Japanese sake, or Nihonshu, is a fermented drink made from rice and containing around 15% alcohol. Making it is a complex operation that takes place in a brewery known as a "Kura" in Japanese. The master brewer, or 'Toji', is in charge of production. He is assisted in his task by the "kurabito". For a sake producer, the year is divided into two periods: the warmer months, devoted to growing rice, and the colder months for sake production.


Rice is the main ingredient in sake (along with water and ferments). Before entering the production process, it must be stripped of its brown cuticle and polished. Vertical millstones are used to remove the outer layers, leaving only the heart of the grain. The degree to which the rice is polished is called "semaibuai" in Japanese. It determines the grade of the sake, without completely prejudging its taste qualities. During this stage, the rice can lose up to 75% of its weight.

When we talk about the degree of polishing, we always consider what remains of the material. The rice is initially considered to be 100%. If 40% of the outermost layers are removed, the degree of polishing will be announced as "60%", i.e. what remains.
Polishing is an important stage because it concentrates the starch. The heart of the grain is rich in starch, while the periphery contains more fatty acids, vitamins, proteins and amino acids. So the more the rice is polished, the higher the starch concentration.

books on sake, for more in-depth information

Once polished, the rice is washed, moistened and placed in the "koshiki", a traditional cooking device. The rice is cooked by steam from the bottom of the device. At the end of cooking, the rice has a particular consistency: it is tender on the inside and firm on the outside.
lavage et cuisson du riz à saké

As soon as the rice is cooked, it is transferred to a special room called the "Kojimuro", where the temperature and humidity are closely controlled. The rice is de-husked by hand, with each grain carefully separated from the others to encourage exposure to the ferments. A crucial stage is about to begin: the rice will receive the Koji mushroom.

The role of Koji : rice contains starch, a macromolecule made up of chains of sugars that cannot ferment as they are. It is essential to separate these chains, and this is done by a reaction known as saccharification. Koji Kin", a microscopic fungus of the aspergylus orizae type, will grow on the rice and release amylases, enzymes capable of breaking down the rice starch into simple sugars. These simple sugars can then be fermented into alcohol by yeast.
Koji mushroom comes in the form of a green powder, the strain of which is kept on rice. This powder is dispersed over the cooked rice and the Koji fungus develops over a period of three days. The rice + Koji mixture is stirred to encourage the action of the enzymes. At the end of the process, the rice is worn down by the koji and releases a pleasant chestnut smell.

préparation du riz koji

After three days, the action of the koji allows the first simple sugars to be produced. Now it's the yeast's turn to come into play. The toji prepares a vat in which he places the sake rice + koji, to which he adds the yeast and spring water. He prepares what is known as the "moto", the start of fermentation. The yeasts develop and begin to produce alcohol and alcohol esters. The temperature rises and bubbles form on the rice.
ajout des levures dans la préparation du saké

The bottom of the vat is placed in larger fermentation vats. The actual fermentation process then begins, lasting between 3 and 5 weeks. During this period, the contents of the vats are mixed very regularly, and water and more cooked rice are added step by step to fuel the reaction.
cuves de fermentation utilisées pour la production de saké
At the end of fermentation, the contents of the vats are collected and pressed. The remaining material is the rice particles formed during the reaction. It is called "kasu" and is used in cooking. The sake is then filtered (or not) and pasteurised (or not). Six months later, it is bottled and ready to be enjoyed.

pressage et filtration des cuves à saké