Cultivated with Patience
Koji is not merely an ingredient — it is a living collaborator. We partner with Aspergillus oryzae to transform humble grains into vessels of extraordinary flavor, guided by traditions passed across four centuries.
Living Culture
Every batch begins with a living culture — koji spores nurtured across generations in our cedar-lined chambers. The mold breathes, transforms, and reveals the hidden sugars within each grain.
Ancient Mastery
Our head brewer has trained under fifth-generation koji masters in Nishiki, Kyoto. Each technique — from the temperature of steamed rice to the timing of inoculation — carries four centuries of memory.
Umami Depth
Koji enzymes — amylase, protease, lipase — unlock umami compounds invisible to the naked tongue. We guide this biochemical alchemy to create layers of flavor that unfold slowly over time.
Signature Ferments
Our Sacred Chamber
The muro — our cedar-lined fermentation chamber — is held at 28–32°C with 85% humidity. Within this womb of warmth and moisture, koji spores awaken and colonize steamed rice grain by grain over 48 hours of continuous care.
The Art of Transformation
Grain Selection
We source single-origin heirloom rice and barley from Yamagata prefecture, polished to precise ratios that expose the starchy heart for koji colonization.
Steaming
Grain is soaked overnight and steamed in cedar-slatted koshiki vessels at dawn. The texture must be firm on the outside, soft within — the perfect medium for spore growth.
Inoculation
While still warm, steamed rice is spread on koji tables and dusted with tane-koji spores using a hand-held sieve. Uniformity of distribution is essential; experienced hands guide every movement.
Incubation
Over 48 hours in the muro, the brewer sleeps in two-hour intervals, rising every second hour to turn and knead the koji by hand, managing heat and moisture with precise intuition.
Harvest
At peak enzyme activity, the koji is harvested — a bloom of white mycelium covering each grain, releasing a chestnut-sweet fragrance that signals perfection.
Four Centuries of Living Craft
The koji tradition traces its lineage to the Edo period, when brewers first codified the muro rituals that remain largely unchanged today. KOJI Fermentation Studio was founded to carry this knowledge beyond Japan — not as appropriation, but as devotion.
"Koji does not submit to the brewer. The brewer submits to koji. You learn to listen."— Hayashi Kenji, Head Brewer & Founder
What Chefs Say
Begin Your Fermentation Journey
We welcome inquiries from restaurants, wholesale partners, and private collectors. All products are made in small batches and available by pre-order. Please allow 2–4 weeks for fulfillment.