Rice a culprit in many food poisoning incidents

Cooked rice dishes should be kept in the fridge or thrown away after four hours.
Cooked rice dishes should be kept in the fridge or thrown away after four hours. Photo: Quentin Jones

That rice salad or reheated nasi goreng may look innocent but health experts have warned such dishes could be the culprit in many mystery cases of food poisoning.

A survey commissioned by the Food Safety Information Council found that while 96 per cent of Australians were aware of the dangers associated with chicken and raw egg products such as mayonnaise being left in the "temperature danger zone" of 5-60 degrees celsius, far fewer realised that eating cooked rice dishes that had been left to cool slowly, or even those left out of the fridge overnight, could also make them ill.

"What was amazing was that nearly one-quarter of people thought it was OK to leave rice dishes out of the fridge for up to six hours or even overnight," said FSIC spokeswoman Lydia Buchtmann of the Newspoll survey conducted nationally for this month's Food Safety Week.

"We want to get the message out, particularly as we head into barbecue weather and the festive season when over-catering can be a real issue," she added.

"Most people realise they need to keep meat dishes in the fridge but they might take out a rice salad to make room."

Chair of the FSIC Dr Michael Eyles warned reheating rice dishes, such as risotto or a Pad Thai did not eliminate the potential for food poisoning.

"Spores from the bacteria Bacillus cereus [found in rice] can survive the cooking process and once the rice begins to cool they can grow and form a heat-resistant toxin."

"This toxin is not destroyed by further reheating, with only very small amounts needed to make you sick."

The toxins thrive when the rice is left for long periods - more than four hours - in temperatures above five degrees.

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People who eat rice dishes containing this toxin can experience symptoms such as vomiting and diarrhoea, similar to those caused by norovirus - the most common cause of food poisoning. 

The most recent study prepared for the federal Department of Health by the Australian National University estimated that approximately 4.1 million Australians are affected by food poisoning annually, with people experiencing an incidence of food-borne gastroenteritis on average every five years. The FSIC estimates that 20 per cent of food poisoning cases in Australia are caused by mistakes made by home cooks.

Of the cases of food poisoning in Australia each year, only the cause of one-fifth is identified. Identifying cases caused by Bacillus cereus is difficult because unlike other organisms that cause food poisoning such as norovirus and salmonella, it is not a notifiable disease.

The FSIC advises cooks adhere to the following steps to reduce the risk of poisoning from cooked rice and other foods:

1. Keep your fridge at 4-5C and use a fridge thermometer to monitor on a regular basis.

2. Don't pack your fridge too tightly as this will prevent cool air from circulating.

3. Freshly cooked food not intended for immediate consumption should have the temperature reduced as quickly as possible. Divide into serving-size portions and place in fridge or freezer as soon as it stops steaming. 

4. If you are keeping a dish warm for someone, keep it at 60C or above. 

5. Bin it: If perishable food has been left in temperatures between 5-60 degrees celsius for 2-4 hours it should be consumed immediately. Anything left in the danger zone for four hours or more should be thrown away.