons why fresh sweet potatoes deteriorate rapidly:
- Mold growth. Mold can develop if sweet potatoes get wet, are bruised, or are stored incorrectly.
- Shrinkage. Sweet potatoes shrink and wrinkle as they lose moisture over time after harvest.
- Sprouting. Exposure to light and warmth causes sweet potatoes to sprout early.
- Yeast and bacteria. Naturally occurring microbes grow and cause decay.
- Cellular breakdown. Enzymes and oxidation slowly break down cell structure.
- Physical injury. Bruises, cuts and impact injuries speed up spoilage.
Proper post-harvest curing, handling and storage helps maximize sweet potato shelf life.
6 Signs a Sweet Potato Has Gone Bad
Watch for these common signs that a sweet potato has spoiled and is no longer good to eat:
Soft, Sunken Textures
A fresh sweet potato should be firm with smooth, taut skin. Soft spots, shriveling, or sunken dents indicate spoilage underneath.
Discoloration
Good sweet potatoes are vibrant orange inside with uniform flesh. Gray, brown or black hues suggest mold and decay developing internally.
Mold Growth
The appearance of fuzzy white, gray, green or black mold on the outer skin is a sign of advanced spoilage and possible toxins.
Rancid Odors
A spoiled sweet potato gives off an unpleasant, musty smell instead of its usual mild, sweet aroma.
Liquid Leakage
Exudate leaking through the skin happens as starches and sugars break down. This sticky fluid signals deterioration.
Bitter, Off Flavors
Unpleasant bitter, fermented, or sour tastes when cut mean spoilage has occurred. A bad sweet potato should not be eaten.
Catching spoiled sweet potatoes early prevents foodborne illness. Know what to look for before cooking. Next, we will cover how storage affects shelf life.
How to Store Sweet Potatoes
Properly storing sweet potatoes helps maintain quality and prevent spoilage so you can enjoy their delicious flavor as long as possible.
Here are tips for storing sweet potatoes from purchase to final use:
Purchasing Sweet Potatoes
Start with high quality, fresh sweet potatoes:
- Choose firm, smooth sweet potatoes without cuts, bruises or mold.
- Avoid potatoes with soft, wet areas which signal spoilage.
- Small to medium sized sweet potatoes tend to be sweeter. Oversized potatoes can be fibrous.
- For storage, pick potatoes with thin, light tan skin rather than thick, dark skin. The thinner skin extends shelf life.
- Purchase only what you plan to use within a week to avoid waste from spoiling.
Key Point: Select smooth, firm sweet potatoes free of damage, mold and with thin, light tan skin.
How Long Do Whole Sweet Potatoes Last?
The shelf life of fresh sweet potatoes varies based on variety and storage method:
- Cured, room temperature – 3-5 weeks
- Refrigerator – Up to 2 months
- Freezer – 6 to 12 months when frozen properly
For maximum shelf life:
- Select unbruised sweet potatoes without wrinkled skin.
- Cure freshly dug sweet potatoes for 7-10 days in a warm, humid place.
- Store cured sweet potatoes in a cool, dark place up to 1 month.
- Refrigerate to extend life another 1-2 months.
Storing Uncooked Sweet Potatoes
Follow these guidelines for whole, uncooked sweet potatoes:
At Room Temperature
- Whole, unwashed sweet potatoes can be kept at room temperature out of direct sunlight for around 1 week before quality declines.
- Place them in a basket, bowl or wire rack to allow air circulation. Avoid stacking in piles.
- Room temperature between 60°F to 70°F (15°C to 21°C) provides ideal short-term storage conditions.
Refrigerated Storage
- Refrigerating extends the shelf life of whole sweet potatoes up to 2-3 weeks.
- Keep whole, unwashed potatoes loose in the crisper drawer. Do not refrigerate if damp or wet.
- Maintain a consistent refrigerator temperature between 40°F and 50°F (4°C and 10°C) for optimal preservation.
Root Cellar Storage
- Whole sweet potatoes can keep for 2-3 months stored in a dark, humid root cellar with temperatures around 60°F (15°C).
- Avoid cellar temperatures below 50°F (10°C) which causes starch conversion and undesirable sweetening.
- Check potatoes occasionally for signs of mold or shriveling, removing any that are spoiling.
Key Point: Unwashed whole sweet potatoes keep 1 week on the counter, 2-3 weeks in the fridge, or 2-3 months in a root cellar.
Storing Cooked Sweet Potatoes
Cooked sweet potatoes require refrigeration. Use these methods:
- Store baked, boiled or steamed potatoes in an airtight container for 5-7 days.
- For longer storage of up to 2 weeks, wrap individual cooked potatoes in foil or plastic wrap to exclude air.
- Place in shallow airtight containers or resealable plastic bags, removing excess air.
- Maintain a refrigerator temperature no higher than 40°F (4°C). Monitor for mold growth or drying out.
- Avoid storing cooked sweet potatoes with foods having strong odors which may be absorbed.
Key Point: Cooked sweet potatoes keep 5-7 days in an airtight container, or 2 weeks individually wrapped in the fridge.
Freezing Cooked Sweet Potatoes
Freezing extends the shelf life of cooked sweet potatoes for 6-12 months.
Preparation
- Bake, steam, or boil potatoes until easily pierced with a fork. Let cool completely.
- Peel and cut potatoes into cubes, slices, or mash. Raw potatoes should be blanched 2-3 minutes before freezing.
- Portion into resealable plastic freezer bags or airtight freezer containers, leaving 1⁄2 inch headspace.
Freezing
- Freeze potatoes immediately at 0°F or below. Rapid freezing preserves quality.
- If freezing mashed potatoes, do not store blocks larger than 2 pounds each, as slower freezing causes starch and cell damage.
- For best texture, do not keep frozen sweet potatoes longer than 6-8 months at 0°F (-18°C).
Key Point: Freeze cooked sweet potatoes in airtight bags or containers at 0°F or below for 6-12 months.
Storing Canned Sweet Potatoes
Commercially canned sweet potatoes have a shelf life of 2-5 years stored at room temperature. For qualitative guidelines:
- Store unopened cans in a cool, dry place under 85°F (29°C). Avoid areas with high heat or humidity.
- After opening, transfer contents to a tightly sealed container and refrigerate. Keep for 5-7 days.
- Discard any cans that are leaking, rusted, badly dented or swollen when purchased or before opening. Do not consume contents if any abnormal odors or off colors are noticed.
- Consume contents within 18-24 months for highest quality, rotating oldest cans to front. Canned potatoes kept over 5 years risk changes in texture and flavor.
Key Point: Unopened canned sweet potatoes keep 2-5 years in a cool, dry place. Refrigerate opened cans for 5-7 days.
How Long Do Sweet Potatoes Last in the Freezer?
Frozen properly, sweet potato pieces, slices or casseroles can last 6-12 months in the freezer. Here are freezing guidelines:
- Scrub sweet potatoes and cook until tender. Remove skin if desired.
- Mash cooked sweet potatoes or cut into 1/2 inch slices or cubes.
- Spread pieces in single layer on tray and freeze until solid, about 2 hours.
- Transfer frozen sweet potato portions to freezer bags or containers.
- Squeeze out air, label with date and contents.
- Store frozen sweet potatoes no longer than 12 months for best quality.
Sweet Potato Storage Troubleshooting
Having trouble keeping sweet potatoes for as long as you would like? Here are some common issues and solutions:
Problem: Sweet potatoes shriveling and wrinkling prematurely
Solution: Increase humidity around 80% for storage area. Keep potatoes from direct air vents.
Problem: Visible mold growing on sweet potatoes
Solution: Check storage area for excess moisture. Discard moldy potatoes immediately and separate from others.
Problem: Soft dents and sunken spots
Solution: Avoid stacking sweet potatoes or placing heavy objects on top that can cause bruising.
Problem: Excess sprouting before cooking
Solution: Store potatoes somewhere cooler around 55°F next time prevent sprout emergence.
Problem: Unpleasant bitter taste
Solution: Do not refrigerate sweet potatoes. The cold converts starch to sugar affecting taste.
With the proper storage conditions, you can keep sweet potatoes fresh for months.
What Happens When Sweet Potatoes Go Bad?
As sweet potatoes spoil, here are the internal changes that occur:
- Starches convert to sugar causing overly sweet taste.
- Cell walls break down making flesh soft and waterlogged.
- Natural sugars ferment giving off alcohols and acids.
- Mold growth produces hazardous mycotoxins.
- Bacteria accumulate possibly causing foodborne illness if eaten.
Eating a spoiled sweet potato can make you sick, especially if mold is visible. It’s important to learn the signs before cooking.
Can You Get Sick from Eating a Bad Sweet Potato?
It is possible to get sick from eating moldy, spoiled, or rotten sweet potatoes. Potential risks include:
- Foodborne Illness – Microbes like salmonella, listeria or E. coli can cause nausea, vomiting, diarrhea.
- Digestive Problems – Off-flavors or textures may irritate the digestive tract.
- Allergic Reactions – Mold spores can cause problems for those with sensitivities.
- Toxins – Decaying sweet potatoes may contain higher levels of naturally-occurring toxic compounds like solanine or chaconine.
- Choking Hazard – Fibrous, rotten pieces could potentially obstruct airways if swallowed.
To avoid sickness, compost spoiled sweet potatoes rather than eating them. Prompt refrigeration prevents microbe overgrowth.
Is it Safe to Eat Moldy Sweet Potatoes?
It is not recommended to knowingly eat sweet potatoes that have mold growing on them. Moldy sweet potatoes should always be discarded due to the potential health risks:
- Mold filaments can penetrate into the sweet potato, beyond what’s visible.
- Molds release spores that can cause allergic reactions if inhaled or ingested.
- Mycotoxins may persist even if moldy parts are removed.
- Decayed tissues have an unpleasant taste and texture.
- Increased risk of foodborne illness if moldy sweet potatoes are consumed.
While cutting away moldy spots works for some firm produce, softer produce like sweet potatoes should be discarded at the first sign of mold. Don’t take chances when mold is present.
Can You Eat Sprouted Sweet Potatoes?
It’s best not to eat sweet potatoes that have begun sprouting. Here’s why:
- Toxins – Sprouts and green skin from sun exposure may contain glycoalkaloids which can cause illness if consumed.
- Digestion inhibitors – antinutrients are produced to protect the growing sprouts.
- Rancid fats – enzymes break down fats into nasty flavors.
- Poor texture – flesh becomes extra soft and spongy around sprouts.
While not immediately poisonous, sprouted sweet potatoes have biochemical changes making them unpalatable and hazardous if eaten in large quantities.
How to Revive a Wrinkly Sweet Potato
If you catch a sweet potato just starting to shrivel, you may be able to revive it:
- Trim away any soft spots or dents with a clean knife.
- Soak in cool water for 1-2 hours to rehydrate.
- Dry thoroughly before returning to storage.
- Use quickly within a few days.
- Avoid letting wrinkled potatoes remain in storage to prevent spreading spoilage.
Soaking plumps up any small wrinkles, but deeply shriveled or moldy potatoes cannot be revived. Consume revived potatoes soon after rehydrating.
Can You Freeze Bad Sweet Potatoes?
Freezing cannot save spoiled sweet potatoes. The high water content causes them to get mushy and lose flavor in the freezer. However, you can salvage slightly wrinkly potatoes using these freezing methods:
- Cut away all soft or discolored parts.
- Peel and cut into cubes no more than 1 inch thick.
- Blanch 2-3 minutes in boiling water or steam.
- Cool, drain, and pack cubes into airtight bags or containers leaving 1/2 inch headspace.
- Seal and freeze below 0°F.
- Use within 8-10 months for best quality.
Freezing cannot reverse actual spoilage but can extend the shelf life of potatoes that are just starting to show signs of aging.
What to Do With Bad Sweet Potatoes
While you should never eat spoiled or moldy sweet potatoes, you have some options for how to use up aged ones:
- Cut away damaged parts and cook immediately using extra spices to mask off flavors. The remaining flesh is likely still usable if mold has not set in.
- Pickle in vinegar brine to preserve and add flavor. Refrigerate pickles for 2-3 months.
- Make sweet potato vinegar by fermenting sliced potatoes in vinegar. Strain out solids after 2-3 weeks.
- Bury in garden as nutrient-rich compost. Avoid composting moldy potatoes.
- Feed to livestock like chickens, cows, goats, and pigs. Do not give excess moldy potatoes.
With creativity, you can avoid wasting old sweet potatoes and transform them into something useful. Of course, discard those that are overtly spoiled.
Frequently Asked Questions
How can you tell when a sweet potato is cooked inside?
Use a fork to poke the center. If it slides in easily with little resistance, it’s done. The skin may also split open. Cooked flesh will be soft and tender when pierced.
What happens if you eat undercooked sweet potato?
The texture may be unpleasantly firm and difficult to chew. Raw sweet potato also contains higher amounts of toxins like solanine and chaconine that cooking reduces. Fully cooked is recommended.
Can you eat very sprouted sweet potatoes?
It’s best to remove sprouts and use sprouted sweet potatoes quickly before quality declines further. Peel deeply to remove potential mold and bitterness from the skin and sprouted areas.
Why might sweet potatoes cause stomach pain?
The high fiber content could irritation the intestines in some individuals. Toxin levels also increase as sweet potatoes spoil, which can cause cramps or pain when eaten. Stick to fresh, properly cooked sweet potatoes.
Can you substitute yams for sweet potatoes?
Sweet potatoes and yams are not the same. Yams have thicker skin, white/purple flesh, and are less sweet. Due to taste and texture differences, they are not recommended substitutes in recipes.
Final Takeaways
Knowing how to determine if a sweet potato is still fresh versus spoiled can prevent foodborne illness. Choose those with intact, taut skin free of mold, bruises and wrinkles. Avoid sweet potatoes with soft spots, sprouts, foul odors, or ooze. Maximize shelf life by curing and storing properly. Refrigerate cooked sweet potatoes promptly. Practice caution when introducing sweet potatoes to infants, the elderly or those with mold allergies. Following these guidelines helps ensure you can safely enjoy the great taste and nutritional benefits of sweet potatoes.