The Pressing of Japanese Sake: Understanding Traditional and Modern Methods

In this communication, we would like to address a technical aspect of sake production that proves far more decisive than it may seem: pressing, or shibori in Japanese.

Today, it seems obvious that once fermentation is complete, the brewer must press the moromi — this fermented mixture of rice, water and koji — in order to extract the clear liquid that corresponds to the sake we know.

Preparation of Fukurozuri, pressing the moromi in cloth bags

But this has not always been the case. Before the appearance of pressing techniques, sake was a cloudy drink with a thick texture, carrying powerful and rustic flavors. From the 16^th century onward, with the gradual implementation of new methods, sake began to refine, becoming clearer and more structured.

Brewers then started distinguishing the different pressing fractions — beginning, middle and end — to vary styles and increase aromatic complexity. Ultimately, the introduction of pressing marked the beginning of a standardization of sake’s flavor profile.

Different ways of proceeding were developed over time. Here, we briefly retrace their historical evolution while describing the influence of each on the aromas of the final product.

The main pressing methods

Fune-shibori (槽搾り)
Traditional box press

This method appeared in the 16^th century with the rise of independent breweries and marked the beginning of a new era. Its principle consists of placing the moromi in cloth bags (saka-bukuro) stacked inside a wooden press (fune). The liquid first drains under the weight of the bags, then under controlled pressure applied manually or mechanically.

Pressing method used for Fune-shibori sake production

This method makes it possible to separate three fractions:

• Arabashiri: liquid that flows without pressure, slightly cloudy, lively.
• Nakadori: the middle fraction, more balanced and aromatic.
• Seme: the final fraction, more bitter and tannic.

Chemically, Arabashiri contains many volatile esters (ethyl acetate, ethyl caproate) responsible for fruity and floral aromas. Its higher levels of succinic, lactic and acetic acids increase freshness and acidity, and it also contains glutamic acid (umami).

In the Nakadori fraction, organic acids and aromatic alcohols are well preserved: isoamyl alcohol (banana), ethyl lactate (creaminess), succinic acid (umami) and malic acid (fruitiness). The Seme fraction contains more phenolic compounds, bringing bitterness and structure.

Today, this method is reserved for high-end sakes: it requires skill and can take up to two days.

Fukurozuri (袋吊り) or Shizuku-shibori
Gravity pressing

Appearing in the 17^th century, this technique is an evolution of Fune-shibori. Here, the moromi is poured into small bags suspended above a tank. The sake drips out slowly, purely by gravity, without any applied pressure.

Fukurozuri during the sake pressing process

Tobinkakoi, jars containing high-end sake

This gentle extraction preserves fragile volatile compounds. Fewer proteins and lipids are extracted, resulting in silky, clear, elegant sakes highly valued in competitions.

The yield is low: a slow, expensive method, but one of remarkable finesse.

Assaku-ki (圧搾機)
Yabuta pressing machine

Introduced in the 1960s, the Yabuta machine was designed to automate pressing. It was quickly adopted for its efficiency and is now the most widely used system in modern breweries.

Yabuta machine in a sake brewery

The moromi is placed between frames equipped with inflatable membranes that apply uniform pressure through cloth filters. The sake is extracted while the lees remain trapped.

Its advantages:

• Fast pressing (under 24 hours)
• High yield
• Clear, stable sake
• Suitable for both large volumes and premium Ginjo/Daiginjo

In return, some subtle aromas are less preserved due to mechanical pressure. Succinic and lactic acids remain, contributing body, umami and roundness.

Kasubuaï: a key indicator

Kasubuaï, composed of kasu (lees) and buai (ratio), is the percentage ratio between the weight of the lees and the weight of the rice used.

• High Kasubuaï (>40%): incomplete fermentation, gentle pressing, or a richer, less filtered style.
• Low Kasubuaï (<30%): more complete transformation, typical of refined Daiginjo.

Use of kasu in Japanese cuisine

What about kasu?

Kasu is produced in large quantities each season. It