In Part One we talked about measuring the SMV (Nihonshu-do) of your sake. In this part we will discuss two ways to measure the percent alcohol by volume for your sake. Because Heikou Fukuhakkou (並行複醗酵) or multiple parallel fermentation is used to make sake, we cannot employ the same simple method for determining the percent alcohol as is used for other fermented beverages. In particular, the simplest methods used for both beer and wine depend on knowing the initial specific gravity prior to fermentation. For sake, there is no point prior to fermentation when all the sugar is available for such a measurement. Rather, koji enzymes work side by side with yeast in the fermenting mash. Enzymes create sugar and yeast creates alcohol using the sugar; this is multiple parallel fermentation.
The first way to measure the alcohol level we will discuss uses what is known as the boiling method. It is a modified version of the distillation method that can be done at home with relative ease. The basic idea behind this method is that the alcohol in sake has a known specific gravity and a known effect on the specific gravities of substances it is in. Given this we can measure the specific gravity of our sake to get an initial state, replace the alcohol with distilled water and then take a new specific gravity reading. The difference between these two specific gravities can then be used to determine the percentage of alcohol by volume.