Arase-san of Heiwa Shuzo says he uses Yeast #9 because it’s, “strong against other bacteria, and consistent.”
The main ingredients of sake are rice, water, yeast, and koji. I have discussed rice types and koji at length in the past, but I’ve never zero-d in on yeast.
The first function of yeast in making alcohol is to convert sugar into alcohol. As you may recall, koji in sake-making converts the rice into usuable sugars for the yeast (in beer, malting converts the grain into sugar first). In sake-making, the koji and yeast work together, and undergo a process unique to sake called multiple parallel fermentation, where the rice is converted into sugar and alcohol simultaneously. Without yeast, there is no sake!
But what else does the yeast do? The yeast affects the aroma, which in sake can be very assertive – from an avalanche of apples, a blast of banana, to a punch of peach. These aromas are deliberately drawn out by the toji (master brewer) by their choice of yeast.
Most sake brewers in Japan get their yeast from the Nippon Jōzō Gakkai, or the Brewing Society of Japan. Their mission is to to deepen the understanding of brewing among the Japanese people through research with support from the government and by supplying pure strains of yeast to the brewing community.
This month, I’m focusing on Yeast #9. It is one of the most popular yeasts used for sake-making. Originally discovered by Professor Kinichi Nojiro in Kumamoto Prefecture in the 1950s, this yeast is also known as Kumamoto Kobo, and still lives today at a brewery in Kumamoto called Koro. The Brewing Society of Japan took this yeast, numbered it, propogates it, and offers it to brewers. While most brewers get this yeast from the Brewing Society, some brewers get it straight from the source in Kumamoto and propogate it themselves (like Tensei, in Level 2). Yeast #9 is highly coveted because it creates a robust and steady ferment even at low temperatures, therefore, ideal for making ginjos and daiginjos. Yeast #9 can create a bursts of apple and melon in the aroma of sake, with refreshing acidity.
If you want to read more about multiple parallel fermentation, koji and the process of sake, you’re in luck! This month, members get a free copy of Sake + Shochu Talk, a zine that we self-published last month that includes all you've ever wanted to know about sake and shochu! I’d also like to give a shout out to Umami Mart’s newest baby, Shochu Gumi! Join the one-and-only quarterly club featuring shochu, one of Japan's best kept secrets, curated by Kayoko (the other co-founder of Umami Mart). Incidentally, one of the shochus for this first installment of Shochu Gumi uses Yeast #9 too!
Co-Founder + Sake Director
LEVEL 1: Introductory Membership (Two 300ml bottles)
Tonoike Brewery (Tochigi, Japan)
Seimaibuai: Gohyakuman-goku 55%, SMV: +1.4, Yeast #9
A textbook Yeast #9 sake, this is a ginjo that wafts fresh-picked apples, and a hint of fennel. Clean, fresh, and smooth, this delicate honjozo is made in a town called Mashiko, which is popular for pottery and sake. The dry finish lends itself to pair agreeably alongside a range of foods including liver pate, tomato sauces, and poultry. Enjoy the calm mellow fragrance of Yeast #9 in this sake slightly chilled or at room temperature.
Sawahime Yamahai Junmai
Inoue Seikichi Brewery (Tochiji, Japan)
Seimaibuai: Hitogokochi 65%, SMV: -1, Yeast KT-901
A deviation from the fresh-picked apple scent, this sake smells of warm cooked apples - just in time for the holidays! This custardy brew is acidic, tart, and full-bodied because it is a yamahai (brewing technique using naturally occuring lactic acid). Notice the yeast used for this sake is KT-901, a non-foaming version of #9. Non-foaming yeasts allows brewers to fill the tank more, and it can also reduce the amount of bacteria that sticks to the sides of the tank while the foam rises and falls. With a recent bottling date, this sake feels fresh and alive with a touch of effervescence, reminding me of the kombucha I had recently at Cultured in Berkeley. Great with rich foods like buttery brussel sprouts, smoked salmon, tsukudani (soy simmered condiment), or foggy morning cheese. Loved this warm!
LEVEL 2: Premium Membership (Two 720ml bottles)
Kid Junmai Daiginjo
Heiwa Shuzo (Wakayama, Japan)
Seimaibuai: Yamada Nishiki 50%, SMV: +2, Yeast: #9 and 1801
When we met Arase-san of Heiwa Shuzo, he told me he likes using Yeast #9 for this sake because, “It’s strong against other bacteria, and it’s consistent.” He describes this sake as, “Not very rich for a daiginjo. Try it chilled first then as the night progresses, enjoy it as it gets up to room temperature, as thicker flavors are better when you start getting tipsy.” Contrast this sake full of fuji apple, banana, and green melon with vinegared salads, shabu shabu, and yakitori.
Tensei Junmai Ginjo
Kumazawa Shuzo (Kanagawa, Japan)
Seimaibuai: Yamada Nishiki + Gohyakuman-goku 50%, SMV: +3.5, Yeast #9
Igarashi-san, the toji of this Kumazawa Shuzo, gets his yeast directly from Koro in Kumamato as opposed to buying it from the Brewing Society of Japan (see other side for more information). He prefers to use the yeast from its origin because the yeast naturally evolves over time. Thanks to this yeast, Tensei has an aroma of fresh green apples, and a touch of nutmeg. I loved the weighty mouthfeel of this sake that seems to have a slightly briny aftertaste that reminds me of salted caramel. This may be thanks to the coastal location of Kumazawa Brewery. Pair chilled or at room temperature with grilled lamb chops, herbed chicken, or couscous.