Today we’re tackling a traditional Asian ferment that everyone loves, but many feel intimidated by – Miso! Miso is actually very easy to make to home, once you’ve sourced the special cultures needed. The main challenge is the waiting. 😉 You see, like a fine wine, miso gets better with age. You’ll need to allow at least 1 year for aging, but letting it go 2-3 years can give outstanding results!


Making Miso at Home

First, let’s talk about what miso is: Miso is a paste of cooked beans fermented with rice that has been inoculated with a culinary mold, or koji. Koji – steamed rice used as the growing medium for Aspergillus oryzae – is the magic that makes miso work. Aspergillus oryzae converts the carbohydrates in the rice to sugars, which can then become food for fermenting bacteria and yeasts.

Sourcing Koji

Making koji at home can be a bit of a challenge, because it requires incubating steamed rice inoculated with koji spores (koji-kin) for 36+ hours until the mold blooms. If you own a tempeh incubator, this might be a fun challenge. Shop for koji-kin or koji starter to try this at home. However, most people will choose to purchase ready-made koji. Here in the Portland-Metro area of Oregon, I’m able to buy ready-made koji at homebrew stores, Asian markets like Uwajimaya Beaverton, and Portland Homestead Supply. If you can’t source it locally, koji can be purchased online. Koji of white rice, brown rice, and barley are available; they are all sold dried and ship well. For this recipe I use Cold Mountain White Rice Koji.


Sourcing Seed Miso

In addition to the koji, you also need a small amount of live miso to provide the bacterial cultures. This is called “seed miso”, and using it helps ensure best results and good flavor. Read labels carefully to make sure the miso you buy for this is live and unpasteurized. I prefer Jorinji Miso made in Portland, OR and available at Uwajimaya Beaverton. Miso Master is another good brand of unpasteurized miso available nationally.

Choosing Ingredients and Supplies

Miso is a big time investment, requiring aging of 1 year or more, and for something like this I feel it’s important to do everything you can to guarantee the best outcome.  Additionally, since it is used as a seasoning and base for soups, sauces, and dressings, you don’t want to find any strange or unwanted flavors in the final product. Best quality ingredients are important here, as is optimal equipment. These are the choices I make, which you may wish to consider:

  • Salt: At the minimum, it needs to be unadulterated with anti-caking agents or iodine – read the labels! Since salt provides so much of the flavor in miso, I like to use Pink Himalayan Salt. Here’s how to choose a good salt – take a tiny pinch and put it on your tongue. Does it taste harsh or bitter? That’s not the salt you want.
  • Water: Generous amounts of water are used to soak and boil the beans, and some of that liquid is used in the miso. If your tap water smells or tastes bad don’t use it. Filter the water so it tastes nice when drinking plain, or use spring water.
  • Beans: Make sure you’re buying beans from a supplier who has good turnover. Beans that have sat around for a couple years get very hard and don’t cook up well. Soybeans are traditional, but any bean can be used. I buy organic, non-GMO beans in bulk at a local grocery store with a top quality bulk foods section.
  • Fermenting Vessel: 2 years is a long time to have moist food sitting around in your house. It’s going to be vulnerable to oxidation, mold, and yeasts, and it will definitely be a source of interest to any critters in your home. Although you can make miso in pretty much any jar or crock, I much prefer to use European hermetic jars. These have a clamp and rubber gasket that seals the jar tightly, keeping air, mold, and insects out. Two 1.5L jars or one 3L jar is perfect for this recipe.


Homemade Yellow or Red Miso
Makes About 8 cups

1lb. dry soybeans
Plenty of cool fresh water
9TBS good quality salt, divided
2½c. dried koji
1TBS mature seed miso
1 chopstick
2 1.5L or 1 3L hermetic jar
Small piece of butter muslin
Small weight(s)

Pick over and rinse soybeans. Place them in a bowl and add fresh water to cover by 2-3″. Allow to soak overnight, or at least 12 hours. Drain and rinse well. Now it’s time to cook them. Soybeans take a long time to cook. A really long time. Longer than any other bean you’ve ever cooked. When cooking soybeans for miso, they need to be very tender. On the stove they will need a good 2-3 hours of cooking time. If you have a pressure cooker, it will cut down the time considerably. I prefer to cook mine in a slow-cooker on low for 10-12 hours. Place the soaked beans in a pot and cover with 3-4″ fresh water. Cook the beans until one can be smashed easily between your thumb and ring finger.


Place a colander over a bowl and pour the beans into it to collect the cooking liquid. Drain the beans and transfer them to another large bowl.


Measure 8½TBS. salt into a small bowl and ladle 1½c. of the cooking liquid over it. Stir the mixture to dissolve the salt and set it aside to cool.



Now it’s time to mash the beans. Here’s where you get to use your muscle and work out all your frustrations. 😉 Mash the beans until you have a kind of chunky dough-like paste. You might need to add a little cooking liquid if it gets too thick.


The mashed beans should now be cool to touch, or just barely warm – if not, let it cool.  Mix in the 2½c. dried koji, 1TBS seed miso, and salty cooking liqud. Stir and stir, and let sit a few minutes, so the rice can soak up the liquid.

miso8 miso9 miso10

Time to start mashing again. Mash to get everything evenly mixed, so there aren’t any super-salty patches. Mash to make the bean bits and rice bits uniform, and uniformly small. After you’ve mashed as much as you can take a look at the consistency. Is it still a bit chunky? That’s OK. You’ve got a “country miso”.


If you would like it to be smoother a food processor or blender will help. I like to use a stick blender (my favorite kitchen tool!) for this. Insert the blender blade and pulse it over and over again, working your way through the mash, until it’s smooth enough for your liking. Keep in mind that homemade miso isn’t meant to be as perfectly smooth and even as commercially produced.


Now stir it a few times to check the consistency. If it’s too dry, add some more cooking liquid, a little at a time, stirring well after each addition. What’s the ideal consistency? Something between mashed potatoes and peanut butter. If you regularly buy miso you’ll have a good idea what you’re looking for. If not, keep in mind that it’s better for it to be a little too wet than a little too dry. You can always strain the excess liquid when it’s done fermenting


Now it’s time to prepare your jars. What I suggest is using two 1.5L jars for aging. This way you can have one of yellow miso to eat in a year, and one of red miso to eat later. However, you can make one big batch in a 3L jar, as pictured below. First, rinse the jar with a little clean fresh water and shake out the excess. Do you remember that you reserved ½TBS salt? Now is the time to use it. Take half of that and sprinkle it evenly around the sides and bottom of the jar. The water will help it to stick. (Note: if you’re using two jars you may need more salt.)


Now it’s time to start packing in the miso. After adding each spoonful, use the back of the spoon to spread it around and pack it down. It won’t be perfect and there will be some air pockets, but we’ll fix those in a minute.


Now that it’s all packed in you’ll need one clean chopstick. Use this to poke down through the miso from the top all the way to the bottom of the jar, anywhere you have air pockets. This will get rid of them! (If you’re a home canner, you’re probably familiar with this method.) Be sure to pick up the jar and inspect it from every angle to make sure you’ve removed the air pockets on the bottom as well as the sides.


Smooth the top of the miso and sprinkle the remaining salt. Now, place your jar on a layer of butter muslin and draw a line around it. Then cut out a piece to fit perfectly on top of the miso. The fabric will help keep the top from turning crusty and protect it from mold. (For the miso below, I was out of muslin. Instead I used a small spice sachet cut open.)

miso17 miso18

Place the weight(s) on top of the muslin. Some ideas for weights are: small jars filled with water, clean rock wrapped plastic bag, purchased glass or ceramic weights.


Seal the jar and write the details and start date on the lid with a Sharpie pen. Be sure to note what kind of beans you used – you might forget in 2 years! Set the jar in a cool dark place to ferment and age. Since this is going to take a while the back of your pantry, a cupboard, or a closet is an ideal place.


Ferment the miso for a year or more. If you’re really impatient you can crack it open around 9 months, with one caveat – miso should age through at least one full summer. Spring and fall are the traditional times for starting miso, with fall being the preference.

When you’re ready to start eating the miso, open it and check the consistency. If it seems too wet, strain out the excess liquid using a nutmilk bag or a colander lined with butter muslin set over a bowl. Save the liquid! This is delicious tamari that you can use for seasoning like soy sauce. Spoon the miso into smaller clean jars and keep in the refrigerator for use.


Will My Miso be Yellow or Red?

Time is what makes a difference here. As miso ferments and ages, it changes color via the Maillard reaction. Maillard reaction is a chemical process between amino acids and sugars that results in browning and the creation of unique flavor molecules. We usually see Maillard reaction when we use heat to brown meats, but it can also occur during long fermentation of protein-rich foods. Maillard reaction creates complex flavors, and gives food its umami richness, which is prized by chefs and home cooks alike. The longer a miso ages, the more Maillard reaction occurs, and the darker and more flavorful it will be. This is why I suggest dividing the miso between two jars. After a year you can open one and enjoy the yellow miso, while leaving the other one to age into a lovely red miso.


So, now you know how to make miso at home! If you love miso, I recommend getting into a rhythm of starting a new batch each fall. You might even want to try a double batch so you can let some age for 3, 4, or 5 years, and see how it changes as it gets older. You can also experiment with other kinds of beans. The possibilities are endless!

Happy Fermenting!
Sarah M.


Wild Fermentation, by Sandor Katz
The Art of Fermentation, by Sandor Katz
Preserving the Japanese Way, by Nancy Singleton Hachisu
The Book of Miso, by William Shurtleff & Akiko Aoyagi (out of print but may be purchased used from Powell’s Books and available for free online)

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12 Responses

  1. Ida says:

    How does the salt content compare with commercial miso?

  2. Colleen says:

    Thanks for this detailed post and presenting it at the festival over the weekend! Questions: (1) Can I use a tablespoon of my last batch as the seed miso if I follow your directions? (2) If I use a different bean (e.g. chickpea) is it okay to use a soybean seed miso or should I only use the same type? (3) Is it supposed to be stored in an airtight container, or would be be okay in a jar covered tightly with fabric?

    Thanks so much! Can’t wait to try it out!

    • Sarah Miller says:

      1. No need to buy miso ever again once you have your own homemade. 🙂 It will be a wonderful seed miso.
      2. Any yellow or red miso can be used as the seed miso, regardless of type of bean. On thing to be aware of is if you’re serving or sharing a non-soy miso with someone who has a soy allergy and you used a soy miso as starter you will need to mention that and they may need to abstain.
      3. Miso can be made in any type of jar or crock, and cedar barrels are traditional in Japan, but I have best results with sealed hermetic jars so this is what I recommend.

  3. Ben Turner says:

    Hi Sarah,

    Thanks for the encouragement to make miso. I used the 1# dry soy beans, cooked thumb soft, 2.5 cups cold mountain koji, the 1c H2O and salt, and I ended up wit less than 2l, packed into the 3l jar. Looks moist enough, although I expect it will dry out a bit as the koji absorbs water. Should I make another half recipe to fill the jar (or I could transfer to smaller jars) but main thing is I want to make sure there is not a problem somewhere since it came out so differently than the recipe. Thanks!

  4. James says:

    Do you need to have a seed miso? I’ve looked up a few other recipes and this is the only one that calls for using a seed miso.

    • Sarah Miller says:

      Miso has unique bacteria and yeasts involved in its fermentation that give it a complex flavor, and a seed miso is needed to provide them. Seed miso is not used for sweet white miso because it is not aged.

      • James says:

        I thought that’s what the koji is for – providing the bacteria to facilitate the process

        • Sarah Miller says:

          Koji is rice inoculated with a culinary mold – Aspergillus oryzae. It is a fungi, not a bacteria. This fungi converts the starches in the rice into sugars, turning the grains from plain to sweet. One the sugars are created, they can be converted to alcohol, if you introduce yeast, or to acids, if you introduce bacteria. You do need to add some mature miso to get the desirable yeasts and bacteria that can feed on the sugars created by the mold.

  5. Chiman says:

    Is it really necessary to have mature seed miso? I read from other recipes that it is not a must. Thanks.

    • Sarah Miller says:

      Miso has unique bacteria and yeasts involved in its fermentation that give it a complex flavor, and a seed miso is needed to provide them. Seed miso is not used for sweet white miso because it is not aged.

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