In all episodes, we talked about "moromi brewing".
As sake brewing becomes increasingly busy, it is not enough to just add all the ingredients after the "Tome-Zoe" step to make sake. There is still work to be done to ensure that the moromi continues to ferment healthily.
This time, I will talk about how to manage mash.

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.

● Moromi health check: Baume degree
The important thing in managing moromi is to understand the changes in its components and to balance the saccharification and fermentation. To do this, we measure the specific gravity of the moromi.
As the amount of glucose increases, the specific gravity increases, and as the glucose is converted into alcohol, the specific gravity decreases. This determines whether saccharification or fermentation is dominant, and is measured as the "Baume degree."
Baume degrees is a unit of measurement that is determined by measuring the specific gravity of a liquid, and in the case of moromi, it is used to measure the percentage of sugar. The unit name was named after Antoine Baume (1728-1804), a French chemist known for his research into liquid density measurements. The unit symbol is Bh. The higher the Baume degree number, the more sugar there is. The "Nihonshu-do" (sake meter), which is also a unit of specific gravity, is Nihonshu-do = (-10) x Baume degrees, and 3Bh is about Nihonshu-do -30. If the specific gravity is high (a large negative number. Most sake brewers use -30 as the standard), the Baume degree is used instead of Nihonshu-do. The Baume hydrometer, which measures the Baume degree, is shaped like a fishing float with a scale, and is submerged in liquid to measure how much it protrudes above the surface. People have their weight and body fat measured during health checkups, but for moromi, the specific gravity is measured.
For the first 3 to 4 days after fastening, the Baume factor increases as saccharification takes place first. From the fifth day onwards, the Baume factor begins to decrease.

● A nerve-wracking battle!? ~ Temperature control to the nearest tenth
When managing mash, it is important to check whether the desired yeast is multiplying purely and to ensure that the mash follows a temperature course that suits the characteristics of the yeast used.
If the temperature of the mash, which generates heat due to yeast proliferation and alcoholic fermentation, is too high, fermentation will proceed too quickly and easily volatile aromatic components will escape into the air. If the temperature is too low, the steamed rice will not dissolve easily and fermentation will stop. Sake brewers are placed in a state of nerve-wracking, continually adjusting the temperature by 0.5 to 0.3 degrees while keeping an eye on the state of the yeast and the dissolution of the steamed rice.
Some breweries use jacket tanks, which are double-layered tanks with an outer tank called a jacket, through which cold or hot water flows depending on the situation, while others wrap hoses around the tank to allow cold or hot water to flow. Recently, many breweries have introduced thermal tanks with temperature sensors that circulate refrigerant liquid or refrigerant gas, in an effort to reduce the burden on brewers.
The number of days spent checking the mash's condition can be as short as 15 days or as long as over a month... The fermentation period from the addition of the mash to the squeezing of the mash is called the "moromi days."

● Bubbles
The last topic is about "foam" which is an indicator of the progress of fermentation. (However, if you are not using non-foaming yeast)
Two to three days after the addition, the surface of the still-hard mash is pushed up from below by fermentation, causing several cracks and the appearance of streaky bubbles called "sujiawa" (also known as "crab bubbles").
After the streaky bubbles come the soft, white raised "mizuawa" (water bubbles). When the bubbles become more viscous, thicker and higher, and resemble rocks, they are called "iwaawa" (rock bubbles).
When the rock foam grows taller and becomes thick, sticky, and resistant to disappearing, it is called "takaawa."
During this time of vigorous fermentation, a process called "defoaming" is required to prevent the foam from overflowing.
Once the high foam has passed, fermentation has reached its peak and the foam, having lost its viscosity due to the alcohol produced, disappears. This is called "ochiawa".
After the foam falls, what appears is the "tamaawa" foam. Puffy bubbles float on the surface of the almost liquid mash.
Once past the Tamaawa stage, the fermentation speed slows down, the amount of carbon dioxide produced during fermentation also decreases, and tiny "crepe bubbles" can be seen on the surface.
When the crepe bubbles become even smaller, no more bubbles form, and the surface becomes almost flat, it is called "ji" or "bouzu".
In the final stage of moromi, the yeast dies from the alcohol it produces. During this time, dead yeast cells and rice residue may rise to the surface of the moromi, which is called "futa" (lid).

The rice has finally disappeared, but it will be a while before it turns into sake and is ready to be enjoyed by all.

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