What type of rice is typically used to create koji?

The correct choice identifies white rice as the typical variety used to create koji because of its optimal characteristics for fermentation. Koji is produced by inoculating steamed rice with the mold Aspergillus oryzae, which converts the starches in the rice into sugars that can then be fermented by yeast in the sake-making process.

White rice has a higher starch content and a more suitable texture than other rice varieties, which allows for better absorption of the koji mold and more efficient conversion of starches during fermentation. While short-grain rice is also commonly used in sake production, it is not specifically chosen for koji production when compared to white rice, which is processed to remove the bran and germ, enhancing the koji-making process.

Brown rice, although nutritious, does not create the same results in the koji fermentation due to its outer bran layer, which inhibits the mold's ability to penetrate and act on the starches efficiently. While it's true that koji can technically be made from various types of rice, white rice remains the standard in sake production for its proven efficacy and historical use.