Can you freeze onions?

Onions freeze without blanching, which is unusual among vegetables, because their sulphur compounds already inhibit the enzymes that spoil most frozen produce. They thaw soft and watery, so they are for cooking only. Freezing chopped onion in a flat layer means you can break off a handful for a pan without chopping anything. Caramelised onions freeze even better, and are worth making in bulk for exactly that reason.

How to do it properly

1. Peel and chop, then spread on a tray and freeze before bagging
2. Freeze in a flat sheet in a bag so you can snap off portions
3. Add straight from frozen to a hot pan — do not thaw
4. Double-bag, because onion smell travels through a single bag

What goes wrong

• Onion odour transfers to everything else in the freezer through thin bags
• Thawed onion is limp and unusable raw

Other "can you freeze" questions

• Can you freeze cheese? It depends — Yes, and it stays safe indefinitely — but hard cheese comes out crumbly and soft cheese comes out wet.
• Can you freeze milk? Yes — Yes — leave headspace for expansion and shake it hard after thawing.
• Can you freeze eggs? It depends — Not in the shell. Beat them first, or freeze whites on their own.
• Can you freeze bread? Yes — Yes — freezing is the best way to store bread, far better than the fridge.
• Can you freeze bananas? Yes — Yes — peel and slice them first, because the peel turns black and welds itself on.
• Can you freeze cooked rice? Yes — Yes, and freezing quickly is the safest way to keep leftover rice.
• Can you freeze raw chicken twice? It depends — Only if it thawed in the fridge and never got above 4 °C (40 °F).
• Can you freeze breast milk? Yes — Yes — freeze it flat in bags, and use within six months for best quality.
• Can you freeze avocado? It depends — Yes, but only as a purée — frozen slices go grey and watery.
• Can you freeze soup? It depends — Yes for most soups; cream, milk and potato-based ones separate or go grainy.
• Can you freeze butter? Yes — Yes — butter freezes better than almost anything else in the fridge.
• Can you freeze cooked pasta? Yes — Yes — undercook it slightly and toss it in oil first, or it thaws into a solid block.