Moto (元), Shubo (酒母), Yeast mash are all names for the Sake yeast starter. In this article I will only use the term “moto” but the three can be used interchangeably. Moto is where the number of yeast cells is increased to the needed level. The moto is used to inoculate the main sake fermentation, the Moromi (諸味). To build the moto we start with rice (米), koji (麹) and yeast (酵母). These three ingredients along with water were the only ones used for moto originally. The method to produce this original moto is known as Kimoto. It features a vigorous mixing, taking many hours, to produce a puree of the ingredients. It was thought this vigorous mixing, called Yama-Oroshi, was needed for the ingredients to properly work together.
In 1909 a modification to the Kimoto method was developed. The modification was to drop the vigorous mixing. As it turned out, the mixing was not really needed. The modified process was called Yama-Oroshi haishi moto or Yamahai moto for short.
Both Kimoto and Yamahai moto depend on lactobacillus bacteria from the air to infect the moto and create the needed lactic acid. Lactic acid prevents wild yeast and other types of bacteria from getting a firm foothold in the mash which could ruin the moto and the final sake. In this process it takes some time, maybe a week, for there to be enough lactobacillus bacteria and hence lactic acid to protect the moto. Infestations of wild yeast and other bacteria that started prior to the lactobacilli reaching critical mass will be controlled by the low pH created from the lactic acid. However, up until about 1910-1915 there was no understanding of the role that lactic acid played in the moto.
With the discovery of the role of lactic acid in the production of sake a new moto method was developed: Sokujo moto. Sokujo moto added the direct addition of lactic acid at the beginning of the moto. This resulted in halving the time needed to create the moto, protecting it from wild yeast and bacteria from the start and lowering the final acid levels. Sokujo moto is the mainstay of today’s brewers. It produces a cleaner tasting sake. While Yamahai moto is still used, it is more of a specialty method used to produce an earthy full flavor sake higher in acid than the norm.
So to recap the moto methods we have:
- Kimoto, the original and only method up until 1909, uses a vigorus and time consuming mixing called Yama-Oroshi
- Yamahai, which is kimoto minus the Yama-Oroshi mixing, developed in 1909
- Sokujo, adds an addition of lactic acid at the beginning of the moto and was developed a few years after yamahai
Which method should you use? There really is no advantage to using Kimoto, so we do not need to consider using it. Sokujo moto takes less time (one week) and produces a clean sake so this is a good method for beginners, those not wanting to spend extra time or those wanting a clean tasting sake. Yamahai moto should be used when you have the extra time (two weeks) and want a more earthy or funky tasting sake.