Whole raw onions will last for up to 2 months in the fridge.
Chopped raw onions will last for up to a week in the fridge, or up to 8 months in the freezer.
Once cooked, onions will usually last for up to 5 days in the fridge, and up to 12 months in the freezer.
Different types of onions
The Taste of Home details the different types of onions:
Yellow onions: are your standard cooking onion. When stored properly, whole yellow onions have a shelf life of about 4 to 6 weeks, and 1 to 2 months in the fridge.
White onions: are often found in prepared salads, salsa and commonly served in barbecues. White onions last as long as yellow onions.
Red onions: are used for salads, sandwiches, and other raw dishes. They’re also great for roasting, grilling, and pickling. Red onions last 30 to 60 days if stored in the fridge. Outside of the fridge, these onions last for up to six weeks.
Spring onions: also called scallions, can be eaten cooked or raw, and have a milder flavour than regular onions. They can keep for up to 3 days on the shelf, or two weeks in the fridge.
Sweet onions: are often eaten raw in salads, relishes or chopped as a garnish.
Shallots: have a mild onion flavour and are used in sauces.
How to store onions
According to Still Tasty, to ensure maximum freshness, store whole onions in a loosely covered paper or mesh bag or basket to allow for air circulation.
Don’t store onions in a plastic bag, as the lack of air movement will reduce their shelf life, or near potatoes, as the chemical reaction will make the onions go off quicker.
Once peeled and chopped, keep raw onions in a covered airtight container in the fridge.
Onions can also last in the freezer and the best way to store them is to first peel off the first layer, then slice or chop the onions before placing them in airtight containers or heavy-duty freezer bags.
What are the signs if an onion has gone bad?
When choosing your onions look for ones that are firm, free of soft spots, and fully wrapped on their skin, which should be papery and dry.
Don’t pick onions that have mould, discolouration, bruises, cuts or any odd smells.
Key signs that show if an onion has gone off include black or brown spots and soft spots, which can indicate that mould is growing.
What do I do with bad or mouldy onions?
According to Cooking Light, like any other type of food grown in soil, there is a very rare potential for onions to have E.coli, salmonella, or other viruses that can be spread via toxic fertilisers.
But the risk is quite low and overall, there are “no safety precautions that are unique to an onion.”
Just like most vegetables, when handling onions make sure you have thoroughly washed your hands and kitchen tool, and wipe down counter before preparing your food.
While small mould and spots can be cut off the onion and still used, severely mouldy onions are not safe to eat, especially if they have turned soft.