Koji - How a Mold Can Define a National Beverage

Shochu is to Japan what Bourbon is to the United States or Tequila is to Mexico. Unique to Japan, Shochu is a distilled alcoholic beverage that was discovered through an encounter when the traditional sake production of Japan was met with the distillation techniques of Asia. 

Traditionally, Shochu is distilled using two methods, traditional pot still distillation and the more recently explored column still distillation. However, just as Bourbon and Tequila have their own distillation properties that make them uniquely American and Mexican, Shochu similarly relies on the usage of a mold known as koji. 

What is Koji? 

Koji is a mold that contains enzymes which help convert starch from the base ingredients in the distillation process to sugar. This process is known as saccharification. In the production of beer and whiskey, the base ingredients are saccharified by the enzymes in malt. Similarly for shochu, the saccharification process is done using koji.

Shochu Base Ingredients

The base ingredients of shochu production, coupled with the koji mold, help to define the offering and give it its unique flavor. Koji can most easily be grown on rice, as is with sake production. However, other ingredients have been introduced to give different flavor profiles to shochu, including barley, sweet potatoes, and buckwheat. As it is more difficult for koji to multiply on these ingredients, producers have had to come up with methods to encourage growth, including cutting sweet potatoes into smaller cubes and experimenting with steaming methods. These ingredients can vary depending on desired taste profile as well as the region.

Various Koji Molds

Koji mold can be broken down into three different categories: black, white, and yellow. Black koji was used traditionally in the making of Okinawa’s awamori. The usage of black koji produces a citric acid which helps contain bacteria, especially in warmer climates. White koji is very similar to black outside of its apparent color. Many producers have adopted using white koji as it does not soil their workers’ clothing, tools, and workspaces. White koji is also attributed to white, cleaner tasting shochu. Yellow koji mold has been introduced more recently to help diversify the offerings in shochu. It produces a flavoring more similarly related to sake. 

Fermentation and Distillation 

The first step in making shochu is creating the starter culture, which is also known as the seed mash or first moromi. Koji, water, and a small amount of yeast are combined in a container which promotes the conversion of starch in the koji to sugar and the multiplication of yeast from the sugar. After anywhere from 3-8 days, the steamed base ingredient is added to the starter culture with water for main fermentation. Once the fermentation has completed, the remaining is transferred to a pot still for distillation. Single distillation results in the shochu having an approximate 37-43% ABV. Before packaging, water is added to lower the ABV to 20-25% before  being sent out to be enjoyed by whoever is lucky enough to experience the offering.

While some may not appreciate mold and all that it offers, one must look no further than shochu and sake to realize all of the positive applications it can have. So next time you and your friends or family are imbibing over a glass of shochu, make sure to thank the koji. Kanpai!