How long can you really use foods past their best-before date?

If you spent the past few months stocking up on extra food or hanging on to old pantry items, you're likely not alone. Now, as the weeks tick by, you may be wondering how to avoid throwing it all away.

Between the different expiry and use-by labels, plus the risk of frozen foods starting to spoil, it's no surprise many people may be confused about what is safe and not so safe to eat.

Here are some helpful guidelines on how long to keep your fresh and packaged goods.

The first and most important thing to consider when it comes to food safety is whether a food has a "use-by" or "best-before" date.

For "use-by", which will often be found on perishable seafood, meat, chicken and dairy products, the food should not be eaten after that date. It is actually an offence for retailers to sell food past its use-by date.

"Best-before" is a little different. Unlike "use-by", you do not need to consume a food before its best-before date, but the best-before does mean that food will retain its quality and be in the condition you would expect before this date. After this time, while the quality of the food may change, it will still be safe to eat if you are happy to. Best-before dates are commonly found on less perishable items such as spreads, for example peanut butter, and dry goods such as flour and pasta.

Always take a chiller bag with you when you are out shopping.

Cathy Moir, food microbiologist

Cathy Moir, a food microbiologist from CSIRO Agriculture and Food, says that "use-by" dates should be taken very seriously.

"Pâte, smoked salmon, deli meats and soft cheeses are specific foods that may contain listeria, which is a particularly nasty organism that can cause serious illness," Moir says.

"These foods should always be stored correctly, and never consumed after their use-by date. This is even more important for those at risk in the community - pregnant women, the very young, the elderly or those who are already immune suppressed.

"It is also good for consumers to be aware that eating raw products including uncooked eggs and products such as raw seafood sashimi poses an element of food safety risk because they are raw. So be careful of these foods too and certainly don't serve them to the vulnerable groups described above."

Lydia Buchtmann from the Australian Food Safety Information Council says food safety is a significant issue in Australia, with about 4.1 million Australians reporting food-related illness each year and more than 30,000 hospitalisations.

"While we are all trying to reduce food waste, we cannot do it at the expense of ensuring the foods we are eating and preparing at home are safe," Buchtmann says.

"Pay attention to use-by dates, and most importantly store foods correctly to minimise risk."

Once foods are past their best-before date, the nutritional quality of the food may also be affected, Buchtmann says.

"It is also important to make a concerted effort to follow the guidelines spelt out clearly on label," she says. "If a product says consume within five days of opening, you are best to do that."

While guidelines around fresh foods can be relatively easy to understand, things become a little more blurry with foods such as sauces and dressings, which can sit in fridge doors for months if not years.

Buchtmann says this can be a tricky area to navigate but says once the bottle has been opened for several months, it is probably best to treat yourself to a new bottle of dressing or sauce.

"As a general rule of thumb, once a food is open you are best to replace it every couple of months," she says.

The risk with condiments is lower than with fresh foods but is still significant especially for creamy dressings and sauces such as mayonnaise, which contains egg, she says.

Freezing is another consideration, Buchtmann says.

"Once you have frozen a food you will get lots of extra time from it - months, if not longer," she says.

"All you need to do is clearly label your frozen foods [with the date] and where possible freeze in smaller portions so the foods are easier to defrost and use in the future.

"Many, many foods can be frozen including bread, leftovers and even milk and unshelled eggs if they are stored correctly."

Fresh and refrigerated foods, on the other hand, usually need to be used up quickly.

"Always take a chiller bag with you when you are out shopping," Moir says.

"And pay attention to the temperature of your fridge. Always defrost foods in the fridge to ensure the temperature of the food remains cold."

So keep an eye on those use-by dates, put your air-tight containers to good use in the pastry and label your frozen foods. And yes, just as you suspected, that bottle of three-year-old mayo needs to go.

Pantry checklist

Canned soups and vegetables: 12-24 months. Once the best-before date is reached the quality may reduce but the food will still be edible.

Rice and pasta: 12-24 months. Store in air-tight containers once opened to extend shelf life.

Flour and sugar: 6-12 months and again transfer to an airtight container once opened.

Honey, jam, syrup: 6 months and keep refrigerated.

Oil: 3-4 months if stored in a cool, dark place. If it looks cloudy, don't use it.

Butter/nut spreads: 3-4 months if kept away from sunlight.

Breakfast cereal: 6 months, keep in air-tight container once opened.

Fridge and freezer checklist

Milk: Up to 1 week unopened. Consume within use-by dates. Can be frozen for 3-4 months.

Eggs: Up to 1 month. Consume by use-by date. Can be frozen without the shell in ice-cube containers for 1 year.

Meat, chicken, fish: 3-4 days and up to 6-9 months in the freezer. Consume by use-by date if fresh.

Nuts: Will have an extended shelf life of up to 12 months in the fridge. Can also be frozen for 12-24 months.

Sauces: Most should be used within 6 months.

Seafood: 2-3 days in the fridge and 2-3 months in the freezer.