I'm attempting to make sake. My first mistake was doing so in the summer. As it turns out, sake is best made during the winter months. Nevertheless, we press on. The first thing to do is make the kome koji (malt rice).
What I'm making for my first attempt is doburoku (a simple home brew version, it should end up like a "chunky nigorizake"). The first step is to make the actual malt-rice (kome koji) from the koji-kin mold spores. I thought this would the hard part. It ended up being simple:
- Rinse 400g sushi (short-grain) rice. Several times. Get it clean.
- Soak it at room temperature for a couple hours. You can also apparently soak it overnight in the fridge. This completely permeates the rice grains with water.
- Drain for an hour. The purpose of this step is to dry the outside of the rice grains. If they are not dry on the outside, then they will become gelatinous during the steaming process and you will end up with a bunch of mushy rice rather than individual grains.
Steam the rice in a bamboo steamer (wrapped in cheesecloth) for one hour. The steam heats the water that the grains of rice have already absorbed thus cooking the rice without turning it into a sticky mess. Simmered short grain rice will turn into a mush or slurry when the koji-kin starts to grow.
(I had a problem in that the rice stuck to the cheesecloth after it was done steaming. I was able to scrape the rice off of the cloth but it seems there ought to be a better technique here.)
- Let rice cool to ~30C. At this point the rice will be rubbery when chewed and will seem dry and underdone. Don't worry! This is apparently what you want. Or, more to the point, what the koji-kin wants.
- Evenly distribute ~1.5g of koji-kin (mold spores) onto the rice and mix well. (I had bought Vision Brewing's 10g Koji Kin packet. This should provide enough koji kin for several batches.)
- Put the rice into a plastic tub, cover it with a damp towel to keep it humid and store it out of the light. It should be kept around ~30C to promote mold growth. Since it's currently summer, maintaining a ~30C temperature is easy. I just stuck it on top of my refrigerator.
- Twice a day mix the kome koji to help spread the koji.
- Two days later it should be done. It took about three days before I felt satisified that the koji-kin had done its job (I don't think I was keeping it as humid as I should have been). That morning the rice was covered with nice white fibers but didn't smell like much. Six hours later the entire tub had turned light tan and had very clearly become kome koji.
At this point, use the kome koji to make sake; or freeze it for later. I'll be making sake with it.