Japanese whisky has evolved into some of most coveted alcohol on the planet, regularly being sold for thousands of pounds. Much of the appeal lies in finding rare releases from distilleries that are no longer active, how Japanese whisky is produced, and the ingredients used to make it.
A unique production method linked to whisky making in Japan is the use of mizunara wood. Read on to learn about the qualities of mizunara, how it affects the flavour of whisky and why it’s only used for select casks.
Japanese casks vs Western casks
Before diving into what mizunara is, it’s worth noting the differences between how Japanese coopers make casks in comparison to western coopers.
It’s important to understand that Japanese whisky giants like Suntory and Nikka make and use new casks, rather than simply relying on second-hand barrels like many Scottish whisky distillers. This gives Japanese whisky makers more control over their production and there are no specific rules that indicate certain casks must be used to mature whisky in order for it to qualify as Japanese.
To this end, there are far more Japanese-style cask makers in Japan than there are Western cask makers. Japanese coopers make cylinder-shaped barrels out of Japanese cedar that are bound with split bamboo cane and don’t have the wide mid-sections of Western barrels. Instead they fan out towards the top.
Japanese-style casks are usually reserved for ageing sake and shochu instead of whisky, but that hasn’t stopped Japanese coopers from producing whisky barrels. Kyushu-based Ariake Barrel is a good example.
Ariake chars its casks by placing them over a fire and then loading the insides with sawdust, causing the flames to shoot up and burn the wood. The cask is rolled through the warehouse and is hosed down by a cooper, showcasing Ariake’s focus on a hand-made approach.
What is mizunara?
While the majority of Japanese whisky is aged in American white oak barrels, mizunara stands out as a unique offering. Also known as Japanese oak, mizunara is split into two words. Mizu means water, referring to the moisture inside the oak, while nara means oak.
Japanese oak can be found all across Japan and has been used at various times throughout the history of whisky production. The Yamazaki distillery started ageing whisky in mizunara casks during World War II when it became harder to import the typical sherry casks that were used to impart dark and spicy flavours in their whisky.
In 1934, Nikki founder Masataka Taketsuru chose Hokkaido for his first Nikka distillery because of the abundance of Japanese oak trees. He also hired the famed beer cooper Yoshiro Komatsuzaki to chop the Japanese oak into casks and had him stationed at Yoichi.
Nikka used mizunara to age whisky up until 1965 and then the business started experimenting with American white oak. After five years, Nikka made the transition towards ageing nearly all of its whisky in American oak because it was less prone to leak.
What makes mizunara special?
The popularity of mizunara is attributed to its unique characteristics. One such feature is that when it’s cut it produces markings called torafu (tiger stripes). This exotic appearance made Japanese oak a premium export in places like the US and UK during the late 19th and early 20th century. It was used to make chairs, desks, hand railings and wood panels.
In the modern day, mizunara is favoured in whisky ageing because it broadens the range of flavours. Described as imparting a ‘struck match’ taste, Japanese oak creates more sulfery and candle-like flavours.
In Japanese Whisky: The Ultimate Guide To The World’s Most Desirable Spirit, Brian Ashcraft references a study carried out by Suntory and Heriot-Watt University in Edinburgh to compare 27-year old whisky aged in Japanese oak and American oak barrels. The mizunara-aged whisky had fewer cereal and grassy notes than the American oak but had a much higher concentration of coconut aromas.
Using mizunara in the maturation process doesn’t make a whisky better than other woods. It simply makes it different, providing other qualities. It’s another fascinating aspect of Japanese whisky!