Making Miso: A Step-by-Step Guide

June 27, 2012 § 4 Comments

The first in an on-going series of home fermentation projects. An oft-repeated legend from Japanese history holds that the gods bequeathed miso to the Japanese people, a blessing that would ensure health, longevity, and happiness. While some might describe those gods as mere myth, one must admit that they might have been right about miso. A fermented paste of soybeans, salt, and grains, miso has strong health benefits thanks to lactobacillus acidophilus, the same healthy bacteria found in yogurt. Like other “living foods” such as cheese, yogurt, and wine, the fermentation process transforms the soybeans into a nutrient-dense food product that can be used in soups, stews, pickles, and marinades. Depending on the ingredients used, the length of the fermentation process, and how the ingredients are processed/mashed together, miso can exhibit a wide range of textures, colors, and flavors, from the ochre tones of shiro miso to the dark brown hue of hatcho miso, which might resemble your Oaxacan abuela’s chocolate mole at first glance. But all types of miso are aged through the fermentation process, a period that ranges from six months up to three years. As a result of this aging process, the protein-rich paste has a deep and complex taste with wonderful benefits for digestion and health, as the gods would tell you. Some studies have claimed that miso and other fermented bean pastes can fight some forms of cancer and heart disease while others suggest miso is a powerful agent to counteract aging. Miso was first brought to Japan from China in the 7th and 8th centuries, part of the same trading network that brought Buddhism and tea to the Land of the Rising Sun. Nurtured by Zen Buddhist monks, miso quickly spread across Japan and in the process evolved away from the Chinese style (chiang) and into its present incarnation. Until fairly recently, a large chunk of the production of miso (and in Korea, its close cousin, doen jang) occurred at home, especially in more rural areas. However, Japan also has a considerable tradition of different regional styles of miso, which originated in the Edo period as people flocked to urban centers. Now, of course, there are many easily available miso options, ranging from several different kinds usually on offer at an Asian supermarket or, if you happen to be lucky, more tasty artisanal varieties in specialty shops. However, making miso at home is a reasonably easy task if you can set aside some time over the course of a couple days. Of course, this is hardly something that you might make in time for the next morning’s bowl of miso soup; letting the lactobacillus bacteria and other micro-organisms do their work in the fermentation process takes several months. But if you can manage the wait, the resulting miso will be a robust tasting experience, full of the complex range of flavors that fermentation brings forth.

Dried soybeans

Under the tutelage of miso mentor J.M., I made my first batch of miso, using a simple recipe. Really, miso is just three simple ingredients, soybeans, salt, and koji, one of the reasons that it is a salubrious addition to your diet. For those who are unfamiliar with it, koji, or koji-kin, is rice (or another grain) that has been inoculated with spores from the aspergillus oryzae mold, the same fungus that helps to create sake and soy sauce. In a traditional miso-making process, two different fermentation processes are actually at work. Rice is soaked overnight, drained, and then gently cooked. After it cools down to room temperature, the cooked rice is mixed with a strain of the aspergillus mold and left to ferment in shallow trays for a couple days in a humid room. For many artisanal miso makers, the cultivation and harvest of a specific koji mold is crucial to establishing the unique flavor profile of their misos, and some have guarded their koji strain for generations. (This piece from the archives of the Los Angeles Times gives a fascinating account of the work of a fourth-generation koji master.)

A tub of koji

Koji still resembles rice but has a puffed-up, almost jagged appearance, like oblong grains of salt. Once added to the soybeans, the koji is the active element that breaks down the proteins, starches, and fats in soybeans and through the wonders of kitchen alchemy, transforms it into miso. Fortunately for miso makers, koji is available at most Japanese markets. (The one I used came in a plastic container that looks like the ones used to sell yogurt.) Ingredients

  • 369 grams of dried soy beans (though of course fresh ones would be quite tasty)
  • 1 tub (567 grams) koji
  • 200 grams of salt
  • Quarter cup or so of cooking wine or soju

Step One Start with the dried soybeans, which should be available in most Korean, Japanese, or Chinese markets. Wash the dried beans several times, until the water runs clear after soaking the beans in a new bath of water (much like rinsing rice). Put the soybeans in a large pot, and fill it up with water several inches above the beans. One recipe calls for adding three times as much water as the weight of the beans, though the important part is to make sure the beans don’t dry out. Soak the beans for 18 hours, checking at a couple of intervals to make sure the beans are absorbing water and expanding, and that the water amply covers the beans. Step Two

Cooked soybeans

Once the beans have expanded, drain the beans and add them to a large pot. Add water until the beans are covered by more than an inch. Bring the beans to a boil, lower the temperature, and then cook for four hours. (You can also cook the beans with a pressure cooker, in which case the beans can be cooked in about 20 minutes.) During the cooking process, the beans will emit a protein-rich foam, saponin, which can be skimmed off for another use. Once the beans become soft enough to squeeze between your fingers, they are ready for the next phase. After draining the beans, you can refrigerate them and continue the process the next day, or once the beans have cooled, move on to the next step. (Be sure to let the beans return to room temperature; if the beans are too warm, they may kill the koji.) Step Three

Mashing soybeans

Mash the soybeans into a paste using either a grinder or a food processor. The degree of mashing is left up to the discretion of the miso maker; some misos are chunkier than others, though a miso that has larger bits of soybean may take longer to ferment. For this miso, we used a few whirs of the food processor to chop the beans before crushing it into a mostly fine paste with a potato masher. Step Four In a large bowl, mix the salt and koji together. Take particular care to distribute the salt well so that the koji will ferment as evenly as possible Step Five

Mixing the koji-salt mixture into the mashed soybeans

Add the mashed soybeans to the koji-salt mixture, taking care to mix the two well, kneading and folding it several times to distribute the salt and koji throughout the soybeans. Step Six

Forming the mix into balls

Once the ingredients are thoroughly combined, form small balls with the mixture. Take special care to squeeze as much air out of the balls as possible: the fewer pockets of air in your miso container, the less opportunity for miso to grow unhealthy mold. Step Seven

Wiping glass jar with alcohol

Find a container to ferment the miso. A wide-mouth ceramic jar is preferable. Avoid potentially toxic plastic or metal containers that may affect the taste of the miso. Although miso should be strictly shielded from the sun (to prevent its rays from killing the lactobacillus bacteria), we both decided to use glass jars to better observe the ongoing changes in color during fermentation process. Before adding the miso balls, lightly spray the already sterilized jar with the rice wine or soju. This step adds another layer of disinfectant that will discourage the formation of harmful germs during the fermentation process, especially the ones that might grow in corners. You can also dust the bottom of the jar with salt for the same result. Step Eight

Pushing the balls into the jar as tightly as possible

Add the miso balls to the jar, pushing them hard against the jar. Again, the goal is to remove as much space in the miso paste as possible to prevent the growth of mold. Once all the miso is in the jar, press the mixture down several times with your hands, packing it as tight as you can. Even out the top of the miso, making sure the surface of miso is mostly flat. Step Nine

After packing the paste into the jar, flatten the surface.

Spray a little bit of the alcohol around the sides of the jar and across the surface of the miso (or a light dash of salt for similar effect). The presence of alcohol or salt will discourage the growth of harmful mold on the miso. In addition, I lightly soaked a paper towel and draped it across the top of the young miso paste. The towel functions as a disinfectant and also provides a way to sop up the thin layer of moisture that will occur during fermentation. Step Ten

Pouring salt into a bag on top of the miso paste

Before sealing the jar, place a weight on top of the miso. A suitably heavy stone would work or in this case, I poured salt into a plastic ziplock bag placed on top of the miso. The plastic bag filled the space in between the miso and the top of the jar, packing most of the remaining space (the goal being to provide as little area for mold to grow as possible). Once the jar is stuffed as full as possible, seal the jar with a top and then some thick packing tape if you want to secure it.

Finished jars of miso, ready to ferment for many months

After the jar is prepared, stow it away in a dark place and let the fermentation commence. Depending on the season (warmer temperatures will accelerate the process), fermentation can take anywhere from six months to a year, though a longer wait may be rewarded in a more full-flavored and delicious miso. Though research is scarce on the topic, J.M. recommends conversations with your miso. Regular bon mots will help develop a strong relationship with your new fermenting roommate, and loving care and attention can only help improve the taste. Miso Resources There are loads of recipes floating around, from the ones featured on cooking blogs to the instructions that come with a tub of koji. For more information about the miso-making process, including several different recipes, William Shurtleff and Akiko Aoyagi’s magisterial Book of Miso is an absolute treasure trove of information about miso.  Now in its third or fourth edition, the book has all sorts of wonderful tidbits about the science, production, and history of miso, including recipes for miso and miso-related food (such as miso pickles) and fascinating digressions, such as an illustrated tour of the Japanese farmhouse miso tradition and a peek at a modern, mechanized miso factory.

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