How Sake Is Made, Step by Step

Sake is brewed from just three things: rice, rice koji, and water. The path from milling to bottling runs in a single line, but it branches at several points along the way, and those branches are what give one sake a different flavor from the next. We'll start with a table of the whole process, then walk through each step with a quick note on what happens and why it matters. By the end, you'll have a feel for where the terms on a back label come from, and why unpasteurized sake tastes so different from the pasteurized kind.

There's an old saying in sake brewing: "first the koji, second the shubo, third the mash" (ichi-koji, ni-moto, san-tsukuri). It ranks the three most important stages in order: koji (mold-cultured rice) comes first, the shubo, or yeast starter (moto, the seed mash where yeast is raised) second, and preparing the main fermentation mash third. Keep that order in mind and the rest of the process falls into place.

The big picture

Let's start with the overall flow. Turning raw rice into sake follows roughly this sequence. The fermenting blend of rice, koji, and water is called moromi (the fermenting mash). From the first addition of ingredients to bottling takes about 60 days, with the moromi fermentation alone accounting for about 20 of them (long-aged sake is a separate case).

From here we'll cover these 12 steps in four groups: preparation, setting up fermentation, pressing and finishing, and storage and shipping.

Before the rice is brewed (steps 1-3)

The first three steps (milling, washing and soaking, steaming) are the prep work that comes before fermentation begins. Grind the rice, wash it, let it drink water, and steam it. The fourth step, koji making, gets its own section below. These stages look unglamorous, but this is where the backbone of the sake is set.

1. Seimai. The outer part of the brown rice grain is ground away. The surface layers are high in protein and fat, and too much of them brings out rough, off flavors. How far the grain is milled is expressed by the rice polishing ratio (seimai-buai). Junmai, Ginjo, and Daiginjo: What's the Difference covers how to read that number and how it shapes flavor.
2. Senmai and shinseki. The rice is washed, then soaked so it absorbs water. Because even a few seconds of soaking change how the rice steams, the more highly polished the rice, the more precisely the timing is controlled.
3. Mushimai. The rice is steamed rather than boiled. Steaming produces a texture that is firm on the outside and soft in the center, known as gaiko-nainan ("hard outside, soft inside"). That texture is what lets the koji mold grow well.

The steamed rice is then split for three uses: koji, the yeast starter, and the main mash. The same steamed rice plays all three roles.

Making the koji (step 4)

Koji making is the pivotal step that makes all the fermentation to come possible. It's valued so highly that it comes first in "first the koji."

Sprinkle koji mold (yellow koji, koji-kin) over steamed rice and let it grow, and you have rice koji. The mold produces enzymes that break the rice starch down into sugar, a process called saccharification. Yeast can turn sugar into alcohol, but it can't use starch directly. That's exactly why the koji, which converts starch into sugar, is needed.

Koji making takes about two days in a koji muro (a room held at controlled temperature and humidity). It involves a great deal of hands-on work, and it's where a brewery's character shows through. How the mold is worked into the rice, the pattern of haze (the visible bloom of mold on the grain), changes how saccharification proceeds, and that carries through into how light or rich the sake tastes. We dig into this in Milling, Koji, and Three-Stage Mashing.

Making the yeast starter (step 5)

The shubo is the step that raises a large population of yeast, the star of fermentation. Also called moto, it holds the "second" spot in the saying.

Yeast is added to steamed rice, water, and koji, then multiplied intensively. At the same time, lactic acid holds unwanted microbes in check, creating an environment where the yeast can grow safely. How that lactic acid is supplied is where the brewing method branches.

• Sokujo. Brewing-grade lactic acid is added at the outset. It's easy to manage and the process is relatively short.
• Kimoto and yamahai. Traditional methods in which lactic acid is generated naturally through the action of microbes. Sokujo takes about two weeks, while the kimoto family takes about a month and calls for more labor and time.

Kimoto and yamahai also tend toward different flavor profiles, which An Intermediate Lesson in Sake explores.

Three-stage mashing (step 6)

Once the yeast starter is ready, the main mashing begins in earnest, and this is where three-stage mashing (sandan-jikomi) comes in. Rather than adding the rice, koji, and water all at once, they go in over three separate additions.

Why split it up? Adding a large amount of rice and water at one go would dilute the yeast and lactic acid you worked so hard to build, opening a gap for stray microbes to move in. Adding a little at a time lets the yeast keep its concentration while it multiplies, and it makes the temperature easier to control.

The sequence runs over four days.

The deliberate pause on day two, odori, is the key. Only after enough yeast has built up does the volume get ramped up quickly. Working in stages lets the mash grow without ever losing the yeast's upper hand.

Moromi fermentation (step 7, multiple parallel fermentation)

Inside the moromi that comes out of three-stage mashing, something distinctive to sake is happening: multiple parallel fermentation. It's the single most important mechanism to grasp if you want to understand sake.

Multiple parallel fermentation means that saccharification and alcoholic fermentation proceed at the same time in the same tank. The koji enzymes turn starch into sugar. The yeast immediately turns that sugar into alcohol. The two run side by side.

Wine already has sugar in the grapes, so the yeast simply ferments it (a single fermentation). Beer saccharifies the malt first, then ferments it in a separate step (a two-step, sequential process). Sake handles saccharification and fermentation together in one tank. This approach is found in almost no other alcoholic drink.

Because they run in parallel, sugar never builds up too high, and the yeast can keep producing alcohol steadily. The moromi ferments over about 20 days, slowly and patiently pushing the alcohol content up.

Pressing, filtration, and pasteurization (steps 8-10)

When fermentation ends, the moromi is still a mix of sake and solids. From here it's finished into sake you can drink.

Joso (pressing) is the step that presses the moromi to separate the liquid from the lees (sake kasu). Pressing methods include the automatic press (Yabuta), the fune (a box press), and fukurozuri (hanging the mash in bags to drip), and the method itself changes the flavor. Depending on the moment it's drawn off during pressing, the sake also splits into three distinct-tasting portions.

• Arabashiri. The first portion, which flows out on its own before any pressure is applied. Aromatic and lively, with a rough, youthful edge.
• Nakadori (also nakagumi). The middle portion that comes next. Well balanced in aroma and taste, and considered the finest.
• Seme. The final portion, drawn out under strong pressure. Rich in flavor, with a slightly higher alcohol content.

The Craft of Pressing (Joso) covers the finer points of pressing timing and method.

Roka (filtration) adjusts fine cloudiness, color, and rough notes. How much a brewery refines depends on the flavor it's aiming for.

Hi-ire (pasteurization) is a sterilizing step that heats the sake briefly to about 60-65°C. It halts any lingering enzyme activity and holds back hiochi-kin, a spoilage microbe that damages sake. This is what stabilizes quality. Pasteurization is usually done twice: once before storage and once before bottling.

How many times, and when, the sake is pasteurized changes what it's called.

Namazake, which skips pasteurization entirely, is prized for its fresh taste, but its quality shifts easily and it needs refrigerated handling. How to spot these "nama" types on a label is covered in How to Read a Sake Label.

Storage, aging, and bottling (steps 11-12)

Freshly pressed sake has sharp edges. It comes across as harsh and a little rough, so it's rested for a set period.

Much sake is brewed in winter, and the new sake is stored through a single summer. Over that time the flavor pulls together and turns mellow. When a sake improves by passing through the summer, it's called akiagari ("rising in autumn"; for more on seasonal vocabulary, see The Language of Seasonal Sake). Storage most often takes place under controlled conditions such as refrigeration.

To finish, the alcohol content is adjusted with cutting water (wari-mizu), and the sake is bottled and shipped. Every branch point along the way — the rice polishing ratio, the type of yeast starter, whether or not it was pasteurized — is what gives each bottle its own character.

The process in brief

Here are the key points of the sake-brewing process, briefly.

• The order is "first the koji, second the shubo, third the mash." Build it up in the order of koji, yeast starter, then the main mash.
• Koji turns starch into sugar (saccharification); yeast turns sugar into alcohol (fermentation).
• Saccharification and fermentation running at the same time in the same tank is multiple parallel fermentation, the mechanism that sets sake apart.
• Three-stage mashing is a split addition that grows the volume while protecting the yeast.
• The number and timing of pasteurizations produce the differences between namazake, namachozo, and namazume.

Now that you have the whole process in view, the next thing to explore is how the terms connect to flavor. To start from the basics, head to A First Introduction to Sake; to go deeper on the classifications, try Junmai, Ginjo, and Daiginjo: What's the Difference.

• This article is intended for readers of legal drinking age (20 in Japan). Please drink responsibly. Avoid alcohol during pregnancy or breastfeeding, and never drink and drive.