How is sake rice different from table rice?

Different rices produce sake 's with different tastes, just as different types of grapes produce different wines. The best types of rice for brewing sake contain less protein. The grain should be firm and not easily break during the rice polishing process. Sake rice typically has a bigger grain than table rice and has a lot of starch at the center of the grain called "shinpaku". Because shinpaku is white and very soft, it easily absorbs the Koji mold which converts the starch into sugar. 

The individual character of a particular sake is due in part to the variety of sake rice used in brewing (See diagram that shows the varieties of popular sake rice.) 

Currently there are approximately 100 kinds of sake rice grown in Japan, and sake is not always made with the sake rice that is harvested in the same local region where the sake is made.  

The various shuzo (sake breweries) usually contract with a rice grower in a particular region where the best sake rice is cultivated. That is one of the reasons why sake rice is so much more expensive than table rice.