The Hidden Engine of Sake Brewing:

Hiro
3 days ago
3 min read

Why Multiple Parallel Fermentation Sets Sake Apart 【BLOG FOR SAKE CONNOISSEUR】

When most people think of sake, they picture a clean, refined drink—perhaps enjoyed warm in winter, or chilled alongside sashimi. But behind this graceful simplicity lies a complex process unlike anything else in the world of alcohol: multiple parallel fermentation.

It sounds technical—and it is. But understanding this one concept reveals why sake tastes the way it does, why it carries a unique elegance, and why brewing it demands such extraordinary skill.

Fermentation, Reimagined

In wine, fermentation is simple: grapes contain sugar, and yeast converts that sugar into alcohol. In beer, the starch in barley is first converted into sugar (through malting), then fermented. Each step is sequential.

But sake starts from rice—pure starch, with no sugar at all. To create alcohol from starch, two biological processes are needed:

Saccharification: breaking starch into fermentable sugar
Alcoholic fermentation: converting sugar into alcohol using yeast

In almost every other drink, these happen in sequence. In sake, they occur at the same time, in the same tank.

This is multiple parallel fermentation. And it's the heart of what makes sake possible.

Harmony in a Tank: How It Works

The magic starts with koji—a mold that produces powerful enzymes. As steamed rice is inoculated with koji, these enzymes begin breaking down the rice starch into sugar. At the same time, yeast is introduced to the mash (Moromi), fermenting the sugars into alcohol.

Because sugar is consumed as soon as it’s created, the overall sugar level in the tank stays surprisingly low—unlike, say, grape must in wine. This is crucial. If sugar were allowed to accumulate, the solution would become too syrupy (like sweet amazake), putting stress on the yeast due to osmotic pressure. Yeast would falter before fermentation really got going.

By keeping saccharification and fermentation in balance, sake brewers allow the yeast to thrive. The result? A slow, stable, and clean fermentation that typically reaches 15–16% alcohol—remarkably high for a naturally brewed beverage.

Precision, Not Luck

Executing this process isn’t automatic. It demands exceptional control over variables like:

Temperature (too hot and enzymes break down; too cold and fermentation stalls)
Koji activity (different rice types and polish ratios affect enzyme access)
Aeration, water quality, and rice absorption

It’s a process of orchestration, not automation. And because it's all happening simultaneously, there's no “pause” button. Brewers must anticipate changes before they occur, adjusting the balance hour by hour, often based on little more than touch, smell, and decades of experience.

This is why sake brewing is often called tsukuri-jōzu—“a matter of skilled making,” not just recipe-following.

Tradition Meets Technical Brilliance

Though multiple parallel fermentation dates back centuries, it remains as relevant today as ever. Modern breweries use temperature-controlled tanks and advanced yeast strains, but the core principle is unchanged.

What makes this process so special is that it represents the perfect meeting point of art and science. It’s deeply traditional, but also intensely biochemical. For professionals in wine, beer, or spirits, sake’s brewing process offers a rare look at how fermentation can be both elegant and extreme.

Why It Matters for the Drink in Your Glass

Understanding multiple parallel fermentation helps explain why good sake feels so “complete.” There's no sharp break between sugar and acidity, no aggressive alcohol spike, no rough edges. It’s smooth, layered, and balanced—because its very fermentation is smooth, layered, and balanced.

At Somm Cellars, when we select sake, we look for producers who master this process—not just technically, but expressively. Producers of Zaku, Gangi, and Hakkaisan don’t simply make sake—they shape it from the inside out.

So next time you raise a glass of Junmai or Daiginjo, consider the silent symphony inside that tank: enzymes working with yeast, starch turning into flavor, and centuries of know-how condensed into a single, pure sip.