The magic of dancing spores
By JOHN GAUNTNER
Sake fans these days are quite often inundated with information (much of it extraneous) about how a sake was made. The rice, yeast strain, water quality, nihonshu-do (specific gravity) and acidity are commonly found listed on the labels of most decent bottles of sake.
One can indeed determine a bit about the style of sake from this information. Still, the difference between sake brewed with one rice or one yeast strain and another is often quite subtle. In the end, the numbers should be considered not much more than a diversion, or interesting facts to note.
One thing that is never listed on the bottle is the type of koji mold used in brewing. This is curious, as making koji from this mold is the heart of the sake-brewing process.
First a quick review. Koji works to break down starch molecules into sugar molecules, which can then be processed by yeast cells, which is what fermentation is all about. In wine making, there is sugar already present in the juice of the grapes, and the yeast can then be added to that.
For beer and other malt-based beverages, malted barley contains enzymes that are activated when soaked in hot water at very specific temperatures. These enzymes break the starch in the barley into sugar to be used as food for the yeast. After this step, yeast is added, and fermentation begins.
In sake brewing, there is no way to malt since the husks have been milled away, and only white rice remains. Enter the mighty mold Aspergillus oryzae, the scientific name for koji spores. The dark greenish-yellow, fine powder is sprinkled lightly over freshly steamed rice and coaxed into propagating on and into the rice grains. As it does so, the necessary enzymes are created and activated, turning starch into sugar along the way.
The process takes 42 to 50 hours or so, and is done in a special room, warmer and more humid than usual.
When finished, koji looks like rice with a bit of white frosting on it, and smells a bit like chestnuts. This finished koji is used in the brewing process four times, mixed with water and plain steamed rice in the fermenting mash.
Simplifying the koji-making process, about which reams of research and eons of experience have been accumulated, into the above few paragraphs borders on insulting. But that is it, in a nutshell.
Terminology sticklers remind us that koji refers to the finished product; the mold itself is referred to as tane-koji, or koji-kin. It is often nicknamed moyashi by those in the industry.
Tane-koji was first brought over from China in about the year 200, and eventually harnessed, studied and manufactured. The word itself is a shortened form of the word kabitachi, meaning “bloom of mold.” There are about 4 billion spores in a single gram of tane-koji, and it takes about 100 grams to make a large tank of sake.
There are several thousand strains of tane-koji. Various strains are used in the production of shoyu and miso as well as sake, shochu and awamori. It is also used in production of the Chinese beverage laochu, although the methodology is somewhat different from that of sake brewing.
Koji is produced by only about a half-dozen companies in Japan. This is surprising in light of the fact that annual production of shoyu, miso and sake combine to exceed 1 trillion yen, and make up almost 2 percent of the gross national product of Japan.
The various strains of tane-koji differ in their capacity to produce various enzymes (proteolytic, lipolytic and amylolytic enzymes, for those who simply must know). Each enzyme performs a different chemical activity, and different types of sugars are produced by each as well. Naturally, shoyu, miso and other products all call for different types of enzyme activity.
The tane-koji is prepared at the factory by inoculating the spores onto brown rice, treated with wood ash which acts as a preservative and source of mineral nutrition. This is how the sake brewers receive it; it looks like exactly what it is — moldy rice. The tane-koji is shaken inside a screen-bottomed can or small cloth bag, and the spores come delicately dancing out to rest upon the rice. From there the mold begins to grow.
Even within those tane-koji strains used for sake brewing, there are subtle differences. Several types are mixed in exact proportions, not unlike a recipe, to create a blend for very specific needs. A catalog from Akita Konno, one of the handful of tane-koji producers, lists about a dozen selections for sake brewing. All have proprietary names, and a description of their special characteristics.
For example, one may be specifically for making fragrant sake, another for ginjo-shu in general, yet another may help create sake with a higher than average acidity. The chemical characteristics of each, including the relative strength of the various enzymes, are listed in chart form for comparison.
There is not, it seems, a lot of experimentation with tane-koji in the sake-brewing industry, in the way that there is with rice and yeast. Most brewers stick with one producer and specific tane-koji for a specific job, preferring it to be one of the few constants of the brewing process. With so much affecting the quality of the final koji while making it, one more variable is not needed.
Perhaps the reason that more information about koji is not available on labels and such is that its use is so deep in the recesses of the process. Perhaps it is simply because most laymen would not likely be interested. In the end, the flavor of a sake and our preferences are all that matters, but the moldy world of tane-koji at least deserves a look.
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Kariho (Akita Prefecture)
Seimai-buai: 55 percent
Kariho, brewed in the same prefecture where tane-koji maker Akita Konno is located, is in general a dry and crisp sake, with a flavor a bit more full than most Akita sake. This particular ginjo, Rokushu, has a light, flowery fragrance and a light presence as well. There is a softness and a slight milky tone in the recesses that seems to increase the sensation of a gentle sweetness.
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