Aspergillus oryzae (Koji-kin)

Aspergillus oryzae, also known as koji-kin, is a fungus that ferments rice, barley or soy and produces enzymes that break down starches and proteins. It is the key to miso, soy sauce, sake and mirin.

Ingredients

▢ Aspergillus oryzae (tracks)

What is it?

Aspergillus oryzae is a noble fungus that has been used to ferment foods in Japan for more than 1,000 years. By producing enzymes (amylases and proteases), the fungus breaks down starches and proteins into sugars and amino acids → the source of umami.

Use in the kitchen

Fermentation of miso (soybeans + rice/barley koji)
Production of soy sauce
Brewing sake and mirin
In shio-koji, a marinade that tenderizes meat and fish

Flavor Profile

Not edible by itself, but gives sweetness and umami to fermented products through enzyme action.

Details

Considered a national fungus of Japan(cook).
Safe for consumption and traditionally cultivated.

Is Aspergillus oryzae safe?

Yes, this fungus is completely safe and has been used for centuries in Japan for food.

What do you use koji-kin for?

For the production of miso, soy sauce, sake, mirin and shio-koji marinades.

Can I buy Aspergillus oryzae myself?

Yes, koji starters are available in specialty Asian stores and online.

What exactly does Aspergillus oryzae do?

The fungus produces enzymes that break down starches and proteins, creating sugars and amino acids → the source of umami.

Is Aspergillus oryzae the same as the fungus in natto?

No, natto is fermented with Bacillus subtilis, not Aspergillus.