秋田県産米「あきたこまち」を用いて味噌用の米麹を造る部屋です。麹蓋（こうじぶた）と呼ばれるお盆状の箱に種麹を振った蒸米を１・５㎏～２㎏入れます。仕込み中は毎日約２５０枚の麹蓋を朝夕一枚一枚丁寧にほぐして麹を育てます。出来上がった米麹は、味噌以外にも塩麹・みそたまり・味噌漬けや甘酒にも使います。蒸米を麹にするための種麹菌は、秋田今野商店さんが石孫だけの為にご用意してくださったものです。種麹を振った蒸米を麹室に入れると、二日目、三日目とどんどん甘い香りが強くなり麹室の外まで甘い空気があふれてきます。

This room is where the koji is made for making miso. Locally grown Akita Komachi rice is steamed and then covered with koji enzymes. The mixture is then laid 1.5-2 kilograms at a time, into what is known as Koji Buta, tray-like boxes. Every day about two hundred and fifty boxes are placed in the Muro and each box is observed from morning to night to ensure successful koji cultivation. Once the process has finished then the koji is ready to be made into not only miso, but Shio Koji, Miso Tamari, Miso Pickles and Amazake.