It can be frustrating when onions begin spoiling after being freshly bought, but this may be because you are storing them in the wrong place in your kitchen. 

Onions, like all allium vegetables, should never be stored in the kitchen as the cold temperature will convert the starch in the onion into sugar at a much faster rate. 

Merissa, a cooking expert and founder of Little House Living, shared that the humid environment of a fridge also leads to onions becoming soft, mushy and even mouldy before their time. 

She said: “While whole onions can be stored in a fridge, it is not recommended. That is because whole raw onions absorb moisture quickly and can turn softer in the fridge.”

If stored “properly” in a cool and dry environment then onions should stay fresh for more than three months after being bought according to Melissa. 

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How to store whole onions to keep them fresh? 

The most important tip for storing whole onions is to keep them away from moisture and extreme temperature, which is why they should always be stored in a cupboard or drawer.  

Melissa said: “Store your onions in a dry [spot] where moisture cannot seep through to keep them from spoiling or rotting. Avoid storing onions in areas such as under the sink or in the basement, where it is humid.” 

She added: “If onions are stored in a hot area, they will start drying out and sprouting, which can lead them to rot and spoil quickly. If they get too cold, onions will become moist, lose their hardness, discolour, and even mouldy” 

You can keep onions on your countertop but is highly recommended to also keep onions away from sunlight as it can cause onions to sprout and begin rotting. 

Make sure to remove onions from their original plastic packaging from the supermarket, and instead place them somewhere which allows a lot of airflow such as a paper bag or a mesh bag. 

Melissa said: “Plastic bags will invite a great deal of moisture and make the onions rot faster than you want them to.” 

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How to store sliced-up onions?

Once the onion bulb is broken it will only last a few days, and this is the only time they should be placed back in the fridge. 

Melissa said: “Sliced, chopped, and cooked onions should always be stored in the fridge. These types of onions are not suitable for pantries and will rot quickly outside your fridge.”

She added: “Half-cut onions should be wrapped tightly in cling film or plastic wrap and then put into an airtight container, while chopped onions should be put in a plastic zipper bag.”

Make sure to keep pieces of onion stored in a container to avoid exposure to ethylene gas, a growth hormone emitted by certain fruits and vegetables which speeds up the ripening process. 

Onions are very sensitive to ethylene and when stored with other vegetables it can cause them to sprout and spoil quickly. 

Peeled onions will last seven to 10 days in the fridge when stored correctly while peeled onions will last between 10 to 14 days.