Making yeast starter (mototate) is the process of multiplying the yeast.
Yeast is a microorganism that lives in various places in this world, including in the air and on the surface of plants. Bread, beer, wine... Different types of yeast are used depending on what you are making, and sake yeast is used for sake brewing. In this article, we will talk about the manufacturing process of fast-fermenting yeast starter (sokujomoto).

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.

● Alcohol is yeast farts and pee
Sake yeast feeds on the sugar in rice to survive. The starch in rice is converted into sugar by the enzymes in the koji, and the yeast feeds on the resulting sugar. When the yeast becomes full, it excretes alcohol and carbon dioxide. Sake is made by utilizing the physiological phenomena of yeast.

● Mizukoji and preparation
To cultivate the yeast that turns rice into alcohol, first koji rice and water are placed in a small vat (tank) called a motooke and mixed well. Mizukoji is made by dissolving the enzymes in the water so that the enzymes in the rice koji can act evenly throughout the yeast starter. This mizukoji is mixed with cooled steamed rice, brewing lactic acid, and yeast to create what is called the fast-fermenting yeast starter, which is the most commonly used type today, and takes about two weeks to complete. In contrast, kimoto yeast starter, which incorporates lactic acid found in nature (inside the brewery), takes about one month to complete. For more information on the difference between fast-fermenting and kimoto yeast starters, please refer to "Sake Begins with Moto" in this series.
Because the motooke (shubo tank) is open, the shubo is made in a room called the motoba (motoba), which is kept at a room temperature of about 5°C, to prevent the infiltration of microorganisms that are not beneficial for sake brewing (germs and wild yeasts).

● Pumping
The yeast starter is not made just by adding ingredients, mixing them, and waiting. As soon as the ingredients are added, a cylindrical container with holes smaller than a grain of rice called a kumikake vessel is inserted into the center of the tank. This allows the enzyme liquid from the koji to accumulate inside the kumikake vessel. The accumulated enzyme liquid is scooped out with a ladle and sprinkled on the steamed rice on the outside of the kumikake vessel. This ensures that the enzymes are distributed evenly throughout the vessel. The process is carried out once or twice an hour, over the course of a day and a night.

● Utase (watering) and warm air (air supply)
The period during which the product temperature is lowered and kept low is called Utase. A paddle is used every 4 to 5 hours to even out the temperature.
Next, barrels called dakitaru, which act like hot water bottles (they are often made from resin or stainless steel; wooden ones are rarely used), are placed into the tank to raise the temperature and promote saccharification.

● Swelling, starting the brewing, resting the brewing, dividing, drying the yeast starter
As saccharification progresses, the yeast grows using the sugar produced as a nutrient source. Alcoholic fermentation begins, carbon dioxide is released, the volume of the yeast starter increases, and bubbles form on the surface. This initial appearance of bubbles is called "rising."
The temperature is further raised to activate fermentation. The amount of carbon dioxide released increases and bubbles cover the entire surface. This period is called "wakutsuke" and the temperature is raised again the next day. The temperature reaches about 20 degrees.
Active fermentation causes the yeast to generate heat and maintain the temperature of the sake itself. During this period, workers can take a break from heating the sake, so the brewing is called "wakatsuki hiatus."
Once the fermentation is moderate, the fermentation process is slowed down by rapid cooling. After dividing, the temperature is kept below 10 degrees, suppressing yeast activity and allowing the microorganisms to continue to work peacefully, bringing out the aromatic compounds. This resting period of about 1 to 2 weeks is called drying the yeast starter. It is no exaggeration to say that the enchanting aroma and relaxing flavor depend on drying the yeast starter. Keeping the microorganisms working happily or resting... sake brewers are kind of like middle managers.

Next time: [Tell me what you can't ask now!? Series 11]Don't let germs get in your way! ~A sake brewery where germs are not allowed to enter~
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