Production

Only in Japan

We look at Japan-specific casks used in the maturation of whisky
By Stefan van Eycken
MD Yoshitsugu Komasa with his brand new stills at Kanosuke Distillery
MD Yoshitsugu Komasa with his brand new stills at Kanosuke Distillery
What makes Japanese whisky uniquely Japanese? It’s one of those thorny questions that folks working (or playing) in the field have trouble with. Sure, it can be sidestepped by waxing lyrically about the ‘cultural DNA’ – with soundbites like ‘attention to detail’ and ‘kaizen’ (the business philosophy of continuous improvement) thrown in – but when pressed to give specific examples, chin stroking and perspiration tend to be the order of the day.

Woe betide the expert who reaches for the “terroir” argument, because almost all raw ingredients (i.e. malted barley, maize, etc.) are imported from abroad. A few craft distillers have started working with local barley on a small scale, but none of the whisky distilled using local barley has been released yet. The equipment and processes used maybe? Not really. Most malt distilleries in Japan use equipment and processes imported (in the former case often literally) from Scotland. A few of the recent ones use slightly different-looking stills of the type found in craft distilleries around the world, i.e. hybrid or small alembic stills. The yeast may be proprietary or the processes may be calibrated slightly differently, but that’s the case at distilleries in other whisky-producing regions, too.

“Climate” is the easy way out – that’s different everywhere, but unfortunately, Japan lacks the extremes to be able to drive home that argument as you could in say India or Taiwan. No, climate won’t cut it. We’ll need something a little more solid to get us out of the woods… Ah, the wood, of course. Mizunara to the rescue! Now we’re on to something: Japan-specific maturation vessels.

Mizunara, i.e. Japanese oak, is the most well-known example and it has been featured in these pages a few times during the past years. This time round, however, we’ll be looking at some more under-the-radar examples.

In terms of previous contents, there are two intriguing cask types used, albeit on a small scale, in Japan: ex-umeshu and ex-shochu casks. Shochu is a traditional Japanese distilled spirit made from a very wide range of base ingredients. Some of the more orthodox varieties are barley shochu, rice shochu and sweet potato shochu.

In terms of production method, there are two types: one is distilled in a continuous still to a very high ABV and then diluted for sale; the other (authentic) type is single distilled, usually in a stainless steel still, to an ABV of no more than 46%. Most quality shochu is ‘aged’ in large earthenware pots or stainless and enamel-lined steel tanks. However, some shochu – typically, barley and rice shochu – is matured in oak barrels.

To avoid ‘confusion’ with whisky, the Japanese government put certain regulations in the shochu category in place. One of those pertains to the colour, which cannot exceed a certain (very low) absorbance value – meaning, shochu must be markedly lighter in colour than whisky, by law. This means either a very short period of maturation in oak or filtering the barrel-aged shochu prior to bottling to dial down the colour, but this inevitably also has an impact on aroma and flavour.

Shochu is made all over Japan, but it’s concentrated in Kyushu. At the time of writing, there are two whisky distilleries in Kyushu: Tsunuki and Kanosuke, both in Kagoshima and both owned by companies whose main business is shochu (Hombo Shuzo and Komasa Shuzo, respectively).

Most quality shochu is ‘aged’ in large earthenware pots or stainless and enamel-lined steel tanks. However, some shochu – typically, barley and rice shochu – is matured in oak barrels.


For them, it obviously made sense to re-use some of their ex-shochu casks to mature whisky. They can’t be used as is, though. Yoshitsugu Komasa, managing director at Komasa Shuzo, explains, “For our flagship shochu, Mellowed Kozuru, which is a barrel-aged rice shochu, we use 450l American white oak casks. We fill the shochu into the casks at 44% ABV and leave it for just half a year before it’s moved to a tank. We can’t leave it any longer, otherwise it would become too dark in colour and the wood would overpower the character of the shochu. Each cask is used for about 10 years and by then, it’s tired and almost completely stripped of tannins.”

Putting those casks to use in the production of whisky would be meaningless, so the casks are sent to independent cooperage Ariake Sangyo, based in neighbouring Miyazaki prefecture, where they are rejuvenated and recharred. Both Komasa Shuzo and Hombo Shuzo use this procedure to prepare their ex-shochu casks before using them to mature whisky.

At Kanosuke Distillery, it is still early days. They are just a few months into their first season, having started production in November 2017, but these re-charred ex-shochu casks will be a definite priority. As Komasa explains, “Of the first 200 or so casks we are filling at Kanosuke Distillery, 30 are ex-Oloroso sherry butts, 100 are re-charred ex-shochu puncheons and 90 are ex-bourbon barrels.”

At Hombo Shuzo, we can already see that re-charred ex-shochu wood and whisky is going to be a winning combination. On a recent visit to Hombo Shuzo’s warehouse on the island of Yakushima, I had the pleasure of sampling a variety of casks. The pick of the bunch was a rejuvenated ex-barley-shochu cask that had been filled with lightly-peated new make from Mars Shinshu Distillery in 2015. The balance of fruit, sweetness and exotic spices was superb and the finish followed me all the way back to the ferry off the island.
There were four more casks of the same type at the Yakushima Aging Cellar and some more in the Tsunuki warehouses, so we’re in for a treat when these are ready to be bottled.

Umeshu is a traditional Japanese liqueur made by steeping whole, unripe ume fruits in alcohol and sugar. Often translated as ‘plum liqueur’, ume is actually more closely related to the apricot. The alcohol used is typically shochu, but sake is also used as a base and some whisky producers like Eigashima Shuzo and Wakatsuru Shuzo have a whisky-base umeshu in their portfolio. Umeshu is available wherever alcohol is sold in Japan, but it’s also commonly made at home. Between 10 and 15% ABV, it’s usually served on the rocks, mixed with soda or as a ‘sour’ (in the Japanese sense of the word, i.e. mixed with shochu and soda / a clear soft drink). The attraction of well-made umeshu is the balance of acidity, sweetness and umami.

Suntory pioneered the use of ex-umeshu casks and killed two birds with one stone in the process. By maturing their umeshu in toasted casks previously used to mature Yamazaki whisky, Suntory created a product that stood out from the competition on the shelves (while commanding a premium, of course). They could then re-use those ex-umeshu casks to fill whisky into.

The use of ex-umeshu casks was driven by the desire to create a malt component that would contribute a distinctive stone fruit note to a blend, but not derived from ex-sherry wood. Malt whisky finished in ex-umeshu casks was a big part of Hibiki 12, which has been discontinued unfortunately. The only chance to try it in isolation was the 2008 release of Yamazaki Plum Liqueur Cask Finish, which was limited to 3,000 bottles and restricted to the bar trade. Suntory still has an ex-Yamazaki barrel-aged umeshu on the shelves, so it’s likely they’re continuing to re-use those barrels to mature / finish whisky in. As they say, watch this space.

Recently, the Ariake cooperage has started to encourage whisky makers to explore different wood types, such as Japanese cherry (sakura), Japanese cedar and Japanese chestnut.


Craft producers are also pursuing ex-umeshu maturation, albeit on a tiny scale. Hombo Shuzo makes umeshu and a little bird told me there are two 450l ex-umeshu casks in one of the warehouses at Tsunuki Distillery. According to master distiller Tatsuro Kusano, “They were filled with non-peated new make from Mars Shinshu, our sister distillery, in August 2015, and the whisky is already fabulous in taste, with notes of annindofu and… well, umeshu!” Kiuchi Shuzo also makes umeshu and head distiller Isamu Yoneda is hopeful he may be able to barrel-age some of next season’s production, so that he can re-use the cask(s) at a later stage to fill with whisky made at Nukada Distillery.

It’ll be interesting to see who will be the first to release a single cask ex-umeshu whisky.

Unlike other major-whisky producing countries, whisky does not necessarily have to be aged in oak in Japan. Recently, the Ariake cooperage has started to encourage whisky makers to explore different wood types, such as Japanese cherry (sakura), Japanese cedar and Japanese chestnut.

At Nukada Distillery, a cask with sakura heads was filled in March 2016. According to Yoneda, the impact of the cherry wood is unmistakable. “It’s distinctly floral and quite sweet on the nose, although the sweetness may have come from the half-wheat, half-barley grain bill. I want to let it sit for a while and release it as a single cask when it’s ready. In a blend, it would be overpowered by ex-Bourbon or ex-sherry wood.”

At Tsunuki Distillery, there are three casks of the same type. They jump out visually when walking through the warehouse because the heads have been painted with kakishibu (the fermented juice of unripe, astringent persimmons) to prevent leaking. According to Kusano, this is the only feasible way to use cherry wood for the maturation of whisky.

Even then, he feels they’re not ideal for full maturations. “You get lovely notes of pomegranate and red fruits – a different sort of fruitiness compared with oak – but the wood can quickly overpower the character of the whisky. Our casks were filled with Tsunuki new make, but I think the way to go is to leave the liquid in for a while and then re-rack into a more traditional, oak cask for further maturation. The good thing is that, then, we’ve got re-fill sakura-head casks that we can further play with.”

Other wood types offer intriguing possibilities, too. Yoneda has ordered some chestnut casks for the new and bigger distillery Kiuchi Shuzo is currently building in a different location in Ibaraki prefecture. “The chestnut sample I got from Ariake had a lovely sweet, nutty and berry aroma to it. I also want to try to use wood from the Ibaraki ume tree, but I haven’t gotten round to finding a wood supplier, yet.”

At Nagahama distillery, small-scale trial maturations using cedar, chestnut and cherry wood – both toasted and charred – were carried out in September of last year. The cherry wood sample was suggestive of wasanbon (traditional Japanese sugar), whereas the cedar sample was found to be a bit like otoso (spiced sake drunk during New Year celebrations in Japan). Clearly, these wood types have strong culturally specific connotations, and it’s likely that the maturation of whisky in these unusual wood types will be explored by the growing number of craft whisky makers in Japan on an ad hoc basis.

It’s easy to get excited by all of the above, but one has to keep in mind that – even with mizunara lumped in – these Japan-specific cask types constitute a tiny part of what’s slumbering in the warehouses in Japan. Most of the whisky made here, like elsewhere, is matured in ex-bourbon and ex-sherry wood of the kind used by whisky makers all over the world.

So the question remains: what makes Japanese whisky uniquely Japanese? Guess the only answer is we’ll have to sleep on it a bit more.
Three casks with cherry woods heads maturing at Tsunuki Distillery
Three casks with cherry woods heads maturing at Tsunuki Distillery
A sample from cherry wood heads cask maturing at Nukada Distillery
A sample from cherry wood heads cask maturing at Nukada Distillery
Suntory's limited release Yamazaki Plum Liqueur Finish, which is now as rare as hens teeth
Suntory's limited release Yamazaki Plum Liqueur Finish, which is now as rare as hens teeth
Nukada head distiller Isamu Yoneda in his still house
Nukada head distiller Isamu Yoneda in his still house