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Koji-Making Machines; Pasteurizing

# 45

July 2003

Sake World Sake e-Newsletter

Issue #45
July, 2003

- Koji-Making Machines
- Pasteurization
- Good Sake To Look For
- Sake Events/Announcements
- Home-Brewing Sake

Koji-Making Machines
As most readers surely recall, the creation of proper koji is really the heart of the sake brewing process. Koji is rice that has had a mold (koji-kin, i.e. koji mold) grown on it. Not just any mold, mind you, but one known in the scientific world as aspergillus Oryzae, which is found more commonly in the humid climates of Asia.

Enzymes in the koji mold work to break down starch molecules into sugar molecules which can then be processed by yeast cells, which is what fermentation is all about. Without koji, there is no sake.

The leverage that koji-making exerts on the final flavor profile of sake is immense. The types of sugars created by the various enzymes as they chop up the starch molecules, the strength and speed of this conversion, and the quality of the rice are just a few of the factors involved at this stage that can make or break a sake. Temperature, water chemistry, air quality, and desired flavor profile are a few more factors that go into the massively complex and intuitive decision-making process of koji creation.

Naturally, from long ago, this was done by hand. It is a very labor-intensive process that can take from 40 to 60 hours of constant attention on the part of the brewers. And just as naturally, over the last few decades, the industry has developed many automated and semi-automated methods and contraptions to save labor and time.
These koji-making tools and machines come in many manifestations. At one end of the scale are long machines that fill a large room and are fully automatic. Put your rice in there, put your mold in here, push a couple of buttons, stand back and voila! Here is your koji in 40 hours or so. (Well, OK, it's not quite that simple…) Yet others allow much more human intervention, some being only temperature controlled tables or boxes.

There are several objectives, but most important are temperature control and humidity control. Temperature and humidity determine which enzymes become the most prominent in the koji, and how the koji works its way into the grains. The "best" temperature is again dependent on a multitude of factors, and is actually a curve that slowly rises from about 30C to about 40C over the two-day incubation period. It is very important in making good koji to maintain a very even temperature and humidity distribution throughout all of the mold-crusted rice, and machines must try to duplicate this.

Also (unlike other beverages in Asia that use koji), it is paramount to prevent the grains from clumping together in a mass. In the end, each grain of rice becomes coated and permeated (to a degree that varies with the type of sake) with koji mold, becoming its own little enzyme factory.

So preventing this clumping is one more thing good koji machines need to do. This is accomplished by using very thin layers of rice, or cutting through the stuff with constantly-moving gentle blades or - in some cases - cute little mechanical fingers that drop down and mix the contents around.

Naturally, the higher the grade of sake, the more important all this becomes. It is of course possible to cut a few corners in lower grade sake.

Most of these machines work well, some better than others. While quite a bit of labor indeed can be saved with koji-making equipment, it is interesting to note that almost every kura in the country makes koji for their best sake by hand. Even those kura that make wonderful sake utilizing good koji-making machines will almost always make their top class sake with hand-made koji.

Then again, there are exceptions to this rule too. I have had on several occasions some truly sterling sake that I was genuinely surprised to hear was made with machine-made koji. But in the end, that is what it's all about: if the flavors and aromas are enjoyable, the means is justified.

For a series of photos of several manifestations of koji-making machines, see


Almost all sake out on the market has been pasteurized before shipping. Sake that has *not* been pasteurized is known as nama-zake, and while not as stable, is often just a tad livelier, more aromatic, and fresher. (For more information on all things nama, see newsletters #9 May 24, 00 and #32 June 1 02, archived at

The pasteurization process is known as "hi-ire," (putting in the fire), and while there are many ways of doing this, let us look at the main methods.

First of all, why is sake pasteurized? To kill off bacteria, to kill any remaining yeast cells that have finished doing their job, and to deactivate enzymes that might otherwise affect the flavor of the sake in the bottle. When sake is not pasteurized, it must be kept quite cold to ensure the bacteria, yeast and enzymes remaining will not send it out of kilter.

Of particular concern is a certain bacteria known as "hi-ochi-kin," which actually thrives in an alcohol-based environment. If these bacteria are not kept in check with low temperatures, or killed off, they can make a namazake murky, cloying and weird. While it will not hurt you, it is not enjoyable to drink sake that has been affected in this ill way.

But once the sake has been heated to about 60C for about two or three minutes, it is safe from these changes, as these bacteria and yeast cells will be killed off, and the enzymes will rendered inactive as well.

The most common way of pasteurizing sake is to run it though a coil of pipe that is submerged in a tank of water at about 60C on its way to the storage tank. This gentle method is usually sufficient to ensure the sake will be fine over the warm summer. (A photo of this coil is at the *bottom* of this page of photos:

Actually, most sake is pasteurized twice: once before over-summer storage and once again before shipping. Very often the second pasteurization is performed in-vitro, with the sake being warmed as it goes into the bottles. This has the added advantage of creating a bit of a vacuum inside the bottle as the cap is put in place with the sake still warm, creating that vacuum when it cools inside the capped bottle.

Also, especially lately, many brewers are finding that another method of pasteurizations seems to leave the sake a bit livelier: pasteurization in bottles. After bottling at cool or cold temperatures, the full bottles will be placed in a big tub of hot water to sit for a while

While namazake *can* be a bit fresher and zingier, very often the subtle aspects are masked by the lack of pasteurization. Indeed, there are many connoisseurs that do prefer sake to be pasteurized. The point is that one style is not unequivocally or inherently better or worse than the other.

Finally, it is interesting to note that the first written record of pasteurization being used to prevent sake from spoiling was in a brewing text called the Tamon'in Nikki, in 1568. This was almost 300 years before Louis Pasteur made his discoveries, in 1865.

Good Sake To Look For

Here is a collection of tasting notes from the recent spring-season tasting rounds.

Masumi "Sanka" Junmai Daiginjo (Nagano Prefecture)
Green, lively, fresh fruit, classic  No. 9 yeast aroma, although gracefully restrained. Very slight lactic sweetness in the flavor and recesses as well, but wonderfully clean.

Masumi "Yumedono" Daiginjo (Nagano Prefecture)
Fruity-sweet and nut-laced aroma, delightfully reigned in, very clean, balanced, but yet with an excellent dancing presence and overall lively flavor.

Yuki no Bosha Daiginjo (Akita Prefecture)
One of the most all-around well-brewed and enjoyable sake of the spring sessions. Made with Akita Komachi rice, which is usually not a top-grade sake rice, but in the hands of a brewer like this, it does just fine. A very faint sweetness at the beginning leads to a very tight, focused and compacted rice-like flavor, with a clean and balanced finish. Almost a bit of pine and melon lacing the aroma.

Shida Izumi Junmai Daiginjo (Shizuoka Prefecture)
This is a sake I am becoming increasingly fond of; they seem to be really coming into their own lately. (I believe this is due at least in part to a toji from another well known brewery arriving here.) Full breadth to the flavor, nice grainy touch to the feel, fresh and cherry tinged aroma with a rich sweet tone to the otherwise light flavor.

Shidai Izumi Junmai Ginjo "Muroka Nama Genshu" (Shizuoka Prefecture)
"Muroka Nama Genshu," i.e. unfiltered, unpasteurized, and undiluted. Too often this means a huge, overpowering flavor profile, but not in this case. Honey and ripe cantaloupe in the well-grounded aroma lead into a soft, spreading sweetness well diffused by a nice acidity, with a barely perceptible tart/bitter tone at the end to round out the balance. Hard to find, but thoroughly enjoyable.

Oroku "Hiyaoroshi" Junmai Ginjo (Shimane)
Hiyaorishi (basically) refers to sake that has only been pasteurized once, and not the second (usually pre-shipping) time. Oroku has a faint, goldenrod touch to the color, well crafted through very precise filtering. Pineapples and prunes wrestle in the comparatively heavy aroma. Soft initially, not sweet but not all that dry. Lots of mouth feel, soft and round and heavy in. Viscous and rich, but not over the top, with faint spicy and slightly citric touches in the recesses of your perception.

Naraman Junmai-shu Nama-zake (Fukushima)
An *un*pasteurized sake, i.e. namazake. Plum aroma, with a full but balanced flavor and a moderate acidity that tapers near the end. Made with F701, a yeast used only in Fukushima prefecture, and exhibits the best fruity aspects this yeast promotes. (Discovered with a light pork dish with a mild vinaigrette sauce that was a perfect match.)

Sake Events and Announcements

On the evening of Saturday, August 9, from 6:00 to about 9:00, I will hold a sake seminar at Takara, near Yurakucho Station. The topic will be sake rice "varietals," and the effect they have on sake flavor profiles.

The cost for the evening - half a dozen sake, ample food, a lecture and printed material - will be 7000 yen. Those interested can reserve a spot by emailing me at No deposit is required.

Takara is located on the B1 level of the Tokyo Forum, the convention
center just outside Yurakucho Station. More detailed instructions for
getting there will follow with the confirmation email.

Do you work for a company in Japan? John Gauntner is available for corporate sake seminars. A wide variety of formats are possible: in house, at a sake pub, with food, without, with lectures on a variety of sake-related topics. Please contact John by email for more information.

Home-Brewing Sake

If you have even a passing interest in brewing sake at home, you must check out The Sake Digest, a mailing list on sake home brewing maintained by Jim Liddil at On this list, issues both stylistic and technical, detailed and general, are discussed by enthusiastic and knowledgeable home brewers. Fred Eckhardt, easily the most experienced sake home-brewer in North America, regularly generously imparts his experience and wisdom to readers. A message is generated perhaps twice a week, so one in not inundated with information and countless emails. It is quite interesting to follow along with the apparently successful efforts of these brewers from a cyber-distance.

Most recently, several brewers are experimenting with koji obtained from SakeOne Corporation in Oregon, with apparently significantly improved results. This koji can be purchased from F.H. Steinbarts for about $8.00 for a 2.5 lb. Batch. For more information call Steinbarts, at 503-232-8793.

Also, koji spores (as opposed to completed koji) are also available from Vision Brewing in Australia. According to proprietor Brendan Tibbs, the product is available online for anyone, and is particularly suitable to the home brewer. Contact him at Vision Brewing:, and see their site at

To subscribe to The Sake Digest, send the word "subscribe" without the quotes to . To unsubscribe, send the word "unsubscribe", without the quotes, to For a list of other useful commands, send the word "help", less the quotes, to Comments or questions related to the operation of this list should be directed to

Questions and comments should be directed to John Gauntner

Copyright 2003 Sake World


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