Kosu keisan (count calculation)

Kosu keisan (literally "count calculation") is a method used in sake production to quantitatively understand the effect of specific components. It is carried out using component values such as alcohol content, sake meter value (SMV), and acidity. In practice, it is used when alcohol or seasoning alcohol is added to the moromi (fermentation mash), to predict changes in component values and to determine the amount to be added or the blending ratio. For example, suppose the moromi has an alcohol content of Am %, and V liters of added alcohol with an alcohol content of 30% are added to M liters of that moromi. If the alcohol content of the moromi after the addition is As %, the following equation holds: Am × M + 30 × V = As × (M + V). This equation shows that the sum of the moromi's alcohol count before the addition and the count of the added alcohol equals the alcohol count of the moromi after the addition. In this way, kosu keisan is an important tool supporting quality control and production technique in sake brewing.