Often when you search around on-line, looking for a recipe for sake you find recipes for Doburoku (濁酒). No, they don’t say they are for doburoku. But if you brew them you don’t end up with what we in the U.S. think of as sake; I would venture to say the world. In Japan, “sake” is a much broader term. It is really for any type of alcoholic drink. However, outside of Japan, sake is the same thing to us as Nihonshu (日本酒) and Seishu (清酒). Even, in Japan, if a westerner asks for sake, it is mostly assumed he is not asking for just any alcohol.
Doburoku is kind of a farm house or home brew style of sake. It is, well, rustic and unrefined. This is the point Fred is making at the top of his recipe when he explains “refined.” If you are interested in making the beverage we think of when we say sake, the one in the store or at the restaurant, then you don’t want doburoku. It will never live up to your expectations. However, it does have its place. The fact that it is unrefined also means it is easy or easier to make than its more refined cousin.
Doburoku is sweeter than sake with a lower percentage of alcohol. Both of these characteristics are from the method used for the ferment. The method does not give the yeast the conditions it needs to convert more of the sugars to alcohol and CO2. The yeast simply shuts down before it gets the job done. The more refined processes used to make sake are designed specifically to extend the conditions that are more favorable for yeast. This allows the yeast to work for a longer period and to dry out the sake while producing more alcohol.
Both sugar and alcohol are toxic to yeast if their concentrations are too high. Too much of one, the other, or both will prevent the yeast from completing its task. In the case of doburoku, it is the sugar that wins, killing off the yeast before it finishes. By placing all of the koji, rice and yeast in at the same time, the koji converts the starches to sugar pretty fast while the yeast are multiplying. As the oxygen runs out, the yeast completes their growth phase. This happens before enough yeast can be produced to handle the massive sugar buildup. As the yeast start to convert the sugar to alcohol they are in a constant state of stress, from the high sugar concentration, that steadily saps their strength until they can work no more.
The process of making sake is careful to slow the additions that produce the sugar and to stir regularly. Stirring does two things, it mixes the ingredients as you would expect but it also introduces more oxygen. More oxygen means we will have more yeast growth. Slow the sugar production and the environment is less toxic to the yeast and the yeast can keep up with the amount of sugar being added. Under these circumstances, the yeast will eventually convert almost all of the sugar to alcohol. With sake, it is the brewer who needs to decide when to stop the ferment so the desired dryness or sweetness is reached.
Is doburoku sake? Is Pluto a planet? Both these questions can legitimately be answered with a yes or a no; it is all in your definitions. Now that doburoku is becoming more popular and kura are producing it commercially I believe we will lean more to yes.