Spotlighting the art of aged sake, koshu

Koshu doesn’t make the headlines very often. Produced only by a tiny fraction of sake brewers, the drink is so rare that one would be hard pressed to find it even in sake bars.

Not to be confused with the Koshu grape, which is now used to make grape wine in Japan, koshu is a rather unusual breed of sake that sees extended ageing. For an alcoholic beverage appreciated for its freshness and vivacity, koshu is an eccentric anomaly. But it would be a mistake to think that it’s a modern invention.

“We have written records that show koshu was brewed and enjoyed since the 13th century,” says Genta Onodera, a sake expert who works with Beam Global Asia. In those days, koshu was typically aged for about three to five years. By the Edo period, nine-year-old koshus were considered to be the most premium sakes available.

But political struggles and wars with China and Russia that followed in the Meiji era changed the landscape of sake production. To ensure that the country had enough funds to finance the wars, the government levied a heavy tax on sake, payable as soon as the brewing was completed (instead of when the sake is sold). This put a heavy burden on the sake producers, who then wanted to get their financial returns in the shortest time possible. “Brewers stopped making koshu and gradually the drinking culture disappeared,” Onodera says. “This form of taxation is already abolished, but this period destroyed koshu’s popularity.”

Today, with an increased demand for sake and the availability of modern equipment and technological know-how, producers find an impetus to experiment with ageing sake.

But the koshu of our day is likely very different from those of yesteryears. “In the past, there was no refrigeration. Sake was often aged in cedar wood barrels, which could have led to very unusual flavours,” says Adrian Goh of Interrice Asia. “Now with modern technology it is possible to age sake at lower temperatures, which would create well-rounded characters with deep aromas and flavours.”

Various vessels are used in ageing koshu, with stainless steel tanks being a popular choice. “In Kyoto, brewers age koshu in earthenware, while some others age theirs in 18 litre bottles called tobin, which is Japanese for ‘ten times’, named for the fact that they are ten times the volume of a 1.8 litre sake bottle,” says sake ambassador and chef Tetsuya Wakuda, owner of Waku Ghin at Marina Bay Sands in Singapore.

Ageing, which can take anywhere from a year to 30 or 40 years, happens either at room temperature or at controlled low temperature, and the method is mostly based on traditional brewing conditions. Historically, the peak of sake production in Japan happens in the cold winter months. “In winter, the temperatures fall below 0°C. Wine is kept in underground cellars for maturation at a consistent temperature, but not sake — sake benefits from varying temperatures for maturation,” Wakuda explains.

But that is not to say koshu that has been bottled should be subject to extreme temperature fluctuations. “Wines are cellared at around 15°C, but if sake is aged at the same temperature, its taste and aroma would be drastically changed,” says Onodera. “One should avoid temperature changes to maintain maturation under good conditions.”
Even with the rise in sake consumption — with Hong Kong and Australia leading the trend — koshu production remains infinitesimal. According to general estimates, koshu accounts for less than one per cent of Japan’s total sake output, which also explains its rarity on the market.

There are, however, a couple of notable koshu producers. “Daruma Masamune of Shiraki brewery in Gifu prefecture, Azuma Rikishi of Shimazaki brewery in Tochigi prefecture, and Kidoizumi of Kidoizumi brewery in Chiba prefecture are the most significant brewers in the current koshu market,” says Onodera. “Kidoizumi has 35 to 40 years history of making koshu, while Daruma Masamune and Azuma Rikishi have been producing it for more than 40 years. Kukurihime of Kikuhime brewery is particularly known for its rarity.”

Keeping It Cool
Koshu is quite the chameleon of the sake world. When made at low temperatures, it can be mild, light, and fruity, but when matured at room-temperature, its savoury aromas and flavours may be likened to soy sauce, sherry, caramel, nuts, truffle, and mushrooms.

For koshu matured at low temperatures, Onodera recommends serving it between 10°C to 15°C in order for it to best express its aromas and taste. Room-temperature matured koshu is somewhat more forgiving — depending on individual preference, it may be served slightly chilled at 20°C, or warmed up to about 40°C.

Matching Koshu with Food
Koshu’s versatility lends itself well it a wide range of dishes such as fish, meats, and fermented foods like cheese and miso. Rich foods such as foie gras and uni are also excellent pairings.

Tetsuya Wakuda’s sake menu at Waku Ghin offers 62 sake and koshu selections, including a very unusual label from Masuizumi. The brewery, based in Toyama prefecture, ages one of its sake at low temperatures in wine barrels sourced from Chassagne-Montrachet wine estate Domaine Ramonet. The sake’s nuanced vinous character, underpinned by a subtle savouriness and driven by notes of ripe fruits, makes for a perfect accompaniment for oysters and caviar.

Wakuda also offers a Tenryo 8-year-old Junmai Daiginjo koshu from Gifu prefecture, which is paired with a dish of barramundi en papillote with Alba white truffle served on a bed of fennel and rocket. Savoury, rich, creamy, and complex, the sake complemented the dish with weight and balance, without taking anything away from the flavour of the fish.

The oldest koshu on the menu is Born:Wing of Japan 14-year-old from Fukui prefecture, which won an award at the 2000 London Wine Challenge. Although it has seen prolonged maturation, the sake retains a very pretty nose and precise balanced palate. It was matched with a roasted pigeon breast dressed with sancho sauce on konnyaku (konjac). Building on the pepperiness of the sauce and the sweet/spicy savouriness, the gaminess of the bird and the koshu proved to be a seamless match, with the latter lending a nice contrast by bringing a sweet overtone to the dish.