This person will explain

Toji shop owner/producer Eri Nakano

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In 1995, he opened the Japanese sake bar "Janapese Refined Sake Bar Tojiya" in Tenjinbashisuji, Osaka. He is active in various fields as a sake critic, seminar lecturer, and lyricist.

●Floor massage/sideburns massage
The steamed rice is pulled in, the seeds are removed, and it is wrapped in a cloth to keep it warm. It is then spread out again and kneaded. This is a process called toko-momi, where the rice is thoroughly mixed so that the koji seeds are evenly planted. The process is called toko-momi because the action of mixing looks like the steamed rice is being kneaded.
After the floor massage, the rice is piled up again, wrapped in cloth, and left to sit for about eight hours, sometimes even more than ten hours, trusting in the potential of Aspergillus oryzae.

● Cutting and serving
After kneading, small white dots appear on the steamed rice, and the rice grains stick together and become hard. The white dots are mycelium; when they start to become visible, heat is generated, so they must be loosened and broken up to prevent the temperature from rising. If the temperature rises too much, Aspergillus oryzae will lose its vitality. Breaking it up also supplies oxygen, making it easier for the mycelium to extend further. This is called "kiri-kaeshi." From here on, we will refer to this as koji rice rather than steamed rice.
Immediately after the cutting, the next step is mounding, which is the process of dividing the koji rice into small portions and piling them up to a set height. The container used to hold the rice is often a small wooden container called a koji lid (also called "morobuta" or "lid"; commonly known as a lid) (approximate dimensions: 45cm x 30cm, depth: 5cm, made from straight-grained cedar), but this varies depending on the amount of koji rice and the facilities of the brewery. Recently, plastic ones are also being used.

● Assistance and closure work
After the mori stage, the temperature of the koji rice rises again and the mycelium continues to grow without losing its momentum. Once the koji rice has reached the target temperature (approximately 34-35°C), the naka-shigoto stage is carried out. To prevent the temperature from rising too high, the koji rice that has re-bonded due to the growth of the yellow koji mold is broken up, spread out, and allowed to release heat and moisture, then covered again with cloth. To prevent the mycelium from growing only on the surface of the rice, a rapid rise in temperature is suppressed and the temperature is raised slowly to encourage the mycelium to penetrate into the center of the rice.

Once the nakashigoto is finished, the koji rice will be warmer than room temperature. The final task is shimai-shigoto. Lines are drawn with a finger on the koji rice, which is rapidly heating up, to release heat and encourage the evaporation of moisture. Three lines are usually drawn, but recently some witty sake brewers have drawn pictures and words to soothe the soul.

● Koji making
After being kept at a high temperature of 40-43 degrees for over 10 hours, the koji rice gives off a sweet chestnut-like aroma and is ready to be taken out of the koji room, as the word "de-koji" suggests. After the "de-koji" is taken out, it is cooled down to a temperature suitable for use in brewing and dried, a process called "de-garashi."

The steamed rice is mixed and kept warm, then loosened and released, mixed again, and when the temperature rises again, released... The work in the koji room continues for two days and nights, with time spent paying close attention to the ever-changing appearance of the steamed rice. This is koji making.

● Machine-made koji
This can be said for all processes and work in sake brewing, but each brewery has different facilities and production volumes.
Some breweries use fully automated machines to make koji, from the drawing in process to the production of koji, while others only use machines for the process after mori.
The performance of the machinery also varies widely. Some breweries use aeration koji-making methods, which control temperature and humidity by blowing air over the koji, while others use a completely automatic, windless VEX (Vapor pressure Equalizing Control System) system (manufactured by Fujiwara Techno-Art) that achieves the right temperature progression by controlling the amount of water evaporation through the difference in water vapor pressure in a no-ventilation environment and ensures sufficient water evaporation from the surface of the koji.
Nowadays, with the word "craft" becoming established, drinkers tend to have a negative view of mechanization, but I think it's important to think of machines as supporters of sake brewing, capturing, sharing, and recreating the essence of the sake brewer's vision.

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