Can leftover rice make you sick?

Leftover rice is something many of us have on hand often, whether it’s surplus from a takeout order or homemade batch.

Despite, or because of, its ubiquity, there are plenty of myths and misconceptions surrounding leftover rice. Here are answers to some common questions, including whether it can actually make you sick and how best to store it.

Can leftover rice make you sick?

As with just about any type of cooked food that has 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 (see below), 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 foodborne illness. Both types of illness are usually short-lived and resolve in 24 hours. The Centers for Disease Control and Prevention estimates that annually there are 63,000 cases of foodborne illness (and zero deaths) caused by B. cereus. As is the case with other foodborne illnesses, the young, elderly and immune-compromised are more susceptible to complications. Echoing the Bad Bug Book, Kowalcyk notes that illnesses from B. cereus, as well as other foodborne illnesses, are probably underreported because they are brief and often chalked up to other causes, including the “stomach flu,” which is not a scientific diagnosis. (If you suspect you have a foodborne illness, report it to your local health department in the event that there is a potential outbreak.)

How long does leftover rice last?

Kowalcyk recommends using refrigerated leftover rice within three to four days, which is in line with the government’s overall advice on leftovers. If you are part of a vulnerable population, you may want to use leftovers with 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 for ideal quality.

Cooking rice won’t necessarily make it safer. Scott Suchman for The Washington Post/food styling by Lisa Cherkasky

Does cooking rice make it safer?

Not necessarily. The spores, designed to survive extreme temperatures, are heat-resistant. Remember: The spores themselves will not make you sick. 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 at Ohio State University Extension. 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 degrees, 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 by email. 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?

Getting rice cooled as quickly as possible is key. 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. As always, don’t let cooked rice sit out at room temperature for more than 2 hours (1 hour in warmer temperatures), and, really, less is better. The longer it sits, the more the bacteria can grow and reach an infectious dose, Kowalcyk says.

Leftover rice is something many of us have on hand often, whether it’s surplus from a takeout order or homemade batch. Scott Suchman for The Washington Post/food styling by Lisa Cherkasky

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 degrees Fahrenheit. A blog entry on Zojirushi, for example, says you can leave rice warming in a cooker for up to 12 hours (24 for models with an extended warm feature) while maintaining flavor and texture. And though it’s tempting to directly pop those takeout cartons in the fridge, consider moving the rice to something shallower for rapid cooling. Aim for containers no taller than 4 inches, advises Shauna Henley, family and consumer sciences senior agent and affiliate agent in the department of nutrition and food science at the University of Maryland. If you want to freeze rice, spread it out in a shallow layer on a pan, cool in the fridge and then pack into a container or bag before transferring to the freezer. As with heating, freezing will not eliminate bacteria spores or toxins.

How can you use leftover rice?

Fried rice is one of the best, most flexible dishes for using leftovers. You can also incorporate extra rice into frittatas, soups and salads. Keep in mind that using the rice in a new dish does not reset the clock on the three- to four-day window for safety. And, again, rice should not be reheated more than once.

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