When it comes to unique drinking cultures, Japan is a country with plenty to talk about. Drinks like nihonshu and awamori are complex and contradictory, adding to the intrigue of the Japanese alcohol industry. For anyone who is interested in learning more about sake, there are podcasts like Sake On Air, which go into detail about the industry and why Japanese beverages have become so popular in the west.
Understanding the sake brewing process is an integral part of learning how to drink it and koji is an essential ingredient. In case you’re scratching your head and wondering what koji is, the creators of Sake On Air have released an episode that gives a helpful introduction into Japan’s national mold.
What is koji?
Known by the scientific name of Aspergillus oryzae, koji is a mold that is vital to the sake brewing process. It converts the starch in rice to sugar, and while that might sound straightforward, the process is far more complex. Fortunately, Justin Potts, Chris Hughes and Sebastien Lemoine’s koji basics episode clarifies how important it is.
According to them, the word ‘koji’ gets thrown around a lot and there is a lot of confusion as to what it is. Potts and Hughes explain that koji can mean one of two things:
- Koji-kin – the koji spores that are sprinkled onto rice to start the starch-to-sugar conversion.
- Koji – The finished rice product that is produced at the end of the koji making process.
Another part of the episode is dedicated to explaining the different types of koji and they can be broken down into three categories:
- Yellow koji – Commonly used for nihonshu and shochu.
- Black koji – Used to make shochu and Okinawan awamori.
- White koji – A natural mutation of black koji that can be used to make shochu.
All three variations produce different flavours, such as a fruity and delicate taste for yellow and a richer, stronger taste for black.
Koji craftsmanship
The episode also covers the amount of care that people in sake breweries put into the koji making process. It’s common for brewery workers to stay overnight and constantly check that the mold is stablised. Chris Hughes compares it to looking after a baby and I thought that was a great comparison because it shows how much energy brewers devote to making sake.
Another important thing to note is that koji is used in a wide variety of Japanese products, such as soy sauce and mirin. It’s an invaluable part of Japanese cuisine, and while koji may not be the first thing on someone’s mind when eating or drinking, it’s still worth knowing about from a cultural perspective.
Listen to the Sake On Air koji basics episode to learn more.
Yamato Magazine 
It makes sense that the complexities of Japanese culture would be reflected in the production of sake! This was all new information for me. Thanks!
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Happy to help. The science behind koji is interesting and I’d recommend listening to the podcast to find out more!
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