What does the term "milling" refer to in sake production?

The term "milling" in sake production specifically refers to the process of polishing rice to remove the outer layers. This is a critical step in sake making because the degree to which rice is milled influences the flavor and quality of the final product. The outer layers of the rice contain fats and proteins that can negatively affect the taste of the sake. Consequently, milling helps to enhance purity and refine the character of the sake.

The extent of milling is also a determining factor for the classification of the sake; for example, the more the rice is polished, the higher the potential quality as defined by various sake types. Thus, proper milling is essential for producing high-quality sake and is a fundamental practice in the brewing process.

The other options refer to different aspects of sake production that do not involve rice polishing. For instance, fermentation is about converting sugars into alcohol, cooling occurs post-brewing, and aging takes place after fermentation to develop flavor profiles. Each has its significance but is distinct from the milling process.