Senmai and mushimai – washing and steaming

After rice is polished, it is washed, soaked, aerated, and steamed. In craft breweries, sake makers wash the rice in small batches—just 10 kilos at a time. Until recently, this was done by hand with brewery workers leaning over tubs, wearing thick rubber gloves to protect their hands from freezing cold water. The grueling nature of this job has pushed even the smallest breweries to use rinsing machines. In some breweries, like the Saiya Brewery, makers of Yuki No Bosha, this is one of the most important steps. 

The step of rinsing and soaking, “senmai,” has two goals—one, to remove “nuka,” rice powder, and, two, to absorb water. 

After rinsing and aerating the rice, it is steamed, not boiled. Roughly 25% of the steamed rice is used to make “koji,” malted rice, while the other 75% goes directly into the brewing tank. Brewing rice is “kakemai.”


One of the constant goals in sake making is to extend or stop the progress of a step. Slowing a process down allows for better development while stopping leaves more to be done next. In senmai, sake makers rinse and soak the rice in ice cold water to slow absorption. They precisely calculate and limit the time to limit absorption, as well. 

One of the reasons sake makers make less expensive sake at the beginning of the brewing season is to determine how quickly the new year’s rice absorbs water. This is also true for different rice varietals, which absorb water at different rates, also variable by year. Brewmasters are constantly evaluating and adjusting. By the time they are making the most expensive daiginjos, they have a firm grasp of this variable.


Sake makers rinse rice until the water is clear of “nuka,” polished rice powder. In soaking, they aim for the rice to increase in weight by 30%. Polished rice is portioned in 10 kilo increments, rinsed, soaked, and drained so the bag weighs 13 kilos. In the total process of sake making, roughly 30 times as much water is used to rice, in weight. A large portion of that water is used here.


STEAMING – Mushimai

Rice is steamed, not boiled to limit, but all allow for some water absorption and decomposition of the rice grain. 

Rice is steamed in a “koshiki,” in layers using cloth dividers. The koshiki blasts super-hot, compressed steam through the rice. The different layers of rice may consist of different kinds of rice – either polishing ratios or varietals. These “mini batches” within the larger steamed batch may be used for different sakes or steps in the process – making koji or brewing. 

Steaming, “mushi,” is the first job of the day at a sake brewery and, if you arrive early, you will see the steam rising through the roof as you approach. After steaming, rice is broken up and cooled down. 


After steaming, the rice is either transferred by hand to an area outside the muro, the koji-making room, or it goes through a conveyer-bed machine, either method achieving the goal of breaking up and cooling down the steamed rice.