One question that comes up over and over in sake brewing is how to hit the SMV value desired. Puzzling over this question I asked one of the brewers from Yoshi-no-gawa when the opportunity presented itself. This was well over a year ago now, but what he told me was that they monitored the moromi (main ferment) and when it reached their desired SMV value, it was time for Shibori or Joso, that is time to press the lees from the sake. Using an assaku-ki machine (an accordion like press), often referred to as a yabuta, they are able to remove virtually all of the lees and even the yeast. Because this leaves only trace amounts of the yeast, fermentation is stopped and the SMV value is stabilized.
Very nice! However, if you have seen my videos of the pressing process you may be wondering if something is amiss. Well, yes, something is amiss. My pressing method leaves a large amount of the lees in my sake so there is no way I am removing the yeast. This is true for most homebrewers. There are filters used for brewing that may be able to do what is needed. I have one but have not used it yet. In any case to use it I will have to first press and let settle or fine before filtering because the amount of lees would hopelessly clog the filter if the sake isn’t pretty close to clear. So, for now, I can’t use their method.