I’m a food waste expert and here’s how to freeze foods you didn’t know you could – from crisps to hummus and even sandwiches – that’ll save you so much time and money

As I write this, the contents of my freezer contain a sad-looking, half-empty packet of peas; two jumpers (moths); a haphazardly filled ice cube tray; and a sliced ​​loaf of bread in a plastic bag with a huge tear in the middle.

Kate Hall’s freezer is a bit more ambitious.

The drawers are arranged by category – dairy, cupboard, bakery, fruit, vegetables, fish, meat, raw meat – and within those categories, individual food groups are individually packaged in sealable plastic bags. (Hall likes the ones from Ikea, which cost £2 for 25 and can be reused.)

These bags are then labeled and dated. In January, Hall appeared on BBC’s Morning Live. When presenter Gethin Jones saw a photo of her freezer, he gasped and said: ‘It’s like a Filofax!’

Hall, 38, is a frozen food expert based in Kent. Her Instagram account @the entire freezer, where she shares freezer tips, has 68,000 followers. When Hall announced her debut guidebook, The complete freezer methodOn social media, it reached number one on the Amazon Home Guides bestseller list thanks to pre-orders alone.

Hall froze after having her second child. She wasted “so much food” – and money – and didn’t have time to batch cook. But she did have time, for example, to cut a pepper into pieces and put it in the freezer. Soon she started doing this to all the food that was about to spoil in her refrigerator. “It was like finding a magic pause button,” she says.

Intrigued, Hall wanted to know how much she could freeze – and in what ways. So she took a restaurant-level food hygiene course online to learn what was safe and unsafe, but then felt the cold.

The first trick, Hall says, is to make sure the food is flattened when you pack it in the plastic bags. This way it thaws faster and you can fit more bags in your freezer.

Although, she warns, a freezer should never be too full: “You want it to be about 70 percent full so it doesn’t have to work too hard.” For example, a freezer of 70 to 100 liters must be filled with approximately a carrier bag’s worth of groceries.

Hall is also strict about how long cooked food should cool before freezing: most dishes need about two hours, while rice needs an hour. As for optimal freezer temperatures, Hall thinks of -18C. And, she says, while food can be stored in the freezer indefinitely, it is best eaten within three to six months.

In addition to her flat-packed bags, Hall saves space for ‘open-freezing’ on trays. She cuts bananas into pieces or cooks pieces of chicken, ‘freezes them open’ and decants the results into plastic bags.

Ice trays are filled with leftover hummus or coffee, for example. Hall even saves eggs, which she has lightly beaten and then carefully poured into the containers. There is approximately one egg in every two cubes. Apparently they freeze brilliantly. Who knows?

Beaten eggs and hummus aren’t the only strange things in Hall’s freezer. She has peeled, pre-cooked potatoes that, once thawed, she roasts (an excellent time saver for Sunday lunch); lemons (she says frozen lemons are easier to peel); sandwiches she has made in advance (perfect for packed lunches); nuts (for snacks); even chips.

“If you have a bunch of half-eaten packets of chips left over from a party, just put them in a plastic bag and put them in the freezer,” says Hall.

You shouldn’t decant all the room temperature chips into a bowl – ‘they get stale very quickly’ – but they’re fine if ‘you just want a handful with a gin and tonic on a Friday evening’.

In fact, says Hall, “I like eating chips straight from the freezer when they’re really cold better than eating them fresh.” They’re so crispy.’ After our interview, I try some frozen chips for myself. It’s strange at first, but then quite nice. The only problem is that I rarely have just a handful of chips. But that’s a me problem, not a freezer problem.

What cannot be frozen? Almost nothing, says Hall, although mayonnaise—or any emulsion sauce—doesn’t freeze because it separates after thawing. Other dairy products will also split as the fats separate from the water, but you can recombine them by “running them in a food processor, heating them, using them in cooking or, sometimes, by shaking them very well.”

Hall also warns against freezing food that you haven’t cooked yourself (e.g. takeaways) because you don’t know how many times it has been cooked or cooled. (You only have to do both once.)

Hall estimates she saves £1,000 a year by freezing food that would otherwise have ended up in the bin. It is also good for the environment; Britain wastes 9.5 million tonnes of food every year. Some of it ends up in a landfill, where it releases rot and methane.

People have been freezing food for a long time. In 1000 BC, Chinese emperors had underground icehouses built so they could store ice and food during the summer.

There are still four ancient examples in Beijing’s Forbidden City; They are made of stone, about two meters high, eleven meters long and over six meters wide, with walls two meters thick. Hall would love them.

More recently, frozen foods have become gourmet. At Waitrose you can buy 200 grams of frozen miso butter for €3.50. The times calls it a ‘miracle product’ and ‘umami bomb’.

And British brand The Truffle Company sells black winter truffles – the underground kind, not chocolate – that can be shaved from the freezer. Yours for £39 per 50 grams.

Despite Hall’s Filofax freezer, she insists she’s not perfect. ‘I’m just someone who tries. I’m trying my best! I find that people often grew up in households where it’s either, “We don’t waste anything.” Or, “Oh, is that okay? I’m not sure. I’ll throw it away just to be safe.” And I come from the latter.’

Freeze or throw away?

Five foods you can freeze

EGGS Break, beat and freeze. Perfect for baking, omelettes or scrambled eggs.

CRISPS Frozen foods are crispier and tastier, Hall says.

FLOUR Beetle beetles can hide in flour, but freezing kills their eggs. Eek.

COOKED PASTA Make sure it is al dente to avoid mushyness during defrosting.

CITRUS FRUITS Sliced, whole or peeled and segmented.

And five foods you can’t eat

HARD BOILED EGGS The white becomes rubbery. Bah.

SALAD Freeze salad separately? Tick. Freeze a ready-made salad? Expect boggyness.

JELLY When thawed it becomes cloudy and mushy (but freezing in lollipop molds and frozen food is fine).

EMULSION SAUCES Mayonnaise and hollandaise separate during thawing.

TAKEAWAY LEFTOVERS High risk, says Hall – you don’t know how many times it has been heated.

The complete freezer method by Kate Hall is published by Ebury, £14.99. To order a copy for €12.74 through March 31, go to mailshop.co.uk/books or call 020 3176 2937. free UK shipping on orders over £25.