What is significant about koji termentation is that most of the koji ferments involve yeast and bacterial activities as well as molds’. This is the the case for sake, mirin, shochu, miso, soy sauce, rice vinegar etc. Amazake and shio-koji (as well as Katsuobushi) are only a few exceptions in which mold (or enzymes, rather) solely works on the ingredients.
This is because the substances secreted by koji (such as sugar, vitamins etc) attract other good micro organisms and helps them to proliferate. Not only that, koji keeps the ratio of these favourable microbes in good balance. The reason why they can do this is not scientifically known yet, but they have long proven records. If you throw a few grains of koji into nuka (rice bran) bed when it becomes funky, the bad smell disappears very quickly (Nukazuke has very complicated fermentation mechanism and once the microbes are out of balance, it smells really funky
). I find it really fascinating.
When you rub shio-koji into vegetables, lactic fermentation kicks-off almost immediately. To me, chinese leaf is the most obvious case (To make it even more obvious, you can add tiny quantity of yogurt).
Koji is an excellent all round fermentation starter
麹の発酵でとても特徴的なのは、麹は単独では働かないってこと。
酒にしても、みりんにしても、焼酎にしても、味噌にしても、醤油にしても、米酢にしても、酵母や乳酸菌などが麹と一緒に仲良く働いてくれる（塩麹、甘酒、鰹節なんかは、麹（というよりも酵素）が単独で働く例外）
これは麹が分泌する糖やビタミンなどの物質は、他の発酵微生物の大好物であるため。なので発酵微生物たちが元気になる。そして何故かはわかっていないけれど、トータルで微生物のバランスを丁度良く保ってくれる。ぬか床が臭くなっちゃったときに麹を数粒いれると、良い匂いや香りが戻ってきてくれるのなんて、すごいわかりやすい例。
塩麹を野菜に揉み込むと、乳酸発酵が即スタートしてくれるのもこのためです（少量のヨーグルトを足すともっと明らか）。私の一番の好物は白菜の漬物。
麹って小さいけど本当にすごい奴
