For more about the differences between soju and shochu and how a couple of independent soju brands are being produced, see Soju and Shochu: Cousins in Craft Distilling.
One of the most important distinctions between soju and shochu is the difference in fermentation starters—it’s nuruk for soju, and for shochu it’s koji.
Nuruk is a mixed culture cultivated from grains and local air, and it typically includes yeast and bacteria as well as the Aspergillus oryzae mold whose enzymes aid saccharification. Koji, on the other hand, refers to the mold itself (though the word can also be used for grains that have been inoculated with it, especially if used as a starter).
Koji is important to Japanese cuisine, used in the production of sake as well as miso, soy sauce, rice vinegar, and more. For all sake and most shochu, the koji ferments cooked rice—turning its starches into sugars that can more easily be fermented, while adding subtle flavors of its own.
There are a few main types of koji:
- Aspergillus kawachii is known as white koji. Thought to have originated from a black koji mutation, it is hardier than yellow koji and has become the most popular type for shochu production. It tends to add a lightly sweet taste.
- Aspergillus oryzae, known as yellow koji, was once the traditional mold used for making all shochu. Producing drinks with a rich, fruity character, it remains the most important type for making sake.
- Aspergillus luchuensis, or black koji, is more specialized, and it produces some citric acid that lowers pH and is thought to help preserve quality. This is the koji used to make Awamori, a type of shochu that is special to Okinawa and made using Thai indica rice.
Making Mizu Shochu
“Koji is the umami, the magic behind shochu, what distinguishes it from every other spirit in the world,” says Jesse Falowitz, who founded the Mizu Shochu brand with Jeremy Kono in 2013. To produce the shochu, they partner with the Munemasa Shuzo distillery in Arita, in the Saga Prefecture, on the western end of Japan. They produce it in the honkaku style, which denotes a traditional method that includes a single distillation.
As with sake, regional variation makes a difference with craft shochu; the importance of terroir is part of what resonated with Falowitz as he was learning more about the spirit. Shochu from smaller craft producers also typically clocks in at a higher ABV. (Mizu Shochu is bottled at 35 percent ABV, while larger commercial brands are often closer to 25 percent.)
The shochu-making process begins with polishing, washing, and steaming rice. A specialist then adds koji spores—in the case of Mizu, it’s black koji. “It all happens in the koji room with a koji master,” Falowitz says. “They’re responsible for being at the distillery for 48 hours straight. They sprinkle koji spores over the rice, and every couple of hours, either by hand or sometimes with a slightly mechanized process, they turn the rice.”
After those two days of koji propagation, they mix the rice with local spring water and a bit of yeast for the first moromi, or preliminary mash. This mash continues in a tank for five to 10 days, undergoing a process that’s special to sake and shochu: multiple parallel fermentation, which means saccharification and fermentation happen simultaneously.
At Mizu, the distillers then transfer this mash to a larger tank for a second moromi, mixing one part black-koji rice with two parts barley. They use local Saga two-row barley—unmalted, with its husks polished away—which they press and steam before mashing in with the rice.
Once the fermentation is complete, the shochu undergoes a single pot distillation, a hallmark of honkaku shochu. Falowitz says the single distillation is vital for preserving the spirit’s full flavor. It comes off the still at 88 proof, and they rest this undiluted (or genshu) shochu for at least a year before bottling it at 70 proof.
Besides the Mizu Saga Barley Shochu, Munemasa Shuzo also produces a few other varieties:
- Mizu Lemongrass Shochu, made with white koji, rice (no barley), and locally harvested lemongrass that’s added to the mash a few days before distillation.
- Mizu Green Tea Shochu, made with black koji, rice, and barley; locally picked green tea leaves join the grains in the second moromi.
- Mizu Sakura Cask Shochu, which is the Saga Barley Shochu that’s rested in Japanese medium-char cherry-wood casks for at least nine months.
Courtesy Iichiko. Photo credit Daniel Schwartz.
Mugi Shochu with Iichiko
Like Mizu’s flagship, Iichiko Saiten Shochu is a mugi shochu—that is, it’s made with barley, and in this case, it’s 100 percent barley.
As a leading brand of mugi shochu in Japan, Iichiko’s batch size is 160 hectoliters. That size mash requires seven tons of barley, says Ken Oka, the brand’s manager of U.S. operations. Iichiko’s mash-and-fermentation can take 10 days to two weeks.
Following the honkaku style, Iichiko gets a single pot distillation. “We blend both atmospheric pressure and vacuum pressure,” Oka says. “By combining the two distillation methods, we achieve a balance of flavor and aroma.”
The Iichiko shochu rests for up to six months. They bottle their stronger Saiten at 43 percent ABV and recommend it for cocktails. The Silhouette is bottled at 25 percent ABV, and is popular with those who prefer a lighter shochu on the rocks; the Seirin is even lighter, at 20 percent. Finally, a more recent product is Iichiko Special, aged five to seven years in white oak as well as in Japanese oak (mizunara) barrels, including some sherry casks.
Craft Shochu in California
Given how specialized the koji-driven, multiple parallel fermentation is, it’s worth noting that there may be another route for craft distillers who want to take a stab at shochu: You can outsource it.
That’s what St. George Spirits in Alameda, California, does to produce its California Shochu, which is bottled at 40 percent ABV.
St. George master distiller Lance Winters says they work with a local sake producer who steams California-grown Calrose rice, inoculates it with koji, adds yeast, and ferments the mash. They allow the solids to settle out, clamping the mixture in a press to squeeze out as much sake as possible. Those solids form a lees cake that still includes some liquid at about 14 percent ABV; St. George blends this with a neutral spirit made from non-GMO corn before distillation.
“This affords us a very concentrated expression of what koji is all about,” Winters says of the lees-cake starter. “It’s beautifully earthy and mushroomy, as well as having some cashew, pistachio, cocoa, and dried fruit.”
Winters runs this combination through the still the way he would an eau de vie, sampling it along the way to fine-tune its characteristics. From there, the distillate goes into stainless-steel tanks to rest for anywhere from six months to a year before bottling at 80 proof.
While St. George hasn’t aged its straight shochu in casks, it does have another twist up its sleeve: It uses the shochu to produce an umeshu flavored with California-grown plums, and that does go into casks. Winters and team then have aged their Japanese-inspired Baller American Single Malt Whiskey in those casks that previously held their umeshu.