How to avoid food poisoning

Monday, April 23, 2007
You tuck into a nice bit of chicken and then about four or five hours later, the headache and the cramps start. Before you know it, you're spending the rest of the day camped inside the loo. Can you relate to this?

Food poisoning affects more than five million Australians every year. So our reporter Dr Andrew Rochford has set himself a mission — to find out what it is, what causes it and most importantly how we should cook, store and treat our food to avoid food poisoning.

1. Undercooked meat

Our expert to help us out is Dr Patricia Desmarchelier, from Food Science Australia in Sydney, who specialises in the delicate art of food safety. And what better way to tackle the subject of undercooked food than over a snag or two?

So on the barbecue today is lamb loin chops, chicken breasts, sausages and brown beef burgers.

What are we looking out for and trying to avoid?

"Bacteria can be on the surface of this meat, but in the brown products such as the patties and the sausages, the meat gets churned in the inside. So you have to make sure that the heat's penetrating far enough to kill the bugs right through," says Dr Desmarchelier.

What bugs? The bacteria Dr Desmarchelier is talking about are called pathogens.

These are the big three:

  • salmonella
  • campylobacter
  • E. coli

Salmonella and E. coli feel right at home in meat of all kinds but campylobacter is a purely poultry-loving bug. Eating food that contains high levels of these bacteria, or the toxins they produce, can cause food poisoning.

So how do we know when the meat is ready and it's not going to give us food poisoning?

According to Dr Desmarchelier: "If you like your beef rare, even though that's still pink in the middle or bloody, you could eat it that like that and still be safe — if that's your preference."

But if the snags are still pretty pink and soft in the middle, being processed meat, they'll definitely need a few more minutes.

Andrew: So you can't have a rare sausage?
Dr Desmarchelier: I wouldn't have a rare sausage.

That's how to cook on the barbie, but what about cooking meat in the oven?

Roast chicken needs to be cooked right through, so a good rule of thumb is to allow 20 minutes per 500 grams plus 20 mins extra. With poultry and pork, always make sure the juices run clear and that the stuffing is completely cooked. It's a good idea to check that the centre temperature of any meat you're cooking is at least 74 degrees Celsius.

So next time you crank up the barbie, you need to remember to pay special attention to chicken, burgers and sausages.

2. Can you eat food that's been dropped on the floor?

We've all dropped food on the floor and most of us have heard of the five-second rule. The theory goes that if your food hits the floor for more than five seconds then it's not safe to eat. But can it really pick up bacteria that quickly and what's down there anyway? It's time for a little experiment.

Andrew: Two pieces of toast, one will be on the ground for five seconds, one for 20.

He drops both pieces on the floor of his kitchen. After one has been on the ground for five seconds he picks it up, then the other after 20 seconds. The pieces of toast are placed into separate plastic bags.

Andrew: So that's the toast test. There's another one we want to check — apples. Kids drop them everywhere, so do these pick up more germs than toast? Let's find out.

Andrew cuts an apple into four and then drops two pieces on the floor — one for five and for 20 seconds. He then repeats the process with the other two quarters that he then washes under the tap.

Andrew: Well, mum always does that doesn't she?

All of the apple quarters are then also bagged separately and are ready to be sent off with the toast to the lab for testing.

Next up it's a date with senior microbiologist, Melissa Pai at George Western Technologies to find out the score on Andrew's food tests.

Melissa's team tested the apple and toast samples for salmonella, E. coli and Listeria — all of them harmful in their own way.

The results came up negative for Listeria and salmonella but if the test tubes look cloudy, we could have E. coli.

Andrew: Okay, the pieces of toast that were on the ground for five seconds — did we grow anything?
Melissa: Well in this instance the five-second sample is showing up with no gas production. So it's good in this instance.
Andrew: So nothing. Surely the 20 seconds on the floor we've got something for that?
Melissa: Twenty seconds? Once again, looking good. No turbidity.
Andrew: What about the piece of apple that mum washes under the tap?
Melissa: No that's also good. So it seems like you probably have quite a clean kitchen there.
Andrew: So overall I could have eaten that food off the floor?
Melissa. Ah, I wouldn't quite put it that way, but in this instance this kitchen floor appears to be rather clean.

Needless to say, not all floors are as clean as Andrew's. In fact, if you have a dirty floor, food can become infected as soon as it touches the deck: no matter if it's there for one second, one minute or one hour.

3. How long can you leave food out of the fridge for?

So you've cooked yourself a lovely meal, but is it safe to leave your leftovers in the pan? At which point does it go from a tasty treat into a potential poison?

It's over to our expert, Dr Desmarchelier for the answer: "An easy way to remember is to use what we call the four-hour, two-hour rule."

So how does it work? Food that's been left out for up to two hours can be eaten straight away or stored in the fridge.

If it's been out two to four hours, you can reheat it and eat it straightaway but if it's been out for longer than four hours, definitely throw it.

Now remember, these are only general guidelines. Be extra careful with seafood and, if it's a warm day, get those leftovers in the fridge as quickly as you can — the longer you leave it out, the more bugs you'll get. Within seven hours, one million bacteria can double their number!

Here's another one for you: do you need to wait for food to cool before you can refrigerate it?

"After you've cooked food, it's not a good idea to put it straight into the refrigerator while it's bubbling hot, but as soon as that heat's gone off you should get it into the refrigerator as soon as possible," says Dr Desmarchelier.

And if you're having a party and need to free up the fridge, always keep the raw and prepared foods like pasta salads chilled.

But what about the leftovers you've put in the fridge? How safe are they to eat?

4. How long can you leave leftovers in the fridge?

Although most bacteria can survive in the fridge, the cool temperature slows down their growth so, as a general rule, it's okay to keep food for up to three or four days, but definitely no longer than a week.

"Some foods are what we call potentially high risk foods. These are foods where they might have some contamination and they also have the ability to support the growth of bacteria which might lead to infection," says Dr Desmarchelier.

Meat, poultry and fish are the obvious ones, but egg-based dishes like quiches or pasta and even rice can also make you sick.

That's high risk foods sorted. But what about high risk fridges?

Here's a checklist for some do's and don'ts:

  • A tiny drop of chicken blood dripping onto the cooked food underneath it could cause cross contamination. So always store the raw stuff under the cooked stuff.
  • Transfer left-over tinned food into an airtight container to store in the fridge to prevent the food getting a metallic taste.
  • Make sure your fridge temperature is around three degrees Celsius and keep the air circulation constant by stacking your fridge neatly. Packing too much in will increase your risk of food poisoning and whack up your energy bill.

5. Freezer tips

Here's a question for you. You've opted for a steak tonight but you need to defrost it first. Where should you leave it — on the bench top, or in the fridge?

Back to the expert, Dr Patricia Desmarchelier: "When you defrost food it's best to be organised and plan to have your food out of the freezer and have it thaw out in the refrigerator for a day or two. That's going to vary on the bulk and the size of the food. If you're thawing out a turkey it may take a few days to thaw out in the refrigerator."

But what if I'm in a hurry?

"If you're in a hurry you can put it in the microwave," she says.

But if it's meat that you're defrosting, cook it straight away in case you've partially cooked it while microwaving.

How about cooking straight from frozen?

"Some food can be cooked from frozen and if you're buying frozen products you can read the instructions on the packet. The manufacturers have gone to a lot of trouble to make sure if you use their cooking instructions that you will get the thawing and heat penetration," says Dr Desmarchelier.

All those tips should keep you out of trouble but if you've eaten something dodgy, and you're starting to feel a bit rough, don't hang about — get to your GP.

So, if you follow all our food hygiene tips, you should avoid getting sick — but remember, if in doubt, throw it out!

Read more

Fast facts

  • We've heard about meat, but what about non-animal products? Can something like beans give you food poisoning? Yes, especially red kidney beans which contain a natural toxin. The toxin is easily removed by soaking the beans in water overnight before cooking.

ThinkstockBrush your teeth – or risk a heart attack ThinkstockCutting sleep leads to serious health problems ThinkstockMost asthma deaths could be prevented: report ThinkstockHow old is your heart? Researchers create online test to determine heart attack and stroke risk