As I am thinking about some experiments to do with sake I began thinking about the difference between various moto methods. Not so much the procedures but what makes the sake different. Most homebrew sake is made with either the sokujo or yamahai methods. The yamahai method, much like the kimoto method is known for producing a deeper and richer, even earthier sake.
In the sokujo method lactic acid is added at the start of the moto while in the yamahai method various bugs are rallied to provide the lactic acid. It is this early stage of the moto that makes the difference in outcome. Once the bugs have done there thing and there is enough lactic acid built up the moto is protected from any further trouble and the yeast are free to thrive and grow.
At the start of this early period for the moto the ingredients are brought together; rice, koji and water. Bacteria that convert nitrate to nitrous acid are the first bugs to get a firm hold. They feed on the nitrates in the water. Wild yeasts and film yeasts are also present at this stage but the amount of nutrients in the moto is quite low. However, as the koji enzymes start to work nutrients and sugars are produced. The nutrients help not only the wild and film yeast but also lactic acid cocci and bacilli like leuconostoc mesenteroides and lactobacillus respectively. The cocci are the next to get a firm hold after the nitrate converting bacteria.
At this stage in the moto, the two strongest bugs are producing nitrous acid and lactic acid. The nitrous producing bacteria cannot handle the lactic acid though so it dies out. Lactic acid bacilli are also coming on strong by now and the combination of nitrous and lactic acids are concentrated enough to even kill off most of the wild and film yeasts. As the lactic acids build up, even the lactic acid cocci and bacilli are over come and begin to die off as well. It is at this point that the desired yeast strain is added. From here on, both moto methods proceed in the same fashion.
Much, if not all, of the nitrous acid breaks down as it is quite unstable. This leaves only the lactic acid and bi-products from the activities of all these bugs that adds to the moto and its contributions to the sake. It is in these bi-products that the deeper, richer and earthier aspects of the sake lie.