Sake is made from 4 ingredients - rice, water, koji and yeast. The type of rice used has a big impact on the taste of sakes, similar to how different grapes produce different wines. Sakamai (酒米) or rice for making sakes are different from table rice. Sakamai are larger in size with higher starch content and has lesser fat and protein.
The four main types of sakamai are:
Yamada Nishiki (山田錦) - Known as the king of sake rice, Yamada Nishiki produces fragrant and balanced sakes with mellow soft flavour. Specifically bred by agriculturist for sake making, Yamada Nishiki is easier to grow compared to other sakamai, thus making it the most popular rice for sake making.
Omachi (雄町) - The oldest strain of sake rice, Omachi is temperamental, hard to grow and difficult to harvest. It also has soft grains which are prone to breakage during the polishing process. Omachi rice produces flavourful sakes with subtle, restrained flavours.
Gohyakuman-goku (五百万石) - Smooth and clean, usually used for making dry sakes.
Miyama-nishiki (美山錦) - Produces sakes that are mellow with a well rounded profile and mild sweetness.