A potato that has lost some firmness is not automatically rotten. Potatoes gradually lose water during storage, so they can wrinkle and give slightly when squeezed. The useful distinction is between dehydration and rot or other major deterioration.
If it is only a little soft or wrinkled
A slightly flexible potato that is dry on the outside and has no off odor may still be usable. Its texture may not be as good as a fresh, firm potato, but the softness can simply reflect moisture loss.
Peel it or trim dried areas if needed and use it in a dish where texture matters less, such as mashed potatoes, soup or stew.
When softness becomes a discard sign
If the potato is very limp, watery, slimy, collapsed or has soft brown areas that are breaking down, that is more consistent with spoilage than simple moisture loss.
Discard it as well if you see mold, leaking liquid, a rotten odor or decay that extends through a substantial part of the potato.
Check for green areas, sprouts and bitterness
Potatoes naturally contain glycoalkaloids. EFSA notes that levels can be higher in green, damaged and sprouted areas. High exposure can cause gastrointestinal symptoms such as nausea, vomiting and diarrhea.
A slightly wrinkled potato with no greening is a different situation from one that is soft, green and heavily sprouted. Small sprouts and limited green areas can be removed generously when the rest of the potato is sound; extensive greening, major deterioration or a distinctly bitter taste are reasons not to eat it.
Cooking does not rescue a rotten potato
Processing can lower glycoalkaloid levels to varying degrees, but it does not make a rotten potato acceptable. EFSA reports that peeling may reduce glycoalkaloids by roughly 25–75% and boiling by about 5–65%, depending on conditions. Those reductions are not a reason to use a badly deteriorated tuber.
How to slow softening
Store potatoes in a dark, dry, cool and ventilated place. Light promotes greening, while warm storage speeds sprouting and water loss. Avoid washing them before longer storage because surface moisture can encourage deterioration.
The practical rule
Slightly soft and dry can still be usable. Very soft, wet, rotten, extensively green, bitter or foul-smelling should be discarded. Texture is one clue, but color, odor and the overall condition matter too.
Softness changes cooking quality before it changes safety
A potato that has lost some water may become flexible, wrinkled, or less crisp while still looking clean and smelling normal. That texture is often disappointing for fries or roasting because the potato no longer has the same moisture balance, but it may still work in soup, mash, or a purée after trimming minor dry defects.
By contrast, wet soft spots, leaking tissue, dark decay that extends into the flesh, or a sour or rotten odor point to breakdown rather than simple dehydration. Those potatoes should be discarded.
Green color and extensive sprouting are separate concerns
Greening indicates light exposure and can accompany increased glycoalkaloids. Sprouts and the area around the eyes can also contain higher concentrations. Small sprouts on a firm, otherwise normal potato can be removed along with any green tissue, but heavily green, very bitter, or extensively sprouted potatoes are poor candidates for rescue.
Do not use bitterness as a challenge test by eating a suspicious potato. If the potato tastes distinctly bitter, stop eating it.
Store potatoes dark, dry, and ventilated
Light encourages greening, while trapped moisture encourages rot. A breathable bag, basket, or box in a cool dark cupboard or pantry is generally better than a sealed plastic bag on a warm countertop. Keep them away from direct sunlight and check the batch periodically so one rotting potato does not remain pressed against the rest.
Peeling does not turn a badly deteriorated potato into a good one. If a defect is superficial and the rest of the tuber is firm and normal, trimming can improve quality; if softness extends through the potato or decay is widespread, the problem is not confined to the skin. Use the whole condition of the potato rather than focusing on a single blemish.
Cold storage is sometimes discussed for potatoes, but the ideal temperature depends on how they will be used and how long they are stored. Very cold conditions can increase sugars in raw potatoes, which may affect browning during high-temperature frying or roasting. For most homes, the priority is a cool, dark, well-ventilated place and buying quantities that can be used before they dehydrate or sprout heavily.
Sources
- EFSA — Glycoalkaloids in potatoes: public health risks assessed — Glycoalkaloid risk and reductions from peeling and cooking.
- UK Food Standards Agency — Consumer guidance on potatoes, greening and sprouts — Guidance on removing sprouts and green or rotten areas and storing potatoes cool, dark and dry.