Alcohol; alcohol content/ level of alcohol

The alcohol in seishu consists largely of ethyl alcohol, and the percentage of alcohol by volume (as measured by hydrometer) is called arukoru-bun or arukoru-dosu in Japanese. The alcohol content is measured as the volume of ethyl alcohol per 100ml of sake, measured at 15°C.

The alcohol content of genshu depends on the amount of water used for mashing (kumi-mizu), the alcohol yield (shuka ritsu), and whether (and in what volume and at what level of alcohol) brewer’s alcohol was added.   At the high end of the scale, it is around 18% for junmai-type sake, and around 21% for alcohol-added styles. Most sake on the market is in the 15% range, but there are plenty of examples of products higher or lower in alcohol. Under the amendment made to Liquor Tax Law in 2006, seishu is defined as being less than 22% alcohol, but before that, it was possible to find sake at more than 25%.

Other varieties of alcohol besides ethyl alcohol are found only in the minutest quantities in sake. These include n-propyl alcohol, isobutyl alcohol, active amyl alcohol, isoamyl alcohol, 2, 3-butylene glycol, βphenylethyl alcohol, tyrosil and so on. These are known collectively as higher alcohols or fusel oils (or fusel alcohols).

Methyl alcohol can be found in very small quantities in other alcoholic beverages such as wine and brandy, but is almost non-existent in sake.