Distillery Focus

Shooting for the stars

We visit the Tsunuki Distillery and Yakushima ageing cellar
By Stefan van Eycken
Awards are a dime a dozen and sometimes you just scratch your head and wonder how on earth… but when Hombo Shuzo was named Craft Distiller of the Year by our magazine last year, everyone who knew what they had been up to the past few years said, “well, of course!” Hombo Shuzo has a long history of whisky-making – long by Japanese standards – with lots of ups and downs. In 2011, they decided to give it another go and started making whisky at Mars Shinshu Distillery again after a 19-year hiatus.

Towards the end of 2015, they surprised friend and foe by announcing they were opening a second whisky distillery in their home prefecture of Kagoshima. I was there when the site was being prepared, saw the copper for the stills being hammered into shape and paid them a visit a few months into their first season. Now halfway through their second season of distilling, I thought it was high time we had a look at what they had done with their toy box and so I flew down to Kagoshima on a cold February morning.

Just like at Mars Shinshu, distilling at Mars Tsunuki takes place during the colder half of the year. The season at Mars Shinshu used to be six months, but with demand for whisky at an all time high, the decision was made to start a little earlier and finish a little later, making it closer to eight months now. At Mars Shinshu, the 2017-18 season started mid-October. At Mars Tsunuki, they were keen to start even earlier. Mashing started on September 21 and the final distillation of the season is planned for June 16.

As I enter the distillery, I’m greeted by the white noise of the mill and by Tatsuro Kusano, the 29-year old distillery manager who is clearly in his element in his new playground. Kusano spent three years at Mars Shinshu, learning the ropes from master distiller Koki Takehira there, before he was transferred to Kagoshima in the summer of 2016 to oversee the construction of Tsunuki Distillery. Kusano may be young and it would be tempting to see him as Takehira’s “remote hands” at the new distillery, but spend some time talking nitty-gritty with Kusano and it quickly becomes clear that’s not the case at all. He’s got his own ideas and his own vision for Tsunuki and an inquisitive mind with lots of little experiments and plans for the future lined up. Is there an element of rivalry between the two distillers? “Oh yes, there’s no doubt about that,” company president Kazuto Hombo says with a smile, “but that’s good.”

Not everything is wildly different at the two distilleries, of course. Just like at Shinshu, barley with four different peating-levels is used: non-peated, lightly peated (3.5ppm), heavily peated (20ppm) and super-heavily peated (50ppm). The ratios vary, however, even between seasons at one distillery. Whereas last season at Tsunuki, 80t of the 180t of barley processed was lightly-peated, this season the amount of non-peated barley has been more than doubled (90t) compared with last season. Lightly peated malt is still a significant 70t. Heavily and super-heavily peated malt account for 30t and 40t of the 230t total, respectively.

He’s got his own ideas and his own vision for Tsunuki and an inquisitive mind with lots of little experiments and plans for the future lined up


Walking to the mashtun, Kusano explains he has recalibrated the temperature of the mashing waters slightly. “I lowered the temperature of the first water to 72°C,” he points out, “which seems to help drain off the wort more easily.” The temperature of the second (79°C) and third water (82°C) is kept low, too.

As he tastes a sample of the wort from the underback, Kusano stresses the importance of having a clear wort. The mashtun is fitted with a special side-glass allowing the staff to keep a close eye on the mashing process. Time and again at the distillery, this sort of attention to the minutiae of the whisky-making process is striking.

A few minutes later, we’re standing among the five stainless fermenters. An innocent question about the capacity reveals exciting plans for the future. “Up until recently,” Kusano explains, “one batch used to be 1t of malted barley, but at the start of this year, we moved to a 1.1t/batch system.” Increased production and efficiency one would assume, but that’s not how things are done at Hombo Shuzo. Decisions are always driven by quality and innovation, and that is the case here, too. “One of the things I want to do next season,” Kusano whispers in my ear, “is start using specialty malts – caramelised and roasted malts – and the idea is to add 100g per batch, so that’s why, in preparation for that, we have moved to a 1.1t batch size.”

The fermenters are filled with about 5.5kl of wort and the fermentation time is around 90 hours. Nothing out of the ordinary, that is until Kusano opens the fermenters and we focus on what’s going on inside. Just like at Shinshu, three types of yeast are used: a distiller’s yeast, the old Shinshu slant yeast, and the yeast used to make the Weizen beer at their craft brewery next to the Shinshu Distillery. But around every corner of Tsunuki Distillery, the plot thickens.

As we check the aroma of a fermenter, I ask which of the three yeasts was used for this batch. “Well, this one is half distiller’s yeast and half shochu yeast,” Kusano says with a twinkle in his eye. “The added shochu yeast doesn’t seem to have made much difference so far, but we have to wait and see, and then distil it to find out.” Suspecting there might be more experimentation going on in the fermentation department, I enquire what other yeast types have been tried out. “I’ve been trying out some other yeast types since the beginning of this year, for example ale yeast, Belle Saison yeast, Munich wheat beer yeast and Windsor British-style beer yeast. I always use these 50-50 with distiller’s yeast. The Windsor, in particular, works really well. It brings out an incredibly intense fruitiness. The ale yeast is very interesting, too. On the second day of fermentation, it brings out a lovely yoghurt aroma and something akin to tsukemono (Japanese pickles).”

As we check out two fermenters further down the line, something else catches my attention: a bunch of 10 oak staves, each about half the size of a barrel stave, suspended on a chain, floating in the wash. “These are American white oak staves custom made by a local cooperage.” They’re clearly not there to impart any oak flavour, which wouldn’t happen anyway, so what’s the deal here? “This is part of my strategy to increase the growth of lactic acid bacteria. Our fermenters are stainless steel so there wasn’t much activity as far as late lactic fermentation was concerned.” Sniffing a bunch of staves hung up to dry underneath the fermenters, there’s a definite yoghurt aroma. “Something else I started using to keep the pH lower and encourage lactic acid fermentation is the ‘sour mash’ procedure,” Kusano explains.

“If we were to clean the spirit still, the spirit would become lighter. We want a more robust spirit and we also want the accumulated residue to become an aromatic part of the spirit.”


“Simply put, I take a bucket of wash from the fermenter that’s done and ready to be sent to the wash still and pour that into the fermenter being filled with wort.” It’s a procedure familiar from Bourbon making, but also used in shochu making – which is the bread-and-butter of Hombo Shuzo – so they know a thing or two about fermentation. All this, together with careful temperature control, is starting to pay off results according to Kusano. I wonder out loud if any of this is happening at Mars Shinshu. Kusano shakes his head. “The fermenters there are cast iron so it’s a different situation.”

Moving on to the still house, it’s remarkably cold. As it turns out, there’s no distillation going on that day. “We distil for 14 days and then take a break for one day for maintenance,” Kusano points out. Not that I see much maintenance going on in the stillhouse. “Ah yes, well, the wash still is cleaned every day, after distillation, but the spirit still isn’t. In fact, it hasn’t been cleaned since the beginning of the year.” This isn’t laziness, Kusano assures me. As he opens the spirit still, the aroma of the accumulated residue and oils – think vegemite plus clay – enters our nostrils. “If we were to clean the spirit still, the spirit would become lighter. We want a more robust spirit and we also want the accumulated residue to become an aromatic part of the spirit.” I can’t imagine any of the staff complaining about the no-cleaning policy for the spirit still.

“This year,” Kusano continues, “I’ve slowed down the distillation speed considerably, both for the first and second distillation. This seems to fly in the face of using worm tub condensers, which are aimed at creating a heavier spirit, but we are using this approach to get a rich, yet clean spirit.” One batch results in about 500l of new make at 64% ABV, so at filling strength (60% ABV) that is about three barrels per day. “We’ve also experimented with entry proof,” Kusano points out. Why am I not surprised? “We tried a range of filling strengths between 55% and 67% ABV. We’ll see what the future says.”

There are several old stone warehouses on site, but this time we’re checking out the new state-of-the-art racked warehouse, which used to be the bottling hall. There’s room for 2,000 casks so they’re good for a while. We discuss the maturation policy. “It’s about 50 per cent Bourbon barrels, and the rest is made up of sherry casks, butts, hogsheads and puncheons, virgin American white oak casks… and things we find left and right: rum casks, brandy casks, an ex-Laphroaig cask, that sort of stuff. We’re looking for port pipes now, which are a bit hard to get it, and also hogsheads which are not so common in Japan but, being slightly bigger than Bourbon barrels, would work better for maturation here in Tsunuki as the temperature is higher than in Shinshu.”

That would wrap it up for most distilleries, but at Hombo Shuzo this is where things start to get really exciting. The company has two whisky distilleries in different climatic settings, but they also have a small, traditional shochu distillery on the island of Yakushima. Yakushima is situated about 60km south from the southern end of Kagoshima prefecture. It’s the last ecosystem dominated by Japanese cedar and one fifth of the island is registered as a World Heritage Site.

There’s no doubt that some very special whiskies will be coming out of this warehouse in the future. Meanwhile, at Tsunuki Distillery, Kusano and his team are carrying on with their creative work.



So I find myself on the ferry to Yakushima to check out the warehouse there. The trip takes about two hours and the waters are pretty wild, but it’s a treat to see the Yakushima Aging Cellar. It’s not big, but it’s a very special place. The inside is clad with local cedar, obviously not the protected 1,000+ year old type, but replanted cedar that’s about 100 years old. When I’m there, on one of the coldest days of the year, it’s 11°C in the warehouse and the humidity is 51 per cent. “It does drop to 30 per cent some days,” Okizono explains, “but in summer, we have highs of 38°C and 85 per cent humidity in the warehouse. The angels’ share here is around eight per cent, whereas at Mars Tsunuki it’s six per cent. At Mars Shinshu, it’s equivalent to Scotland.”

The warehouse has a capacity of 400 casks, which isn’t much. “At the moment, there are 114 casks here,” Okizono points out. “Most of them are Bourbon barrels, but we have some sherry hogsheads and butts, too”.

The system that’s in place is that Tsunuki and Shinshi Distillery swap 6,000l of new make to mature at the other distillery, and send 6,000l of new make each to be matured on Yakushima. The oldest Shinshu vintage maturing on Yakushima is 2014. For Tsunuki, it’s still early days. Only one shipment, from the first season, has been received so far. That arrived in March 2017.

Outside the warehouse, we taste some cask samples of 2014 and 2015 Shinshu whisky. The non-peated 2014 Bourbon barrel sample reveals just how strong the impact of the climate on the maturation process is. Okizono has a soft spot for the non-peated Bourbon and so do I. “I prefer the non-peated spirit and in a way, without the peat, the natural conditions can ‘enter’ the whisky more easily.”

Later that night, Mr Hombo expresses a similar liking for the non-peated spirit. The day after, Tatsuro Kusano agrees, but for a very different reason. “I feel that the climate on Yakushima drives out the good qualities of the heavy peat. They kind of evaporate into thin air, if that makes sense, so I’ve come to see non-peated or lightly-peated spirit as more suited to the maturation conditions.”

As we are enjoying the various cask samples, we keep coming back to the 2015 Shinshu 3.5ppm spirit maturing in a puncheon made from ex-barley shochu casks. The balance of fruit, sweetness and gentle exotic spices is exquisite, and it’s just two and a half years old. There’s no doubt that some very special whiskies will be coming out of this warehouse in the future. Meanwhile, at Tsunuki Distillery, Kusano and his team are carrying on with their creative work.

As I leave the distillery and cross the parking lot, he casually reveals he’s also working on sourcing malted barley that’s smoked, not using peat but using cherry wood, pear wood and so on. But that’s for another time… We’ll be back.
Tsunuki Distillery
Tsunuki Distillery
Ex-Bourbon barrels at the Yakushima Aging Cellar
Ex-Bourbon barrels at the Yakushima Aging Cellar
A peek into the mashtun through the side-glass
A peek into the mashtun through the side-glass