Make sure your rice stays nice

Despite, or because of, its ubiquity, there are plenty of myths and misconceptions surrounding leftover rice.

Here are answers to some common questions, including about storage and reheating safety.

CAN LEFTOVER RICE MAKE YOU SICK?

As with just about any type of cooked food that's been improperly stored, yes. You can blame Bacillus cereus in part for that. This bacterium is ubiquitous in the environment and commonly found in soil. Its spores can contaminate rice, along with other starchy products, such as potatoes and pasta, though any food that comes in contact with soil is susceptible. Not all rice is contaminated, but there's no way for home cooks to tell. The good news is that the spores themselves will not make you sick, says Barbara Kowalcyk, director of the Food Policy Institute and associate professor of exercise and nutrition sciences at George Washington University. But, under the right conditions, the spores can grow and germinate into bacteria that produce illness-inducing toxins.

Those toxins from B. cereus can cause two different types of illness, one whose symptoms are primarily diarrhea and the other vomiting, the latter of which is most associated with rice, according to the Food and Drug Administration's Bad Bug Book on food-borne illness. Both types of illness are usually short-lived and resolve in 24 hours. As is the case with other food-borne illnesses, the young, elderly and immune-compromised are more susceptible to complications. Kowalcyk notes that illnesses from B. cereus, as well as other food-borne illnesses, are probably under-reported because they are chalked up to other causes, including the “stomach flu,” which is not a scientific diagnosis.

HOW LONG DOES LEFTOVER RICE LAST?

Kowalcyk recommends using refrigerated leftover rice within three to four days, which is in line with overall advice on leftovers. If you are part of a vulnerable population, you may want to use leftovers within one day, Kowalcyk says, which is what Britain's National Health Service recommends about rice for everyone. The NHS also advises not to reheat rice more than once. Frozen rice will last for months, though many sources recommend using it within one to two months.

DOES COOKING RICE MAKE IT SAFER?

Not necessarily. The spores, are heat-resistant. Unfortunately, the toxins produced by the bacteria are heat-resistant as well, at least in the context of a home kitchen microwave, says Nicole Arnold, assistant professor and food safety field specialist. The original cooking or subsequent reheating will not get rid of the spores or toxins. If you do choose to reheat rice, be sure to heat it to “piping hot,” or 165 F (74 C), which can help “kill harmful bacteria that may have grown or contaminated the food (like within the refrigerator) since the food was originally cooked,” Arnold said. If rice was properly cooked and cooled, it's fine to use it without reheating, as in a salad.

HOW SHOULD YOU STORE LEFTOVER RICE?

Get rice cooled as quickly as possible. Eating freshly cooked rice, even if it was contaminated with the bacteria spores, will not make you sick. “In my opinion, the primary risk lies with cooked rice being improperly cooled,” Arnold says. Don't let cooked rice sit out at room temperature for more than two hours (one hour in warmer temperatures). Less is better.

If you would like to have rice warm and ready for a longer window, invest in a rice cooker or other appliance with a warming feature that keeps the rice out of the temperature danger zone in which bacteria can proliferate, 40 to 140 F (4.4 to 60 C).