If you've thrown out a carton of eggs or milk that has just passed its best-before or use-by date, you've probably wasted food - and money.
The British Food Standards Agency has sparked new debate, advising English consumers that it is safe to eat eggs two days after their best-before expiry date. They are hoping to reduce food waste.
New Zealand experts have also jumped into the fray, confirming most products are safe to consume long after their advertised dates.
New Zealand's Ministry for Primary Industries agreed eggs would be safe to eat after the best-by date, though did not want to say for exactly how long. But Otago University's Phil Bremer said eggs would be safe to eat at least a fortnight after the date expired.
Best-before dates indicate when a product will taste the best and shops can continue to sell products that have passed those dates.
Use-by dates are a stricter indicator of expiry for things such as milk - and expired products must not be sold.
But even products with use-by dates were safe to eat for a while after the date, Bremer said. He said milk sometimes was safe for up to a month.
Conrad Perera, of Auckland University, said most food products' best-before and use-by dates were decided by accelerated shelf life testing. The date took into account the possibility that the product, such as milk, could be left out for periods, even before the consumer bought it.
He said manufacturers would err on the side of caution. "If the product has a one-month shelf life and they say two and then it's spoilt, the company has a liability."
He said milk should be useable up to three days after its stated date, if it had been stored well. Every 10-degree increase in temperature doubled the rate at which products deteriorated. A tin of food kept in the fridge would be at its best much longer than the same sealed tin kept in a cupboard.
Massey University's Steve Flint said companies kept dates short because they did not want products perceived as going off easily. He said people were likely throwing out food that was quite edible. By the time milk became unsafe, he said, it would be obviously off.
Convincing Kiwis it is safe to eat older food is another issue. Kaikohe mum-of-one Te Arapera Tauri said she always threw food out when it reached its best-before date. "I'm too afraid of getting sick if we eat it."
But Bremer said cases of food poisoning by expired food were probably zero because by the time food deteriorated enough to be dangerous, it would look and smell bad enough that no one would want to eat it.
Shops such as Reduced to Clear offer food that is near or past its best before dates. Merchandise manager Aaron Foley said they were experiencing 40 per cent year-on-year growth. "Every product will deteriorate. But it's usually long beyond the best before date on almost every product."
Consumers were looking for more everyday items at Reduced to Clear, he said, such as milk. "It's cheaper because mainstream supermarket chains won't purchase it. We pay a great deal less for stock."
Reduced to Clear has 13 stores.
How long are eggs edible?
Eggs bought: 23/7/2013
Best before date: 21/8/2013
British experts: 23/8/2013
NZ Experts: 4/9/2013