Here’s a photo from a while back when I tried to make two kinds of rice koji side by side in the same vessel, to see how differently they grew. I am always experimenting. The left one is more for amazake, the right one is more for miso. They can be used interchangably, though.
What you see in the photo are not examples of my better rice koji, but they are plenty good for miso. The great thing about miso making is that it is designed to be done at home and is forgiving. Even embarrassingly bad rice koji can produce good miso.
Koji making is like gardening. Very short term, but very similar. It starts with soaking and steaming rice perfectly. That’s the soil. Then we plant, as in, sprinkle the koji spores onto the rice. Then we provide the temperature and moisture for the koji to grow.
For the first 12 hours or so, we see nothing. Then we start to see little white dots in the rice. That is an indication that the koji mold has started to grow. Around the same time, it starts to produce heat. In the second half of the growing process, I have to check temperature every several hours and cool it down if necessary to keep it in the range for optimal growth.
From washing and soaking rice in water to the finished rice koji, it is a 3 day process. It is an immensely satisfying 3 days to watch the creature take hold.
Life is a miracle. Miso is a miracle.