Onigiri (Japanese Rice Balls)

When hunger strikes, I find myself yearning for something simple and satisfying: onigiri. Filled with salmon, tuna, and preserved plum—among many other savory flavors—these Japanese rice balls, which are also referred to as omusubi, are a satisfying snack easily enjoyed on the go. Onigiri are typically sold in Japanese supermarkets or convenience stores called konbini, and are also something parents frequently make for their children to take to school. 

According to Japanese-American food writer Sonoko Sakai, both onigiri and nigiri (a type of sushi) share the same meaning: “to mold.” Despite the two words sharing the same definition and a very similar technique, nigiri is something meant to be prepared by professionals and enjoyed at restaurants. Onigiri, on the other hand, is frequently in the domain of home cooks and seen as “both a comfort food and the darling of convenience stores,” notes Sakai in her book Rice Craft. 

“The Japanese,” writes Sanae Inada in her book Onigiri, “believe that the humble rice ball reflects the time and place where the person making the onigiri lives, his/her family and cooking philosophy, and that all these will be passed onto the person eating the onigiri.” Beyond just being a handy, satisfying lunch, onigiri is a powerful cultural symbol in Japan that represents love, care, and magic. 

“In popular children’s stories,” cultural anthropologist Gavin Hamilton Whitelaw observes, “the gift of a rice ball, even when by accident, ultimately leads to reciprocity, prosperity, and deeper interpersonal ties.” For example, in Hayao Miyazaki’s animated film Spirited Away, the protagonist Chihiro is able to rescue her parents (who have been turned into pigs) after she eats a rice ball she’s gifted from a friend. It’s almost as if the rice ball is “infused with a kind of emotional magic” that comes from the love and care required of someone who will take the time to physically make and shape onigiri for you.

The History of Onigiri

Records from the Heian Period (794 AD to 1192 AD) reveal that people have been making and eating onigiri in Japan for thousands of years. According to Whitelaw, documents tell us that onigiri were included in ceremonial gift exchanges between nobles and included in military rations, as they “could be produced in bulk, rapidly distributed, carried into battle, and consumed when necessary.” Whitelaw credits agricultural reforms and the expansion of Japan’s rail system with helping to make rice a “more prominent part of the Japanese diet,” and in 1885, the first train station lunchbox—called an ekiben—was sold. What did it contain? You guessed it: onigiri. And when the country launched its school lunch program in 1889, it, too, included the rice ball. It continues to be a popular lunch menu item.

What pushed onigiri into modern convenience territory, though, was the arrival of 7-Eleven in the country in 1973 and later, the chain’s decision to sell onigiri in 1978. Eager to offer a snack that would appeal to locals, rice balls were the perfect choice: not only were they culturally meaningful, but they were also the epitome of convenience and portability. Though onigiri is still prepared at home, it remains a popular option in cafeterias, grocery stores, and konbini across Japan.

Popular Fillings for Onigiri

Perhaps the most fun part of onigiri is deciding what to fill it with: there are numerous possibilities, each just as delicious and satisfying as the next. Popular fillings include, but are not limited to:

• Tuna with mayonnaise
• Salted salmon (shiozake)
• Preserved plum (umeboshi)
• Bonito flakes (katsuoboshi) marinated in soy sauce
• Mentaiko (cod roe), with or without mayonnaise
• Japanese fried chicken (karaage)
• Simmered kelp (kombu)

The following recipe offers three filling options to pick from. You certainly don’t have to make all three fillings in order to use up the rice, and you’re more than welcome to use other fillings of your choice.

Starch Matters: The Best Type of Rice for Onigiri

There are two molecules—amylose and amylopectin—that make-up starch. As Sho Spaeth has written for us previously, both amylose and amylopectin react to water differently during the cooking process, resulting in vastly different textures of rice depending on which type you use. Japonica varieties are typically short-grain ones with more amylopectin, a water-soluble starch that gives cooked rice its sticky quality. Indica varieties, like jasmine or basmati, tend to be long-grain and contain less amylopectin and more amylose (which, unlike amylopectin, isn’t as water soluble), resulting in cooked grains that remain separate and don’t cling to one another.

For onigiri that holds its shape well, it’s important to use short-grain Japonica rice, such as “sushi” rice, a category that includes Calrose and Koshihikari rice and, as Sho notes, simply refers to varieties of rice preferred in Japan. Because of the rice’s high amylopectin content, the cooked grains are fluffy and tender but sticky enough to adhere to one another, making it ideal for sushi and onigiri. Use long-grain rice, and you’ll find yourself struggling to keep your onigiri. On the opposite spectrum, glutinous rice tends to be too sticky—you still want the grains to be distinct—and isn’t ideal for shaping onigiri.

How to Shape and Wrap Onigiri

Though triangles are arguably the most recognizable shape of onigiri, they can be formed into spheres, flattened disks, rectangular barrels that resemble sandbags, and even cute animals like cats, pandas, and fictional characters like Pokémon. Using your hands to make onigiri is the most traditional way, but if time is of the essence or if shaping onigiri simply isn’t your forte, you can use a mold instead. 

Whichever route you choose, I recommend covering your work surface with plastic wrap. The plastic will keep your kitchen counter clean, and if you’re shaping onigiri by hand, you can lift up the sides of the plastic wrap to help you gather the rice into a tight, firmly shaped ball. You should also keep a bowl of salted water next to you for dipping your hands in, which will prevent the rice from sticking to your hands while also seasoning the rice as you shape it. Be sure to shape the onigiri while the rice is still hot (further proof you truly love the person you are making it for!) as this is when the grains are stickiest and will be able to best hold their shape. 

Next comes the question of nori: to wrap or not to wrap? It really comes down to personal preference. Covering onigiri in nori makes it easier to transport, but results in softened seaweed that’s no longer crisp. For the best texture, I recommend leaving the onigiri unwrapped until you’re ready to eat. Alternatively, you can coat the outside of your rice ball in furikake, a Japanese rice seasoning that typically consists of dried seaweed, sesame seeds, sugar, and salt, which adds a pleasant crunch to each bite.

Is it Safe to Keep Onigiri at Room Temperature?

There's no question that onigiri are carried around and eaten by millions of people every year, and most of them are just fine. But we'd be irresponsible not to note that cooked rice is a particularly dangerous breeding ground for some food-borne pathogens, thanks to the ample surface area of all the grains packed together, a bacteria-friendly moisture level, and tons of starch for the bacteria to eat. One bacterium in particular, called B. cereus, lives on uncooked rice and is able to survive the cooking process. (Pleasant, I know.)

According to the U.S. Department of Agriculture’s Food Safety and Inspection Service, food should not be kept unrefrigerated for longer than two hours, and “bacteria grow most rapidly in the range of temperatures between 40ºF and 140ºF [4 ºC to 60ºC], doubling in number in as little as 20 minutes,” a terrifying statistic that keeps me up at night. Though onigiri is a famously portable food, our advice is to practice good food safety: make your rice balls and eat them within the two-hour window (refrigerating onigiri isn't a great solution, as gelled starch goes through a hardening process known as retrogradation when cold, leading to overly firm grains once chilled).