The Truth about Rice
- Fiona Sinclair
- May 14
- 2 min read
Technical deep dive: The Truth about Rice
Have you ever wondered what the fuss about rice and food poisoning is all about?
Everyone says ’never reheat rice’… but how true is this? Well, whilst it’s always best to cook and serve rice fresh, it can, in fact, be safely reheated if each step is correctly controlled.
The REAL truth is ‘never leave rice too long at room temperature’ – that’s where the real trouble starts, and what the saying should really be!
Curious? Let’s understand how exactly how food poisoning can arise from rice, handy not only for when catering commercially, but for in our homelife too - whether it’s cooking a meal or deliberating over whether to keep that leftover takeaway!
Spore Survivors
You may already know that rice can be naturally contaminated with spores of Bacillus cereus. When the rice is harvested and dried, the Bacillus bacteria form a spore, a resilient, protective structure, which survives throughout its journey across the world to your store room!
Once we add water and cook the rice, the spores remain. However these are harmless to eat, so if we cook and serve, or keep rice at 63°C – no problem!
Poison in the food!
If, after cooking or keeping rice hot, it’s left at room temperature for too long - in the ‘RISK/DANGER ZONE’ – the spores germinate, releasing the Bacillus food poisoning bacteria into the rice. Given time in the ‘risk zone’, the bacteria continue to multiply and excrete a poison into the rice - this toxin is actually a waste product of the bacteria’s metabolism (it’s wee, if you like!)
The result of eating this poison in the food is food poisoning, kicking in around 1-6 hours after eating - predominant symptoms are vomiting and stomach pain, lasting around 12-24 hours.
This poison toxin is heat stable, which means once it’s in the food, you can’t get rid of it by then heating the rice – this poison remains!
Poison in the stomach!
But that’s not all – unusually, Bacillus can provide another form of food poisoning - a ‘double whammy’!
When eaten in large enough numbers, the Bacillus bacteria produce another type of poison in our intestine that causes diarrhoea. This takes longer to develop – around 6-24 hours, typically lasting 1-2 days. Good news is, as this poison is part of the wall around the bacterial cell, it IS destroyed if the rice is heated until piping hot before eating.
(NB. you may have twigged that the vomiting form of food poisoning from rice is therefore most common).
The truth about rice?
So to sum up, whilst Inspectrum agree that it is best to always cook and rice serve fresh (and no, we would not keep that leftover rice from your takeaway which may well have already been reheated once!), the golden rule is in fact ’never leave rice too long at room temperature’.
Fiona, Director @ Inspectrum Food Safety
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