Getting to grips with onigiri

Over the centuries, many of the world’s food cultures have developed a handy dish that is easily prepared, easily transported, and easily eaten on the move.

Often these “grab-and-go” convenience foods cover a range of nutritional needs. They may combine some sort of carbohydrate—for a starchy, slow-release energy boost and a dose of fiber—with a range of fillings or toppings that provide protein, or maybe plant-based vitamins and minerals.

Most readers will be familiar with some variant on the sandwich, while generations of Mexicans have sworn by their quesadillas, and many across East Asia enjoy snacking on a handy steamed baozi bun.

In Japan’s case, however, the clear winner in the battle of the lunchbox is the onigiri, or rice ball. This lunchtime staple, also commonly referred to as omusubi, may feature a range of fillings, but the constant is a serving of rice, packed, traditionally by hand, into a hearty mass that may be—as the English name suggests—ball shaped, but comes just as often in triangular or hockey-puck-like forms.

The term nigiri (meaning “hand-gripped,” and in the case of onigiri prefixed with an honorific “o”) may be familiar to sushi aficionados from the diverse array of nigirizushi that are deftly pressed into bite-size morsels by the practiced fingers of sushi chefs behind serving counters all over the world. But while sushi frequently features exquisite toppings (or neta), onigiri is known for more downhome (though no less tasty) fillings, known as gu.

Get your fill of fillings

The character for gu also crops up in the term gutai-teki, or “specific,” so let’s take that as our cue to examine in more detail some common varieties of onigiri.

The simplest form is shiomusubi, a tablet of salted white rice, sometimes with a sprinkling of sesame seeds for added crunchiness. Satisfying as this combination is, it doesn't make a particularly interesting meal in its own right. That is why shiomusubi are perhaps most regularly spotted rubbing shoulders with a range of side dishes as part of the rich tapestry of bento packed lunches expectantly opened by schoolchildren and office workers across Japan each day.

Another basic variant is sekihan. This red rice with azuki beans is often served with a meal at times of celebration. Sekihan onigiri, though, are not reserved for such special occasions, and are frequently found on the shelves of convenience stores.

Other varieties that eschew plain white rice include genmai (brown rice). They may employ zakkokumai (rice with mixed grains); chahan (fried rice with egg, pork, and sometimes even piquant Korean kimchi); or rice mixed with sea vegetables such as wakame, fish fry like jako or shirasu, herbs such as shiso (often matched with chunks of the fruit ume), or okaka, another name for katsuobushi—the dried, smoked skipjack tuna flakes that are a key seasoning in Japanese cuisine.

As one might expect, seafood is particularly well represented in the selection of gu that is encased in—rather than mixed with—the rice.

Flaky pink salmon (sake) is one trusty favorite, as is a tuna and mayonnaise tag-team that would be equally at home on any sandwich. You might find a selection of fish eggs, including cod roe lightly seasoned as tarako, or salted and cut with red chili powder as mentaiko.

One sea vegetable that commonly forms the centerpiece of onigiri is shredded konbu, often preserved by simmering in soy sauce and mirin (sweet rice wine).

Other fillings to tempt diners who prefer something plant based include takana (leaf mustard), and umeboshi—salt pickled ume, used since samurai times as both a storable source of mineral nutrition and a natural sterilizing agent to keep rice from spoiling in the humid Japanese climate.

From the distant past to the cutting edge

The history of this “movable feast,” however, goes back further still. Carbonized rice balls presumed to be onigiri have been retrieved from Yayoi period (c. 300 BC–c. 300 AD) archaeological sites in Ishikawa and Kanagawa Prefectures.

After a long evolution, the triangular modern onigiri took shape in the Edo period (1603–1868), when sheets of nori (dried, pressed seaweed) were first used as a kind of edible wrapper. But in the mid-20th century, the use of nori became a problem. With onigiri prepared hours in advance and shipped to convenience stores and supermarkets, how to prevent the nori from getting soggy through prolonged contact with the rice?

The answer came in the form of innovative (though, for the uninitiated, often infuriating) packaging that places a layer of film between the nori and the rice. When the numbered tabs are pulled open in the correct order, the film slides away, leaving a triangular onigiri immaculately swaddled in satisfyingly crisp, shiny nori. These days even puck-shaped rice balls without nori have their own ingenious packaging to save consumers from having to touch their onigiri with bare fingers.

Onigiri continue to evolve into the 21st century. Many readers will have seen the use of cut-out pieces of nori and other garnishes to decorate rice balls as part of the delightfully creative kyara-ben (character bento) that have focused global attention on Japan’s kawaii (cute) food culture through the prism of social media. And one other relatively new development is onigirazu, a hastily-wrapped, pseudo sandwich incarnation of the onigiri whose name is a play on words meaning “not pressed by hand.”

Text: David McMahon