Onigiri

Freshly cooked rice is pressed firmly enough to hold together but loosely enough to stay soft inside. Cooks wet and salt their hands, place a filling in the centre and shape the rice with a few firm movements. The triangular shape is the most common, particularly in eastern Japan; round and barrel shapes are also traditional.

Nori may be wrapped round just before eating, to keep it crisp, or in advance so it softens and clings to the rice. Convenience-store onigiri use a packaging film that keeps nori and rice apart until the wrapper is opened.

Traditional fillings are salty or sour preserves that complement plain rice. Modern fillings range much further, including mayonnaise-based mixtures and fried chicken. Filled onigiri are often labelled by the filling on the wrapper in shops.

Many regions have their own rice balls, from the large, nori-covered bakudan ('bomb') onigiri to rice balls with local pickles. Some well-known variants are wrapped in something other than nori.

In 1987 archaeologists excavating the Sugitani Chanobatake site in Nakanoto, Ishikawa Prefecture, found a lump of charred rice from the Yayoi period, about 2,000 years old, which has been described as Japan's oldest rice ball; it may have been an offering rather than food. In the Heian period, pressed rice balls called tonjiki were handed out at court gatherings, and from the medieval period rice balls served as field rations for soldiers.

Nori wrapping became common in the Edo period, when nori cultivation developed around Edo Bay. The modern convenience-store onigiri, with its film that separates nori from rice, turned the rice ball into one of Japan's best-selling ready meals. Nakanoto marks 18 June as Onigiri Day.

Onigiri are eaten with the hands, including in company, and need no sauce. Convenience-store onigiri have a numbered opening sequence printed on the wrapper: pull the tab down the middle, then pull the two sides outward so the nori wraps itself round the rice.

Home-made onigiri are strongly associated with care and family. Rice balls made by a parent for school excursions or sports days, and those handed out in emergency relief, carry an emotional weight far beyond their simplicity.