7. Selection of raw rice

Some sake brewing rice has a fragile part in the center called shinpaku, which is not found in rice for eating. If the rice is polished down to this shinpaku, it will break and cannot be used for sake brewing. The size and shape of the shinpaku varies depending on the rice variety, and flat polished rice is characterized by the fact that it is polished from the depth, so it is not suitable for varieties with a large shinpaku.

The cloudy part of sake brewing rice

In addition, like table rice, sake rice is soaked in water before use, but the amount of soaking is strict when it comes to sake, and when it comes to flat-polished rice, it tends to be difficult to judge the soaking amount just by appearance. Therefore, we will utilize our experience with conventional spherical polished rice.

The four varieties of rice used at Taketsuru Sake Brewery are Hattan 35, Hattan Nishiki No. 1, Kairyo Omachi, and Nakasei Shinsenbon. Due to the shape of the core, Hattan 35 and Nakasei Shinsenbon are most suitable for flat polishing.

Hattan 35 is characterized by its ability to develop a deeper flavor as it ages, making it a variety well suited to Taketsuru Sake Brewery's theme of "making food delicious." As a result, it is also well suited to observing the change in the deterioration odor caused by aging. For this reason, we chose Hattan 35 as the raw rice.

8. Rice polishing ratio

As for the extent to which the rice should be polished (called the polishing ratio), we decided to remove 35% of the surface rice (65% in terms of the polishing ratio), based on the condition that the germ remains and that Taketsuru Sake Brewery has a proven track record of doing so.

Hattan 35 size flat polished rice

Spherical polished rice of 8tan 35 size

9. Selection of yeast ~How to deal with "rapid fermentation"~

As mentioned in 6 on the previous page, in "flat-polished rice with germ left in,"

II. Fermentation progresses rapidly in the early stages, affecting quality

This problem occurs. In sake brewing, yeast has a certain life span, and if the early fermentation is too active, it will die early in the later stages, leading to insufficient fermentation and the development of unpleasant flavors. This can be solved by forcibly cooling the sake with a cooling machine to suppress the activity of the yeast, but this is a method that is difficult to adopt at Taketsuru Brewery, which is committed to brewing sake rooted in the local climate and reducing the environmental impact.

Taketsuru Sake Brewery has a yeast called "Taketsuru No. 6", which is a mutation of the sake yeast "Kyokai No. 6" sold by the Brewing Society of Japan. There are several "Kyokai yeasts" in order from No. 1, but No. 6 and onwards are related (excluding No. 8), and all except No. 11 have a strange property for sake yeast, being weak against the alcohol they produce. In 2000, Taketsuru Sake Brewery obtained a yeast that had acquired resistance to alcohol through a mutation of Kyokai No. 6, and uses this yeast as "Taketsuru No. 6". Yeasts that are resistant to alcohol often become sluggish in the early stages of fermentation, and this yeast is no different.

Therefore, we decided to address the issue of the initial rapid fermentation that occurs with "flat-polished rice that retains the germ" by using "Taketsuru No. 6".

Taketsuru No. 6

The yeast starter is a culture of yeast necessary for the fermentation of sake, and there are several methods for this. Taketsuru Sake Brewery uses two methods: the "kimoto" method established in the Edo period and the modern-day "sokujo" method.

Kimoto brewing contains many ingredients that bring depth to the flavor of sake, but they also interfere with each other and make the flavor difficult to understand. We felt that this was not suitable for the purpose of comparing the flavors of flat and spherical polished rice, so we decided to use a quick brewing method for the yeast starter.

10. Types of yeast starter (moto)

11. Preparation period

We decided to use Taketsuru No. 6 to deal with the rapid initial fermentation, and to be on the safe side, we decided to brew it around Daikan, the coldest time of the year.

The rest of the process was carried out in the usual manner at Taketsuru Sake Brewery, and perhaps as a result of careful prior research, there was no rapid initial fermentation and everything went smoothly.

Fermentation process of flat polished rice

Fermentation process of spherical polished rice

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