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How to avoid food poisoning

Contaminated food can be hard to spot, but it helps to know what to look for.

raw chicken in container food safety food poisoning
Last updated: 23 December 2019

Nausea, vomiting and diarrhoea are generally not anyone's idea of a good time, but the 4.1 million Australians who come down with food poisoning every year experience such symptoms. And it's not uncommon for the cause to be home-cooked food!

different raw meat isolated

Don't let raw meat or juices come into contact with food that's going to be eaten uncooked.

Three top rules to avoid food poisoning

Whether the food comes from your kitchen or the local café, the basic rules of avoiding uninvited guests such as Escherichia coli O157 H7 (better known as E.Coli) or Bacillus cereus are the same.

1. Avoid the temperature danger zone

Bacteria thrive at temperatures between 5°C and 60°C. In ideal conditions, their numbers can multiply and reach dangerous levels in just a few hours. So, store cold food below 5°C and hot food above 60°C. See our fridge temperature guide for more details on safe food refrigeration.

2. Avoid cross-contamination

At home, the most likely sources of harmful bacteria are raw meat and unwashed fruit and vegetables. Don't let raw meat or juices come into contact with food that's going to be eaten uncooked or defrosting meat drip onto other food in the fridge. Always wash your hands before starting to prepare food – and wash them again after handling raw meat.

3. When in doubt, toss it out

Most food-poisoning bacteria and their toxins have no taste or smell. The smell of putrefaction is usually due to relatively harmless bacteria called pseudomonas. So it might not be obvious that food's contaminated. See our FAQs on what's safe to eat (below) for the answers to your commonly asked dodgy-food-in-the-fridge questions.

Buying safely from the supermarket

We'd hate to think Australia's big (or little) supermarkets aren't always practicing due diligence when it comes to food safety, but an ounce of prevention is definitely worth a pound of cure when you're filling up your trolley.

What to watch out for

  • Frozen chickens that are slightly soft to touch have already begun to thaw. Look for another or go to another store. And frozen chickens which look 'dented' may have been thawed and refrozen.
  • Frozen vegetables, such as peas, which are frozen into a solid mass have probably been semi-thawed and refrozen – don't buy them. Spinach is an exception to this rule.
  • Frozen food cartons that are wet, damp or sag in your hand have also probably begun thawing – don't buy them.
  • If you find frozen or chilled foods left standing unattended in the aisle, go to another store.
  • Don't buy frozen foods if they're stacked above the 'load line' in horizontal freezers (usually a blue or black line with the words 'load limit' written above it) – they may be at too high a temperature.
  • Cans that look swollen or dairy products, like yoghurt, with the foil cover bulging may be going off.
  • Don't buy leaking cartons, cans, bottles or other containers.
  • Don't buy products with broken or imperfect seals or badly dented cans.
  • If a vacuum-packed product isn't tightly packed, and the packet is loose around the product, don't buy it.
  • Check for mould on foods such as cheese and crumpets – don't buy them if you find it.
  • Check use-by dates and dates of packing, particularly on meat and dairy products.
  • Shop last for chilled and frozen food. Keep them in an insulated cooler or wrapped in several layers of paper until you get home. Make sure meat products are packed separately from other groceries. Take these kinds of groceries straight home to the fridge or freezer.
  • If you find things wrong in your local store report it to the store manager. If they don't take action, shop elsewhere next time and let your local authority know. Food Standards Australia New Zealand (FSANZ) has contact details for your local food enforcement agency.
woman chosing frozen food at supermarket

Don't buy frozen food cartons that are wet, damp or sag in your hand.

How to spot a dodgy cafe

Avoiding contaminated food in a restaurant can be especially tricky. The place may look squeaky clean, but that doesn't mean it is. If it looks like hygiene is not high on the list, however, it probably isn't. 

What to watch out for

  • Dirty floors, counters and tables – they can carry bacteria and attract pests. If people can't keep their premises clean, chances are they don't do much better with the food.
  • Staff with dirty hands or fingernails, dangling jewellery and long hair not tied back.
  • Staff wiping surfaces or equipment with a non-disposable cloth – or not disposing of it afterwards. Just because a cloth looks clean doesn't mean it is.
  • Staff using the same set of tongs for different types of food – for example, salads and meat.
  • Staff not washing their hands after handling raw meat.
  • Wearing the same gloves when handling different foods or handing you your change and docket – this defeats the purpose of gloves.
  • Dirty crockery, cutlery or glasses – including chips and cracks.
  • Lukewarm foods that should be hot and cold foods that aren't quite cold. Hot foods should be kept above 60°C (steaming hot) and cold foods below 5°C to stop most bacteria from multiplying.
  • Unrefrigerated pre-packed sandwiches.
  • Foods that aren't cooked right through – watch out for pink bits in the centre of hamburger meat and pink uncooked chicken (particularly near the bone).
  • Raw and cooked foods, such as salads and meats, touching each other in display units.
  • Food displayed uncovered or unwrapped on counters.
  • Condensation dripping from display cabinets onto foods.

Use-by dates explained

Foods that have a use-by date should be eaten or frozen before the end of the date shown. You shouldn't eat them after this date and it's illegal for shops to sell foods once a use-by date has passed.

Foods that have a best-before date are less perishable, and this date gives a guide to how long you can expect the food to keep its quality (not safety). It's OK to eat (and sell) these foods after the date has passed. Use your common sense – although they'll often be perfectly acceptable, they may sometimes not be as good-quality as they once were.

Bread can have a 'baked on' date or even a 'baked for' date, instead of a best-before date.

All dates only apply if the food has been properly stored and transported, so if the packaging looks damaged or otherwise suspect, give it a miss.

feeding a baby more suceptable to food poisoning

Infants, babies and people with weakened defences are more susceptible to food poisoning.

The different types of food poisoning

We've used the term "bacteria" here to refer to the micro-organisms that grow on food and can infect anyone who eats it. Strictly speaking, these harmful bacteria are known as "pathogens". Many other bacteria are harmless.

The symptoms of "food poisoning" are sometimes caused by toxins produced by bacteria and other times caused by bacteria themselves infecting the body. The most common symptoms are vomiting and diarrhoea, usually preceded by abdominal cramps and sometimes a headache.

Usually it takes large numbers of food poisoning bacteria to cause illness, as our body's natural defences can usually take care of most smallish invasions. But infants, babies and people with weakened defences (such as those who are already sick, the elderly and those on immunosuppressive drugs) are much more susceptible. Preparing food for anyone in these categories demands extra care.

In Australia, the bugs that commonly cause problems are:

Salmonella

Just one drop of contaminated chicken juice can make you very sick. It usually strikes within 8 to 72 hours of eating contaminated food. You're likely to feel really awful for a couple of days, and may not fully recover for weeks.

Clostridium perfringens

Likely sources in the home are meat, poultry dishes, casseroles and the like that are cooled slowly and inadequately refrigerated. It can cause intense abdominal cramps and diarrhoea that begin 8 to 22 hours after eating the contaminated food. The illness is usually over within 24 hours.

Vibrio parahaemolyticus

It's often caught from seafood produced in warm coastal waters. Oysters and other seafood eaten raw are a likely source. The illness is usually mild or moderate and lasts about two to three days.

Staphylococcus aureus

Staphylococcus aureus from the human body can grow and produce its toxin in foods like home-made pasta and fermented sausage – typically foods that get a lot of handling during preparation. Wash your hands!

Campylobacter

This is usually caught by eating contaminated poultry that's not adequately cooked. It's mostly spread by cross-contamination, and just low numbers of the bacteria can cause illness, with similar symptoms to salmonella. The effects will last for several miserable days.

Bacillus cereus

This can be a problem in cereal-based products, mashed potato, vegetables, minced meat, liver sausage and soups, and it's often associated with fried or boiled rice. There are two forms of poisoning, caused by two different toxins. A fairly mild form that presents with diarrhoea develops within 8 to 16 hours and usually lasts for about 24 hours. A more severe form starts within 30 minutes to 5 hours of infection and generally lasts for less than 24 hours. It produces nausea and vomiting and occasionally abdominal cramps and/or diarrhoea as well. It's often associated with fried or boiled rice.

Escherichia coli (E. coli)

E. coli don't often cause illness, but the bugs are very common. They are found in the guts of animals, including humans. Most E. coli are harmless and normally serve a useful function in the body by suppressing the growth of harmful bacteria and by producing appreciable amounts of vitamins. But the presence of E. coli in food is an indication of faecal contamination and the possibility of the presence of far worse bacteria that could cause serious illness. Unfortunately not all E. coli are harmless. The strain E. coli O157 is particularly dangerous for two reasons. Doses of just a few cells can result in illness, and the toxin it produces is extremely potent, causing anything from mild diarrhoea to serious urinary and gastrointestinal complications, including internal bleeding. As with other strains of E. coli, E. coli O157 is normally found in cows' and other animals' guts and gets into meat in the abattoir. It's a relatively new type of infection, first recognised in Canada in 1985.

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