Last week’s purpose was cleaning and preparation. This week, it was making the season’s first batch of koji (麹) for the yeast starter (moto). What is koji you may wonder? Simply, it is the mold (Aspergillus oryzae) that is responsible for turning the rice starch into sugar, which can then be used by the yeast to make alcohol.
We started by washing rice that had been polished to 65% (ie. 35% of the outside gone) using a slick little machine, and then soaked the washed rice in water for about 15 min. It was then removed and allowed to sit overnight. The next day, we steamed the rice (70 kg) for 1 hour, shoveled it out, and spread it out to cool on large trays. After cooling, we carried it upstairs to the muro (koji-making room) which is always kept around 33C and has a great smell from the cedar walls. The rice was spread out on a large blanket, flipped, broken down into small clumps, allowed to cool, and then the mold spores, which are very green, were sprinkled over top. After flipping the rice, the other side was covered with spores and the rice was piled up into a large mound.
We then covered the koji-rice mountain with several blankets to keep it warm while the spores began to germinate. Controlling the temperature, and in turn controlling growth rates, is key to making good koji, which is considered to be the most important step in making sake.
The koji-rice mountain was then allowed to ‘sleep’ for about 7 hours. What happens next? stay tuned…..