Process of brewing Japanese sake

1. Polishing rice

This operation is to sharpen (polish) the whole rice, the main ingredient of sake.
Proteins and fatty acids in the layer surrounding of brown rice are diminished by polishing because too much gives a varied taste that influences the taste and flavor of sake.
The polishing ratio is called the polishing rate of the rice, and it is said, for example, that polishing at 30% of the whole rice yields a polishing rate of 70%.
Depending on the polishing rate and ingredients, sake is classified into the following categories.

2. Washing rice

* The picture above shows the cleaning method using an air mixing water jet pump. 

This is the stage where we wash the rice that has been polished.
Thanks to this work, the bran and dust that cover the surface of rice are removed. It is an operation to which one must pay careful attention, important enough to be referred as “second polishing”.
The washing process, especially by machine or manually using a dish rack or bag, differs depending on the breweries and produced sake.

3. Soaking rice

After cleaning, water is absorbed in rice for a fixed period of time.
The soaking time varies according to the variety of rice, the state of the harvest different from year to year, the rate of polishing, and the targeted quality of sake. Rice that has been bleached to a high degree, absorbs water fast, so we control soaking to the nearest second with a stopwatch (limited water absorption).
After soaking, draining is done, and steaming is prepared for the next day.

4. Steaming rice

This operation comes after cleaning and soaking rice.
It takes approximately one hour.
As a steamer, the traditional instrument, koshiki, or the latest continuous steaming machine is used; some brewers place a lot of importance on these facilities.
The steamed rice is mixed with malt, yeast mash and main fermenting mash. It is let cool to the appropriate temperature for each stage (cooling).  

5. Preparation of malt

This is the stage where we prepare malted rice that changes starch contained in rice into sugar (kome-koji) . This takes place in a high temperature and high humid space (30℃) that the we call room for koji (koji muro).
The work involves sprinkling seed malt (spore of yeast cell, known as bean sprouts) over the horizontally spread steamed rice, unraveling the rice so that seed malt spreads uniformly and fermenting with wrapped in a sheet of cloth.
Then, to ferment it for two days under the control of rice temperature lets yeast cell increase in steamed rice and it becomes malt finally.
Some brewers are starting to use automatic processing machines that can reduce labor and get malt in a consistent quality.


6. Preparation of yeast mash

The yeast mash cultivates yeasts that turn carbohydrates into alcohol, and makes them reproduce in large quantities.
The yeast of this sake is called “Moto”, and is an important element to become the basis of sake.
In the culture room (or chamber of the yeast mash) maintained at low temperature, malt obtained previously, water, yeast mash and steamed rice are added and mixed, and the yeast mash is prepared.
At the moment when this must is prepared, lactic ferments are added to prevent bacteria from developing.
Depending on how the lactic ferments are added, yeast mash is either “quick leaven (sokujô)” or “natural leaven (kimoto)”.
Quick leaven is yeast mash that adds lactic ferments for artificial fermentation at a high level of purity. The culture time is 2 weeks. Most of yeast mash of current sake are made in this Sokujô method.
Natural leavening is a traditional technique established in the Edo period. The lactic acid bacteria in the air are mixed in yeast mash and the lactic ferments develop. Crop time is 1 month. It requires more time and work than quick leaven, but Breweries that use this method are increasing.
“Yamahai” is a process that simplifies this process of natural yeast, and thus constitutes a type of “Kimoto yeast mash”.


7. Preparation of main fermenting mash (moromi)

This is an operation to get main fermenting mash by adding malt, steamed rice and water to yeast mash obtained in the previous step.
This work is divided into three phases, first addition, second addition and third addition, they call this unique method of sake “the three stages of preparation”.
The day after the addition of the priming mash in the vats full of cooked rice and water, the preparation is allowed to rest for a day, a pause that is called “the rice dance”, and thus accelerates the reproduction of ferments.


8. Fermentation

departure: the fermentation takes between 20 and 30 days.
During this time, two processes take place at the same time in the main fermenting mash, the conversion of starch into sugar by malt and “the fermentation of alcohol” that is due to the yeasts. This is called “parallel multiple fermentation”, this high-level fermentation system is unique in the world.

9. Pressing

This operation includes the action of pressing main fermenting mash at the end of its fermentation and that of dividing the alcohol of Sake and sake lees.
Among the means of pressing, there is in particular “the automatic press (type Yabuta)” which works with bellows and press on both sides, “the press fune (type Sase)”, a system where bags of sake are piled on a wooden structure called fune and which gradually presses from the top, “the draining in bags of Sake (tobindori or shizukudori)” which collect drops in drums that fall under their own weight, or “centrifuges” which use centrifugal force thanks to a high speed rotation movement.
At the moment of pressing, we call the first cloudy sake “Arabashiri” which flows naturally before pressing, “Nakadori (Nakazumi)” the middle sake which comes out when the pressing force is gradually applied, and “Seme” obtained last by pressing strongly. The first sake “Arabashiri” has a light aroma and provides a refreshing sensation, the second “Nakadori” has an excellent balance of aroma and flavor, while the latter “Seme” has a strong bitter taste.
The three decoctions are usually mixed and the product is marketed, but these are sometimes bottled separately and are sold as items that prompts you to enjoy their different peculiarities. “

10. The removal of dregs

This work consists in letting sake rest for a certain time at the end of pressing, and let the last dregs settle in the bottom.
These dregs are called “Ori”.
Normally we sell only the top clear layer without any dregs.

11. Filtering

This process is removing lees left in sake, even though the dregs have been removed. sake that are unfiltered are specified “No filtration”.

12. Pasteurization

This is the most important step that decides the quality of sake.
Pasteurization means the thermally sterilized at low temperature. The goal is to stop action of the last germs in sake and remove bacteria that could affect the flavor and taste of Sake. By pasteurizing, it becomes possible to keep for a long time.
There are two methods of pasteurization: (1)”Bottling of pasteurized sake” which uses a pipe or a hot plate (a heat exchanger), a method of bottling after pasteurizing, or (2) “Pasteurization of bottle” that is heated in a water-bath using the latest pasteurizers which allows pasteurization after bottling. The second method helps sake keep even more fresh.
Until now it was normal to carry out two pasteurizations before shipping, but recently the improvement of pasteurization techniques, the development of transport technologies and the deepening of the control of refrigeration allows more and more Sake brewers to choose only pasteurize with fewer damages to sake. sake that hasn’t been pasteurized at all are called “Nama-zake”.

13. Bottling


This operation involves filling the bottles one by one with sake.
There are manual and automatic methods.
In the case of bottled pasteurization, pasteurization occurs after this operation.
sake that has been bottled and kept at low temperature (bin chozo) is shipped waiting to be drunk.