Trading Standards Institute Advice

Food borne illness and contamination: Bacillus cereus

This leaflet is for all food businesses, including those involved in catering, food production, food preparation, retail premises, restaurants, pubs, cafes, and fast-food shops.

What is Bacillus cereus?
Bacillus cereusis a bacteria that is found in soil and dust.

Although Bacillus cereus is not as common as some other bacteria that cause food borne illness, it can be specific in the types of food it contaminates. The most common food associated with Bacillus cereus is rice.

It may also be found in other foods such as:

  • pasta
  • corn flour
  • vanilla and herbs and spices
  • couscous and bulgur wheat

How does food get contaminated?
Spores are a resistant form of bacteria and may be present in the husks of rice. Spores are not a serious risk to a healthy adult, but as they can survive in difficult conditions for a long time, they could be a problem. They can survive with no water or nutrients and can tolerate high temperatures.

When rice is boiled but not immediately cooled, these spores may find the warmth and moisture needed to germinate into bacteria. Bacteria then start to multiply which may then leave a poison in the food.

The poison produced (known as a toxin), is a natural by-product of the multiplying bacteria. The poison is also heat-resistant, so further reheating or cooking is unlikely to get rid of it.

What are the effects or symptoms of eating contaminated food?
The most common toxin or poison formed by this bacteria causes vomiting and abdominal pain. The symptoms may start one to six hours after eating contaminated food. The poison is not passed from one person to another and symptoms don't usually last longer than a day.

Some Bacillus cereus bacteria may produce poison that causes fever and diarrhoea. The symptoms, which may be serious, usually start six to 24 hours after eating and can last for one or two days.

As with other bacteria that cause illness from food, there is no way of telling that the food is contaminated. Cooked rice that contains poison produced by Bacillus cereus will not taste, smell or look any different to normal rice.

How do I control or prevent bacillus cereus?
Serving the rice hot immediately after cooking is the easiest way to make sure it is safe to eat.

If you are cooking rice in advance you shouldn't cook too much at once. Large amounts may take too long to cool.

Caterers and cooks who cook rice before reheating for a customer's order later on, must make sure that once the rice has been cooked, it is cooled as rapidly as possible to stop bacteria cells from multiplying. This can be done by putting rice under cold running water and thoroughly rinsing it in a saucepan or colander until it is cool. This method will also wash away excess starch.

Once you've drained the cooled rice, you should put it into sealed containers, and label and date the containers before storing them in a refrigerator between 1°C and 4°C.

You can now use the rice in cold food dishes, which should be refrigerated while being stored or displayed.

You can use refrigerated rice in hot dishes if it is thoroughly reheated (a minimum temperature of over 75°C is recommended) in a wok or in boiling water. Once the rice is hot, keep it hot and store it or display it at a minimum temperature of 63°C.

You should only reheat rice once. Throw away any leftovers, and do not cool the rice again to be eaten later.

You need to make sure that you have an efficient stock-rotation system so that you use your oldest rice first. Remember: FIFO ('first in first out'). 

More information
You will find further guidance in our other leaflets on this website. Information can also be found on the Food Standards Agency (opens in a new window) website.

Alternatively, contact your local environmental health service for advice.

Please note
This leaflet is not an authoritative interpretation of the law and is intended only for guidance.

© 2017 itsa Ltd.