Koji, is the fungus, aspergillus oryzae, that grows on grain substrate. It is used in many East Asian cuisines to ferment food. The rich enzymes of koji break down starches and proteins of grains into sugars and amino acids, for making various miso, soy sauces, sake, amazake, etc.
The koji starter I use here for making koji rice is Light Rice Koji Starter from Gem Cultures in US. If you live in Canada, Culture Mother is going to launch those koji starters soon. In Taiwan, you can find various koji starters at Da Shan and 錦池。The whole procedure of making rice koji takes about 3 days.
米麴（rice koji，米こうじ，米糀），是米麴菌（種麴，tane koji，koji starter，學名：Aspergillus oryzae）接種到煮熟的飯粒上，經過一段時間發酵而成。做好的米麴可以再加工做成鹽麴、味噌、豆腐乳、味霖、甘酒、清酒等健康又美味的食物，是很多發酵食品的基本和必需素材。
對立志成為一個自給自足的宅農婦來說，米麴是我手作發酵食品裡的鐵咖。沒有米麴，我的櫃架上就變不出那些瓶瓶罐罐的各式手作味噌和豆腐乳。宅婦喜歡自己動手發米麴。我的米麴菌來自美國的GEM Cultures。他們有很多不同的米麴菌，這裡用的是light rice koji starter，屬於日本丸福麴種，發好的米麴可以做成甘口白味噌、信州淡黃味噌、甘酒和清酒等。整個發米麴的過程約時三天。
600g Rice 白米
1g Rice Koji Starter 米麴菌
* The ratio of rice and koji starter is 〔1000 : 1〕 or 〔1000 : 2〕。
Late evening, January 29, 2015
Rinse the rice and soak it overnight or for 8 hours, then drain it.
Morning, January 30, 2015
Steam cook the soaked rice for about 30 minutes.
After 30 minutes, the rice is steamed and cooked. Set it aside to cool around 35-40c (95-104F).
While steamed rice is cooling down, measure 1g of koji starter.
When steamed rice cooled to 35c (95F), inoculate the koji starter to the steamed rice by spreading it over the rice evenly.
Mix the koji starter and steamed rice well and thoroughly, then place the inoculated rice in the koji tray evenly.
I don't have a koji muro, so I incubate my koji in my oven with the light on and the door cracked open by a kitchen towel (the temperature is 31.5c when the light is on). I also cover the koji tray with a damp cheesecloth for maintaining the moisture inside of the oven.
The oven door cracked open by a kitchen towel in order to improve the air circulation. If it's too cold, I'll put a cup of hot water to warm the oven up. The proper humidity for fermenting rice koji is 68%, so check the rice occasionally, if it's drying out, damp the cover cheesecloth or mist the rice.
Morning, January 31, 2015
Second day morning, saw some white spots appeared which is a good sign, also I can smell a trace of sweet aroma. It means the koji mold is developing well.
Morning, February 01, 2015
Third day morning, the rice has been incubating for 2 days at 28C. It's 3/4 covered by white furry mold, the sweet aroma is stronger. Everything is going so wonderfully! I think it will be ready to harvest later today.
Crumbled the rice koji, spreaded it evenly in the koji tray. Place the try beside heat vent overnight.
Morning, February 02, 2015
Double check the dryness of koji rice. Make sure no trace of moisture in order to prevent bad mold growing. Place dried koji rice in a plastic bag and store it in cool and dry place without direct sunlight. Use it within six months.
Last Updated on February 02, 2015