Going underground: Brewers raise glass to subterranean-stored sake

The Yomiuri Shimbun

20:00 JST, June 22, 2022

Sake brewers are increasingly turning to underground locations to store and age their products.

Unused mine pits and tunnels for checking dams are proving particularly popular, as such spots are usually surrounded by thick concrete walls and are relatively unaffected by external air conditions, meaning temperature and humidity remain stable year-round.

Some brewing experts say storing sake in this way makes for a milder taste. Sake varieties aged in pits and tunnels are made into branded products, and it is hoped that some of the subterranean-stored drinks will become local specialties.

In late May, Yoshinotomo Sake Brewery Co. in Toyama City placed 490 bottles of its high-end junmai daiginjo sake in a mine pit that runs 1 kilometer deep under the former Kamioka Mine in Hida, Gifu Prefecture. The old mine is famous for the Super-Kamiokande large water Cherenkov detector, which sits deep underground and monitors neutrinos.

Kenji Yoshida, 64, president of Yoshinotomo, said sake is usually stored in room-temperature warehouses or in refrigerated facilities. The longer a sake is aged “the milder and more rounded its taste becomes,” he explained. However, in room-temperature warehouses, temperatures fluctuate throughout the seasons, which affects the stability and quality of the drink. In the mine pit used by Yoshinotomo, the temperature remains consistent, at around 15 C. “Mine pits are ideal for aging sake, as temperature does not change very much,” Yoshida said.

The company sells its aged sake under the “kisaki” brand, and is planning to market different versions based on how long it has been stored, ranging from one to five years. “I’m looking forward to discovering how the different sakes taste,” Yoshida said, adding that the company aims to introduce the brand to markets in Singapore and Hong Kong.

Masuda Sake Brewery Co. — also based in Toyama City — has been aging its products in Arimine Dam in the city since 2019. The sake is stored inside a tunnel used for checking the dam, which sits 80 meters below the top of the structure.

Temperature in the tunnel remains under 10 C throughout the year, and it has a relatively stable humidity of between 70% and 90%. Water from Lake Arimine is used in brewing the sake, and the bottle labels feature photos of the Arimine district.

On June 10, the company began selling 270 bottles of Arimine sake in two varieties: junmai daiginjo (the highest grade of sake) and junmai genshu, which skips the process of adding water to lower alcohol content. Kota Yanagihara, an official of the company, said, “We want people to enjoy the rarity [of our products], which conventional sakes don’t have.”

In November, Sakuragawa Sake Brewery Co. began storing and aging its sake in a maintenance tunnel of Yokokawa Dam in Oguni, Yamagata Prefecture, about 60 meters below the top of the dam. The move was made possible after the town government and the Uetsu River and National Highway Office in Murakami, Niigata Prefecture, which manages the dam, signed a memorandum.

The brewery plans to store its sake products for about three years and serve it during events held in the town. “The sake will have value added,” a town government official said. “I want the products to become a trigger for revitalizing our local community.”