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035-How-to-make-sake
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From Grains to Glass: How Sake is Made

Tom Inoue

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Have you ever wondered how sake is made?

Sake is made through a complicated process, which may be quite difficult to understand. But learning it is key to understanding its flavor and diversity, which will no doubt aid you in selecting one for yourself.

This article helps you understand the basics of sake-making and will help you identify the sake that will best suit your preferences.

Brief overview of Sake-making

  1. Preparation
    • 1.1 Rice
    • 1.2 Koji
    • 1.3 Yeast
  2. Fermentation
  3. Squeezing
  4. Filtration, Pasteurization, and Mellowing

1. Preparation

1.1. Rice

Polishing

Sake uses the starch found in the white core of the sake rice grain (as seen in the picture).

rice

Photo Credit: https://www.pref.chiba.lg.jp

The outer, transparent layer is rich in vitamins, proteins, and fat. While these can add a rich flavor to sake, they may also generate unfavorable flavors.

Because of this, rice is polished to create a finer, cleaner-tasting sake. Generally speaking, the more polished the rice, the higher the quality of the sake becomes.

It does not necessarily mean, though, that the higher quality sake always tastes better. As a matter of fact, sake using less polished rice tend to have richer flavors (i.e. Regular Junmai-type, Honjozo-type, or regular sake). While those using highly polished rice tend to be light and more aromatic (i.e. Ginjo or Daiginjo-type). Select the type of premium sake with your personal preference in mind.

polishing

Photo Credit: A comprehensive guide to Japanese Sake

polishing

Do note that the type of premium sake doesn’t necessarily equate to rice-polishing ratio. For example, a Honjozo-type sake may be polished to more than 60%. Use the label to find the rice-polishing ratio of the sake you’re interested in.

When rice is polished, the heat that is generated changes the properties of the rice and dries it out. To minimize this impact, polishing is done slowly. To polish rice to 35% of its original size takes an entire three days!

rice polisher

Rice polisher at OZAWA brewery

Once polished, the rice is stored for 2-3 weeks in order to stabilize its temperature and moisture.

Steaming

In order for rice starch to be used for sake-making, it needs to gelatinize. This is because Koji mold can only convert into alcohol starch that has gelatinized. Steaming is the best method to attain this.

Rice grains are first washed, then soaked in water. The grains absorb water while water vapor effectively heats and softens the grains. However, over-soaking the grains may cause them to break. Thus, soaking time is strictly measured on a second-timed scale.

steaming cauldron

Soaking process at IZUMIBASHI brewery

Steaming takes place in a cauldron. Steam works through the rice from the bottom of the vat making rice slightly hard on the outside and softer inside. As a result, Koji fungi can easily adhere to the rice surface for the next process.

steaming

Steaming at YAMANAKA brewery

steamed rice

Rice right after steaming

To prepare for the next steps, rice is first cooled down to room temperature.

cooled rice

Photo taken at OZAWA brewery

1.2. Koji

Koji is rice that has been inoculated with Koji fungi. Koji fungi decomposes rice starch into sugar (glucose).

koji

Koji Fungi (Aspergillus oryzae)

To make Koji, the fungi are sprinkled onto the steamed rice gently by hand. The rice is kept warm and hand-mixed several times to ensure that majority of the rice grains are covered with Koji fungi.

mixing

mixing by hand

Photo taken at YAMANAKA brewery

The mixing process takes place in a room at >85°F (>30°C) and is done every couple of hours for several days, making this process tedious and laborious.

The finished Koji has white patches on its surface.

finished koji

Koji is then stored and cooled. As you see in the picture below, it is laid out in a ridged pattern to increase the surface area for drying.

drying

Photo taken at IZUMIBASHI brewery

1.3. Yeast

For the next step, the newly prepared Koji and a new batch of steamed rice are mixed with yeast and water to produce yeast mash.

yeast mash

Yeast mash at Yoneda Brewery
Photo credit: http://www.toyonoaki.com

The key to this process is to keep the mash acidic, since yeast can only survive and compete against other microbes in an acidic environment.

To keep the mash acidic, two different methods are employed:

Traditional, slow method

This method uses naturally-occuring lactic acid bacteria. Lactic acid bacteria are placed into the mixture of rice, koji, and water. As they grow, they produce acid. The yeast is then added.

The mash is kept at low temperatures for long periods of time to control the activities of the lactic acid bacteria.

traditional

The by-products of the lactic acid bacteria used in this method contribute to the rich taste of sake. Choose Kimoto or Yamahai types of sake to taste this richness.

Quick Method

In this method, artificially-produced lactic acid is added into the mash. This is much easier to manage and doesn’t require great care, unlike the slower, traditional method.

quick method

The sake produced through this method tends to have a light flavor. Majority (90%) of sake in the market are produced through this method.

2. Fermentation

From the yeast mash, more water, steamed rice, and Koji are added to create a fermentation mash.

fermentation mash

Photo taken at YAMANAKA brewery

Similar to the yeast mash, the fermentation mash should also be kept in acidic conditions. Since adding ingredients to the yeast mash may disrupt its acidity, most breweries add the steamed rice, water, and Koji mixture in three parts for four days.

mash mixture

Once the fermentation mash is developed, it is kept under strict temperature control. Generally the temperature ranges between 50-68°F (10-20°C).

Fermentation lasts for 2 weeks to 1 month.

fermentation

Fermentation Tanks

tanks

Fermentation mash inside one of the tanks in OZAWA Brewery

As fermentation occurs, a separate reaction called ‘Saccharification’ (conversion of starch to sugar) occurs simultaneously. This ‘parallel fermentation’ makes sake production unique.

parallel fermentation

The appearance of the mash changes through time. Once the form of the mash becomes more homogenous, fermentation gradually slows down.

Day 2
day 2

Day 4
day 4

Day 6
day 4

Day 8
day 6

Day 10
day 8

Day 12
day 10

Day 20
day 12

At the end of fermentation, a small amount of alcohol is often added (less than 10% of rice by weight).

When this done, the sake is called Honjozo-type. Honjozo-types of sake include Honjozo, Ginjo, and Daiginjo sake. They have a more aromatic and lighter taste compared to other sake due to the addition of distilled alcohol.

When no distilled alcohol is added, the sake is called Junmai-type (i.e. Junmai, Junmai Ginjo, Junmai Daiginjo), which has a richer taste but is less fragrant than Honjozo-type.

Other sake, like regular sake or Futsu-shu may have more than 10% alcohol added to increase its volume.

3. Squeezing

After the fermentation, sake goes through some more processes before going commercial. These processes may alter its flavor, positively and/or negatively.

Having this in mind, some types of sake are not made to go through these processes. And they are named accordingly, in each case.

Once fermentation is completed, sake is squeezed out from the mash. There are three ways of squeezing. The quality of sake also changes depending on the method used.

3.1. Automatic squeezer

automatic squeezer

Photo taken at OZAWA brewery

This machine has 100 filters with an automatic pressing system that enables mass filtration of fermented mash. Among the three methods, this is the easiest and also the most utilized. The downside to it is that this strong, automatic pressure may extract unfavorable flavors from the fermented mash or sake cake.

3.2. Fune-shibori

In this method, the fermented mash is placed in pieces of filtering cloth which are piled up on a rectanglular box called ‘Fune’ (this means ‘ship’ in Japanese). The bags are then pressed. Sake made through this method tends to possess natural flavors brought about by gentle pressing.

To try this sake, find one that is labeled ‘Fune-shibori’.

fune-1

Fune-shibori at ASAMAI Brewery
Photo credit: amanoto.co.jp

fune-2

Photo taken at IZUMIBASHI brewery

3.3. Fukuro-tsuri (hanging-bag)

This is the most superior method among all 3 methods. In this method, sake is placed in pieces of filtering cloth and then hanged together. The new sake drips down to the bowl or catch basin. Only a small amount of sake can be extracted through this method, making the end result very expensive.

fukuru-tsuri

Photo credit: www.fukukoma.co.jp

The resulting sake has a gorgeous and delicate fragrance. Find ‘Shizuku zake’ or ‘Fukuro-zuri’ label to experience this sake.

Sake that has not gone through the squeezing process is also available. It is called ‘Nigori’ or cloudy sake. It is characterized by its rich and creamy taste, and it often comes sparkling.

The leftover – sake cake – is often used in Japanese dishes or drinks. When you visit a sake brewery, you have the option of buying this as part of the brewery experience.

sake cake

Sake cake

Separating the sake from the lees

Squeezed sake is yellowish in color and contains lees.

lees

To remove the lees, sake is skimmed. In the picture below, the supernatant liquid is separated and goes through the upper pipe of the tanks.

skimming tanks

Photo taken at OZAWA brewery

The lees themselves contain savory notes of roasted meats, herbs, and spices which are preferred by some people. Sake made without skimming is called ‘Origarami’ or ‘Usu-nigori’.

4. Filtration, Pasteurization, Storing, and Mellowing

Filtration

To remove the yellowish color of newly made sake, it is filtered. Dozens of filters remove small particles from sake in the photo below. Activated charcoal is sometimes used in addition to regular filtration, thereby creating a completely transparent liquid.

filtration

Photo taken at OZAWA brewery

The second-round of filtration, using activated charcoal, is often done when the sake is still turbid after initial filtration. But doing so may remove flavors from sake. In this case, some breweries choose to omit this step. The sake produced is called ‘Muroka’. Muroka sake has a richer taste compared to charcoal-filtered sake and retains its yellowish color.

Pasteurization

The sake is then pasteurization at around 140-150°F (60-65°C) to prevent the growth of unfavorable microbes and to stop the action of the enzymes.

A spiraled pipe in the photo below is commonly used for pasteurization. Sake goes through the pipe which is immersed in hot water.

pasteurization

Photo taken at YAMANAKA brewery

Pasteurization also affects the taste of sake, in that some of its freshness is lost. Although there is no “good” or “bad” effect on the taste, some people prefer non-pasteurized sake. If you want to drink fresh, unpasteurized sake, find ‘Nama’ sake. Keep in mind that since it is unpasteurized, consumption should be immediate (within a week is recommended).

Storing

The newly produced sake contains large clusters of alcohol molecules and has peppery traits. As time passes, the cluster breaks down and the alcohol starts integrating with the water molecules, resulting in a more mellow taste. For this purpose, newly produced sake in spring spends the entire summer in storage at around 15°C.

If you want to try fresh sake with a strong punch, find ‘Shin-shu’ or ‘Shibori-tate’. Stored and mellow sake available in autumn is sometimes called ‘Hiya-oroshi’.

After this storage period, sake is once again filtered and pasteurized.

Mellowing

Raw sake has 18-20% alcohol by volume (ABV). The high alcohol content tends to negate the delicate flavor of sake. Thus, most sake are diluted with water to 15-16% ABV, on average.

In addition, sake is also diluted since Japanese law demands less tax for beverages with lower ABVs.

If you want to try strong, raw sake, look for ‘Genshu’ or undiluted sake.

Sake is made through a long and arduous process, usually taking at least 3 months of hard work. But this process has also led to the birth of diverse products and a variety of taste for us to enjoy. Once you get familiar with the world of sake, you will be able to enjoy it in all its forms!

ACKNOWLEDGEMENT

Most of the photos are taken and displayed through the kind cooperation of OZAWA brewery and YAMANAKA brewery.

OZAWA brewery

ozawa

Website (in Japanese only): www.sawanoi-sake.com
English guide available at: www.att-japan.net
Sake brand: SAWANOI

YAMANAKA brewery

yamanaka

Website (in Japanese only): www.hitorimusume.co.jp
English guide available at: —
Sake brand: HITORI-MUSUME (“Only Daughter”)

IZUMIBASHI brewery

Izumibashi

Website: http://izumibashi.com/
Sake brand: TONBO (“dragonfly”), IZUMIBASHI

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Comments:

  1. Thank you for this great post! I’m a long time home beer brewer and wine maker in California who has wanted to attempt to make homemade sake. Digging into the resource I have found in the states has been disappointing since I can’t find much beyond “kits”, something I would never do for beer or wine. BUT I resonantly started watching ‘the birth of sake’ on netflix and saw that they polish the rice by hand! And your details about Fukuro-tsuri I see a path forward. however I can’t find anything online about what those mats they polish on are. Could you point me in the right direction? Thank you!

    1. Hello Leimore
      Thank you for leaving us comments and questions. We were glad that the post was insightful for you.

      About polishing rice, I have never heard of doing it by hands. Usually stone does. A grind stone of emery polishes the rice as it rotates in a cylindrical part of a polishing machine. I guess you misinterpreted the scene of koji making as “hand polishing”. There, workers simply break rice up to single grain on a clean bleached cotton cloth.

      FYI, the clean bleached cotton cloth is also used for Fukuro-tsuri in most cases!

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