The imo shochu of Kagoshima and Kokubu Shuzo

Mamoru Sasayama

9th July, 2022

Kawahara Valley which flows under the kura

Imo syochu is made from sweet potatoes in Kagoshima Prefecture, the southernmost prefecture in mainland Japan. Kagoshima Prefecture is also known as Satsuma, and sweet potato is such a deeply rooted crop in Kagoshima that the name of the place is the name of the crop.
Since Kagoshima's hot climate is not conducive to sake production, imo shochu, which uses the local culture, has become popular and is produced in many parts of the prefecture.

Sake and shochu are two of the most popular alcoholic beverages in Japan, but while sake is made by pressing, like wine, shochu is made by distillation, like whisky, brandy and gin.
Until about 2000, imo shochu was only drunk in certain regions, such as Kagoshima, but with the improvement in the quality of the liquor, it is now drunk in all parts of Japan.

The sweet potato fields

Typically, imo shochu is made from rice malt and sweet potatoes, but in 1997, Kokubu Shuzo's toji (master brewer) Nobuhisa Yasuda developed the industry's first 100% sweet potato shochu without rice malt, and has continued to take on the challenge of making new shochu ever since.

In 2012, he worked on a 100% sweet potato shochu made from a sweet potato called 'Tsurunashi Genji', which he revived from 10 sweet potato plants. We bought the sweet potato in December, just before the end of the brewing season, but it had been sitting in the sweet potato fields for a while and was overripe and damaged. We made a 100% sweet potato shochu using this sweet potato, but it left a strong pungent smell, as if it had been burnt. 

Cutting sweet potatoes

To be honest, we thought this shochu was a failure, but after about six months, that pungent smell started to change. Gradually we started to detect a fruity aroma in the pungent smell. Through this brewing process, we could see that sweet potatoes contain the same fruity aroma components as grapes.

When we named our sweet potato shochu "Yasuda" and launched it in the autumn of 2013, it received great acclaim as an unprecedented type of shochu, and was included in the "New Era of Shochu" published by the Development Bank of Japan in April 2017. Shochu was featured as having the potential to become a benchmark shochu in the research report "The New Shochu Era" published by the Development Bank of Japan in April 2017. Until now, it has been common knowledge in the industry that fresh sweet potatoes should be used for the production of imo shochu, but we believe that this is the beginning of the spread of a new approach to sweet potato storage and maturation.

Nobuhisa Yasuda

Nobuhisa Yasuda then worked on making a 100% sweet potato shochu with a different yeast and distillation method. The result was a shochu with a distinctly fruity taste, which he called "flamingo orange". When he put it on the market, he received a lot of feedback from women and others who normally do not drink sweet potato shochu. Also, when we tried using malted rice instead of 100% sweet potato, we produced shochu called 'coolmint green' and 'sunny cream', which have a distinct banana and melon taste. The result is a shochu with a banana and melon taste.

Kokubu Shuzo's flavoured shochu

Original text



安田宣久はその後、酵母と蒸留方法を変えた芋100%焼酎造りに取り組みました。果実の風味が引き立つ焼酎に仕上がり、「flamingo orange」命名して発売したところ、普段あまり芋焼酎を飲まない女性の方などからも多くの反響を頂きました。更に、芋100%ではなく米麹にこだわって取り組んだところ、バナナやメロンのような風味が引き立った「coolmint green」「sunny cream」といいう焼酎が誕生しました。

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Mamoru Sasayama

Kokubu Shuzo Inc. CEO