(written by Jeremy Loudenback // recipe by Junko Mine)
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.)
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.)
369 grams of dried soy beans
1 tub (567 grams) koji
200 grams of salt
Quarter cup or so of sake
Start with the dried soybeans, which should be available in Asian markets, Whole Foods, or Co-op. (I highly recommend using organic, Non-GMO soybeans). 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.
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.)
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.
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.
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.
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.
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.
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.
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.
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.
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, my friend 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.
Big thanks to my friend, Jeremy Loudenback for writing this article.