What is Koji?

• A. A type of rice used in brewing
• B. A mold used in the sake brewing process
• C. A fermentation vessel
• D. A yeast strain

Answer: (B)

Koji is a mold used in the sake brewing process. It refers to Aspergillus oryzae grown on steamed rice to create koji, which produces enzymes like amylases that break down starch in the rice into fermentable sugars. Those sugars are what yeast later ferments into alcohol, so Koji is essential for making sake. It’s not just rice, not a fermentation vessel, and not a yeast strain.