Shochu with hot water

Last update: Mar. 27, 2016/Feb. 11, 2023 (English translation)

A few years ago, at a bar in Shinbashi (in Tokyo), I learned an interesting thing about drinking shochu (Japanese vodka) with hot water. An elderly, distinguished professor told me, "There is a rule about drinking shochu with hot water: you must pour hot water into the glass first, and then add the shochu."　Being a weak drinker, I asked, "Why?" and "What happens if you do it the other way around?" I asked.
Because I was at a drinking party, no one answered my questions seriously, and several years passed without my having a chance to investigate the matter myself. However, on a business trip to Kyushu in March 2016, we had dinner at a delicious Japanese restaurant. I told this "old story" as a topic of conversation, and since no one had even heard of it, we decided to conduct an experiment.

The following is a summary of the experiment.

Subject: Regarding shochu with hot water, which tastes better, shochu with hot water first or shochu with hot water first?

Experiment: Seven people tasted two different diluted-shochu, one with hot water first and the other with shochu first. The ratio of hot water to shochu was about 1:1, and the muddler was stirred only a few times.

Result: Six out of seven tasters clearly felt the difference. Six out of seven people felt that there was a clear difference between the two, and they rated the shochu with hot water first as more palatable. On the other hand, those who drank the shochu first with hot water thought that the alcohol was more stimulating.

Consideration: A participant who often drinks shochu with hot water pointed out that it is important to use hot water instead of water. After considering this opinion, we reasoned that the evaporation of alcohol from the shochu by the hot water and the stirring effect caused by the temperature difference were the reasons for the difference in taste and aroma. He concluded, "In the case of hot water first, pouring the shochu into the hot water evaporated a moderate amount of alcohol, leaving a large amount of "umami" (tasty) components and resulting in a milder hot water mix." He concluded. (When we read the literature below, the correct answer seems to be a little different. When shochu is poured into hot water, the alcohol evaporates more and it becomes a stronger stimulus. The hot water and shochu mixes mildly, with an alcohol concentration similar to sake (shochu 6:4) or dilutes-shochu (shochu 1:1).

Thoughts: At first, I thought that pouring water into the shochu would mix it better, because the specific gravity of the alcohol is smaller. Also, I thought it was the same as "mixing shochu with water", because "mizuwari" (dilution of alcohol with water) of whisky is usually made by adding water to whisky. However, I learned that "shochu with hot water" is not the same, but something more profound. This research (?) However, I was surprised again at how different the taste and flavor can be depending on the mixing method, and how acute the human senses (in this case, smell and taste) are. Incidentally, I remember learning in junior high school how to dilute sulfuric and hydrochloric acids by "pouring sulfuric and hydrochloric acids into water. This is meant to prevent the liquid from splashing out due to dilution heat. Is this the same?

Cited below.

Literature review: I found several reports on this subject.
How do I make a good whiskey with water?
(Shochu) Surprisingly Unknown? How to Make Delicious Shochu with Hot Water
Is it true that hot water comes first for connoisseurs?　How to make shochu with hot water correctly