I decided to take my love of fermenting things to a new level and make miso. Because I’m insane. Really, though, it’s pretty easy if you can find koji, which is rice that has been steamed and mixed with a certain kind of mold spore. The hardest part about it is you have to wait up to a year to eat it. This will be by far the longest I’ve ever fermented anything.

You can make your own koji if you can get the mold spores. I have some and I’ll probably try it at some point, but I decided to use pre-made koji the first time around. As with most of the cultures I use, I purchased it from GEM Cultures.

The next thing I needed was a crock to make the miso in. The directions that came with my koji instructed me to use a 1 1/2 quart straight-sided crock. All I really have are jars, so I had to find something else with a mouth as wide as the sides. Off to the thrift store with me, again! I found this crock, which was perfect:

Then I was on my way to making miso!


2 cups dried soybeans
1 cup soybean cooking water
1/2 cup sea salt
2 1/2 cups koji (available from GEM Cultures)
1 Tbsp unpasteurized miso (If you can’t find this in stores, GEM Cultures sells it. You can also omit it if you have to, but apparently it really helps your miso along.)

Soak the soybeans in plenty of water overnight. The next day, boil them for 4 to 5 hours or until quite soft, being sure to add water as necessary.

When the soybeans are done …

… drain them, reserving the cooking liquid.

Add one cup of the soybean cooking liquid to the soybeans and mash. I used a blender but I think potato mashers are pretty common.

Here are the mashed soybeans in a bowl.

Add the salt …

… and stir it in thoroughly.

When the soybeans are cool enough to touch, add the koji and the unpasteurized “seed” miso. If you’ve made miso before, you probably didn’t pasteurize it, so you can use it as the seed miso. I ordered some from GEM Cultures in lieu of searching for it in stores because most of the writing on the miso I buy is in Japanese.

Stir very thoroughly again.

Next prepare your crock. I got the idea to rub the sides down with salt from Wild Fermentation, which I read about on Cyn’s blog and realized I needed to own. So what I did was bring water to a boil in the kettle, pour it into the crock to sanitize it, then pour it out without drying. Then I set it on its side and sprinkled the sides with salt while rolling it. It wasn’t the most even of jobs, but I figured it was better than nothing (which is what the other instructions I had indicated for the sides of the crock).

Press the miso firmly into the crock, making sure there are no air bubbles. My knuckles got tired so I used a potato masher for a bit.

Tigger then appeared on the scene to investigate.

Smooth and level the miso.

Sprinkle the top fairly generously with salt. You’ll be removing this layer before eating so don’t worry about it being too salty. Particularly concentrate the salt around the edges.

Cover with plastic wrap, pressing it down onto the miso and up the sides of the crock.

Find a plate that fits just inside the crock. This plate is particularly appropriate for this application because not only does it fit the crock perfectly, but I acquired it from a Japanese restaurant.

Place a heavy weight (at least a pound) on the plate. I forgot to go out rock-hunting today so I used my small molcajete. (I’ll probably go find a rock and retrieve my molcajete!)

Cover the crock, with a lid if it has one, or with a heavy piece of fabric tightly tied around the top.

Label the crock! This seems like a step I’d skip, convinced I would magically remember the date, and then later kick myself about for being so stupid.

Place somewhere out of the way. Here it sits next to my fancy new sauerkraut crock (that I got for Christmas), in which is brewing a new batch of sauerkraut, in a spare bedroom that is inexplicably but handily very cold.

Soon I’ll have a whole row of crocks with things bubbling inside them. I am the mad fermenter!

Check back in 6 months when I try it the first time, and then in a year when it’s fully matured!

Update, July 26, 2009: See results of the six-month check-in.

By the way, Tigger says hi.


  1. Jain Said,

    January 20, 2009 @ 6:35 pm

    A year? That’s crazy. You’d think miso would cost $75 per tub in the store.
    Beauty crock!

  2. Cyn Said,

    January 20, 2009 @ 10:39 pm

    I’m in awe of your fermentation skills! I hope you like the Wild Fermentation book as much as I do. Also, isn’t GEM cultures the best? I want to buy all kinds of crazy cultures from them just because I can.

  3. Melissa Said,

    January 22, 2009 @ 11:50 pm

    That is really the ultimate fermentation product… wow. I think I would forget about it after a year. I’d have to google-calendar it.

    Do you know how misos take on different flavors – why are there white, yellow, red, and mild versus sweet misos? And which one are you making?

  4. renae Said,

    January 23, 2009 @ 12:52 am

    Jain, I guess once you reach the end of your first fermentation cycle, if you’ve continued to stagger batches after it, you’ll always have miso that’s ready to sell, so that’s why they can sell it at a decent price? Although I guess you do have to take the price of storage into consideration. It takes a year, but the good news is you don’t have to do anything with it during that year!

    Cyn, I know, GEM Cultures is awesome! It would never have even occurred to me to make my own miso if I hadn’t seen the starter there!

    Melissa, I may well forget about it myself! I am definitely not a miso expert, but I think white miso is usually sweet, and from the recipes I have, I know that white/sweet miso has a higher percentage of koji and a lower percentage of salt, and also takes much less time to ferment. In fact, I was going to make white miso first because of the more instant gratification, but I wasn’t sure I had enough koji to make it at the scale the recipes called for (it turns out I probably did). White miso only takes a couple of months. I think I will also make a batch because I’m a bit sensitive to salty things (as much as I love salt).

    As for red versus yellow, well, the recipe that came with my koji and the recipe in Wild Fermentation were exactly the same, but the former called it yellow and the latter red. I really need to get The Book of Miso out of the library again and read up on it!

    You can make miso out of all sorts of beans and grains, but as for as soy miso goes, I think basically the differences are the amount of salt versus koji, and the length of fermentation. The recipe I used and the fermenting time puts it at the stronger side of the scale. I figured I’d look at the color when it was finished and decide whether to call it yellow or red!

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