What characterizes the water used in sake brewing labeled as nansui?

The term "nansui" refers to water that is characterized by its softness, which is crucial for sake production. Soft water has lower concentrations of minerals, especially calcium and magnesium, which affects the brewing process and the final flavor profile of the sake. Soft water allows the delicate flavors of the rice and koji to shine through, producing a clean and elegant sake. This is particularly important in styles of sake that aim for a refined taste, and it aligns with traditional brewing methods in regions known for their soft water sources.

In contrast, high mineral content, hardness, or calcium-rich attributes can lead to a more robust and heavier sake that may not be as desirable for certain types of brewing. While these factors can enhance flavors in other contexts, they do not align with the characteristics of nansui in sake brewing that emphasize a softer and more delicate profile.