Japan Sake and Shochu Makers Association | JSS

bg
bg

Shochu Distillation Process Flavor Profile of Shochu

Various Factors

Flavor Profile of Shochu

The flavor profile of shochu builds upon various factors. Above all, the selected base ingredients, type of koji mold, and the koji base all shape the flavor profile of the final product. Another influential factor is the method of distillation used. Atmospheric distillation tends to bring out a fuller flavor of the raw material while vacuum distillation results in a lighter, slightly more floral profile. In addition, while most shochu is shipped without long-term aging, the duration of aging and the vessel used affects the flavor for the products.

Factors Affecting the Flavor Profile of Shochu

Raw Material

There are more than 50 base ingredients legally approved for shochu production such as sweet potatoes, barley, and rice. Of the most common ingredients, sweet potatoes have the most diversity amongst its varieties. Therefore, when making sweet potato shochu, the potato variety can determine the flavor profile of the final product. In contrast, other popular base ingredients, like rice and barley, have a limited number of varieties that are used for shochu production.

Sweet Potatoes

Aromatic Components

Sweet potato shochu, or imo-shochu, contains a number of distinct aromatic components, including beta-Damascenone and monoterpene alcohols. Beta-Damascenone is a compound derived from potatoes with a characteristically sweet, apple compote-like aroma. It is also a characteristic aromatic compound of brandy. On the other hand, monoterpene alcohols produce scents similar to Muscat grapes, lychee, citrus fruits, and flowers. This compound comes from glycosides attached to sugars in potatoes. Koji enzymes then break down these glycosides to produce sugar and monoterpene alcohols. Subsequently, yeast and the distillation under acidic conditions further alter the structure of the monoterpene alcohols, producing a variety of aromatic compounds.

Sweet Potato Varieties

The type of sweet potatoes used to make sweet potato shochu affects the flavor of the final product, much like grape variety in winemaking. There are over 40 varieties of sweet potatoes used for shochu production. These varieties fall into categories sorted by color, including yellow, white, orange, and purple.

  • Yellow Sweet Potatoes

    Kogane Sengan is the most widely used variety in sweet potato shochu production. It has a yellowish-white flesh and makes shochu with a distinctly rich, sweet flavor and chestnut-like aroma.

  • White Sweet Potatoes

    Joy White is another popular sweet potato variety. They have white flesh and contain components with citrus or floral aroma. As a result, they often produce a mild and fruity shochu. The Kyushu Okinawa Agriculture Research Center developed the Joy White variety in 1994. It is the first sweet potato variety bred specifically for shochu production.

  • Purple Sweet Potatoes

    Purple sweet potatoes like Ayamurasaki contain the violet pigment anthocyanin. This pigment is responsible for making shochu with an almost wine-like flavor. In addition, the diacetyl present in purple sweet potatoes produces a dairy-like flavor.

  • Orange Sweet Potatoes

    Some orange-colored sweet potato varieties used in shochu production are beni hayato and ayakomachi. These potatoes contain beta-carotene derived from carotenoids. Shochu made with these sweet potatoes have flavors similar to boiled carrot, pumpkin, violets, and mango.

Barley

Barley shochu has a characteristic aroma of barley and a lightly sweet, mellow taste. Most of the barley used for shochu production is two-row barley. However, some products incorporate hull-less barley and six-row barley as well. Approximately one-third of the barley used in shochu production is harvested domestically while the rest are imported, mainly from Australia. Of the several varieties of two-row barley, the two most popular ones are nishinohoshi and toyonohoshi in Japan. However, the distillation method influences the flavor of barley shochu more than the variety of barley used.

Rice

Rice shochu is made with short and round grain Japonica varieties of rice, and has a fresh and slightly fruity flavor, somewhat similar to that of freshly cooked rice and sake. The rice is polished to a similar rate to table rice, with around 90% of the grain intact. Like barley shochu, the distillation method has greater influence than the variety of rice used in determining the flavor of rice shochu.

On the other hand, awamori production uses long and thin-grained Indica rice. Awamori has a fuller flavor with apple and banana aromas. It also has a unique savory, mushroom-like fragrance derived from the lipids in rice.

Indica rice tends to develop a sweet, vanilla-like aroma through the production of vanillin. First, koji enzymes release ferulic acid from the hemicellulose in cell walls. Yeast and koji enzymes then convert ferulic acid into a smoky aromatic compound, 4-VG (4- vinylguaiacol), during the brewing process. This compound eventually changes to vanillin through distillation and aging processes.

Koji Mold

There are 3 main types of koji mold used in shochu production: white, black, and yellow. These three types each produce slightly different flavor characteristics in shochu.

White Koji Mold

White koji mold is the most widely used type in shochu production. It is a mutant variation of the black koji mold. White koji mold brings out a smooth, rounded flavor of the base ingredients, resulting in a light shochu with a clean finish.

Black Koji Mold

Black koji mold is used in all awamori and some sweet potato shochu. This type of koji mold enhances the flavors and aroma of the ingredients, producing a fragrant, rich, and flavorful shochu. This is especially true with sweet potato shochu. Black koji mold has more vigorous enzymes compared to other koji molds. These enzymes are capable of breaking down the monoterpene alcohol glycosides present in sweet potatoes.

Yellow Koji Mold

Yellow koji mold is less popular than its counterparts due to the extensive care it requires to keep the fermenting mash from spoiling. However, this type tends to bring out fruity and floral aroma from the ingredients when properly treated.

Koji Type and Flavor Profile

Type of Koji Mold Citric Acid Production Flavor Aroma
Yellow No Light Floral, fruity
Black Yes Rich, clean finish Rich
White Yes Fresh and light Mild and smooth

Raw Material for Koji

The majority of koji used in shochu production is made from rice. However, barley koji is popular in Oita and the Tokyo Islands and some distilleries make koji with sweet potatoes. Some believe that rice koji gives shochu a unique sweetness and greater depth of flavor. Barley shochu production uses both rice koji and barley koji. Typically, barley shochu made with barley koji has a lighter, more refreshing flavor than barley shochu made with rice koji. The use of sweet potato koji is exclusive to sweet potato shochu production as it accentuates the flavor of sweet potatoes.

Distillation Method

All honkaku shochu is distilled once in pot still, however, there are two ways to distill the fermenting mash; under atmospheric pressure and under reduced pressure.

Distillation Method

All honkaku shochu is generally distilled once in a pot still. However, two different distillation methods affect the resulting flavor: atmospheric distillation and reduced pressure distillation.

Atmospheric Distillation

Atmospheric distillation is a distillation method performed under normal pressure conditions. The fermenting mash is heated up to 85-95℃, which allows many components to evaporate into the distillate. At the same time, the high temperature facilitates chemical reactions to create new compounds. The new compounds also collect within the distillate along with the alcohol. As a result, atmospheric distillation produces shochu with a rich, full flavor.

Reduced Pressure Distillation

Reduced pressure distillation involves reducing the pressure inside the still to allow the mash to boil at a lower temperature, around 45-55℃. Compared to atmospheric distillation, reduced pressure distillation activates less chemical reaction. Therefore, there are fewer flavor components transferred from the mash into the distillate. In addition, lower temperature helps retain floral aromatic compounds. As a result, shochu made with reduced pressure distillation has a lighter flavor and often floral aromas.

Distillation Method and Flavor Profile

Atmospheric Pressure Reduced Pressure
Distillation Temperature 85-95℃ 45-55℃
Flavor Profile Rich, full flavor of the base ingredient Light, floral note

Aging

While most shochu does not require aging, some distilleries choose to age their product for a few years.

In Okinawa, distilleries age awamori in earthen pots or tanks for over 3 years. The aged awamori, called “kusu” has both a high cultural and market value. Kusu has a distinct vanilla-like flavor that comes from a compound called vanillin produced during the aging process.

In recent years, the process of aging shochu in wooden casks, like whiskey or brandy, has grown in popularity. When aged in this manner, the resulting shochu takes on the aroma and flavor of the cask. Rather than clear, it is often a light amber hue in color.

Aromatic Characters Derived from Production Process

Ingredients Fermentation Reduced
Pressure
Distillation		 Atmospheric
Pressure
Distillation		 Aging
Floral
(sweet potatoes),
grass
(buckwheat),
cereal
(rice, barley),
sweet potato
(terpene in
sweet potatoes)		 Fruity
(apple, banana),
grass
(buckwheat),
dairy/yogurt		 Fruity (apple, banana), floral Sweet
(vanilla, caramel),
cereal,
toast-like,
soy sauce-like		 Sweet
(vanilla, caramel)

Check Other Professional Guides

ARE YOU OF LEGAL
DRINKING AGE?

By entering this website, you certify that you are of
legal drinking age in the country you reside in.

YES NO