The School of Kimoto
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Orthodox sake brewing requires the preparation of a yeast starter, a small batch of steamed rice, koji, water, and of course yeast, interchangeably referred to as the moto or shubo in Japanese. While the vast majority of sake produced today uses the modern sokujo (fast-brewing) method to achieve this, there are several traditional and more time consuming variations developed throughout sake's extensive history. In reverse-chronological order, these are the yamahai, kimoto, and bodaimoto methods. Although there are many instances of crossover in style, they each have the potential to produce a distinctive profile of aromas and flavours. This justifies segregating them into individual categories and, along with such things as rice variety and the legal classification (tokuteimeishoshu), is a significant factor when choosing sake.
The role of lactic acid in sake brewing is of great importance. Therefore, in recent years, there has been a tendency to divide all of these different methods into two distinct groups: those that utilise naturally forming lactic acid in one, the traditional methods, with sokujo in the other, which instead have cultured lactic acid added during the early stages of production. This has undoubtedly made it easier for both educators and consumers alike to navigate their admittedly complex nomenclature.
However, as is so often the case with sake, a complex topic such as this cannot be so easily defined into neat groups. Moreover, the premise for how they are determined isn't technically correct and, for those so inclined, discovering what really distinguishes them from one another makes for yet another, albeit fascinating, rabbit hole for which to get lost in. Nowhere is this more prominent than with the increasingly popular kimoto method, one that's typical description in modern textbooks and product information belies the true complexity of this fascinating style.
What is Kimoto?
In answering this question, it is just as important to explain what kimoto isn't as it is to talk about what it is. Often translated into English as meaning "original method", virtually all descriptions include a mention of either moto-suri or yamaoroshi, both of which refer to the mixing of steamed rice with long poles in small wooden tubs. This is done to macerate the rice and koji, which later aids in the saccharification of starch to sugar. The image of singing brewers working in unison to achieve this has become one of the most iconic in traditional sake brewing, and is firmly established as the defining feature of kimoto.
As much as this makes for a nice romantic piece of marketing, however, it is unfortunately not a defining characteristic of kimoto, at least from a historic perspective. Indeed, the process of pole mixing in this way is merely the most recent form of what could be called "conventional" kimoto from amongst several that have been developed over the course of its history.
Originally pioneered in the once mighty brewing region of Itami, Hyogo Prefecture, pole mixing in this way was later perfected in nearby Nada, the region that would soon take its place as Japan's pre-eminent sake producer. This was back in the mid-to-late Edo Period (1603-1868), and kimoto made in this way became one of the pillars of Nada brewing. It embodied state of the art sake production and drastically cut down on the time it took to prepare a yeast starter. One could even surmise that it may have attracted the same kind of scorn from brewing traditionalists as many of the time saving techniques associated with contemporary brewing do so today...
Although pole mixing has now become synonymous with kimoto within the mainstream, within brewing circles, the term kimoto-kei, or Kimoto School in English, is often used to incorporate a much wider variety of methods that all share one common brewing process. To name but a few, these include earlier variations that didn't utilise pole mixing, such as temoto (hand mixing), along with modern hybrid versions that incorporate some of the traditional elements of kimoto with those of more recent scientific developments. Even the idiosyncratic and much loved yamahai, which famously omits this step, and is often considered a stand-alone category, comes under this banner. The list of differing styles is surprisingly varied, and it is a gross oversimplification to suggest that one particular method defines the entire category.
Notably absent from this list, though, is bodaimoto, synonymous with the monks of the Bodaisen Temple in Nara Prefecture, and widely regarded as the earliest method of making yeast starter. Although bodaimoto also relies on a natural lactic acid fermentation, this step is carried out before the initial mashing of rice, water and koji for the main yeast starter. Instead, orthodox bodaimoto calls for a separate mixture of raw rice and water to create a solution high in lactic acid, known as soyashi-mizu. This is later put into a new mash and processed in much the same way as a modern yeast starter. In this way, bodaimoto is more of a precursor to sokujo that also uses a concentration of pre-prepared lactic acid from the beginning.
However, as distinctive as this process is, what really excludes bodaimoto from the kimoto-kei group, or any other method for that matter, is the pattern of temperature during the course of yeast propagation. Specifically, the temperature of a yeast starter belonging to kimoto-kei is deliberately kept low during the initial mashing stage, and again when yeast becomes present in the mash, whether that be cultured yeast, or yeast that floats in naturally.
This step is known as utase in Japanese, and it involves keeping the temperature to around 4-6 degrees to suppress the development of yeast. If the temperature rises during this crucial 4-5 day period, then the yeast will consume precious sugars that are better utilised later in the main mash. The need to macerate the rice beforehand is due to these initial low temperatures. Like sokujo, bodaimoto differs in that it is typically mashed with a much higher starting temperature, which ensures a quicker saccharification, or dissolving of the rice.
The process of utase is so integral to the kimoto method that it actually determined its early naming. Back when the process of pole mixing was first being practiced in Nada, kimoto was actually known as kanmoto. The kan part of the name comes from the Japanese reading for cold. Without the hindsight that technology would later improve to a stage whereby temperatures could be easily controlled, it was thought that utase could only be carried out successfully during the colder winter months. Brewing during the winter was already a staple of Nada brewing, and the new kanmoto method soon became synonymous with the region, and a sign of the quality of sake produced there.
Moving into the Meiji Period (1868-1912), however, the method had been normalised to the point that it came to be known by the much more generic name of futsumoto, meaning "usual" or "standard" in English. The development of yamahai in 1909, marked yet another step-change in the development of kimoto - an increase in water added to the mash, along with a higher temperature of the added rice, negated the need for the labour intensive pole mixing. Finally, the introduction of sokujo, which quickly became the new "normal", increased the diversity of styles to the point that its current name became redundant. As a result, it was finally given its current name, kimoto.
As mentioned previously, kimoto nowadays exists as a very niche part of the market. The sokujo method, in all of its various differing forms, is simply more time efficient, requires considerably less labour, and is ultimately safer than traditional methods. Therefore, the physical challenges of making kimoto have, for the most part, been relegated to sake brewing history. However, the fact remains that the kimoto method has the potential to yield sake markedly different from that produced by more modern techniques. As a result, in recent years, it has enjoyed a renaissance of such, with many brewers and consumers alike looking to reconnect with the sake brewing traditions of old.
Consequently, the number of brewers that are once again trying their hand at kimoto-kei methods is steadily increasing. This is not just limited to pole mashing, with brands such as Aramasa in Akita Prefecture going back even further and utilising earlier techniques that pre-date kanmoto. Conversely, there are others going in a different direction who have applied the use of more modern equipment to achieve the same result as pole mashing, alleviating some of the strenuous labour that comes with it. One such example is Mioya Shuzo in Ishikawa Prefecture, makers of the Yuho brand, who instead of using poles employ a drill to pound the mash.
All of the above are positive signs that the kimoto style is not quite ready to be consigned to the history books, albeit it will most likely remain as just a small percentage of the overall market. What is important to appreciate, though, is that there is a lot more to it than the oversimplified image often portrayed in mainstream sake literature. In truth, it is an incredibly complex and intricate style, with many different variations, and the potential to develop further given the technology available today. It is, therefore, another example, if ever it was needed, that the intricacies of sake cannot be easily condensed into short, concise descriptions. It is complex, sometimes frustratingly so, and will require strenuous research to fully grasp. But then again, this is the case for most of the interesting things in life.