Rice Washing & Soaking
I would like to talk about second step and third step of rice preparing. The first step was rice polishing. After polishing rice, the rice is stored to allow it to cool down and reabsorb correct level moisture. After this step, the rice is washed and then soaked in cold water to adjust the moisture distribution of the rice grain, but, this washing and soaking is sensitive proess, because if the polishing ratio is low, the rice can absorbe water so quickly. Furthermore, the soaked rice is very fragile than unsoaked rice. Brewers need to handle the rice carefully.
After polishing rice, the rice is washed to remove all of remaining nuka, because nuka is made up of undesirable components for Sake. Also, all of dust attached on the surface of the rice is removed without allowing the rice to absorbe water as much as possible in this step. Some breweries wash the rice with small batches by hand. This is traditional way, but, this is used for premium Sake brewing. Almost brewery uses washing machine, because the recent washing machine is highly improved and it is possible to wash rice with fine air bubbles as perfectly than hand washing. As for more larger scale production, big producition breweries use larger scale washing machine.
(Photo from Kikuhime. Beautiful white colour of rice.)
In this step, the purpose is to increase the moisture content of the the rice to the optimal level before steaming. Basically, the target of the water content level is 30-35%. However, this target level varies depending on the type of rice, polishing ratio, and subtle rice and temperature conditions of the year. If the rice grains absorbe too much water, it is not good for Sake quality. If the rice which absorbes too much water is used for Koji making, the mould will grow too quickly before creating opitmal level of Konji enzymes. If the rice which absorbes too much water is used for fermentation, the rice is broken up by Koji enzymes too quickly and the yeast will acess a lot of sugars and create alcohols before that the required level of flavours are not developed.
Polishing ratio and rice type varies batch by batch. Rice moisture content and its nature vary year by year. Water temperature which is used for Sake brewing varies day by day. In order to make potimal level of rice moisture content, brewers makes some experimenting batches, and decide the target water absorption level.
In case of more highly polished rice which is used for Daiginjo or Ginjo grade, the rice grains can absorbe water easily beyond their ideal . So, brewers use the followings to make precise water distribution.
・Extreme cold water to slow down absorption water
・Using stop watch to count "seconds" not "minuites"
・Soaking in small batches
After soaking, the rice is fragile, so, the rice handles carefuly and is steamed within 24 hours.
I had an experince to work Sake brewing in one of Kuramoto in Toyama, when I came back to Toyama. In this step, I think that persons needs carefullness and sensitivity by each and team work is also needed. Peson in charge of washing, person in charge of time keeper, person in charge of soaking, and person in charge of pulling up the rice....Good moisture distribution is made by team work of each Kuramoto.