The Sake-Brewing Process (Part 2)

For information on the first steps of sake brewing please visit part one of the sake brewing process.

Koji Making (Seigiku)
This is the heart of the entire brewing process,  and could have several chapters, if not books, written about it. Summarizing, koji mold in the form of a dark, fine powder is sprinkled on steamed rice that has been cooled. It is then taken to a special room where a higher than average humidity and temperature are maintained. Over the next 36 to 45 hours, the developing koji is checked, mixed and re-arranged constantly. The final product looks like rice grains with a slight frosting on them, and smells faintly of sweet chestnuts. Koji is used at least four times throughout the process, and is always made fresh and used immediately. Therefore, any one batch goes through the “heart of the process” at least four times.

The yeast starter (shubo or moto)
A yeast starter, or seed mash of sorts, is first created. This is done by mixing finished koji and plain steamed white rice from the steaming and koji making steps, water and a concentration of pure yeast cells. Over the next two weeks, (typically) a concentration of yeast cells that can reach 100 million cells in one teaspoon is developed.

The mash (moromi)
After being moved to a larger tank, more rice, more koji and more water are added in three successive stages over four days, roughly doubling the size of the batch each time. This is the main mash, and as it ferments over the next 18 – 32 days, its temperature and other factors are measured and adjusted to create precisely the flavor profile being sought.

Pressing (joso)
When everything is just right (no easy decision!), the sake is pressed. Through one of several methods, the white lees (called kasu) and unfermented solids are pressed away, and the clear sake runs off. This is most often done by machine, although the older methods involving putting the moromi in canvas bags and squeezing the fresh sake out, or letting the sake drip out of the bags, are still used.

Filtration (roka)
After sitting for a few days to let more solids settle out, the sake is usually charcoal filtered to adjust flavor and color. This is done to different degrees at different breweries, and is goes a long way in dictating the style.

Pasteurization
Most sake is then pasteurized once. This is done by heating it quickly by passing it through a pipe immersed in hot water. This process kills off bacteria and deactivates enzymes that would likely adverse flavor and color later on. Sake that is not pasteurized is called namazake, and maintains a certain freshness of flavor, although it must be kept refrigerated to protect it.

More to come
There are some final steps to brewing sake that will be covered in next weeks’ post. If you would like an even more in depth look at brewing sake take a look at the Sake Production Slideshow, an indispensable tool to visually understand how sake is made.  To learn more about Sake and sample more than 90 other varieties of Sake, join me at the Sake Professional Course in Portland, Oregon on November 7, 8 and 9. For more information, click here, or email us at info@sake-world.com.

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One Comment on “The Sake-Brewing Process (Part 2)”


  1. […] The Sake World Blog Learn About Sake – and read John Gauntner's Sake Tasting Musings « The Sake-Brewing Process (Part 2) […]


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