Shōchū making process

Planting seeds

In early February, sweet potato seeds are planted in greenhouses. It takes about a month and a half for the seeds to grow, meanwhile, the temperature and humidity of the greenhouses is carefully monitored.

Making ridges

While the seeds are growing, ridges are made in the field. The sweet potato seedlings are then planted on these ridges.

Planting

Early April is when planting the seedlings out starts. Once they have grown to about 25 centimeters, the seedlings are cut off and replanted in the field. Over the next 150 days, the seedlings will bathe in sunlight and slowly grow into delicious sweet potatoes.

Rice washing

To make kōji, the rice bran and other debris are washed away.

Soaking

Water is put together with the rice in a drum allowing it to absorb the water. The absorption time varies depending on the size and type of grain.

Steaming

After having been soaked, the rice is steamed, causing the starch to gelatinize, making it more susceptible to the enzymatic action of kōji. The steamed rice becomes hard on the outside and soft on the inside.

Kôji production

Seed kôji is then sprinkled over the steamed rice and cultivated for about 40 hours. Kôji produces glycolytic enzymes that convert starch into glucose and citric acid protecting the unrefined sake from bacteria.

Primary preparation

Kōji is then put together with yeast and water in a tank in order to multiply the yeast. The yeast is the source of unrefined sake, which is why it is called 酒母 shubo (sake mother) in Japanese. The process takes about 6 days during which the temperature needs to be monitored.

Cleaning the sweet potatoes

The sweet potatoes come in the day following their harvest. At this point, they are still covered in dirt and need to be washed clean with water.

Sorting the sweet potatoes

The washed sweet potatoes are then sorted. Any diseased or damaged parts are removed and the sweet potatoes that are too large are split to ensure size homogeneity. Sorting is an essential process as it affects the flavour of the finished shōchū.

Steming the sweet potatoes

After being sorted, the sweet potatoes are placed in a steamer. The steaming time depends on the variety, size, and harvest time of the sweet potatoes.

Secondary preparation

The steamed sweet potatoes are cooled down to a suitable temperature before being crumbled and put together with water and yeast in a tank to brew. Once this is done, the preparation is transferred to fermentation tanks to undergo alcoholic fermentation.

Fermentation

The sweet potatoes will be left to ferment for about 9 days. Inside the tank, the saccharification enzyme of the kōji will cause the starch to turn into glucose that will be metabolized by the yeast to produce alcohol.
The aromatic component of shōchū is also produced in this process.

Distillation

Once the fermentation process is done, the preparation is transferred to the distillation machine. The traditional atmospheric distillation produces a rich, sweet potato aroma while vacuum distillation produces a fruity, flowery aroma. The refined shōchū is 38% alcohol by volume.

Storage

After distillation, the excess oil and foreign bodies are filtered out, the refined shōchū is then left to mature in tanks. During the process, the gas and such escape resulting in a mellower shōchū.

A month after the dilution, the taste has settled down and the shōchū can be bottled.

Bottling is conducted with meticulous care to ensure that no foreign bodies get mixed in. Finally, the bottle is checked by the human eye.