An onion is bad if it is soft, slimy, moldy, leaking, sour-smelling, or badly sprouted. A dry papery outer layer is normal, but wet spots, black mold, mushy layers, or a fermented smell are signs to discard it. Cut onions need more caution because they have exposed moist surfaces.
Quick Signs an Onion Has Gone Bad
| Sign | What it means | What to do |
|---|---|---|
| Soft or mushy spots | The onion is breaking down | Discard if the softness is more than a tiny dry bruise |
| Slime or wet leaking | Spoilage is likely | Discard |
| Mold on the surface or layers | Fungal growth is present | Discard the onion |
| Sour, rotten, or fermented smell | The onion is no longer fresh | Discard |
| Small green sprout | Usually aging, not always spoilage | Use only if the onion is still firm and smells normal |
Whole Onion vs Cut Onion
Whole dry onions can last longer when they are kept in a cool, dry, well-ventilated place away from direct light. Do not seal whole dry onions in a damp bag or closed container. Cut onions should be covered and refrigerated because the cut surface is moist and easier to contaminate.
How to Check an Onion
- Look for mold, wet spots, leaks, or dark sunken areas.
- Press gently. A good onion should feel firm, not mushy.
- Smell it. A sharp onion smell is normal, but sour, rotten, or fermented odors are not.
- Cut it open if the outside looks questionable and the onion still feels firm.
- Discard the onion if the inner layers are slimy, gray, brown, or moldy.
Are Sprouted Onions Safe?
A small sprout does not automatically mean the onion is spoiled. If the onion is firm, dry, and smells normal, you can remove the sprout and use the rest. If it is soft, wet, moldy, or smells off, discard it.
How to Store Onions
- Keep whole dry onions in a ventilated basket, mesh bag, or open bin.
- Keep them away from damp areas and sealed plastic bags.
- Refrigerate cut onions in a covered container.
- Use clean knives and boards when cutting onions.
- Discard cut onions that become slimy, moldy, or sour-smelling.
FAQ
Can you eat an onion with a little mold?
It is safer to discard a moldy onion, especially if the mold is on a cut surface or between layers.
Is a soft onion always bad?
A tiny dry bruise can be trimmed, but a soft, wet, mushy, or leaking onion should be discarded.
Can you use an onion that has sprouted?
Yes, if it is still firm, dry, and normal-smelling. Remove the sprout before using it.
Why does my onion smell sour?
A sour or fermented smell is a spoilage sign. Do not use that onion.
Should cut onions be refrigerated?
Yes. Store cut onions covered in the refrigerator and discard them if they become slimy, moldy, or off-smelling.