Making your own miso answers a lot of questions you might have about this funky, fermented, fungal-powered food, such as “How long does it take?”, “How difficult is it to make?” and “How high is the risk of contamination?” First, miso takes just an hour or two of active prep but needs at least six months to a year to ferment. Next, miso doesn’t require a lot of technical knowledge, but technique can make or break the finished product. Lastly, miso is one of the most forgiving fermented foods, and at most you risk a little surface mold you can scrape off.
Before You Start
Miso needs a cold winter, a temperate spring and a hot summer for proper fermentation. Start the miso about two to three months before the weather turns warm — usually when the temperature hovers around 50 degrees Fahrenheit — to get fermentation off to a steady start. You can also store the miso in the fridge until the weather warms up. You then need to transfer the miso outside — or to a room that stays at least 80 to 100 degree Fahrenheit — during late spring to ferment until the temperature starts to cool in September.
Prep Time 6 months, 22 hours to 1 year, 22 hours
Cook Time 1 1/2 to 2 hours
Total Time 6 months, 24 hours to 1 year, 24 hours
- 2 lb dried soybeans
- 2 teaspoons all-natural miso paste (for starting fermentation)
- 1 ½ cups sea salt, finely ground
- 2 lb white or brown rice koji
- Add the soybeans to a pot and cover them with a couple inches of cold, filtered water. Allow them to soak until doubled in size, 12 to 18 hours, and drain them.
- Clean the pot and return the soybeans. Cover the soybeans with about 5 inches of cold, filtered water and bring them to a boil. Reduce the heat to a simmer and cook until tender, 1 ½ to 2 hours.
- While the soybeans cook, whisk the miso paste with ½ cup of boiling water and allow it to cool to room temperature. Drain the soybeans when tender.
- While still warm, grind the soybeans until coarse using a suribachi, ricer or food processor. You can also use your hands. Let the soybeans cool to room temperature.
- Mix 1 cup of sea salt with just enough water to form a paste. Add the rice koji, diluted miso and salt to the ground soybeans and knead until combined.
- Form the mixed soybeans into baseball-sized (around 3-inch diameter) spheres. Mash the spheres between your fist and heel of your hand to squeeze out the air bubbles.
- Load the mashed soybeans into a 4-gallon crock or other food-grade container and sprinkle the remaining ½ cup of sea salt over the top. The soybeans should only fill the container halfway full. Store the miso in the refrigerator until it reaches at least 50 degrees Fahrenheit outside.
- Cover the miso with a piece of cheesecloth or muslin large enough to hang over the sides of the container. Secure the cheesecloth around the container using twine or a large rubber band.
- Set a plastic or wooden drop lid inside the container and on top of the cheesecloth. Stack about 4 ½ to 5 pounds of weight on top of the drop lid. (Rocks or a barbell plate work well here.) Cover the container with a second piece of cheesecloth or muslin and secure it using twine or a large rubber band.
- Set the miso outside in a shaded area until summer starts. Stir the miso once a month to inhibit the growth of mold. You will find mold spores on the cheesecloth and perhaps on the surface on the miso. Wash the cheesecloth before replacing it and scrape off any mold spores. Clean the inside of the container (where the miso doesn’t reach) with a vodka-soaked towel before replacing the drop lid and weights.
- Stir the miso once a month during summer, scraping the mold and cleaning the inside of container. Taste the miso when the weather starts to turn in September. If you feel it needs a little more time, let it sit out a little longer (as long as the temperature doesn’t drop below 70 degrees Fahrenheit).
- Store the finished miso paste in an airtight container up to 1 ½ years in the refrigerator. Reserve a few teaspoons of miso paste to start your next batch.