Picture the toji presiding with a stopwatch over kurabito as they steep rice for a batch of daiginjo; 18.104.22.168 pull it out of the water. A 31 second steeping to reach the desired 29% uptake of water into the rice kernels. The precision required is just amazing, but why, why is this so time critical?
We need to back up a little and consider what we are trying to do. The goal is to have our steamed rice weigh 1.38x to 1.4x the pre-steeped rice.1 That is to have the rice take up slightly less than 40% of its weight in water by the time it has completed steaming. Steaming will add another 10% or so water uptake. Backing off to pre-steam levels gives us 1.28x to 1.3x for steeping. So how long will this take and why is it different for different grades of sake?
While there are differences between rice variety and milling rates, it turns out that one of the main contributors to the rate of water uptake during steeping relates to the moisture content the rice starts with. In fact it is this factor that is the main cause for highly polished rice to absorb water so quickly and hence the need for a stop watch.
- These targets may vary a bit from place to place. ↵