Tuesday, December 1, 2009

Koji making, no wimps allowed

This episode is all about Koji.
That magical mold that makes sake what it is.

Koji mold, unlike that mold that is growing on the thanksgiving leftovers sitting in the back of the refrigerator, is a needy mold that requires lots of attention to grow into a fine fungi.
This is the story of the little Daishinshu Koji mold, that started out as a spore on his mother's rice kernel, and grew up to be a Ginjo class kome-koji.

Making kome-koji is a process that includes a lot of heavy lifting, dangerous steaming pots, lightly burned hands, and worn thin skin. It takes a lot of determination and attention to detail (apparently monthly massages too, although that's a trade secret) to make sake the traditional way, And thus I have given this post the name "koji making, no wimps allowed."

First off I would like to share with everyone something you don't often see when shopping for, or studying about, sake, the faces behind the sake.

The picture above is team Daishinshu. With a team of only 9 people, Daishinshu brews about 50 different kinds of sake (including seasonal and limited quantity varieties). The person in the white hat in the front row is Daishinshu's Toji (master brewer), who is now the head Toji, after the previous Toji retired last year at the age of 92 (although he still stops by to check on things). The women on either side of the Toji are seasonal workers (although most of them have been working in the brewery for close to 30 years); in the off season they are apple farmers. In the back row (from left to right) are Katsumi-san, Komatsu-san, Hayashi-san, and Morimoto-san, all seasoned sake makers, and full time employees. And last but not least, Yokomizu-san, who started this year at the beginning of the season (October 1st).

If you are going to tell the story of Kome-koji, then the logical place to start would of course be, the Kome (rice). Daishinshu gets most of their rice from two farms in Nagano prefectures. About 70% of the rice Daishinshu uses is grown under contract, which gives them the ability to work with the farmers closely in order to get exactly the kind of rice that they want. Daishinshu's main sake rice varietal is, Hitogokochi (also known as super Miyama-Nishiki, a varietal bred in Nagano), although they also use a mix of Yamada-nishiki, Miyama-nishiki, and others.

These Guys grow the rice.

Of coarse the rice's tale starts in the paddies, but this story will start a little later after the rice has become big and strong Gen-mai (元米 unpolished or brown rice). Daishinshu polishes 60% of their own rice, something that not all sake breweries do these days, as polishing machines cost about as much as a mid sized house. The other 40% is polished in a local polishing facility. The reason that they don't polish 100% of their own rice is simply time. in order to polish 800~1,000 kg of rice to around 60% it takes upwards of 30 hours of continual polishing, and that amount of rice doesn't last all that long. Thus it is hard to polish all the rice they need themselves, especially in the start of the season when they need to start brewing as soon as possible. The 40% they don't polish themselves is mainly used in the first brews of the year, and for their Futsu-shus.

Huge sacks of unpolished rice, (Komatsu-san jumped in for dramatic effect). This pile totaled 9 metric tons.

Daishinshu's polishing machine (costs upwards of $300,000 USD or 3千万円)

Collecting the rice flour from the polishing machine.

It's a dirty job, but somebodies gotta do it.

There is a dirty little rumor floating around that the portion that is polished off the rice, the "Nuka" in Japanese, is wasted, or thrown away. This is in no way correct. The Nuka is used in a variety of different ways, the "red nuka," the first 20% of the rice polishings, is used in Livestock feeds, whole grain foods, and Suke-mono (Japanese pickles), The "naka nuka (say that 10 times fast)", the 20~30% portion, is used in whole grain foods  and other bread products, and the "shiro nuka", the 30%+ portion, is used in High end confections and as high quality rice flour.

After the rice is polished, there is still a thin coating of Nuka on the rice that must be washed away.  Until a year or two ago this was done by hand with large buckets and strainers; A very labor intensive process which took 5 or 6 people, and a lot of time. Now, Daishinshu uses these neat little rice washing machines that wash the rice by circulating it with a jet of water. A method that now only takes 2~3 people, about half the time, and is softer on the rice.

Rice washing machine

Pouring rice into the washer

Washer in action

The rice is washed in about 20 kg loads for about 2 minutes, then soaked in water for a specific amount of time (differs depending on the type of rice and the polish rate). Everything is timed down to the second using a stopwatch.

Morimoto-san soaking a bag of rice (notice he is holding a stopwatch)

Polished and washed Sake rice, in the midst of saoking

How do you know when the rice has sucked up enough water? Weigh it!

Generally when the rice has sucked up around 30% of it's own weight in water it's ready for the next step, Steaming!

The large steaming pot (Koshiki in Japanese) capable of steaming around 800 kg of rice at a time. The white sacks around the rim are full of small plastic beads. The sacks are placed at the bottom of the pot so the steam does not hit the rice directly and cause it to break.

The steaming pot ready to be loaded with rice

The steam is started and then the rice is added in a little bit at a time. this allows the steam to thoroughly permeate the rice and give it an even steaming.

After all the rice has been loaded into the pot a fabric cover is placed over the top of the pot and tightened down to create pressure inside the pot.

The steam flow is controlled by a flap at the top of the cover, closing the flap creates more pressure and increases the heat inside the pot, opening the flap allows more steam to escape, and lowers the pressure and temperature.

The steaming pot is truly a site to see, once turned on a huge plume of super heated steam bellows out, making it a spectacle as well as a true danger, as being horribly burned is quite possible. Steaming the rice takes about an hour, while the rice is steaming the crew eats breakfast.

The freshly steamed (and extremely hot) rice is then shoveled by hand into a bucket

The bucket is then wheeled at break neck speed to the cooling area outside the Koji-muro (Koji room)

The rice is then spread out on a cloth and allowed to cool. (Yes that's me bending over the steaming rice) Even with gloves my hands were mildly burned (when I took the gloves off my hands were bright red). The rice is cooled down to about 35~40˚C before being moved into the Koji-muro. The stands that we are cooling the rice on was hand made by the Toji this year, up until now they cooled the rice on top of rubber sheets on the floor which, as I found out a couple of times when the loads were big and we had to use the floor, was extremely back breaking and knee hurting work.

Once brought into the Koji-muro, the rice is further cooled to around 31˚C before applying the Koji spores. During the cooling process the rice is mixed and flipped several times to allow even cooling.

The Toji then applies the Koji Spores

The can used to apply the koji spores, the lid of the can has a screen mesh built in, from which the spores float out.

Steamed rice with Koji spores on it (the green powder is the koji)

After the spores are applied, it is left to rest for a few minutes before the rice is mixed and flipped. The sporing process is repeated again two or three times.

After the koji spores have been applied, the rice is let to sit for a few hours. Then piled,

And bundled in blankets. It is then allowed to sit for about a day.

The next morning at 5:30 am the rice is unbundled and passed through a metal screen to break up any clumps. At this stage the rice is getting harder, as it dries out a little, but is not yet visibly coated with koji mold. This is one of the thin skin parts.

The Toji then transfers the rice into wooden trays

At first only half of the tray is used. This is to ensure that the rice does not cool too much before the koji has started to fully develop. The koji rice is then left to sit for about a day.

The next day the koji rice is mixed thoroughly and spread out so that it takes up the entire tray. At this point you can just begin to see white spots of koji mold growing on the rice. (more skin thinning)

The trays are then wrapped in blankets and allowed to sit for another day. During this time period the trays are rotated several times to keep the temperature in all the trays even. The temperature of the koji rice can climb to as high as 45˚C during this time.

The next day the koji rice (which, maybe it's just me, I thought would be granulated like you always see in books, but was actually clumped into one big piece in the shape of the tray) is mixed and the clumps are broken up until it is more or less individual kernels. This is of coarse done with your bare hands. Not only is the koji rice hot, if it were bath water at 45˚C you probably wouldn't want to get in, but the rubbing action required to break up the clumps, again makes your skin quite thin. (my hands were bright red at the end of this step too)

Finished koji rice after it has been broken up and mixed. You can clearly see a white coating of koji mold at this point. I don't know if anyone else out there has eaten warm koji rice before, this was a first for me (although I had eaten cooled koji rice before in the past), the sweet koji flavors expand in your mouth, and as long as you keep chewing, even long after the kernels have disappeared, the flavor keeps coming out kind of like gum. A truly incredible experience.

The koji rice is then spread out on the trays again, and a pattern of a circle with two lines in the middle is drawn into it (in order to assure even cooling and drying). The koji rice is then left uncovered for half a day to cool in the koji-muro. At night when the other trays are being shuffled around, the finished trays are pushed out of the koji-muro into the cold brewery rice cooling area. The koji rice is thoroughly cooled over night, effectively halting the koji growth and hardening the koji rice considerably.

This is the end of the Kome-koji making process, but not the end of the kome-koji's story. At this point the kome-koji is ready to be used to make sake, and it's story continues inside the story of brewing sake (told in the next post!).

I hope that this post is helpful, I had a lot of fun working at the sake brewery. It is really hard work, and I have developed a real appreciation for the people who are willing to brave this kind hard work in order to make the sake that we all love and enjoy.

Join me in the next post, and delve into the brewing world of the sake brewery!

Meishu no Yutaka staff


  1. Ilove the photos & commentary!

  2. Thank you!
    I loved writing & taking them!
    Next post coming soon!

  3. thank you! this article took me to another level of conscientiousness. God bless you!
    Q, where can i buy those marvelous koji starter?

  4. I am happy you found this article helpful!

    A, It depends on what country you are living in. If you are living in America, I would suggest contacting a brewery there, like Sake One in Oregon. they might be able to give you contact information on a supplier in the US. There are also many sites offereing the sale of Kome koji on the internet (I would be careful who you trust though). If you are living in Japan, Koji mold can be purchased, for making Japanese Sukemono or Miso, at your local super market, however it is not the same stuff. Kome koji meant for sake production is not available for sale in Japan, as home brewing of alcoholic beverages is ILLEGAL.

    If you are looking to learn more about Kome koji, or want to try eating some yourself, there are many Sake Breweries in Japan that offer tours. I hope that this information is useful.


  5. Carlin,

    Really wonderful posts; this one on making koji and a later one from making sake (I think at the same brewery). This is a site I will continue to watch.

    Selete asked where he/she can buy the koji starter. Both koji-kin and kome-koji are available from HomeBrewSake.com. The komi-koji is a brewers koji made with rice milled to 60%.


  6. Thank you Will,

    The whole series is from the same brewery.
    It is all Daishinshu, a brewery from Nagano prefecture.
    They produce their koji quite a bit differently then most breweries
    in that they make all of their koji (with the exception of their higher class daiginjos) in the same way. which means that even their lowest grade sakes like futsu-shus are getting high grade Koji.

    This make a lot of good sake, at the expense of a lot of hard work and slightly decreased productivity.
    Do you have to make koji this way to make good sake?
    No, but it does make for some killer sake.

    Thanks for the link on the Koji supplies.
    Home brewing sake sounds like fun, I would be doing it too if it weren't illegal in Japan.

    Thanks again


  7. Extremely interesting web page. Thank you very much for the fascinating, detailed descriptions and the extremely interesting photographs.

    Was the fungus you used to inoculate the rice "aspergillis oryzae"?

    Also, is this the same type of koji used to make miso? Could you use the koji shown here in Miso production?

    Thank you, S

  8. Hi S-

    Thank you for your comment.
    The Fungus is in fact a strain of the "Aspergillus Oryzae" specially created for sake making.

    As for the miso Question:
    Yes and no. That is, technically it is in the same family as Miso Koji, however it is not the same strain. You could potentially use Miso Koji in sake making, however I can't imagine that it would make very good sake.

    As for using sake koji for making miso:
    YES! You can in fact use it to make really really good miso!
    Sake Koji and Miso koji both work in the same way (being that they turn starch into sugar), however, sake koji gives you an extra depth of flavor and aroma that miso koji can't.

    There are several places (mainly sake breweries) that make miso with sake koji.
    Check out Akita Prefectures' "Mansaku no Hana (Hi no Maru Jouzo)", they make a really good miso that sells for about ¥700 for 500g.

    I hope this is answers your questions.
    Please feel free to post questions anytime!

    Thank you

  9. Meishu, Can you tell me what temperature was the room where the spores where incubated. It doesnt't look very warm. Some websites say the mold likes 36 degrees C or 96 degrees F. Thanks for the blog!


  10. Hi drveasey,

    I really depends on the brewery, and the kind of koji they are trying to grow.
    I have been to breweries that keep their koji rooms at around 35~37 C, but I have also been to breweries that keep it at around 42 C when making some of their Daiginjo Kojis.
    It has a lot to do with what stage of the koji making process you are in.
    many times when in the first stages of cooling and drying the rice, and then applying the spores, the room will be much warmer to keep the rice from cooling too much,
    While at other points, like when the koji is simply incubating, and wrapped in blankets, they may allow the room to cool a bit.
    The temperatures are all decided on the spot and adjusted according to the condition of the koji.
    if I had to give an absolute average temp between all stages and all breweries, I would say that around 36~37 C is a pretty good average.

    Thank you for the question!
    Please feel free to ask any others you may have as well.


  11. Could you tell me if the blankets used to wrap the rice where wet?

  12. drveasey-san

    Sorry for the late response.
    The blankets are not wet.
    They use the blankets to help equalize the temperature
    around the trays of growing Kome Koji, and to help reduce airflow
    (This helps the koji from drying out too much).
    The number of blankets they use and how tight they wrap the
    blankets, is all adjusted based on the condition of the koji.
    Also the type of blankets they use varies from brewery to brewery.

    This brewery, Daishinshu, grows all of their koji using wooden trays,
    but it is probably more common to use large tray tables, in which they can make large batches of koji at once.
    Hoping to get a post on another brewery I visited that makes koji in this method, but have been really busy lately, which unfortunatley means my blog is getting rather lonely. (^_^;

    Thanks again


  13. I get my koji from vision brewing: http://www.visionbrewing.com/

    I use a styrofoam chicken-egg incubator to keep the temperature around 37C. It works great!

  14. can teaching how make rice vinegar?


    1. Hi Anthonios,

      Unfortunately, I am not an expert on making vinegar.
      From what I hear, good rice vinegar is made by first making sake, and then doing an acetic acid fermentation, but I don't know enough about acetic fermentation to teach.
      My suggestion would be to look up acetic acid fermentation methods (there is probably a lot about wine vinegar), as the process most likely will translate to rice vinegar as well.

      Sorry I can't be of more help,


  15. I'm trying to find a commercial supplier for sake making equipment, do you have any recommendations. I can't seem to find any in the US.

    Thanks, Chuck

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