Kimoto

The traditional ways of doing things always seem to circle back around. Be it sake brewing or any traditional craft, people have spent great lengths of time figuring out the best way to do it. Even if the process was full of hassles, they continued to do it that way for good reason: it led to a better product. While it may be an idiosyncrasy of the sake brewing industry, the more hasslesome a particular method, the better the resulting sake in most cases.

Kimoto is like that. It took hundreds of years for sake brewers to refine the kimoto method (it is first mentioned in a 1687 brewing text, though it likely predates that) and it was generally the sole method used for hundreds more years, until the early 1900s. While it never disappeared completely, it was eclipsed by a modern method that saved time, labor and risk.

There have always been a few holdouts that continued to brew some kimoto, and the number of these has increased slowly over the last 20 years. Without a doubt kimoto is making a small comeback and has become much more visible recently. It is more of a hassle for brewers to make kimoto, but significantly more of them (usually the younger ones) are understanding its appeal. Consumers, too. As its popularity grows, it’s worthwhile to understand what the designation “kimoto” means.

The concise, if over-simplified definition, of kimoto is: a traditional and labor-intensive method of preparing the yeast starter that often–but not always–leads to a richer, more mellow and more fine-grained flavor profile. Let’s look at what actually happens during the kimoto sake-brewing process to understand why.

For any tank of sake (not just kimoto), the first plateau for which the brewer aims is the yeast starter. This is called, interchangeably, a moto or a shubo. It is a small tank that amounts to a miniature batch of sake, the goal of which is to get the yeast started so as to promote a healthy and strong fermentation. The brewer creates conditions that encourage the yeast cells to reproduce rapidly. This will also yield some alcohol, but at this stage, that is not the main objective. The goal is a very large population of yeast cells.

This is crucial because once the yeast starter is ready, brewers will add more ingredients three times, roughly doubling the size of the batch each time. Plenty of wild yeast and other bacteria hell-bent on destruction can and will drop into the fermenting mash along the way. But if cultivated yeast massively outnumbers the intruders, the mash can ferment into the beautiful ambrosia we know sake to be.

Kimoto, then, is all about this yeast starter stage, which is in turn all about getting a high population of yeast cells, and that is all about maintaining a strong, clean fermentation when the rest of the ingredients are added. What physically happens is that brewers put the basic ingredients into a small vat. These include water, steamed rice and koji, which is steamed rice onto which a mold has been grown. That mold provides enzymes that convert starch to sugar, which the yeast later converts to alcohol. These three basic ingredients are mixed and smooshed into a paste-like consistency with tools that are like poles with blunted blocks attached to the end. This mixing takes place several times a day for a couple of days, although it varies from kura to kura.

This thorough mixing with poles is key and one of the main defining aspects of the kimoto method. From this point, there are several chemical developments that take place. The most important one is where chemical conditions inside the small tank eventually favor the growth of natural lactic bacteria, which drop in from the ambient air. These thrive in the small fermenting concoction, reproducing and creating lots of lactic acid as well. This lactic acid in turn kills just about all other stray bacteria and wild yeast in the tank. In fact, it eventually kills the lactic bacteria.

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The miracle of sake brewing is that the one thing that can tolerate and actually flourish in this lactic-acid environment is sake yeast. After about two weeks, when the lactic bacteria have created enough lactic acid to clean the environment well, brewers add sake yeast.

After adding yeast, brewers give the cells about two weeks to reproduce. Once the yeast has reached a certain degree of vitality, the other ingredients (rice, koji and water) are added in stages, after which fermentation commences in full. From this point on the process is the same as all other sake.

Returning to kimoto’s historical development, in the early 1900s researchers came to realize that it was all about lactic acid. Through more research, especially trial and error, they realized that they could just add pure industrial lactic acid to the yeast starter at the beginning instead of waiting for the lactic bacteria to do that for them.

In doing so, they cut the first two weeks off the yeast starter preparation time. It also provided better quality control because there was one less step they had to leave to the whims of nature. This was obviously appealing to brewers, not to mention the government. Sake tax was a significant source of revenue back then, and governments like sources of fast, safe revenue. They encouraged this faster method.

Consequently, kimoto fell by the wayside–not entirely, but very few brewers continued to make it. In fact, the new method, known as sokujo (“fast brew”) is responsible for almost all sake on the market today.

As important as the details of the process is the difference is in the nature of the sake. Again, kimoto tends to be richer and more mellow than other sake. It also tends to be more complex and fine-grained. Some, but not all, have a more prominent acidity. Elevated umami is another trademark tendency of kimoto. This flavor profile is what drives the current resurging popularity of kimoto among brewers. No one likes more hard work for nothing. Conversely, sake made with added lactic acid tends to be lighter and lower in umami. Many consumers may consider this easier to drink, but perhaps this is just a notion breweries have sold to consumers.

Brewers can apply the kimoto method to any grade of sake. The richness achieved by making a kimoto is in line with the characteristics of a junmai, hence most kimoto are of the junmai variety. While there are in fact added-alcohol (non-junmai) kimoto, the addition of alcohol results in a lighter style that stands in contrast to the goal of employing the kimoto method. To do both in the same batch is going in two different directions. But contrary to common sense, daiginjo kimoto or even aruten kimoto, although rare, do actually exist. Why, one might ask? Why not? Why not rewrite the rules, pursue different marketing angles or simply experiment?

There are a couple of misperceptions to watch out for with kimoto. Kimoto does not mean naturally occurring yeast. It means that the necessary lactic acid came from living lactic bacteria that are almost always naturally occurring–meaning, dropping down from the air. With very few exceptions, brewers add cultured yeast like any other sake. Not all kimoto displays the richer, tangier nature described above, either. The fact that a sake is a kimoto will not necessarily indicate exactly how it will taste. Finally, like all things sake, there are many variations among kimoto methods. Perhaps the most interesting one is Akita-ryu kimoto, made only in Akita prefecture. Brewers use a large electric drill-like tool with a meter-long bit decorated with little fins to mix the moto instead of using the poles. While it may seem like an over-engineered solution, some great kimoto comes from the region.

Kimoto is one very visible example of traditional ways returning to favor. It is one way in which sake has come full circle. There will be many more to be sure. Drink them up.

by John Gauntner


This article appeared in Sake Today 7. You can order a copy here.