Onions are that all-important base to so many savory dishes. There’s no worse pain than starting to cook a stew or a spag bol and realizing: “I have no idea how old these onions are!”
The good news? It’s super easy to tell if your onions have gone bad, and there are a handful of nifty methods to keep your onions fresher for longer.
The verdict, for those of you in a rush: If your onion doesn’t have any dark and mush spots, and it doesn’t smell, it’s probably good to cook with.
How Do I Tell If My Onions Have Gone Bad?
If you’ve already peeled an onion and can’t spot anything immediately wrong with it, you’re probably fine, as onions exhibit obvious signs of decay:
Dark spots, which will turn to mold if left long enough
Sprouting, a sign the onion is beginning to go off
Soft or mushy spots
A foul smell
How To Store Onions
Ideally, you want to store onions in a cool, dry, dark place, around 50°F (or 10°C). Think cool pantry or cellar.
And those plastic bags onions come in? Chuck them!
Storing onions in a plastic bag prevents proper ventilation, which is important to prevent molding. You should opt for an open box or loosely covered paper bag instead.
If you already know you’re going to be leaving your onions for more than a few weeks, consider portioning them out into different bags. That way, if one onion starts absorbing moisture and going moldy, it won’t ruin the whole batch.
If you don’t have access to a pantry, or you live in a hot country, then you can always put your whole raw onions in the fridge, completely loose. However, be prepared for your onions’ skin to go softer as they absorb moisture – this shouldn’t be noticeable once you cook them.
Once you’ve chopped, sliced, or cooked your onions, the rules change. Pop them in an airtight container before putting them in the fridge.
Want to know the best part? You can even freeze chopped onions in a freezer bag or airtight container, which can save you a bunch of time when it gets round to cooking meals.
Top tip: Flash freeze your chopped onions by laying them out on a baking tray, covering in cling film, and placing them in the freezer for 2 hours. This ensures that your chopped onions won’t stick together, so it’s easy to get a good portion size out when it comes to cooking.
Of course, you can also freeze onions that are incorporated into dishes already.
Freezing your onions won’t deprive you of any of their nutritional benefits.
One last thing – keep your onions away from fruits and vegetables that contain ethylene, which causes your onions to ripen. Steer clear of tomatoes and bananas!
How Long Do Onions Last?
Onions last varying lengths of time, depending on how you store them.
If you store onions in a cool, dark, dry place that’s around 50°F, expect them to last up to 2-3 months. In the event that you’re planning to store them this long, you should portion them out as detailed above.
Whole, raw onions will last up to a week at room temperature. This is fine for short-term storage, but your onions won’t keep long at all.
Onions will last in the fridge for up to 2 weeks, though their skins will be a little soft within a fortnight.
Raw sliced or chopped onions will keep in the fridge for a week, as long as they’re in an airtight container.
Cooked onions, either on their own or in a dish, will last for up to 4 days in an airtight container in the fridge.
Freezing your onions is by far the method that will allow them to stay fresh the longest. You can freeze raw onions for 8 months and cooked onions for 12 months!
The Verdict: Do Onions Go Bad?
Onions, like any perishable food item, do go bad.
However, they can last for up to 12 months in the freezer and 2-3 months in a cool pantry or cellar. Plus, if you’ve already peeled your onion and it looks and smells fine – it probably is fine.