Rice is one of the most common foods served in Samoa and across the Pacific. It is inexpensive, filling and easy to prepare for the aiga.
But cooked rice can also cause food poisoning when it is left sitting at room temperature for too long.
The danger is not usually caused by reheating rice. It begins with how the rice is cooled and stored after it has been cooked.
What happens to cooked rice
Uncooked rice can contain spores from a bacterium called Bacillus cereus. These spores can survive boiling and remain in the rice after it has been cooked.
When cooked rice is left warm on a bench, in a pot or inside a rice cooker that has been switched off, the spores can begin to grow. The bacteria may then multiply and produce toxins that cause vomiting and diarrhoea.
Some of these toxins are not destroyed by further cooking or reheating. This means heating rice again may not make it safe once the toxins have developed.
How to cook rice properly
Begin with clean hands, clean utensils and a clean pot or rice cooker.
Check dry rice before using it. Rice that has become wet, mouldy, heavily infested with insects or has an unusual smell should be discarded.
Rice can be rinsed before cooking to remove loose starch and dirt, although rinsing alone does not remove the food poisoning risk. Safe handling after cooking remains the most important step.
Follow the water measurements and cooking instructions provided on the packet or rice cooker. Different varieties of rice require different amounts of water and cooking time.
Cook the rice until the grains are tender and the water has been absorbed. Once cooked, serve it immediately or keep it properly heated.
Cooked rice that is being held for serving should remain at 60 degrees Celsius or hotter. Rice should not be left sitting in a switched-off rice cooker for several hours or overnight.
Cool leftover rice quickly
Rice that will be eaten later should be cooled as quickly as possible.
Do not leave a large pot of rice sitting on the kitchen bench while it slowly cools. Divide it into smaller portions and place it in clean, shallow containers. This allows heat to escape more quickly.
Place the rice in the refrigerator as soon as it stops heavily steaming. A practical household rule is to refrigerate it within one hour whenever possible and never leave it at room temperature for more than two hours.
In very hot conditions above 32 degrees Celsius, perishable food should be refrigerated within one hour. The refrigerator should be kept at 5 degrees Celsius or colder.
How long should rice remain in the fridge
Food safety authorities provide slightly different storage limits, but a conservative household rule is to eat refrigerated rice within 24 hours.
Rice can also be frozen in small portions soon after it has cooled. This can be safer than leaving a large amount in the refrigerator for several days.
Do not repeatedly remove rice from the refrigerator, allow it to become warm and then return it to the fridge. The total amount of time it spends between 5 and 60 degrees Celsius matters.
Reheat rice only once
When reheating rice, heat it rapidly until it is steaming hot throughout.
Stir rice heated in a microwave so that there are no cold areas in the middle. Allow it to stand briefly after microwaving so the heat can spread evenly.
Only reheat the amount that will be eaten. Avoid reheating the same rice more than once.
Reheating is not a way to rescue rice that has been left out for several hours. When there is doubt about how long rice has been sitting at room temperature, throw it away.
Rice may look normal and still be unsafe
Spoiled rice may develop mould, a sour smell, unusual discolouration or a wet and slimy texture. These are clear reasons to discard it.
However, dangerous rice does not always smell bad or look different. Food poisoning bacteria and their toxins may be present without changing the appearance, taste or smell of the food.
The smell test should therefore never replace proper cooling and storage.
Signs of rice-related food poisoning
Illness caused by Bacillus cereus can begin between one and 16 hours after eating contaminated food.
Symptoms may include nausea, vomiting, stomach cramps and watery diarrhoea. Most people recover quickly, but young children, pregnant women, older people and those with weakened immune systems may face a greater risk of serious illness.
Anyone experiencing severe symptoms, blood in vomit or bowel movements, an inability to keep fluids down or signs of dehydration should seek medical advice. If you are in New Zealand, Healthline can be contacted free on 0800 611 116.
Rice remains a safe and valuable food when it is prepared correctly. The most important rule is simple. Eat it while it is hot or cool it quickly and place it in the refrigerator.
Leaving cooked rice sitting warm for hours is the mistake that can make you unwell.
