How to store half a lemon — and 17 other ways to keep leftovers fresh

This story was originally published by The Guardian and appears here as part of the Climate Desk collaboration.

Attention home cooks: Do you, like me, have half a lemon, perhaps encased in a beeswax wrap or clingfilm, sitting in your fridge? Half a cucumber, going dry at one end? Or maybe an open jar of capers, barely used, but well past the two-week recommended refrigeration period? So often, a recipe requires just half an onion, or a third of a block of tofu — especially when cooking for one.

According to the 2024 UN Food Waste Index report, about a fifth of the world’s food is wasted. Worldwide, households are responsible for the majority of it: about 60 per cent of the one billion tonnes of food thrown away annually. So how best to keep your leftover food fresh — and for how long does it remain safe to eat?

1. Avocado

Earlier this year, the food magazine Bon Appétit tackled the pressing question of how best to store half an avocado. Its advice was to remove the pit, leave the skin on and place it cut-side down on a plate. Using lemon or lime juice on the cut side, or wrapping the whole thing in clingfilm, can also help to minimize oxidation, which is what causes avocado flesh to turn grey and mushy.

2. Tofu

Firm tofu keeps better than the silken variety for leftovers, according to Amy Poon, the founder of the Chinese restaurant Poon’s London. “Tofu should keep for two to three days if stored in a plastic container, submerged in clean, cold water (not the water it comes in), but you should change the water daily,” she says. “You can also freeze tofu.”

3. Tinned goods

Tins are a big fridge no-no since, once opened, the tin from the can can transfer more quickly to the contents, according to the Food Standards Agency. Many tinned items — such as baked beans or coconut milk — are also available in half-size cans, which may be more suitable for using as part of a meal for one, although they are rarely the most economical option. James Cooper, the deputy director of food policy at the FSA, advises emptying leftover contents into a bowl or airtight container before storing it in the fridge. “Use a clean cover that is suitable for food to protect the contents from drips and spills, and use within two days or freeze if you think this won’t be possible,” he says.

4. Lemon wedges

Often, leftover lemon wedges can simply be served alongside whichever dish they have been partially used to season — but what about for drinks? “Cut fruit is a tricky one,” says Will Meredith, a beverage consultant for restaurants including Fenix in Manchester and Tattu (nationwide). “Citrus will oxidize very quickly due to all the sugar and acid — you can only expect to use slices or wedges on the day you cut them. To keep them looking and feeling fresh, place in a bowl filled with crushed or shaved ice — like you see in a fish market.”

5. Pancake batter

Fancy pancakes two days on the trot? You’re in luck! Joe Fox, the executive head chef for Firmdale Hotels, assures me that batter will keep — “although it may separate a little bit, so you’ll need to give it a good mix,” he says. “I’d transfer it straight away into an airtight container or a jam jar in the fridge, otherwise the air can cause it to discolour, which can be off-putting.”

6. Eggs

At least pancakes use whole eggs — what of recipes that require only the yolks or the whites? Rachel Morgan, co-founder of Twelve Triangles bakery in Edinburgh, keeps leftovers in a plastic container or a bowl covered in clingfilm. “Whites I’ve kept for about 10 days in the fridge; yolks tend to keep not so well and form a bit of skin, so if you have any to store I would freeze them instead,” she suggests.

7. Things in brine

I could probably eat a whole jar of olives in one sitting, but capers and cornichons are more persistent fridge-lingerers. How best to make them last? “Once opened, you want to avoid as much oxygen as possible getting into the jars, as that will create mould and foul odours,” says Meredith. “The simplest thing is get some baking paper, cut a disc large enough to cover the liquid in the jar and pat it down to create a block between the ingredients and the lid. This will prevent oxygen tainting those lovely olives, pickles or any other jarred goods.” He recommends keeping brined foods refrigerated if possible, but it’s not essential (although the storage instructions may disagree).

8. Juice

This is a complicated one — is your juice fresh? From concentrate? Pasteurized? Some unopened shop-bought juices can be kept for many months, but most have a relatively short shelf life once the seal has been broken. The FSA is strict on this: it recommends “reading the label and following the manufacturer’s instructions” — which often means consuming within three to five days. Eat By Date — “a group of contributors from the kitchen and classroom communities who set out to answer the question, ‘How long does food really last?’” — go by brand, advising that refrigerated Welch’s grape juice, for example, is safe to consume seven to 10 days after opening, while Ocean Spray cranberry juice lasts two to three weeks.

9. Non-dairy milk

“They just keep going, don’t they?” says Fox. Anyone who has made the switch from dairy will have noticed that alternative milks often seem to last well beyond the recommended five or so days in the fridge. “You could decant the milk into a glass bottle but it is kind of designed to be stored in the carton,” he says. “I feel like oat and almond milk last the longest — things like soya turn quicker. If you do store it in glass, you will be better able to see if the milk has split, but a good shake would probably bring it back together; you can taste if it’s gone bad.”

10. Bread

“If bread gets warm in a bread bin, it’ll be more likely to go mouldy, as any moisture in it will condense,” says Morgan. Instead, she keeps hers in a cotton or paper bag. But what if mould has already appeared — just a tiny bit on the crust, perhaps? Can you just slice it off and salvage the rest? “I wouldn’t,” she says. Most experts seem to agree, since, although only a few spots may be visible, porous food such as bread can be contaminated beneath the surface — which is enough to put anyone off their toast. However, you can also freeze bread for greater longevity.

11. Cucumber

Is there a way to avoid throwing out that dried-out end slice? “Once cut, I keep cucumber in an airtight container, lined with a little kitchen paper or a clean tea towel [in the fridge],” says Melissa Hemsley, the author of cookbooks including Feel Good and the forthcoming Real Healthy. “If you do feel the need to chop off the end, you only need to slice the thinnest round off. Also, cook with cucumber! If your remaining half is a touch less than fresh, I like to stir-fry it with sesame oil, garlic and chilli.”

12. Cheese

From roquefort to red leicester, Hemsley has useful advice about open packets of cheese: “Beeswax wraps or silicone reusable bags are really handy, or seal the packaging with elastic bands,” she suggests. Cheese buyer Dan Bliss wraps her cheese in wax or baking paper, stores it in a plastic container in the fridge — and suggests adding a sugar cube to the pot to suck up any excess moisture. Unlike bread, if your cheese decides to sprout mould, that doesn’t necessarily mean it’s game over — especially if it’s hard cheese.

13. Open packets of wraps/naans

Again, preventing moisture is key to longevity. Morgan wraps open packs of naan or tortillas in clingfilm before storing somewhere dry, while Eat By Date suggests tortillas “generally last for a week after their ‘best by’ date on the counter and about a month if placed in the fridge.”

14. Things in jars

For me, this comprises almost an entire fridge shelf: harissa, tomato puree, pesto, gochujang and curry pastes can all sit for weeks — perhaps longer — used once, then abandoned. I refuse to let them go to waste and yet, according to Leonard Tanyag, the executive chef at Los Mochis London City, I am doing it all wrong if I want them to remain fit for consumption: really, they shouldn’t be left in their jars at all. “Once opened, transfer to an airtight container to maintain their freshness and add some oil on top to prevent air exposure, which makes it last for weeks,” he says. And, of course, you should “always check or smell the opened paste before use for any signs of spoilage.”

15. Half an onion

Onions are a little like avocados in terms of maintaining freshness: keep the skin on the half you’re not using, then place cut-side down on a plate in the fridge. “If you don’t know when you’re next going to use the leftover onion, chop it and freeze it,” suggests Hemsley. “Then you’ve got it ready to go in a future pasta sauce or soup or stir-fry.”

16. Fresh herbs

Whether it’s mint for your mojito or coriander for your tacos, fresh herbs can bring a recipe to life — but they also wilt fast. “Wrap them in damp blue cloths or kitchen roll and keep in the fridge,” suggests Meredith. “Doing this will extend the shelf life by several days.

17. Jams and chutneys

“Try to always use a clean spoon — double dipping will increase the bacteria risk,” explains Fox, who tells me he has a chutney in his fridge from during the pandemic and it’s “still going, still tasty.” Lillie O’Brien, the owner of small-batch jam and marmalade makers London Borough of Jam, recommends refrigerating jams and preserves after opening, although “if you are going to eat them quickly and it’s not summer, then they will be fine left on a kitchen bench for a week or two.” Products that are lower in preserving agents could go mouldy if left out longer, she says.

18. Salad

“Heads of lettuce generally last much better than bagged leaves,” says Hemsley. Like cucumber, she stores salad in the fridge in an airtight container lined with kitchen paper or a clean tea towel to absorb any excess moisture. “If salad has gone a bit wilted and sad, you can revive the leaves by putting them in a big bowl of iced water for 10 to 15 minutes, then drain and dry in a salad spinner,” she suggests. “If you have a few rogue soggy leaves, remove them so they don’t infiltrate the rest of the lettuce.”