Awamori’s Special Ingredient: Black Mold
Awamori’s special ingredient is kurokoji (black mold). Koji (Aspergillus oryzae) is a fungus used for fermentation in making miso bean paste and soy sauce, as well as sake and shochu (a popular Japanese distilled spirit). Kurokoji (Aspergillus awamori) is its relative; it originated on Okinawa and is used exclusively for distilling awamori.
Kurokoji converts the starch in rice, the base ingredient of awamori, to sugar, which is converted into alcohol during fermentation. This process, known as “multiple parallel fermentation,” also occurs during sake and shochu production. Kurokoji, however, produces more citric acid than the white and yellow koji typically used to make sake and shochu. The high amounts of citric acid prevent airborne bacteria from infecting the fermentation mash. This is a key benefit in Okinawa’s hot and humid climate, as it allows awamori distillers to produce alcohol year-round.
In the past, many varieties of kurokoji were used for awamori production, but almost all were lost when the distilleries were destroyed during World War II. Luckily, a few spores that survived the war were successfully cultivated and used to restart awamori production. In 1998, some samples of other prewar kurokoji stored at the University of Tokyo were discovered by one of the school’s professors, and these have since been used for making awamori.