How Sake is Made

1. Rice Polishing 精米

Brown rice is polished down to remove the outer layers made up of lipids, proteins and minerals that can cause negative aromas and flavours in the final product. Sake is made from the starches found in the center of the grain which will be converted into fermentable sugars. The more the rice is milled, the more aromatic, clean and delicate the final sake will be.

2. Washing 洗米

The polished rice is washed to remove the rice bran and crumbs still clinging to it from the rice polishing process.

3. Soaking & Steaming 浸漬＆蒸し

What may seem like simple steps are actually crucial. The washed rice is first soaked in water for a precise period, timed with a stopwatch under the careful guidance of the head brewer. It cannot be a second too short or long, in order to achieve the perfect water content for each grain of rice. Finding the perfect soaking time requires both experience and some trial and error as there are several factors to consider. These include the temperature of the water on that particular day, the rice polishing ratio, the type of rice being used, etc. Once the right amount of water has been absorbed, the rice is then steamed until it is perfectly firm on the outside and soft on the inside. The condition of the rice at this stage will determine every brewing step down the line.

4. Rice Koji Making 製麹

There is an old saying in the sake world that describes the importance of rice koji making: First the koji; second the moto; third the moromi fermentation. The process involves taking 20% of the steamed rice and sprinkling it with koji mould spores. The rice is then bundled up in a mound to keep it warm and promote the growth of the koji mould. Periodically, the bundles are broken up and mixed to ensure the uniform growth of the mould on every grain of rice. After around 48 hours, the rice is finally spread out to cool. The koji muro, a special room where rice koji is made, is kept humid and at around 35°C, which can make for a tough working environment for brewers. The resulting rice koji is what will release diastic enzymes that will break down the long chain of starch molecules found in the center of each rice grain into fermentable sugars that can be used for alcoholic fermentation.

5. Moto/Shubo 酛/酒母

Our namesake Moto (the word Shubo can be used interchangeably) signifies the yeast starter. As you guessed it, this crucial step increases the amount of yeast which can then be transferred into the main fermentation vessel. Moto is made by mixing rice koji, steamed rice, water and yeast in a small vat. There are different methods of making this yeast starter, depending on whether the brewer decides on taking the modern method of adding commercially available lactic acid, instead of the traditional way of allowing lactic acid bacteria to propagate itself naturally. Lactic acid prevents unwanted bacteria from proliferating and unfavourably affecting the flavour. These differences dictate the quality of the finished sake.

6. Moromi 醪

The shubo is moved into the main fermentation tank, or the moromi. It is made by adding water, rice koji and steamed rice in three stages over the course of four days. This process is called ‘sandan jikomi,’ literally three-stage brewing. Such a process is used so as not to dilute the acidic environment. Each stage roughly doubles the size of the mash and once complete, it is left to ferment for 20-30 days. Saccharification (starch to sugar conversion) and alcoholic fermentation progress at the same time in a type of fermentation called ‘Multiple Parallel Fermentation.’ This type of fermentation is the reason sake has a higher alcohol content than other fermented beverages. Depending on the type of sake, a small amount of pure distilled alcohol may be added to the moromi just before pressing, to lighten flavour and bring out aroma.

7. Pressing 上槽

When the moromi is completed, it is pressed to separate the newly created sake from its lees, or the rice solids. There are several different pressing methods. The most common is the use of the automatic pressing machine, or Yabuta (as pictured). Other methods are more time consuming and labour intensive yet allow for a more gentle handling of the sake, resulting in a more elegant and complex flavour.

8. Optional Steps

At this stage, there are a few optional steps a brewer may implement depending on the desired sake style. These include racking (Oribiki 滓引き), filtration (roka 濾過), pasteurization (Hi-ire 火入れ), blending (Chougo 調合), the addition of water (Warimizu 割水), carbon dioxide (sparkling sake スパークリング酒) and maturation either in tank (Chozo 貯蔵) or bottle (Jukusei 熟成). Observing a sake label can tell you a lot as to whether any of these additional steps were taken. For example, if a sake was not filtered, it would claim ‘Muroka’ (無濾過), an unpasteurized sake would state ‘Nama’ (生), a sake without additional water added would be called ‘Genshu’ (原酒).

To find out more about different sake styles, head on over to our Sake 101 or our journal post regarding Speciality Sake Categories.

9. Bottling

Generally after the second pasteurization, the sake is finally ready to be bottled and shipped off. Sometimes, the brewer may wish to age the sake in bottle. If matured for longer than 3 years, the style of sake can be called ‘koshu’ (古酒). The colour of sake will evolve over time to gold then to amber, while creating complex aromas of honey, dried fruits, wood, dried mushrooms and spices. The flavour will become more condensed, the texture rounded and more richness will be provided.