How do the outer and middle layers of rice grains affect the style of sake?

The outer and middle layers of rice grains play a significant role in determining the flavor profile and overall style of sake. These layers contain the starches that are essential for fermentation, and they also house various compounds that influence the sake's taste and aroma.

The outer layer, known as the bran, contains proteins, amino acids, and other compounds that can contribute to umami flavors, enhance acidity, and provide a range of cereal notes during the brewing process. When the rice is milled to different degrees (a process called "seimaibuai"), the amount of outer layer removed can dramatically influence these flavors. More milling typically leads to more clarity and refinement in taste.

By contrast, when rice is less milled, it retains more of these components, leading to an increase in the complexity of flavors including lactic notes and umami. This balance of flavors is crucial in determining the sake's overall style, from sweet and fruity to umami-rich and savory. Thus, the contribution of these rice layers directly impacts the sensory characteristics of the final product.