In episode 38 of the Japan Distilled podcast, your hosts Christopher Pellegrini and Stephen Lyman dive into national mold of Japan. Without koji (aspergillus oryzae, kawachi, or awamori) there would not be a Japanese culinary tradition as we understand it today. Nor would there be the Japanese spirits we all know and love.
CHRISTOPHER PELLEGRINI Vermont born and bred, long-time Tokyo resident and author of The Shochu Handbook, Christopher learned about delicious fermentations as a beer brewer at Otter Creek (Middlebury, VT). He now spends most of his waking hours convincing strangers that shochu and awamori are unlike anything they’ve ever tried before.
STEPHEN LYMAN discovered Japan’s indigenous spirits at an izakaya in New York City. He was so enthralled that he now lives in Japan and works in a tiny craft shochu distillery every autumn. His first book, The Complete Guide to Japanese Drinks, was nominated for a 2020 James Beard Award.
Stephen and Christopher have been fermentation geeks for a very long time.
If you have any comments or questions about this episode, please reach out to Stephen or Christopher via Twitter. We would love to hear from you.
What is koji?
Koji is the national mold of Japan. Without it there wouldn’t be soy sauce, miso, mirin, sake, shochu, or awamori as we know them. It’s a critical ingredient in Japanese fermentation traditions. Originally introduced to Japan as part of the Chinese yeast balls, or jiuqu, koji was isolated by Buddhist monks for sake production as early as the 700s CE and possibly earlier.
Koji is a mold that grows in hot, humid environments, as do most molds, but this is a productive mold. During its fermentation process it releases generous amounts of two key enzymes: amylase and protease. Amylase saccharifies starches, such as rice or barley, and protease breaks down proteins to create amino acids (umami).
When used to make beverage alcohol, the amylase replaces malting as would be used in beer or whisky production. To learn more about the differences, please listen to episode 27 on Malt v. Koji.
The mold is purchased from one of several mold factories throughout Japan. The spores are spread on freshly steamed barley or rice for most spirits production, though koji can be grown on virtually any starch source. Soba, corn, sweet potatoes, and soy beans have all been used as substrates various fermentations.
Once the spores are inoculated on the starch source, careful temperature and humidity must be controlled to give the koji an opportunity to infiltrate to feed and create the desired enzymes. In addition to protease and amylase, heat is generated so the fermentation must be cooled to maintain optimum temperature. The mold is most active from a range of about 30-42 degrees Celsius (86-108 Fahrenheit).
Three kinds of koji are used for alcohol production. Nearly all sake is made with yellow koji, which has been used in alcohol fermentations in Japan for over 1,300 years. The yellow variety requires assistance from the addition of acidity to protect the fermentation. This was traditionally done with lactic acid bacteria, but more recently commercial acid is added to modern sake fermentations.
Black koji is native to Okinawa and has been used to make Awamori for as many as 600 years since distilling technology first arrived on the islands. Today black koji is the only type permitted for making Ryukyu Awamori. This mold creates natural citric acid when the proper temperature range is maintained during inoculation. This helps protect the ferment in the hot, humid climate of Okinawa. Spirits made with black koji tend to have deep, earthy, umami-laden flavors and aromas.
Finally, white koji is recent to the party. This mutation of the black variety was discovered in a laboratory in Kumamoto in 1918. Today a majority of honkaku shochu is made using white koji, though yellow and black are still commonly used. This white variety also creates copious citric acid when the inoculation is properly temperature controlled. White koji tends to be more reserved, allowing the flavors and aromas of the base ingredients to shine through.
Much More to Explore
These show notes just scratch the surface, but should serve as a useful aid as you listen to the episode itself. As always, please feel free to reach out if you have any questions about koji.