What is the primary role of koji in sake brewing?

The primary role of koji in sake brewing is to provide saccharification, which is a crucial process in converting starches from the rice into sugars. Koji is produced by inoculating steamed rice with koji mold, primarily Aspergillus oryzae. This mold secretes enzymes, such as amylase, that break down the starches present in the rice during the brewing process. As these starches convert into fermentable sugars, they become a vital source of energy for the yeast involved in fermentation.

In addition to saccharification, koji contributes to the overall flavor profile and aroma of the sake. The complex carbohydrates produced not only help in fermentation but also influence the characteristics of the final product, such as its sweetness, umami, and overall depth of flavor. This dual role of driving fermentation and enhancing flavor is essential, making koji a pivotal ingredient in sake production.