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Koji-making, made foolproof.
Salt ratios, chamber heat, enzyme timing — koji has real safety floors, and eyeballing them is how a batch fails or turns unsafe. Kojiology runs Bu Ne Yemek's koji science through eight calculators, so every number you get back is checked against the physics and the safety math, not guessed at.
Never made koji? Read this first
Koji is a mould, Aspergillus oryzae, grown deliberately on cooked rice, barley or soybeans. As it grows it threads through the grain and fills it with enzymes — one kind cuts starch into sugar, another cuts protein into savoury amino acids. That is the whole trick behind miso, shoyu, sake, amazake and shio koji: you are not adding flavour, you are growing the tools that take an ingredient apart into flavour. The work splits into two stages, and each tool below says which one it is for.
- Growing the koji —
- Two days of warmth, humidity and airflow while the mould colonises the grain. Getting rid of the heat it makes is the hard part.
- Fermenting with it —
- Weeks to months with salt, where those enzymes do their work. Getting the salt right is what keeps it safe.
Growing the koji
Two days of warmth, humidity and airflow while the mould colonises the grain. Getting rid of the heat it makes is the hard part.
Soak, steam, cool — and the moisture you actually land on. Tracks every gram of water, including the ~100 g per kilo that steaming condenses onto the food and the amount cooling takes back off.
Koji-kin, tane-koji, or a saved tomo-koji batch — three products, three doses, not one generic "spore" figure. Pick what you have, get the right gram count for your batch.
Size your koji chamber: safe bed thickness, vent count or door-gap width, and a 3-phase heat timeline from mass balance and airflow physics.
Turn the protease↔amylase dial: strain, substrate, temperature, moisture, and bed depth each pull your koji toward umami or sweetness — see which lever is actually doing the work.
Sō-hazé or tsuki-hazé? The six traditional koji growth patterns are positions on two axes — how much of the grain the mycelium covers, and how far into it goes. Aim at one, see where your process lands, and find the lever holding you there.
Fermenting with it
Weeks to months with salt, where those enzymes do their work. Getting the salt right is what keeps it safe.
How much salt keeps a ferment safe? Set weight, water ratio, and duration — get the WPS-based target, checked against the pH / water-activity / botulinum safety floors.
Vacuum-bag miso or shoyu with a backslop starter: find how often external kneading is worth doing before it stops helping.
Age an already-made miso or tamari paste in a warm chamber: salt and water solved from your target depth, plus a mixing schedule that accounts for enzyme denaturation, not just “hotter is faster.”
The only tool here that runs backwards. Name a ferment and a batch size and it works back through the recipe, the koji cycle and the steamer to a weight of dry grain you can buy — then puts every step on a clock, including the one nobody tells you about: when the beans have to go in water.
Build a fermentation recipe from weighed ingredients — koji ferments, vegetable pickles or cured protein — and get the salt figure from the same engine every other tool here uses. Your ratio, our safety floors. The whole recipe fits in a link, and you can ask the assistant about it.
Chat with an assistant grounded in Bu Ne Yemek's koji science — get straight answers on safety floors, technique, and troubleshooting instead of digging through calculators. Free tier available, sign-in required.