1. Rice polishing

The element sought is the heart of the rice, almost exclusively made up of starch, so we start by polishing the rice grains in order to rid them of their protective layer (the rice bran) and the surface layers where the vitamins, proteins and lipids. If these superficial layers are regularly praised in nutrition (brown rice), they on the other hand produce “parasitic tastes” (雑味, zatsumi ) when making sake, this is why we seek to obtain a grain containing only the starch core. We can consider that a minimum polishing trims 10% of the basic rice grain.

2. Washing and cooking the rice

The rice is then washed and moistened – a very controlled process, since the more the rice has been polished, the more quickly it absorbs water – before being steamed for 1 hour in large vats.

3. Making koji

Koji is the ferment that will be used to start the fermentation of rice. Essentially made of starch, rice cannot ferment on its own and must first be broken down by the process of saccharification (literally "transforming into sugar"), a process well known to the French, since it is what happens when our saliva breaks down the starch in the bread and makes it so delicious! This role of saliva even constitutes one of the oldest methods of making sake (called kuchikamizaké , literally “chewed sake”): a virgin woman chewed rice and spit it into a vat, thus beginning the fermentation of the rice which would then be used to make the divine beverage (sake originally serving as an offering to the gods ). It is this ceremony of kuchikamizake which we find in the animated film “Your Name” by Makoto Shinkai.

To create koji, some of the cooked rice is sprinkled with fungal spores called koji-kin (“koji microbe”) and left to rest for 24 hours at a controlled temperature between 28°C and 36°C, after which this first rice is distributed in boxes called tana , stacked and covered, but spaced regularly in order to be able to better control the temperature of the entire production.

4. Addition of yeasts and fermentation

Once the koji has transformed the rice starch into glucose, we add the yeasts which will transform this glucose into alcohol, this is the principle of alcoholic fermentation. This fermentation takes place in large tanks and can last between 10 days and 7 weeks, depending on the process implemented by the sake brewery, including the choice of fermentation temperature (low temperature fermentation obviously takes longer) .

5. Pressing, optional steps, bottling

At the end of fermentation, the sake is pressed to separate the clear liquid from the solid sake lees ( kasu ), which will then be reused in cooking or cosmetics.
After resting for a few days, this new, already clear sake is generally filtered through a layer of charcoal to make it even clearer. Sake not undergoing this filtering is called “ muroka ".
Then come the pasteurization stages: in vats, after bottling, or… not at all! Pasteurization allows for better conservation and also prevents a second fermentation after bottling. However, some brewers decide not to pasteurize their sakes (or part of their production). These unpasteurized sakes called “ namazaké ” are therefore more fragile, must be kept cool and consumed quickly.

6. Maturation

After pasteurization, the sakes are left to rest for a period ranging from 3 months to several years in order to let them round out: we often talk about the “mellowness” that long maturation provides.

7. Reduce alcohol levels
Finally, a little spring water is added to lower the alcohol content of the sake. Sake in which no water has been added is marked “ genshu ” and are therefore often more alcoholic.

Video courtesy of Rodolphe Miez: https://rodolphemiez.com