Koji Growth Patterns
I know, I know: I keep koming back to koji. It's koji this and koji that, koji here and koji there.
Koji, koji, koji. "What's all the fuss?," you might wonder.
Well, it is in fact the heart of the sake brewing process, and furthermore, it is one aspect of the creation of alcoholic
beverages - not to mention many other kinds of fermented food culture - that is pretty much foreign to us in the west. But in truth, we cannot look at it enough if we are to truly understand the subtleties of
(Bear in mind throughout the ensuing monologue that koji refers to the moldy rice in its completed form, whereas the mold alone is koji-kin, here referred to as koji mold.)
As readers surely
recall, koji mold spores are sprinkled on about 20 to 25 percent of all the rice that goes into a batch of sake. This mold then grows onto and into the rice, giving off enzymes that convert starch to sugar,
which then is converted by the yeast into alcohol and carbon dioxide (for starters).
But that is the dumb-down of the decade, the understatement of the century, the oversimplification of the millennium.
Saying the mold is simply sprinkled on a good bit of the rice is like saying, "to make wine, first get go and yerself some grapes." The truth of the matter is that just *how* that mold is propagated
onto and into the rice is *everything.*
The amount of koji mold used, the way it is guided in propagating, the degree to which it is allowed to spread as well as where on the rice grains it is guided are
all different depending upon a myriad of factors, including the house style, the particular grade of the batch in question and the step of the process at hand.
Driving this point yet a bit further home,
perhaps beyond the koji-comfort threshold for many, the moisture allowed to remain in the koji-in-development (alternatively stated, how much it is guided toward drying out), how long it takes to complete the
koji-making process, and of course the actual ratios of koji to rice used are still more decisions that, like those listed above, depend not only on the previously-stated factors, but also others like the
variety of rice, the quality of the harvest, and the climate within which the brewery sits. Consider all that, know that there is much, much more to it, and it's no wonder it takes a high level of experience
and intuition-infused skill to make great koji and then great sake.
Let's look a bit more closely at the process and see what happens along the way, and how the koji is adjusted. First, recall that
koji is actually used four times throughout the brewing process. Each of these four times, it is added to the batch together with straight steamed rice and water. Firstly it is used in the moto (yeast starter)
stage, wherein the goal is to create an environment in which the yeast cells go off on a reproduction frenzy (as opposed to creating alcohol, although that happens too). Then, it is used in each of the three
additions made over four days known as "san-dan shikomi," the trademark method used in sake brewing, the objective of which is to keep the yeast population high enough to withstand the onslaughts of
renegade and rogue bacteria and wild yeast dropping in from the ambient environment.
Grossly oversimplifying again, each one of these stages requires koji that is more developed, i.e. more mold growth,
and more significantly, more enzymatic activity. In other words, the batch needs less sugar-making power in the moto stage, and progressively more along each of the three additions (which, by the way, double in
size each time).
So koji for a moto might have minor flecks of mold visible on it, whereas koji for the third of the three additions might be totally covered in the white frosting-like mold. But wait;
there's more. So much more.
For example, sometimes a brewer wants the mold to grow around the outside of the rice, other times (s)he wants it to grow more in toward the center of the rice. Why?
Simplifying again, because ginjo-like sake calls for slower fermentation at lower temperatures, and this requires the rice dissolve more slowly. This is in turn made possible by the mold and requisite enzymes
being in the center of the rice grain, less near its outer areas.
How do they coax the mold to grow toward the center when this is called for? By drying out the outside of the rice through tedious and
precise control of the humidity in the koji-making room. Mold likes moisture, so when there is little it hightails it toward where there is more. So by drying out the outside, and of course keeping the inside
moist, brewers drive the rice into the center of the steamed rice grains.
Furthermore, the style of the sake will dictate the overall scale and degree of things as well. In short, lighter, crisper sake
calls for less developed koji, and conversely heavy, rich sake needs more opulently grown koji. For those interested in the terms used in the industry here, the term "haze" refers to the manner in
which the mold grows on the rice. "Tsuki-haze" rerfers to growth conditions where we can see specks of mold on the outside, but with threads of the mold growing in toward the center. Conversely,
"soh-haze" indicates a more general development in which the mold engulfs the outside of the grain with its frosting-like growth.
How much of the koji mold do they use? A massively
general number is about 30 grams of spores per 100 kilograms of rice. But bear in mind this will vary humongously from brewer to brewer, style to style, and step to step, so much so that it is almost ludicrous
to list a number here. But there ya have it.
And this is *so* just the tip of the iceburg. Recall that the way the koji is made will give a sweet sake or a dry sake, a refined sake or a heavy one,
a stinky sake or a subtly aromatic one, and that all these objectives are factored in along with the hoard of issues described above. And then revel in the fact that all we consumers have to do is simply enjoy
the final product.
About the Date on the Bottle
Sake bottles have dates printed on them, usually in very small numbers, commonly found in a lower corner of the front label. What do
these dates refer to, how useful are they to those of us buying sake (particularly overseas), and how can we decipher this data?
In short, this date is the date on which the sake was shipped from the
kura where it was brewed. It is NOT the date the sake was brewed or "born on," nor necessarily even the bottling date, since some breweries mature in bottles and others in tanks. Its significance to
the brewing company's accountant is that alcohol taxes must now be paid to the government in Japan for the sale of that alcoholic beverage.
As a side note that will soon be more relevant, note that
when sake is exported out of Japan by a brewer, that company does NOT need to pay alcohol tax to the Japanese government. As such, technically, they do not need to print the date on the bottle, at least not
There are several forms this date can take. Most commonly, though, it is YY MM. And not surprisingly, within Japan, that YY is usually *not* the western years we are so familiar with, but the
year in the current Japanese calendar (based on the number of years the current emperor has been reigning). For reference, 2007 is Heisei 19. So, sake shipped from a brewery in May of 2007 would likely have
"19 05," or perhaps "19 5" printed on it, at least for distribution in Japan.
However, note that many places are now adapting the western dating system, especially for export, so that
you might also see 07 05 for 2007 May, although 2007 05 is sometimes seen as well. It is also wise to remember that as with all things sake, there will be exceptions to this, and conceivably the order could be
As alluded to above, since brewers do not have to put the date on there if they are exporting the sake, sometimes US consumers do not see a date on the bottle. However, when the date of
shipping is not there, this is surely not because they are trying to hide how old it is, but rather that they simply "forgot" (or didn't bother, I suppose) to put it on there, as it was shipped in
a way that differed from the normal routine. There may also be some rare situations where there was no room on the label, as in some 300ml bottles.
How can I be so sure of this? Because most if not all
sake brewers as I know them to be are extremely concerned about quality of their product once it reaches far-off shores. They surely want you to drink it at its best condition, and deliberately hiding the date
will serve no one. While there may be exceptions, I know of none.
What this date does *not* tell you: This date does not tell you how old the sake is, or how long it has been since it was brewed.
Different brewers mature their sake for different periods, based on a gazillion factors including the style of their sake, how each particular batch ended up (some will call for more maturation than others to
get them where they want them), and more.
How old is too old?
Within how long or short a span of time should you consider a sake OK? In other words, based on this date, how long can a sake be
considered fresh and in prime drinking condition? The truth is that there is no short answer to this question.
It depends on a whole range of factors, really. How was the sake shipped? In a refrigerated
container? (Almost all sake is these days.) How was it stored when it got here to the US? A warm-ish warehouse or a cool one? Perhaps even a refrigerated one. How much time has it been on a retailer's shelf,
or getting from the warehouse to the distributor in far-off states? Was it matured much in the kura before shipping? Is it a style that will stand up to maturation or not? This last one is huge, since for sure,
some sake will change much less than other sake over the same time and under the same conditions. Do not forget this salient point. Alcohol content, acidity, whether or not it is junmai or non-junmai, and seimai
buai all have a say in this as well.
While in the end, surely fresher is better, this does not unequivocally mean that after a certain number of days, weeks, or months, a sake is automatically and
definitely "too old." But if I had to give a short answer, a rule of thumb, I would say definitely no more than a year. Still, take this with a grain of salt, and not as a hard-and-fast number. It also
assumes the producer is good and the importer is conscientious enough to have stored it properly.
While the lack of hard, fast rules makes this difficult, the above is the truth of the matter.
what should you do if you are not sure? To the extent that it is possible, taste it. With enough tasting experience, you can taste when sake is too old. And if you drink sake often, your palate will be even more
refined and attuned to the sake in question. Trust your palate and experience, and put nothing above that, since too many other factors are involved.
If you are not in a position to taste before buying,
why then of course err on the side of youth, unless your particular threshold for funk is higher than normal. Yet having stated this, it is also true that using a certain period of time as the be all end all
dividing line between good and bad is not a philosophy that will serve us particularly well.
Sake Events and Announcements
On the evening of Saturday, September 22, from 6:00 pm, pottery
expert Rob Yellin and I will hold a sake and pottery seminar at Takara, in Yurakucho. The topic for the sake part of the evening will be koji: what it is, what makes it special and unique, and the leverage it
commands in sake brewing.
The cost for the evening - a half dozen sake, ample scrumptious food, two lectures and printed material - will be 7000 yen. Those interested can reserve a spot by sending me an
email. No deposit is required.
Takara is located on the B1 level of the Tokyo International Forum, the convention center just outside JR Yurakucho Station. More detailed instructions for getting there
will be included in the confirmation-of-attendance email that is sent out a few days before the event. Questions and comments should be directed to John Gauntner. Email John from this link: