for further study :
This method was discovered after the Sokujo' Method which made it possible to understand the fermentation process of sake. this method got success from the beginning. But it is with the discovery of yeast n°6 in the thirties that the sokujo method really became widespread. In the meantime, the brewers, with the help of scientists, tried to improve the kimoto method which was the most widely used.
It was at this time that the Yamahai' method . Yamahai means without Yama-oroshi. Following the technical progress in polishing, which allows a 70% polishing rate to be reached, it is no longer necessary to crush the rice during the shubo, the koji can transform the starch by itself without needing any help; it also makes the method Method Kimotounnecessary, as long as the rice is polished to at least 80% (of rice remaining after polishing) or less.
Lactic acid is produced naturally, allowing natural selection of resistant yeasts and protecting juice from bacteria. Legislation allows the use of pure selected yeast for the Yamahai method.