Do YOU trust the sniff test? SARAH RAINEY puts the method on trial

So would YOU trust the sniff test? As supermarkets start scrapping use-by dates and advise shoppers to ‘use their noses’, SARAH RAINEY puts the old-fashioned method on trial

  • Brits waste nearly £800 of edible food products a year according to a study
  • The most commonly wasted items in households are potatoes, milk and bread
  • ‘The sniff test’ could save up to £370million a year in wasted dairy products

How much food have you thrown away this week? Go on, be honest.

A recent study by Tesco found that the average British family wastes £800 worth of food a year, with half a million people binning perfectly edible produce on a daily basis.

Potatoes are the most wasted food in this country, closely followed by bread and milk.

But what if we could change this, by returning to the old-fashioned way of working out whether food has gone bad: the sniff test?

In January, Morrisons announced plans to remove use-by dates from its own-brand milk, and last month the Co-op followed suit by scrapping use-by dates on its yoghurts.

Both are asking shoppers to use their noses to tell whether food is good to eat — a move they say could save more than £370 million in wasted dairy.

A century ago, this was how everyone did it; expiration dates didn’t appear until the 1930s. Dr Laura Brown, senior lecturer in nutrition, food and health sciences at Teesside University, says the sniff test can still work today — but advises caution.

The difference, she explains, is between use-by dates — which concern food safety — and best-before dates, about quality. ‘For foods with a best-before date, you can use sight, taste or smell to see if the products have gone off,’ she says. However, when it comes to use-by dates: ‘We cannot always smell the bugs that can cause food poisoning.’

Here, SARAH RAINEY investigates how long it takes our favourite foods to fail the sniff test after their expiry date.

Sarah Rainey tries out the ‘sniff test’ on a number of popular foods and drinks and documents how long they last until they have gone off


I stocked up on everyday essentials, including dairy, meat, fruit and veg. I bought two of each item, both with identical use-by or best-before dates, and unless directed otherwise stored them in the fridge. The day after its expiration date passed, I opened one of each item and sniffed it. My husband, neighbour and (brutally honest) toddler acted as ‘independent sniffers’, to make the test objective.

I repeated the test daily, carefully re-sealing each item in cling film.

When the smell turned bad, I opened the second item, to check if it had lasted longer if the packaging had remained sealed. In every case, by the time the open item had gone off, the sealed one had turned just as bad, too. Here are the rest of the eye-opening results . . .


STORED: In the fridge.

SAFE TO SNIFF? Yes — I’ve selected a Co-op yoghurt, the very product on which use-by dates will be scrapped.

DAY 1 AFTER USE-BY DATE: Looks and smells delicious. ‘Yoghurt usually lasts for at least a few days after its expiration date and up to a week after opening the container if it is sealed tightly,’ says Dr Brown.

DAY 7: There’s a thin, watery layer on top but the yoghurt underneath — I brave a small spoonful — smells of vanilla and tastes creamy.

DAY 9: The sweet smell is fading. I think it’s on the turn but it tastes fine, if a little less sweet.

DAY 10: There’s a tangy, sour smell the moment I lift the lid and the yoghurt looks curdled. ‘Yoghurt should smell fresh and pleasant,’ says Dr Brown. ‘If you detect a smell like sour cream, discard it.’



STORED: In the fridge.

SAFE TO SNIFF? Yes, says Dr Brown, but with great care. ‘Beef that has gone bad will develop a slimy or sticky texture and will have off or foul odours. Ground beef should be used within one to two days of purchase.’

DAY 1: The mince looks pink and smells normal.

DAY 2: It’s turning greyish-brown but smells fine. Dr Brown says: ‘Beef can sometimes develop a brown colour owing to metmyoglobin, a chemical reaction that occurs when the myoglobin in meat is exposed to oxygen. As long as the change in colour isn’t accompanied by other signs of spoilage, it should be fine.’

DAY 3: There’s a strange, sweet smell and the brown colour is spreading. I wouldn’t want to handle this, let alone eat it — it’s gone off.



Granary loaf: Bread is one of the most commonly wasted items, but are known to go mouldy after a few days

SAFE TO SNIFF? Yes. Bread has a best-before — not a use-by — date, so there are no immediate safety issues. I store it in the bread bin. ‘Putting sealed bread in the fridge will make it go stale quicker,’ says Dr Brown. DAY 1: The bread is as fresh as the day I bought it.

DAY 3: No change. It smells fine and is perfectly good for sandwiches.

DAY 5: The bread still smells sweet and nutty, but the ends are going stale. It has lost its freshness but works well as toast.

DAY 6: The whole loaf is drying out and I spot a few spots of green mould — time to bin it. Dr Brown says she would expect bread to last five to seven days beyond its best-before date. ‘If your bread develops a little blue mould, remove it along with a few centimetres around the mould,’ she adds. ‘Dispose of any that’s developed black mould.’



SAFE TO SNIFF? Yes. ‘Broccoli cut into florets — like this one — releases sulforaphane, a compound found in cruciferous vegetables that can give a strong odour,’ says Dr Brown. ‘Any odours that smell especially strong are a sign that the broccoli may be past its best.’

DAY 1: The tenderstem smells fresh and looks bright green.

DAY 3: The stalks are starting to dry out and the colour is fading but it still smells normal. I stir-fry a few stems and they taste delicious.

DAY 5: The remaining broccoli is softening. ‘The stem should be firm as a soft stem is an indicator of spoilage,’ says Dr Brown. You can cut away the ‘bad’ part and use the rest.

DAY 7: The broccoli has almost completely lost its fresh, earthy smell, and the stems look withered and faded. There are some yellowy-brown spots on one floret; a sure sign, says Dr Brown, that it is starting to spoil. While I could technically still cook it, the change in colour tells me it would taste sour and bitter, and the yellow hue is the precursor to white mould, which could cause food poisoning.



Chicken Breasts: Raw chicken that is past its sell-by date can be a health hazard as not all harmful bacteria will give off a smell

SAFE TO SNIFF? No. ‘Raw chicken can harbour bacteria such as salmonella and campylobacter, which is generally odourless and cannot be seen,’ warns Dr Brown. ‘So there is no way to tell by looking or sniffing that it may be off.’

DAY 1: With no intention of eating the chicken after its use-by date, I’m curious to see what happens to the food once it is out of date. The answer? Not much. The chicken breasts look normal and smell, well, like raw chicken.

DAY 2: Already, there’s a sticky, slimy film developing on the meat and, although the smell hasn’t changed, I don’t want to keep it in my fridge any longer.



Eggs: You are likely to smell very quickly when an egg has gone rotten, but it can take some time

SAFE TO SNIFF? Yes. These have both a ‘display-until’ date — after which they can still be eaten but no longer sold — and a ‘best-before’ date.

‘The Food Standards Agency says eggs can be safely eaten up to two days past the date shown, as long as they are cooked to the point where the yolk and white are solid,’ says Dr Brown. ‘But this is a cautious estimate. The sniff test will soon determine whether an egg has gone off.’

If you don’t want to crack the egg, you can put it into a bowl of water. If it sinks, it’s fresh; if it floats, it’s full of air and probably off.

Eggs can stay fresh for months at room temperature, but I stored mine in the fridge to keep them at a consistent temperature.

DAY 1: I decide to crack open an egg a day to test its freshness.

‘Eggs that have gone off will give off an unmistakable smell, raw or cooked,’ Dr Brown says. There’s no aroma at all.

DAY 5: Still no distinctive smell and both parts of the egg look healthy.

DAY 12: I’m now on to my second box of a dozen eggs — that’s a lot of omelettes. They still look, taste and, crucially, smell fine.

DAY 19: This is getting repetitive . . . will they ever go off?

DAY 23: Finally, there’s a pongy, sulphurous smell from the egg. I try another and it’s the same — they’ve turned.



SAFE TO SNIFF: Yes. ‘Potatoes can be perfectly edible three weeks after their best-before date,’ says Dr Brown. I stored them in a cool, dark cupboard, not the fridge, because the cold can increase their sugar levels, which leads to higher levels of a harmful chemical called acrylamide when cooked.

DAY 1: There’s a strong, earthy smell coming from the bag of potatoes and they look healthy.

DAY 5: No change.

DAY 10: White and purple sprouts have started appearing, but if I remove them, the spuds are fine to eat, says Dr Brown. ‘You can also cut away any mouldy parts and consume the potato as long as it’s still firm and a normal colour.’

DAY 15: More sprouts, some with black tips, but I cut away the bad bits and boil some for dinner: they taste fine.

DAY 20: The potatoes are soft to the touch, with dark spots on their skins, and there’s an unpleasant, rotting smell. Time to get rid of them.



Cod fillets: Many eat fish raw regularly, but old or rotten fish will put you off for a while

SAFE TO SNIFF? No. As cod comes from cold water, lots of microbes can grow in the fridge environment, leading to food poisoning. You can’t detect these by smelling the fish.

However, Dr Brown says: ‘Raw fish will develop a shiny, milky colour when it is going off and should be disposed of.’

DAY 1: There is already a very pungent, fishy smell coming from the cod.

DAY 2: There’s a slimy layer on the surface of the fish and the smell is becoming too much to bear. The packet goes straight in the bin.



Whole milk: Likely the most common item to receive the sniff test

SAFE TO SNIFF? Yes — this was the first product singled out to have use-by dates removed. ‘Because all milk in supermarkets has to be pasteurised — that is, have 99.9 per cent of its bacteria removed — milk that has gone off does not pose an immediate risk to health,’ says Dr Brown.

DAY 1: The milk smells and tastes fresh.

DAY 2: There’s a slightly citrussy smell coming from the milk, but I taste it and it’s still fine.

DAY 3: The smell is much stronger and tangier, and when I pour the milk into my tea it floats to the surface in chunks.



Hummus: A popular item often kept in the fridge and dipped back into when needed

SAFE TO SNIFF? Yes. ‘Hummus that has gone off has a distinct sour smell,’ says Dr Brown.

DAY 1: Creamy, smooth and with its usual mouthwatering whiff of garlic and chickpeas, the hummus is perfectly fine to eat.

DAY 3: The smell is still appetising. No change in texture or taste.

DAY 6: It is starting to look a bit bubbly on top but the smell hasn’t altered. ‘Hummus that has gone off changes to a darker colour and gets a yellowish layer on the surface,’ says Dr Brown.

DAY 9: The yellowish layer is much more apparent now and there’s a strong, sour smell of lemon coming from the pot.

‘The hummus is ready to be disposed of,’ Dr Brown says.



Camembert Cheese: Another popular dairy product which will let you know when it’s time to put it in the bin

SAFE TO SNIFF? Yes but because there’s such a strong smell to begin with, it can be tricky to tell when the cheese has gone off.

‘Properly-stored Camembert cheese can last one to two weeks in the fridge,’ says Dr Brown. ‘When it has gone off, it will smell terrible.’

DAY 1: I’m not one for pongy cheeses, so this is tough: the Camembert looks normal and smells, well, like reeky cheese.

DAY 5: The smell has not changed at all — and it is still soft and creamy inside.

DAY 10: It’s getting smellier, but my husband insists it’s not too bad yet. He tries a wedge and declares it delicious.

DAY 14: The stench is now awful, and I spot green spores of mould growing on it. ‘With hard cheeses, you can cut away any visible mould,’ says Dr Brown. ‘With the softer cheeses, you cannot eat them if there is any mould, as this can grow alongside nasty bacteria such as listeria and E.coli.’


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