About Koji
Koji
The Heart of Japanese Fermentation
Koji is a fundamental ingredient in Japanese cuisine, used to produce sake, miso, soy sauce, and many other traditional foods. Often called “Japan’s fermentation magic,” koji is essential for bringing out the deep umami and rich flavors that characterize Japanese dishes.
The Koji Process: Unlocking Flavor
Koji is made by inoculating steamed rice with Aspergillus oryzae, a beneficial fungus. This fungus produces powerful enzymes:
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Amylase: breaks down starches into natural sugars, adding a subtle sweetness.
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Protease: breaks down proteins into amino acids, creating savory umami flavors.
These enzymes make koji a key ingredient in products like amazake and miso, as well as a way to enrich the flavors of many Japanese recipes.
The Magic of Koji
Koji’s transformative powers and its ability to impart unique qualities to food are what make it such a magical ingredient.
Deeply rooted in Japanese culinary tradition, koji is the remarkable ingredient behind products like sake, amazake, miso, and soy sauce. What makes koji truly special is that it also lends itself perfectly to creative experimentation and innovation in culinary fermentation.
How it Works
The main enzymes at work in koji are amylase and protease:
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Amylase breaks down starches into simple sugars, creating sweetness. Amazake, a sweet non-alcoholic beverage, is a great example. When combined with specific yeasts, it can also ferment into sake.
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Protease breaks down proteins into amino acids. This transformation enhances the umami in foods such as legumes, meat, and fish. Products like miso, soy sauce, cured meats, and fish sauces (like garum) showcase this rich Umami* savory flavor.
*Umami is one of the five basic tastes—alongside sweet, salty, sour, and bitter—and is often described as delicious, savory, rich, and deeply satisfying.
Koji & Innovation
Garum
In recent years, koji has captured the imagination of chefs, artisans, and food lovers around the world. Visionaries such as Sandor Katz—the godfather of fermentation—along with the groundbreaking team at NOMA in Copenhagen, as well as authors Jeremy Umansky and Rich Shih (Koji Alchemy), and koji educators Kirsten and Christopher Shockey, have all played a major role in bringing this remarkable ingredient into the global spotlight. Today, chefs everywhere are embracing koji, experimenting with it, and transforming locally grown ingredients into entirely new culinary creations.
One of the most striking examples is garum. Traditionally, garum is an ancient fermented fish sauce used for thousands of years in Eastern cuisine. At NOMA, chefs reimagined this age-old condiment with a bold, modern approach. By incorporating the unique enzymatic power of koji into the fermentation process, they created a gentler, more refined version of the classic fish sauce—essentially a new product altogether.
Their creativity didn’t stop there. NOMA pushed the boundaries even further by crafting garums from meat, insects, pollen, rose petals, shrimp, and more. Their pioneering work has inspired chefs worldwide, revealing just how limitless the potential of koji truly is.
Koji is more than an ingredient — it is a bridge between tradition and innovation, offering endless possibilities for those willing to explore.