The first step is rice polishing. Once the rice has been polished, it is washed, steeped in water, and steamed. It is very important to control absorption of water into rice at the steeping process, because the water content affects the condition of steamed rice.
Steamed rice is used to make koji. Then the koji is mixed with water and yeast and further with steamed rice to make “starter”. The “starter” is, in short, a dense culture of sake yeasts. In the next step, the steamed rice, koji, starter and water are mixed to prepare the main mash. The main mash is slowly fermented at low temperatures: this is one of the unique characteristics of Niigata sake production. For making premiums sake, it takes 30 days or more at temperatures of fifty degree or lower.
After fermentation and prior to filtration, distilled alcohol may be added to make specific types of sake. The whole set of production process is repeated until the sake producer obtains desired volume for the winter season.

After fermentation has been completed, the raw sake is filtered, pasteurized and stored for maturing. It is stored for 6 months to a year for maturation. And then it is blended to level off quality. The final stages are the second filtration, the second pasteurization, and, finally, bottling.

Let’s take a look at the production process step by step.
First comes rice polishing. The outer layer of the rice contains nutrients like proteins, fats and minerals. These substances cause unpleasant flavors in the final product. So, in general, the more the rice is polished, the better the quality of sake.
As friction heat may cause rice to break down, it is polished slowly. It takes 72 hours to polish rice to 40% of the original grain.

Rice milling machines at Kiminoi Shuzo

Polishing is followed by washing and then steaming. After rice has absorbed water at steeping step, it is put onto a steamer called Koshiki which steam comes upward.
In this photo, they are taking out steamed rice after steaming was done.

Steamed rice

Steamed rice is spread out on cloth for cooling it. Cooling machine is also used for a large quantity.

Rice cooling

He is sprinkling koji mold in powder onto steamed rice. They let koji mold grow on the rice for two days.

Koji making

The next step is preparation of starter mash. He is pouring steamed rice into the mash. Selection of yeast variety is very important as it is a decisive factor for quality of aroma.

Yeast starter

This is the main mash under fermentation process. Creamy foams come up on the surface as fermentation proceed. The propeller is rotating to prevent foams to overflow from the tank. The foams goes lower when fermentation nears the end. Skillful sake master can tell how the fermentation is going by checking condition of the surface of the foam.

Main mash under fermentation

After fermentation process, the main mash is filtered by pressing machine like this. He is taking sake lees from the pressing machine.

Pressing

This is traditional pressing. They put main mash into a cloth bag, pile it onto a box and press it. It is very labor-intensive and time consuming method. By using this method, sake has more aroma and clean finish. Only used for ultra super premium sake.

Pressing traditional method

After filtration, sake is pasteurized and stored for maturing in a tank like this. It takes a half to one year for sake to get matured. Storage is at temperature of 60 deg or lower. Degree of maturation varies tank by tank. To obtain quality and taste that a producer wants, sake in these tanks will be mixed to get final products. Until sake is bottled, it is controlled under strict conditions to gain best quality. After bottling, quality is easily deteriorated by high temperature and/or light. It is highly recommended to store sake at dark and cool place. Drink it up sooner rather than later once you open it.

Storage for maturation