While researching rice and enzymes I came across an article on how steep time and temperature influence rice malt enzyme production. Malting is a major part of most beer brewing but while sake is, by some definitions, a beer, it does not use malt; not rice malt, not any kind of malt. Instead the rice used for sake is milled to remove the outer layers of the grain, which destroys all possibility of malting.
Malting is the process of transforming a grain from a seed to a malt that contains not only the starches and proteins that where present in the seed but also enzymes that can be used to convert the starches and proteins in the malt to sugars and amino acids.
To malt seed, the seed is steeped in water and allowed to dry a little in order to awaken the seed to begin to grow. The steeping and drying may be carried out several times to fully engage the embryo’s growth but ensure the seed does not drown. Once the embryo has begun to sprout roots and a shoot, a maltster will halt the embryo’s transformation by heating or kilning the grain. This prevents the enzymes from fully distributing throughout the endosperm and converting it before it is ready to be used.