吟醸酒の条件は精米歩合だけじゃない。で、吟醸造りって？As you can find the classification of “specially designated sake” or ”Premium Sake” at the explanatory tables. It is the rice polishing rate of lower than 60% , And Necessary to use over 15% koji rice and ginjo zukuri. They describe about that as below, “Ginjo zukuri means the process of using low seimai-buai rice and fermenting at a low temperature to create the characteristic fragrance.” Ginjo-shu is made at a rice polishing ratio below 60%, so more than 40% of the rice outer layer is removed. After the rice is carefully washed not to be damaged, it is soaked to attain a certain water content and the time is measured by using a stop watch (this process is called gentei-kyusui (limited water absorption)). For koji making, it seems that kojibuta (shallow tray-like boxes ) is often used to make koji carefully. In the shikomi process of junmai-shu and futsu-shu (non-premium sake) made from a sokujo starter culture, moromi is maintained at temperatures between 15C and17C degrees, and becomes sake in 20-25 days. As for ginjo-shu brewing, saccharification and fermentation are done very slowly at a lower temperature of about 10C degrees, which is the lowest temperature at which yeast come alive and activate. This is why ginjo-shu is brewed in the coldest season of the year from the end of January until February. Also, a less-stressful pressing is often adopted for ginjo-shu brewing, such as a bag-hanging style or so-called fune-shibori.