Why does having a large grain and a well-defined shinpaku benefit the polishing process?

The benefit of having a large grain and a well-defined shinpaku during the polishing process primarily lies in the simplification of removing the outer parts of the grain. The shinpaku, or the starchy core of the rice grain, is the part that contributes most significantly to the fermentation and ultimately to the sake's flavor.

When the grain is larger, it facilitates easier and more precise polishing since the machine can effectively target the outer layers that need to be removed, while preserving the integrity of the shinpaku. A well-defined shinpaku means that less of the valuable inner starch is lost during polishing, leading to a higher quality end product. This ensures that more of the essential sugars needed for fermentation remain intact, allowing for a more efficient brewing process and potentially enhancing the characteristics of the final sake.

While factors like fermentation speed, texture, and flavor profile are indeed important in sake production, they are secondary to the primary goal of effective polishing, which is directly influenced by the grain size and the shinpaku's clarity.