1:23in productionCh. 1 · What the dish is and where it came from/ 1:23 · ceiling 15 min
Ingredients · Technique
Kōji (food)
Koji is a filamentous fungus—most commonly Aspergillus oryzae—or a mixture of that culture with wheat and soybean meal, used in Japanese food fermentation.
Koji is a filamentous fungus, most commonly Aspergillus oryzae, or a mixture of that culture with wheat and soybean meal. It is traditionally used in Japanese cuisine for fermenting food. The term 'kōji' in English refers specifically to Japanese starter cultures. The Chinese term qū, meaning mold used in fermented foods, was first mentioned in the Zhouli (Rites of the Zhou dynasty) in China in 300 BCE.
Koji is a filamentous fungus, most commonly Aspergillus oryzae, or a mixture of that culture with wheat and soybean meal.
0:27
How it works, in terms someone would actually use
Koji is stored for two to three days at 30°C under high humidity to allow Aspergillus oryzae to grow.
0:35
What it gets right
It produces sweetness by splitting starch into glucose.
0:44
What it does not
Koji is not a ready-to-eat food.
0:52
What it changed
Different Aspergillus strains, substrates, and culture conditions—such as temperature, pH, salt content, and humidity—yield products with distinct composition, flavor, and odor.
1:00
Who it is for, and who it is not
It is for people making fermented foods like soy sauce, miso, or sake.
1:17
Is it worth your time
It is worth your time only if you are fermenting foods using traditional Japanese methods.
Worth your time?
Selectively. Start with the brief, then cook the parts we point at.
What works
It produces sweetness by splitting starch into glucose. It delivers umami taste through glutamic acid and aspartic acid released from proteins during fermentation.
What does not
Koji is not a ready-to-eat food. It is a microbial culture or substrate mixture used to ferment other ingredients.
Cook it if
Skip it if
The written brief1 min read
What the dish is and where it came from
Koji is a filamentous fungus, most commonly Aspergillus oryzae, or a mixture of that culture with wheat and soybean meal. It is traditionally used in Japanese cuisine for fermenting food. The term ‘kōji’ in English refers specifically to Japanese starter cultures. The Chinese term qū, meaning mold used in fermented foods, was first mentioned in the Zhouli (Rites of the Zhou dynasty) in China in 300 BCE.
How it works, in terms someone would actually use
Koji is stored for two to three days at 30°C under high humidity to allow Aspergillus oryzae to grow.
What it gets right
It produces sweetness by splitting starch into glucose. It delivers umami taste through glutamic acid and aspartic acid released from proteins during fermentation.
What it does not
Koji is not a ready-to-eat food. It is a microbial culture or substrate mixture used to ferment other ingredients.
What it changed
Different Aspergillus strains, substrates, and culture conditions—such as temperature, pH, salt content, and humidity—yield products with distinct composition, flavor, and odor.
Who it is for, and who it is not
It is for people making fermented foods like soy sauce, miso, or sake. It is not for those seeking a standalone ingredient or snack. Freeze-dried spores are light-protected and stored at room temperature; black koji produces citric acid to inhibit unwanted microbes.
Is it worth your time
It is worth your time only if you are fermenting foods using traditional Japanese methods.