Rice – Are You Really Safe?

Rice is a favorite food of many cultures, and it is so versatile! You can eat it plain, in soup, fried, baked, in puddings, and even in cookies. However, if you are dining at your favorite restaurant and plan to take home the leftovers, be careful. With rice, looks can be deceiving. The nondescript grain that takes on any flavor that is paired with it, can make you extremely sick. However, the usual result is that you have mild case of food poisoning that is self-limiting.

Rice is grown in fields that are flooded with water at certain times of the year. They are also grown in soil, and in that soil are countless bacteria and microbes. Bacillus cereus lives in the soils in which grains and vegetables are grown. This bacterium produces spores, and that is where the issue lies. You can kill the bacterium by cooking, but the spores are very hardy, and cooking does not destroy them (1). These spores produce toxins, which is why you get sick if rice has been mishandled after cooking. The toxin cannot be negated by cooking or cooling. Once it is there you cannot get rid of it. Rice or other starchy foods need to be stored quickly after your meal. Lingering after your meal, letting it sit in your car for an hour or forgetting it on the counter can lead to severe illness. Refrigeration can inhibit the bacteria from growing.

There are different strains of the Bacillus cereus, and consequently, the toxins that they produce are different. One type produces vomiting within thirty minutes to six hours. This type is frequently attributed to improperly refrigerated fried or boiled rice. The other type produces diarrhea within six to twenty-four hours, which is similar to other types of food borne illness (2). This type can usually be traced back to improperly handled meat and vegetable dishes, such as soups or entrees that contain sauces. If a dish contains enough toxins, it can be fatal (3).

When preparing rice or starchy foods, making sure that they are cooked thoroughly to above 165 °F and if you are keeping it warm, make sure that it remains above 135 °F. The sweet spot for growth of Bacillus cereus is between 135°F and 41 °F. Refrigeration temperatures should be below 41 °F to ensure the least amount of bacterial growth. The colder the temperature, the better. This is a great place to use that food thermometer!

In food production facilities, rice is a food that should have a critical control point to ensure that the critical temperatures have been met. Documentation of the cooking cycle should show that the rice has been thoroughly cooked to ≥ 145 °F, cooled to below 70 °F within 90 minutes and cooled to below 40 degrees within five hours (1). Rice can also be acidified with vinegar, with a pH target of 4.1, but below 4.6 for use in sushi. Sushi rice should be disposed of after five hours (4). Temperature is not the only hazard that is addressed when manufacturing rice dishes. Chemical hazards, physical hazards, and sanitation practices are also considered.

You do not have to give up your favorite rice dishes or be afraid of your local sushi restaurant, but keep in mind that you should leave the leftovers unless you are going straight home. Remember, it is not only rice that can be dangerous – pasta, potatoes, and pizza can cause an outbreak of Bacillus cereus, too. As usual, wash your hands, stay safe, and enjoy that fried rice!

1. Government Relations Team. (2016). Fspca Preventive Controls for Human Food. CreateSpace Independent Publishing Platform.
2. Schneider, K. R., Goodrich Schneider, R., Silverberg, R., Kurdmongkoltham, P., & Bertoldi, B. (2015). Preventing Foodborne Illness: Bacillus cereus
3. Naranjo, M., Denayer, S., Botteldoorn, N., Delbrassinne, L., Veys, J., Waegenaere, J., Sirtaine, N., Driesen, R. B., Sipido, K. R., Mahillon, J., & Dierick, K. (2011). Sudden death of a young adult associated with Bacillus cereus food poisoning. Journal of Clinical Microbiology, 49(12), 4379–4381.
4. https://nifa.usda.gov/sites/default/files/resource/Preventing-Foodborne-Illness-Bacillus-cereus.pdf