What influence does using only the core of the rice grain (almost pure starch) have on the style of sake?

Using only the core of the rice grain, which consists mostly of starch, significantly influences the resulting style of sake by changing the balance of flavors and aromas. When the core or the "shinpaku" is utilized, the starches can be fermented into sugars more efficiently, which contributes to the creation of a smoother and fruitier profile in the sake.

This approach tends to result in less acidity and a reduction in umami flavors because the fermentation process and the specific nutrients available in the outer layers of the rice that can impart umami are minimized. Consequently, as less umami is present, more fruity and floral notes become prominent, leading to a sake that is typically light, refreshing, and easier to drink.

The other options represent potential profiles that are less consistent with the use of predominantly starchy rice. For instance, higher sweetness combined with lower alcohol content or increased depth with cereal notes might not align with the effects of focusing solely on the core of the rice grain, which is intended to emphasize those fruity and floral aspects. Therefore, the style of sake produced from this method often showcases these brighter, less structured flavor characteristics.