To clean the rice completely, rinse it a few times until the water runs clear. The rinsing process removes starch, and this is important if you want the fermentation to work.
The rice needs to soak in water between 8 to 12 hours or overnight.
Next, you need to steam the rice until it becomes soft. Do NOT boil the rice. You can use a colander with a sanitized cloth or tea towel to steam it.
Let the rice cool down to room temperature.
Add the ¼ teaspoon of the koji-kin culture to the rice and mix it up.
On a baking dish, spread out all the steamed rice and cover it with a damp cloth. The cloth must be moist but not soaking wet.
It’s now time to incubate the rice at a constant temperature of 90 F or 30 C for the next 48 hours. Read down below on how to incubate the rice.
Every 12 hours, break apart the clumps. This distributes the moisture and helps mold development.
The white mold fibers begin to form after the initial 48 hours. At this point, the rice starts to have a greenish color. If it’s green already, it’s no good!
Remove the grains from the incubator to prevent mold spring any further. Be sure to remove the towel and let the koji rice dry.
Place the koji rice in your freezer for later use or start making a recipe with it.
When you are making the koji rice at home, you only want to use mold powder, so you have to sift it using a fine-mesh strainer.