Handcrafted koji since 1689- Spanning 8 generations


Koji FAQ

When was koji first used in Japan?
Koji is first mentioned in literature in the beginning of the 8th century. It is written that sake was made using the mold that grew on dampened rice that had been left as offerings to the gods.
How is koji made?
Sterilized koji spores are sprinkled over steamed rice and allowed to propagate. The koji is then allowed to grow in a controlled environment. The job of the koji maker is to control the temperature and conditions for optimal growth.
How long will fresh koji keep?
About two weeks.
How should I store fresh koji?
Keep it refrigerated. Do not freeze.
If the koji turns yellowish, is it safe to use?
If it is before the expiration date, it is fine to use. However, koji that is closer to the expiration date is better to use in shio-koji, rather than in amazaké. Fresh koji is best for producing sugars and older koji is better for producing amino acids.
Can you make koji at home?

It’s not impossible, but it’s difficult to maintain the required temperature for three full days. Making it from instructions available on the internet is difficult.

Is it possible to make koji outside of Japan?
If you have set up a proper environment for the koji to grow, it is possible. It may be difficult in a very arid environment.
Is koji from all shops (producers) the same?
Even when using the same spores, each koji shop will have a distinct koji resulting from different fermentation conditions, environment and process.
What is the difference between dry koji and fresh koji?
Dry koji has less than 22% moisture content and will keep for a longer time. However before using it, you need to reconstitute it in water.
Fresh koji is fresh and has 24-28% moisture content. It won't keep as long, but you can use it as is.
What is the difference between the two characters used for koji 糀 and 麹?
糀 is the character developed in Japan. The kanji components derive from the fact that in Japan koji was originally propagated on rice and the koji filaments and spores resembled flowers. 麹 is the character developed in China. In China, koji was propagated on a variety of grains, including rice.
Incidentally, the koji spores used in China, Korea and other Asian countries are a different variety than those used in Japan. In Japan, the koji is Aspergillus oryzae of the Aspergillus genus. This variety of koji has been designated as the national fungus.
Other Asian countries use koji made using spores of the Rhizopus genus. Tempeh and the Chinese sake, shokoshuu, are made using this variety of koji.