Umami Mart Registry

Making koji at Nishi Shuzo

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Koji is a mold used to make sake, shochu, soy sauce, mirin, and miso. There are three main types of koji used in Japan – yellow, white, and black. For sake-making, the most common koji used is yellow koji (aspergillus oryzae). The two other types of koji are white (aspergillus kawachii) and black (aspergillus awamori), commonly used for shochu and awamori. All of the sakes for this month's bottles use yellow koji.

Yellow koji breaks down the rice starch into enzymes for saccharification (the process of making glucose). Then, the added yeast is able to ferment the glucose into alcohol. The use of koji is what sets sake apart from other fermented beverages. For example, if you make a rice beverage with just yeast and water, you would have rice beer. With the addition of koji, you have sake.

When asking different brewers about koji, their demeanor always softens, as though they are talking about their child. To brewers, koji is a living, breathing organism with unique characteristics that define the essence of their sake. While yeast has an influence on the aroma of sake, koji impacts the core flavor of the sake. So much so that all brewers consider koji-making to be the most important part of sake-making. Sasaki-san of Akita Brewery also makes this point, "The umami of koji creates a umami that is more suitable for pairing with food than other alcoholic beverages." In fact, all of the brewers heavily emphasize how beverages using koji beg to be paired with food due to their sweetness and acidity.

Every brewer has their own way of handling koji. The main difference I've seen is handmade versus machine-made, with brewers applying handmade koji to their finest – usually to their ginjos and daiginjos. I also often see brewers playing with how long they cultivate koji and at what temperature. Some brewers, including Hakkaisan, use the handmade technique for all of their sakes: "Koji for all of our sake – from our entry-level seishu up to ultra-premium daiginjo grades – are created by hand," says Tim Sullivan of Hakkaisan. "One major difference at Hakkaisan is that our overall production process for koji run up to 55 hours. Usual timing for koji is 48 hours. This extra time allows us to nurture the koji spores and have exacting control of the temperature."

This month, I've chosen a few sakes that exhibit the power of koji. For Level Two, there's the X3 Amairo Junmai Genshu, which uses three times the amount of koji than regular sake production, while the Hakkaisan Kijoshu in Level One uses sake, instead of water, during the last part of the moromi phase, emphasizing the umami and sweetness of the koji in the final brew. Enjoy the Koji Chronicles!

Co-Founder + Sake Director


Tenbu Junmai
Nishi Shuzo (Kagoshima, Japan)
Seimaibuai: Akihonami 60%, SMV: N/A, Acidity: N/A

As long time fans of their shochu, all of us at the shop were so excited to learn about Nishi Shuzo's sakes. Kudo-san of Nishi Shuzo explains that while the white koji they use for shochu produces citric acid to prevent the rice mash from rotting, the yellow koji they use for sake-making, "is not suitable for preventing spoilage, so the storehouse is kept in a winter state 24 hours a day, all year round." This sake in particular highlights the sweetness of their yellow koji and the intent of the brewer is to have the imbiber enjoy chilled with a meal, particularly creamed vegetables or shabu shabu. Enjoy pineapple, peach, and a hint of lime in this viscous brew.Nishi Shuzo in Kagoshima PrefectureNishi Shuzo in Kagoshima Prefecture

Hakkaisan Kijoshu

Hakkaisan Brewery (Niigata, Japan)
Seimaibuai: Yukinosei 60%, SMV: -36, Acidity: 2.5
"One wonderful thing about koji is that it is alive," says Tim Sullivan of Hakkiasan Brewery, "they are the microbes that make the miracle of sake possible." You can taste the care that goes into their koji-making in this kijoshu, a unique style of sake where during the  third addition of rice, koji, and water, the water is replaced by sake. "The fortification of the mash with alcohol brings an earlier end to the fermentation period and leaves a fair amount of residual sugar behind," says Sullivan, "These extra sugars give kijoshu its uniquely sweet flavor profile." The brewery ages this sake for one year and stamps a vintage year on the bottle. You may elect to age it further and see how the color darkens. I tried Sullivan's recommendation of pairing this sake at room temperature in a sherry glass with blue cheese – it highlighted the notes of honey, dried fig, and nutmeg in this rich sake.


Kawatsuru Olive Junmai Ginjo
Kawatsuru Brewery (Kagawa, Japan)

Seimaibuai: Sanuki Yoimai 58%, SMV: -7, Acidity: 2.0

When President Yuichiro Kawahito and his team isolated yeast from their olive trees, they naturally thought of using it for their sake. Kagawa is known for their Mission olives, introduced to the region from California in 1907. Since then Kagawa has been famous for producing olives. When asked about the process, Kawahito explained, "We focused on narrowing down yeast strains with strong alcohol resistance and selecting yeast that produces a refreshing aroma and clean acidity. For olive yeast sake, we use koji which produces more enzymes that bring out the sweetness of rice." The sweetness is balanced by acidity with notes of muscat grapes, and a slight astringency of persimmon peels. Try this low ABV sake out of a chilled white wine glass alongside Kawahiro's recommendation of peperoncino pasta (with plenty of olive oil!).Kawatsuru BreweryKawatsuru Brewery in Kagawa Prefecture

X3 Amairo Junmai Genshu Sake
Kinmon Akita Sake Brewery (Akita, Japan)
Seimaibuai: Menkoina 70%, SMV: -24, Acidity: 2.5

This sake uses three times more koji than usual during the fermentation process. "The inspiration came from wine, where the culture of eating and enjoying has advanced," says President Sasaki, "Koji has abundant and diverse amino acids. One of the major characteristics of koji is that it complements food and creates a successful marriage." So with more koji, he presumed that more food pairing possibilities would reveal themselves. The sweetness and acidity of this sake complement creamy rich flavors like uni pasta, miso cod, and maitake tempura – all great flavors for a holiday spread. Enjoy at room temperature in a rocks glass.
Column: Sake Gumi News


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