Unanswered Sake Questions: 2 Out Of 3

With approximately 2000 years of history in Japan, sake has a rich and vibrant collection of legends, rituals, categories, types, brands, and more. Of course, all of that history is bound to lead to some unanswered questions, some fascinating sake mysteries. I am devoting this post to three sake questions which have intrigued me, two of which apparently lack answers. And I only discerned the answer to the third question very recently, and more by accident than purpose.

If anyone has any insight to the unanswered questions, or even just wants to offer their own theory, please leave me a comment. Or leave me your own sake questions for which you lack an answer.

1. Why isn't lactic acid a listed ingredient?

Junmai and Honjozo, the two main premium sake categories, can only possess four or five ingredients respectively. A Junmai, a "pure rice" sake, can only contain rice, water, yeast and koji-kin while a Honjozo has those same four ingredients as well as some distilled alcohol. Yet both usually contain another ingredient, which does not get listed on their labels, and I am very curious as to the rationale for that omission.

In brewing sake, a yeast starter, also called moto or shubo, is produced, combining water, rice, koji and yeast. In addition, lactic acid, known as hiochi-kin, is added to the moto to inhibit the growth of unwanted bacteria. This is known as the sokujo method, and at least 99% of all sake is made by this method. The lactic acid is very important to the brewing process, allowing the yeast to safely multiply, and preventing the growth of bacteria which would adversely affect the sake. The term sokujo is not listed on sake labels, but you should assume it was the method used unless the label specifically indicates a different method.

Yamahai and kimoto are two other brewing methods and in both, the brewer does not add any lactic acid. Instead, the brewer allows natural lactic acid from the air to enter the moto over time. This is a lengthier and riskier process, that often creates earthier and gamier sakes. If either of those methods is used, it is usually indicated on the label so you know lactic acid was not added by the brewer.

But why isn't lactic acid listed as an ingredient? The fact it is used in almost all sake is an insufficient reason to omit it, as all sake uses the four ingredients in Junmai too. Is it a matter of the small amount of lactic acid that is added? Maybe, but the great importance of the lactic acid should count for something. I have been unable to locate the answer to this question.

2. Why aren't "half bottles" of sake a standard size? 

There is much standardization in the size of sake bottles and serving sizes.  The smallest unit is the shaku, which is a serving size of 18ml. The masu, a traditional wooden drinking box, held 180ml, and that is considered a single serving of sake, also known as ichigo or just go. A tokkuri is a ceramic flask used to serve sake, most often warmed, and they usually come in a 1 or 2 go sizes, 180 or 360 milliliters. The standard sake bottle, known as a yongobin, holds 720ml or 4 go. There are two larger format bottles too, the ishoobin (or shou), which contains 1.8 liters or 10 go and the to-bin (or to) which contains 18 liters or 100 go.

With all this standardization, then you would assume to find half bottles with 360ml or 2 go, but that is almost never the case. Instead, you will usually find "half bottles" with 300ml, 330ml, 350 ml, or even 375ml. That seems to make no sense, especially as all of their other bottles are so standardized. What is the need for all these different sized half bottles? Why aren't 360ml bottles the norm? Once again, I have been unable to find any answer to this conundrum.

3. Why doesn't 365 Masu equal 1 Koku?

The masu, a traditional wooden drinking box that I mentioned above, holds 180ml and traditionally that was the measure of how much rice was needed to feed one person for one day. Traditionally, a koku was a measure of how much rice was needed to feed one person for one year. In medieval Japan, domains were measured by the amount of koku and samurai would sometimes receive their salaries in koku. Now, by simple math, a person would require 365 masu of rice for one year, so 365 masu should equal one koku.

But, in reality 1000 masu equal 1 koku. So why is that the case? I could not find an answer for some time but recently stumbled upon the answer while researching something else. It seems that in 1891, Japan decided to redefine the koku unit, making it smaller than it once had been (though I am unsure of their reasons). So, under the new measurement system, a koku now is approximately 180 liters, or 1000 masu.