Can you reheat rice?

I get asked this question a lot, and the answer is “yes you can reheat rice” but preventing food poisoning has nothing to do with the re-heating process.

It is a little-known fact that it is actually the cooling and cold storage that is the most important part. Rice and other cereal products such as pasta can contain bacteria called Bacillus cereus which is what is known as a spore-forming organism. The spores survive the cooking process and if allowed to germinate after cooking (by being left at room temperature) can multiply, producing a food poisoning toxin that is not destroyed by heat. So however well you re-heat rice, if you have not cooled it properly, then the toxin could still be there.

The symptoms of food poisoning are usually rapid onset of vomiting (within a few hours) and fortunately the illness is mostly short-lived, and usually not serious, although there was a case reported in Belgium (1) in 2003 where a family was affected badly by a pasta salad that had been kept out of temperature control for some time, and caused one fatality.

There are not many incidences of B. cereus reported because it is often over and done with before anyone gets to the doctor for a test to be done, so we don’t really know how much of a problem it is in the community.

Simple tips to control Bacillus cereus after cooking rice or pasta are:

• Cool rice and pasta rapidly by rinsing in a colander under fresh cold running water. Then refrigerate.
• Or place in shallow dishes and put in the refrigerator as soon as the food reaches room temperature – probably within 30 minutes but no longer than 90 minutes.
• Make sure the fridge is working properly – use a fridge thermometer and check that it is below 5 °C preferably.
• You can freeze rice – defrost quickly using boiling water or the microwave, and don’t allow to hang around at room temperature after defrosting or re-heating
• Don’t leave rice or pasta salads at room temperature for no longer than 4 hours in total – throw any left-overs away.
  1. J Clin Microbiol. 2005 August; 43(8): 4277-4279