Japanese rice wine is really a beer, says Michael Jackson
It was not a dream, though it had the elements of fantasy. There was a team of four young Japanese women, and the earth did move (that turned out to be a minor quake: four on the Richter scale). The women wore white linen head squares, as though they were nurses, and had white towels round their necks. They covered the floor with linen, then knelt to perform the massage, frantically, to shouted instructions from a man with the plaited headband of a samurai, or at least a sushi master. The action moved to a steamy inner chamber, lined with cedar. In this sauna- like room, the magic koji was scattered from a vessel like a pepper-pot, and the massage repeated, this time on a bed.

The object of their attentions was 30 kilos of steamed rice. On the floor, the women were kneading the rice to separate and cool the grains. On the bed, they were folding in the koji. This is a mould that grows on rice and converts the grain's starches into sugars. Its use is a preliminary stage (comparable to malting) in the production of sake.

Two of the women had their own beds in the building, so that they could sleep near the rice to check the progress of the koji during the night. Once the conversion has taken place, over three days, more steamed rice is added and the blend mixed with water in glass-lined vessels. A further culture, closer to a beer yeast, is added, and the mixture is fermented for three weeks, looking like rice pudding at first, gaining the flavours of curd cheese, then pear in cream, before becoming clear sake.

"This can be done mechanically, but we turned this brewery back to the older methods so that our workers can learn the job hands-on," explained Hiroshi Matsukawa, production director of Shirayuki ("White Snow of Fuji Sake").

"The sense of touch is important in establishing whether or not the rice has been steamed to the right degree. We don't want it to be sticky. Every grain must have a hard outside crust but be soft inside. When the rice is being kneaded on the bed, we want the grains to be scratched to allow the koji to penetrate, but not too much. That is a matter of experience and sensitivity. There is a lot of hand-work in the sake you are seeing made, so it will be very expensive. For the consumer, that means a very complex fruitiness of flavour."

When the ancient Sumerians learnt to ferment early forms of barley and wheat into beer, their example spread east to the rice-growing nations, too. The Chinese gave the name "rice wine" to a drink that is really a beer. In legend, it was the dew formed on sacred chrysanthemums. Before koji was understood, the producers chewed the rice to begin the conversion. As with beer in the Western world, monasteries played an important part in early production. Every sake brewery has its own Shinto shrine.

Shirayuki Sake is made in the small town of Itami, near the city of Osaka, in the westerly prefecture of Hyogo, on the main island of Japan. This is said to have been the original region of sake production, though it has a vigorous rivalry with the Niigata prefecture farther north. The regions use different varieties of rice, both low in protein, high in starch and plump in grain.

Shirayuki, dating from the 1600s, is believed to be the oldest of Japan's 1,800 sake-makers, and is garlanded with awards for its products. It has five breweries, all in and around Itami, with varying degrees of mechanisation. The oldest is 400 years old, a symphony of terracotta tiles, cedar beams, hemp ropes and bamboo mats.

There are at least 20 styles of sake, and Mr Matsukawa took me through 10 of his company's examples, each with a different character. The variations depended upon the quality of rice, the degree to which it had been polished, the balance of ingredients, the use of sugar, the precise regime of koji and yeast (sometimes other cultures are used also), and the way in which the brew had been filtered or "squeezed".

Strengths vary from 15 to 20 per cent alcohol by volume, and some sakes are fortified to reach even higher levels. The drink is often mellowed in cedar for six to 12 months, and is usually consumed in the year of its production. The new season's sake is released in the autumn.

As in all fermented drinks, many of the aromas and flavours in sake develop from the action of yeast. Perhaps because of the two cultures used, sake's flavours are complex and difficult to identify. Some sakes are much more aromatic than others, often with a grassy note. I have found flavours reminiscent of apple, lichee and grape. One or two sakes are nuttily sherryish, others have a yoghurty, lactic quality. Some are petillant, most still.

Traditionally, sake is heated, though often only to human body temperature, in a tiny china "teapot" submerged in warm water. About 40-55C (104-131F) is widely accepted in Japan. These days, cooler temperatures are often preferred, especially for the more aromatic styles. Cool sake is traditionally served from a wooden vessel, with a pinch of salt, though elegant glasses are increasingly used.

Just as the traditional brewing nations have been slow to appreciate the difference between beers that serve best as an aperitif, accompaniment to food or digestif, the same is true of sake. Nonetheless, some producers are beginning to present their products this way. At Shirayuki, I was offered a flowery sake, Awa-Nigori (Pale and Misty) as an aperitif, and a warming, peppery example, Chikamatsu-no (named after a classical author) after dinner.

With 70 Japanese restaurants in London, and the noodle chain Wagamama expanding, we may see much more sake in Britain. "Wagamama has done a great job for the drink," says Cheeleong Lau, whose Rice Wine Shop is in a corner of Soho that is fast becoming a tiny "Japantown".

His little shop, which sells a variety of Japanese foods, stocks about 80 sakes. He took me through a tasting, starting with the very basic but good Gokujyo Miyanoyuki, which I found clean and fresh, with a rounded finish (pounds 8.99). Sakes with a very strong local identity are prized, such as Ginzukuri Junmai, from Niigata. I found this notably aromatic and firm-bodied (pounds 29.99), and would regard it as a good aperitif. A five-year-old sake, Senju Tosatsuru (pounds 50) was very sweet, rich and cedary. I will save that one until after dinner

The Rice Wine Shop, 82 Brewer Street, London W1 (0171-439 3705)