Fact Buster

Q: Can you smell if food is off?

A: No. Smell is not a good way to tell if food is off.

Our expert: Lydia Buchtmann



[Image source: iStockphoto PaulF ]

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It's the end of a long day and you're rifling through the fridge in the hope of finding something to eat that doesn't involve any 'cooking' more complicated than two minutes in the microwave.

You strike gold, pulling a bowl of leftovers from the depths of the fridge. You're fairly certain it hasn't seen a birthday, so you peel back the cling wrap to give it a good sniff.

But are you right in trusting your nose to save you from a bout of gastro (or worse)?

No way, is the response from food safety experts. Smell is not a good way to tell whether food is safe to eat, says Lydia Buchtmann from the Food Safety Information Council.

"A lot of people rely on the sniff test, [but] that means nothing whatsoever," says Buchtmann.

When a plate of leftovers starts to pong, it means spoilage bacteria have taken hold. These are different from bacteria that cause food poisoning.

Spoilage is an undesirable change in composition of food. An example of spoilage bacteria is Pseudomonas, which can cause spoilage in meat, fish, eggs, milk and cheeses, and is usually the culprit of the putrid smell and slime that can accompany chilled meats (of the non-vacuum packed variety).

Spoilage bacteria won't usually make you sick, though food with them won't be particularly pleasant to chow down on, and Buchtmann says it's not a good idea to put it in your mouth.

"Normally if a food smells off  for example off milk  it's starting to spoil and decompose," says Buchtmann.

What the sniff doesn't solve

According to Food Standards Australia New Zealand, food poisoning bacteria don't change the appearance, smell or taste of food. These bacteria usually come from animal faeces and soil.

(Bacteria known to cause food poisoning include Salmonella, Campylobacter jejuni, Staphylococcus aureus, strains of E. coli and Listeria monocytogenes. For more see An A-Z of common types of food poisoning.)

In potentially hazardous foods, some of the bacteria that cause food poisoning can flourish between 5 and 60 degrees Celsius. This temperature range is known as the 'danger zone,' so cold foods should be kept below 5°C and hot foods kept above 60°.

"Within a couple of hours it can be contaminated enough that you can get a bout of food poisoning," Buchtmann says.

"The food will still smell fine and taste fine but it can make you very sick."

Storing foods at the right temperature helps prevent illness as it slows down the rate at which bacteria can multiply and they won't grow to the large numbers to make you ill, according to Food Standards Australia New Zealand.

Risky foods left in the 'danger zone' for up to two hours should be safe to refrigerate, but immediately use or dispose of food sitting out between two to four hours, and throw anything that's out over four hours.

However, some bacteria and certain viruses can make people sick even if present in tiny amounts. This is why it's also important to avoid contaminating foods with items known to harbour these bacteria. Less commonly, parasites, such as Giardia lamblia (from raw, ready to eat produce), can also cause illness.

'Tis the season…

So if smelling your food isn't going to help you identify whether food is off, what can you do to reduce your risk of food poisoning?

Buchtmann says it's vital to keep your fridge running at the right temperature, especially when you are catering over the busy summer holiday period. So be sure to:

Check your fridge is running at 5°. Pick up a fridge thermometer in your pre-Christmas supply run, and don't cram the fridge so full that the cool air can't circulate around food properly.

Don't over-cater: "A ham is for Christmas, not for life," says Buchtmann.

Make room for food in your fridge: "Take your drinks out of the fridge," says Buchtmann, "putting drinks on ice stops people opening the fridge and warming it, so bacteria can't grow."

Defrost meat in the fridge, remembering it may take several days for large portions.

Be sure to store raw uncooked foods (such as chicken and meat) separately to ready-to-eat foods, such as salad vegetables or fruit.

When hot leftovers have stopped steaming, divide into small containers and refrigerate or freeze with a dated label. Use refrigerated leftovers within two to three days.

Bacillus cereus spores can germinate in cooked rice, producing toxins that aren't killed by reheating. Remember to refrigerate rice salads too.

And if you want to avoid serving people a side of food poisoning with their meal then you should take the following measures when preparing food:

Make sure anyone handling food has washed their hands with soapy water and dried them thoroughly, and again after handling poultry, meat, or anything visibly dirty such as eggs and vegetables.

Don't let people prepare food if they have recently had vomiting or diarrhoea.

Keep your kitchen surfaces and equipment clean  especially after using them for raw foods such as meat and chicken  to prevent cross contamination. Be sure to use a clean cloth and hot soapy water to wipe down surfaces.

Be particularly careful when preparing chicken. Thoroughly wash chopping boards, knives, bench tops and hands after handling uncooked poultry to prevent contaminating other food, and don't wash your chicken before cooking.

If you're inspired to try new recipes around Christmas involving minimally cooked egg, treat eggs as you would chicken and follow these tips to reduce the risk of illness.

For more take a look at 7 ways to share food, not food poisoning, this Christmas and An A-Z of common types of food poisoning.

Lydia Buchtmann is from the Food Safety Information Council. She spoke to Lydia Hales.