Sake Brewing process

Sake Brewing process

Sake is defined as sake made from rice, rice koji and water.and water. It undergoes fermentation and filtration, with an alcohol content of 22% or less. 

Simply saying,

Making sake is Enzymes in the rice malt break down the starch in the rice into sugar. The sugar is then converted into alcohol by the yeast.

Let's look at each step of the sake brewing process.

sake brewing process
sake brewing process


The outer part of brown rice is hard, making it difficult for the koji mold to grow into the center of the rice when making rice koji. Therefore, to facilitate the growth of the koji mold, the rice is polished, removing the harder outer layers and revealing the softer parts.

 The center of the rice contains a high concentration of starch, while the outer layers are rich in nutritious proteins and minerals. Polishing the rice results in the loss of nutritional value from the outer layers, which is why a significant amount of polishing is preferred to achieve a clean and refreshing taste in sake production. Conversely, when less rice is polished, the resulting sake tends to have a milder flavor.


After rice polishing, there may still be traces of bran remaining in the rice. If the rice is used as is, it might not be possible to achieve the desired flavor in sake production. Therefore, it is necessary to thoroughly wash the rice to remove any remaining bran.


The purpose of soaking the rice in water after washing is to ensure that the water is absorbed evenly throughout the rice, reaching its center. Once the rice has absorbed the necessary amount of water, it is ready for sake brewing

The duration of the rice soaking process varies depending on the condition of the rice and the level of polishing it has undergone. Well-polished rice absorbs water more rapidly, necessitating precise time measurements to adjust the soaking period.


Steamed rice should have a 'hard on the outside and soft on the inside' texture and feel light to the touch. This texture makes it easier to break up during the process of making koji and facilitates the penetration of the koji mold's mycelium.

The rice is typically steamed for approximately 50 minutes. During the final 10 minutes, the rice is steamed at a high temperature to remove surface moisture. Ideally, the rice should have a dry surface while retaining some moisture on the inside.

Column:"Steaming rice" instead of "cooking rice"!?

When rice is 'cooked,' it tends to absorb more water than necessary, resulting in a softer texture on the outside. However, by 'steaming' the rice, we can achieve the desired moisture content, producing steamed rice that is more conducive to the enzymatic breakdown of starch by the koji mold.

Making koji

In sake brewing, there is a saying: '1 Koji, 2 Moto (starter), 3 Making.' This saying emphasizes the order of importance, starting with 'making koji,' followed by 'creating the starter,' and finally 'making the main mash.'

By sprinkling koji mold onto steamed rice, the mold multiplies and leads to the formation of rice koji. The enzymes produced by the koji mold play a crucial role in converting rice starch into sugar, which is then consumed by yeast to produce alcohol and ultimately create sake.

The correct temperature is vital for koji production, prompting brewers to diligently monitor it every few hours, even during the nighttime.


Once the koji is ready, steamed rice, rice malt, yeast, and water are combined to create a starter. The starter is typically prepared in small vats to minimize the risk of spoilage and other issues.

The objective is to cultivate a substantial quantity of robust yeast. The koji mold converts the starch in the steamed rice into sugar, serving as nourishment for the yeast to proliferate rapidly. Lactic acid is introduced to eliminate unwanted bacteria while preserving the necessary yeast. It usually takes approximately 15-30 days for the starter to become to be ready.

Main Fermentation Part

Once the starter is prepared, the main fermentation process commences. Rice koji, steamed rice, and water are incorporated into the starter in three distinct batches, following the "three-step brewing" method.

Within the main fermentation tank, saccharification fermentation by the koji mold and sugar fermentation into alcohol by yeast occur concurrently. This unique process, known as "parallel double fermentation," sets sake production apart from other alcoholic beverages.

Final Part

Since unrefined sake is cloudy due to the presence of lees, it undergoes straining to separate the lees from the sake, resulting in clear sake. Subsequently, the sake is filtered to further eliminate any remaining yeast. Finally, the sake undergoes pasteurization to halt yeast activity before being bottled, completing the process.

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