Soybeans are harvested in Autumn and Miso is made in mid-Winter (Jan-Feb in Japan), and then left to ferment for at least nine months before eating. Miso is made from three ingredients: malted rice or barley, soybeans and salt. The key to making good miso is using a good quality rice malt (koji), getting absolutely all the air out when putting the miso into the container, and keeping it in a really cool spot (under-house storage, or refrigerator) to prevent mold.
Koji starter (malted rice) is usually made by fermenting cooked rice for 48 hours with aspergillus oryzae, a fungus, also called koji-kabi, literally koji-mold. But this is too hard, so I buy nama-koji online in Japan from Tomizawa-shoten. Nama-koji is rice that has already been fermented with the koji mold, so it is ready to use.
Recipe (makes approx. 4-5kg miso)
1 kg soybeans
1kg fresh rice malt (nama-koji)
Also, reserve 100 – 200 ml of the water used to cook soybeans (‘nijiru)
rice malt, soybeans, salt
1. Soak soybeans in 3 times the volume of water, for 17 hours.
2. Cook soybeans for 20 minutes in a pressure cooker, or boil for 2 hours or until soft.
3. Drain, but reserve the liquid (called ‘nijiru’).
reserved liquid, cooked soybeans
4. Crush soybeans, with sterilized hands, potato masher, or food processor.
crushing soybeans (sterilize hands with alcohol)
5. Wash hands. Sterilize hands with alcohol (again). Mix salt with rice malt (koji) by rubbing between hands. Mix well.
6. Add slightly cooled crushed beans a little at a time and mix very well.
7. Add a little of the reserved liquid (nijiru) to get a smooth paste.
8. Grab handfulls of miso and make into balls.
make miso into balls
9. Sterilize a 10 litre container with alcohol. Put miso into the container by slamming each ball in one at a time. Push miso down each time to get ALL air out. If any air is left inside the miso it will allow mold in. When all the miso is pressed into the container, push down on the top of miso with palm of hand to make perfectly flat and air-free.
press down to get all air out
press a bit more, press flat
press edges down neatly
See MISO PART B (STORAGE)