Shochu's Super Power: MOLD!

Koji. Just the word, in my mind, evokes something fun and exciting. Scientifically named Aspergillus oryzae, koji is a fungus and it is a critical ingredient to the making of shochu. It is the power behind so many lovely Japanese edibles and drinkables from sake and shochu to soy sauce, miso, and other traditional foods.

A darn good Shochu!

Where does Koji come from? Koji is the result of cooked rice or soybean that has been fermented or placed in a warm and humid place for a day or two. In Japan, the koji typically does its fermenting magic on wooden trays [koji buta] inside wood panel rooms. Enzymes break down the carbohydrates and proteins.

Are there different types of koji? Yes, three are three types of koji: yellow, white, and black.


1. Yellow Koji, most commonly used for sake production, is less frequently used to make shochu because, of the three kojis, it is the most sensitive to warm temperatures. Yellow koji can easily sour during the fermentation process if overheated. As a result, yellow koji is not as frequently used for shochu making in the warmer climate of Kyushu. The benefits of yellow koji are that it produces a rich, fruity, and refreshing flavoring.

2. Black Koji was first “discovered” in 1910 as an improvement on yellow koji and the efficiency of shochu production. Black koji’s ability to produce excessive citric acid prevents the souring of the moromi [fermented rice mash]. In addition, black koji is the best of the three at highlighting the taste of the base ingredient, resulting in a rich shochu characterized by a slightly sweet, mellow taste. The one drawback to black koji? Envision black dust wafting all over and covering facilities and workers’ clothing. It can be a bit of a mess. For many decades, shochu distilleries were less inclined to use black koji in their shochu production. Now the use of black koji is a point of pride for distilleries.

3. White Koji is a mutation of black koji, “discovered” in 1923. Not as messy as black koji, it is easy to cultivate, and it promotes quick saccharization [sugar conversion]. White koji produces a refreshing, mild, and sweet flavor.

Is koji like a vitamin? As much as I would like to think that all this information about science, enzymes, spores, and fermentation, leads me to understand koji is super cool, I can’t claim it is a vitamin. However, koji does provide some great health benefits. For example, the fermentation process releases flavonoids that is thought to be effective in cancer prevention. And the probiotic properties of the koji process are also thought to aide digestion and boost immunity. Drink up!

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