According to the website, House Beautiful, the National Health Service (NHS) uncooked rice often contains spores of Bacillus cereus — a bacteria strand that can cause food poisoning — that can survive when rice is cooked. And if the rice is left at room temperature after it’s been boiled, the spores can grow into bacteria, which will ultimately multiply and may produce toxins that cause vomiting or diarrhoea.
The longer cooked rice is left at room temperature, the more likely it is that the bacteria will make the rice unsafe to eat — meaning it’s vital that you store your rice the right way if you’re hoping to reheat it later.
So, how do you increase the chances of avoiding food poisoning all together? First off, serve rice as soon as it’s been cooked, and cool any leftovers as quickly as possible. You can keep the rice in the fridge (but for no more than one day) before reheating.