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Can you tell if food is off by sniffing it?

Is your nose the best barometer for food safety? It’s safe to say that practically all of us have sniffed the leftovers from the fridge in an effort to find out if it’s safe to eat. But the actual facts around smell and food safety is a bit more complicated than a simple sniff test.

Let’s take the example of leftover casserole sitting in a plastic container in the fridge. It’s lunch time, you’re hungry, and remember that you had this meal for dinner a few days ago. You try to work out how old it is and realise that it’s actually four days since you cooked it.

You remember that your Mum told you not to eat leftovers if it’s more than two days old. No matter, you’re hungry and don’t feel like making something. You reach for the casserole, take the lid off and take a big sniff. It smells just like the casserole you made 4 days ago! Just to be extra careful and kill off any germs, you nuke it in the microwave for an extra minute on high. Is this a good idea?

Safe Food Production Queensland Principal Science Officer Robin Sherlock says that’s not  the best approach!

“The sniff test isn’t the best way to tell if your leftovers are safe to eat,” she said.

“Leftovers such as casserole should only be kept in the fridge for two to three days. That’s because reheating doesn’t kill off all harmful bacteria that can cause food poisoning and some bacteria produce toxins that survive cooking and reheating.”

Ms Sherlock said some food poisoning could be mild and short-lived (up to 24 hours) but food borne illness could be very severe and it was not worth taking the risk and eating food that has been kept for too long in the fridge.

She said freezing leftovers was a good alternative.

“Freeze the leftovers when it stops streaming and put it in small containers so it cools quickly. Label the containers so you know old they are,” she said.

When reheating food, it’s important to make sure it is hot all the way through.

“It’s best to use a meat thermometer to ensure it is at least 75°C in the center but if you don’t have a meat thermometer then make sure it’s piping or steaming hot.”

“If leftovers have been in the temperature danger zone (between 5°C and 60°C) for more than two hours, it should be eaten or refrigerated immediately and if it’s been in the temperature danger zone for more than 4 hours, it should be thrown out, Ms Sherlock said.

For packaged food, Ms Sherlock said the “best before” date was a quality indicator and after this date the food will lose some nutrition or quality elements.

“The rule for safe consumption is to check the “use by” date,” she said.

So next time you’re tempted to follow your nose when looking at old leftovers, follow expert advice instead – two to three days should be the limit and if in doubt, throw it out!

For more information on safe food handling visit  Microorganisms and foodborne illness and  for information on the 2 hr/4 hr rule check out 2-hour / 4-hour rule.