How Is Sake Made? The Five Steps From Rice to Glass
Sake is made in five stages: polishing and steaming rice, cultivating a mould called koji, building a yeast starter, fermenting the main mash, and pressing the finished liquid away from the solids. The step that makes sake unlike wine or beer is the fourth one, where two chemical jobs — turning starch into sugar, and sugar into alcohol — run at the same time, in the same tank. That single overlap is why sake can reach nearly 20% alcohol with no distillation at all.
Everything else in this guide hangs off those five steps. If you have ever wondered why sake is called “brewed” rather than “fermented like wine,” the answer lives in the process, not the marketing. Here is the whole journey, from a grain of rice to the glass in front of you.
What are the five steps of making sake?
At its simplest, sake production is five moves: prepare the rice, grow the koji, build the starter, ferment the mash, then press and finish. Most of what a brewery does across a season is a careful repetition and refinement of these stages.
| Step | Japanese term | What happens |
|---|---|---|
| 1. Prepare the rice | seimai, senmai, mushimai | Polish, wash, soak, and steam the rice |
| 2. Grow the koji | seigiku | Cultivate koji mould on part of the steamed rice |
| 3. Build the starter | shubo / moto | Combine koji, rice, water, and yeast into a concentrated seed mash |
| 4. Ferment the main mash | moromi | Scale up in three additions; alcohol forms over several weeks |
| 5. Press and finish | joso, hiire | Separate the sake, then filter, pasteurise, and rest it |
Each step feeds the next. A mistake in the koji room shows up weeks later in the tank, which is why brewers treat the early stages with as much care as the fermentation itself.
Step 1: How is the rice prepared?
Preparation means removing the outer layers of each grain, then washing, soaking, and steaming what remains. The goal is clean starch and controlled moisture, because everything downstream depends on it.
The rice is first polished — milled to strip away the outer layers, where proteins, fats, and minerals concentrate. These compounds feed fermentation unevenly and can leave rough, off flavours, so brewers grind them away. How far they go is measured by the seimaibuai, the polishing ratio, and a lower number means more of the grain has been removed.
After polishing, the rice is washed and soaked to a precise water content, sometimes timed to the second for highly milled rice. Then it is steamed rather than boiled. Steaming firms the outside of each grain while keeping the centre soft — the texture koji and yeast prefer to work with.
Step 2: What is koji, and why does sake need a mould?
Koji is steamed rice on which a mould, Aspergillus oryzae, has been deliberately grown. Sake needs it because rice, unlike grapes, contains no ready sugar — something has to convert its starch first.
Brewers spread part of the steamed rice in a warm, humid room called the koji-muro, dust it with koji spores, and tend it for roughly 40 to 50 hours. As the mould threads into each grain, it releases enzymes — chiefly amylases — that break starch down into glucose. This is the quiet engine of the whole drink: no koji, no sugar, no alcohol.
It is worth pausing on the word “mould,” which can unsettle newcomers. The same family of cultured moulds underpins miso, soy sauce, and rice vinegar. Far from a flaw, koji is one of the most controlled, prized living tools in the Japanese kitchen — and in 2006 it was designated Japan’s national fungus.
Step 3: What is the yeast starter (shubo)?
The shubo, also called moto, is a small, concentrated seed mash that grows a large, healthy, dominant population of yeast before the main fermentation begins. Think of it as a strong opening rather than a whole brew.
Brewers combine koji, steamed rice, water, and yeast into the starter and let it develop over roughly two weeks. Lactic acid — either added directly in the modern sokujo method or produced naturally by bacteria in the older kimoto and yamahai methods — lowers the pH and shields the young yeast from unwanted microbes. The result is a robust, acidic seed culture ready to be scaled up.
Step 4: What happens during the main fermentation?
The starter is moved to a large tank and built up into the main mash, the moromi, where alcohol is actually made. Rather than adding everything at once, brewers expand the mash in three stages over four days — a method called sandan-jikomi.
| Day | Name | What is added |
|---|---|---|
| 1 | Hatsuzoe | First addition of koji, steamed rice, and water |
| 2 | Odori | Nothing — a rest day while the yeast multiplies |
| 3 | Nakazoe | Second, larger addition |
| 4 | Tomezoe | Third and largest addition |
The staggering is protective. Diluting the mash all at once would thin out the acidity and yeast, opening a door for spoilage organisms. Building it in steps keeps the culture concentrated and in charge at every stage — a slow, deliberate way of never giving a rival microbe a foothold.
Then comes sake’s defining trick. Inside the moromi, the koji keeps producing sugar while the yeast simultaneously converts that sugar into alcohol — both processes at once, in the same vessel. This is parallel multiple fermentation, and it runs for roughly 18 to 32 days.
In wine, the sugar is already in the grape, so yeast simply eats it. In beer, brewers convert starch to sugar in a separate mashing step, then cool the wort and ferment it afterward. Sake does both jobs together, continuously, in one tank — sugar is made and consumed in the same breath. Because the sugar never piles up to a level that would stall the yeast, sake ferments to a strength no other brewed drink reaches unaided: commonly 18 to 20% before any dilution, the highest alcohol of any undistilled fermented beverage.
That is the sentence to remember. Sake is not distilled and it is not “rice wine” in any literal sense; it is brewed by a mechanism all its own, closer in structure to beer but reaching wine-like strength.
Step 5: How is finished sake pressed and bottled?
When fermentation reaches the target, the mash is pressed to separate the clear sake from the solid rice lees, called kasu. This step is joso, and how it is done shapes the final style.
Pressing can be done under gentle machine pressure, in cloth bags left to drip, or — for the most delicate showpieces — by hanging bags and collecting only what falls under its own weight. After pressing, most sake is lightly filtered, then usually pasteurised in a step called hiire, gently heated to around 60–65°C to stabilise it by deactivating residual enzymes and yeast. Many sake then rest for several months to round out before bottling, though styles left unpasteurised (namazake) skip the heat and are kept cold instead.
From polished grain to sealed bottle, a single tank of sake typically takes around a month or two of active work, on top of the months of rice preparation and rest that bracket it.
Why does this process matter for how sake tastes?
Because flavour is built at every step, not chosen at the end. The polishing ratio sets how clean or rich the base will be; the koji governs sweetness and body; the yeast strain drives aroma; and the fermentation temperature and length decide how dry the finished sake becomes.
This is also why comparing sake to wine only goes so far. A winemaker works largely with what the grape already contains. A sake brewer, or toji, assembles the drink from near-neutral rice, engineering sugar, acid, aroma, and alcohol through living cultures they manage by hand. Neither approach is superior — they are simply different crafts, and knowing which one you are drinking makes the glass more interesting.
Frequently asked questions
Is sake brewed or distilled?
Sake is brewed, not distilled. All of its alcohol is produced by fermentation in the tank. Distilled Japanese drinks exist — shochu is one — but sake is not among them, which is why its strength tops out near 20% rather than the 25% and above of spirits.
Is sake really a rice wine?
Not in a technical sense. “Rice wine” is a convenient shorthand, but wine is made by fermenting fruit sugar directly, while sake requires koji to create sugar from rice starch first. Structurally, sake’s grain-and-conversion process is closer to brewing beer than making wine.
How long does it take to make sake?
The main mash ferments for roughly three to five weeks. Add the rice preparation, koji cultivation, starter, pressing, and a resting period, and a batch commonly spans a few months from milled rice to bottle.
Why is sake made with a mould?
Because rice starch cannot ferment on its own. The koji mould releases enzymes that turn starch into fermentable sugar. The same cultured mould underlies miso and soy sauce, so it is a staple of Japanese food, not a contaminant.
What is the difference between sake and beer brewing?
Both start from grain and both need starch converted to sugar. In beer, that conversion happens in a separate mashing step before fermentation. In sake, conversion and fermentation happen together in one tank — parallel fermentation — which lets sake reach a higher alcohol level naturally.
Written by Dr. Sake. If you enjoy taking sake apart to see how it works, follow along on Instagram @thesakeanatomy for more of the science and stories behind the glass.
