Since its introduction more than 2,000 years ago, rice has been an inextricable part of Japanese culture. Its initial role in the art of sushi, however, was as a fermenting agent and it was discarded before the fish was consumed. After the addition of vinegar to the recipe, in the 14th century, rice became an edible part of the delicacy. Today, true connoisseurs of edomae nigirizushi (or sushi, as we know it), pay as much attention to the pearly ball of sushi-meshi (rice) as they do to the cut of fish on top. 'Japanese are rice pickers. Without rice, our culture would be half as rich,' says Satoru Mukogawa, of Sushi Kuu, in Central. 'Japanese customers judge the quality of the restaurant by three things: the miso soup, pickles and rice. If the rice is not good, even if the fish is fresh, it won't do. Sushi is 70 per cent rice.' The rice of the Koshi-Hakari region is considered the best for sushi. After harvesting, sorting and blending, producers will age the rice for 1? years to two years. Ageing removes moisture and helps the grains keep their shape when cooked, according to Mukogawa. 'You can smell the difference between rice that has and hasn't been washed properly the moment it's done and you open the lid of the cooker,' he says. 'We wash the rice four or five times. First, wet the rice then [drain] the water out right away - this is to soften the rice so the grains don't break during washing. Fill the container with just enough water to cover the rice and use the palm of one hand to press down and rub the rice against the side of the container. We do this three or four times to remove the hardest outer layers.' There are a few traditional flavour enhancers used for sushi rice. Mukogawa cooks his with honey, kombu (dried seaweed used in stock) and sake. Once the rice is steamed to an even, but still firm, consistency, it is placed in a wooden bucket, into which the vinegar mixture is added. 'I use two different vinegars, salt, sugar and dried seaweed. You have to cool down the rice and mix it with sushi vinegar quickly. [A wooden container is always used] because it sucks extra water from the rice. The rice gets too soggy if you use plastic or metal.' That doesn't seem too difficult, so why does it take three years for a sushi chef to learn how to make rice? 'Japan has all the changes in humidity and temperatures of four seasons and every day the water ratio and cooking time changes. For a chef to really grasp that, three years is not considered too long.'