Which two factors have the greatest effect on flavor in sake production?

The production of sake is deeply influenced by various elements, but the combination of yeast and fermentation temperature stands out as having a significant impact on flavor profiles. Yeast is crucial because it converts sugars into alcohol and produces secondary compounds, such as esters and phenols, which contribute to the aroma and taste of sake. Different strains of yeast can lead to a wide range of flavor nuances, from fruity and floral to more savory characteristics.

Fermentation temperature is equally important as it affects yeast activity. Higher temperatures can result in more vigorous fermentation, which can enhance the production of aromatic compounds, while lower temperatures generally promote a slower fermentation that can lead to cleaner and crisper flavors. The interplay between yeast choice and fermentation temperature allows for variation in the final product, making them central to the flavor development in sake.

Although water and rice, koji and temperature, and rice and yeast are all important, they do not have the same direct and profound impact on flavor complexity as the combination of yeast and fermentation temperature does. Water affects the overall quality and smoothness, while rice is fundamental for sugar production and koji initiates fermentation, but it's the yeast and fermentation conditions that largely define the taste profile of the finished sake.