Yes, You Can Make Miso Paste at Home!

What is miso? Miso is a funky, salty-sweet, umami-rich paste of mashed, koji-kin inoculated and fermented grains or legumes, that forms the basis of much of Japanese cuisine. It is an ingredient rich in taste and function: whisk a barley-heavy miso into dashi for a wintry miso soup, Mash a mellower miso into butter for a chicken thigh glaze that tastes like caramel corn. Or, lay leftover egg yolks in a bed of miso. The salt present in the miso will cure the yolks, yielding gratable, tiny suns.

Because of hydrolysis (the breakdown of starches to sugar, in the presence of water), the natural sweetness and roasty toastiness found in grains and legumes gets teased out. Meanwhile, koji-kin—a fungus also used in soy sauce and sake production—are hard at work, breaking proteins down into amino acids. These now free amino acids, or free glutamates are easier for our tongues to access, and hence detect as umami. Funk from the (managed!) decay of beans and grains, sweetness from the conversion of starch to sugars, saltiness from the salt working to inhibit bad bacteria, and umami from the koji-kin doing its enzymatic work.  

So what's the difference between white, red, light, and dark?

Miso is made from of a blend of steamed soybeans, koji-inoculated barley or rice, and salt. White (shiro) miso has a larger percentage of rice koji than red (aka) miso and is barely fermented. Red (aka) miso refers to miso made with koji-inoculated white or brown rice, barley, or soybeans, and the requisite steamed soybeans and salt. Length of fermentation will also contribute to the color. Typically, misos that have fermented for a year or less are lighter in color, while misos several-years-old will be turn a darker, moodier hue. That being said, misos need not be made of soybeans, barley, or rice; all koji-kin need to get going is the presence of protein, carbohydrates, or fat. I've made miso from chickpeas (guided largely by the thought of writing "pea-so" on the label), and my friend, Rich, made one from cookie dough. 

Fermenting 101 (or How to Manage the Flora and Fauna of Your Apartment)

Miso is a living product, one that varies widely—not only from batch to batch, but even across a batch. Even if you make an effort to use a consistent blend of koji (P.S. “koji-kin” refers to the spores, while “koji” refers to dried rice grains that have been inoculated), rice, soy, and salt, two misos will rarely, if ever, taste alike. That’s the beauty (and frustration) of living, home ferments: your final product is truly one of your environment. Despite ferments being like the wild, wild West, there are some very basic things to consider when fermenting at home:

Climate. Warm, humid environments will speed up fermentation; cold temperatures will slow it down.You want to keep the miso somewhere warm—someplace that hovers around 80F, if possible—but not in direct sunlight. Keep everything as clean and draft-free as possible; but also, this practice of fermenting mashed beans is older than many of our modern-day sterilizers, so don’t stress about it too much.

Salt. Adding four to 13 percent by volume salt is necessary (depending on the blend of grains and legumes) to encourage the growth of good, not bad, bacteria.

Label clearly. Include the start and expected end date, as well as notes on your blend and salt content. As good as you think your memory is, these are things you'll probably forget in nine months.

Time. For anything remotely funky and complex tasting, you want to let the miso go for two weeks (expect a miso that's rather salty and not funky, really), and up to several years (funktown). The more patient you are, the more likely you’ll be rewarded with a mellowed, but complex miso. The beauty of miso is in its forgiveness. You can almost do anything to it and it will still ferment. Miso microbes will find a way to survive. That being said, know when to cut your losses: you can scrape off gray, blue, and green molds, but definitely toss at the sight of anything neon.

Enough koji and mold science! Lead me to the land of umami.

The recipe for homemade miso paste is basically mashed beans plus grains mixed with koji plus 4-13% by volume salt. Stuff this paste tightly into your fermentation vat of choice to remove any air bubbles. Or, form balls the size of tennis-balls, and chuck it down, as true artisans do. If you think there might be an air bubble in there somewhere, get rid of it. Smash it. Air bubbles will beget rot (and no the good kind). You can do this paste-stuffing in a designated fermentation crock or a simple plastic food-grade container (I’ve made miso with grea success in a Cambro quart container). Just make sure the container is both non-reactive, and one that you won’t miss for the next year. A batch of miso is traditionally started during the warmer months of summer, so as to jumpstart fermentation at the onset. It then enjoys a full cool winter and spring, mellowing, sweetening, growing all the more complex. It will only be cracked open at the beginning of summer months, and soon enough it will be time to start another batch.

Author of numerous books on Japanese cuisine and culture, Nancy Singleton Hachisu wrote that an organic miso company near her home, in Saitama, Japan, “leaves a small pot of miso out at room temperature year-round, with only minimal weight. A regular stir up is all the care it requires—and the result is absolutely stunning.” And to that, Nancy, I see you and raise you one: Much too eager to wait for warmer weather, I started a batch of miso last winter. It fermented slowly, though happily, in a plastic tub, tucked in by cheesecloth, in the back of my kitchen pantry. And while not stunning, it definitely turned out pretty good, and I’m okay with that.

Identify the warmest, draft-free space in your kitchen—somewhere in your pantry, a cabinet high-up, or even the spot above your fridge. This is where your miso will "summer." To protect against apartment lint, or worse—unwanted bacteria—those of us not in Saitama should use many layers of cheesecloth and a weight. If you have a fermentation/pickling weight, use that; if not, line the mouth of your vessel with an open plastic bag, fill it with salt or some baking beans, seal the bag, and use that as your weight.

Every few months you’ll want to peek at how things are moving along. If some mold has started to grow (remember: gray, blue, and green are okay; neon-colored is not), just scrape it off carefully. Stir the mash well, press it all back down (remember, air bubbles are the enemy), tuck it back in with washed or new cheesecloth, weight it, and leave it be for another few months. When it’s been eight or nine months, begin to taste it. Is it still unbearably salty? Not complex nor funky enough? Leave it to keep fermenting. It’s ready when the salt has mellowed, and given way to some funk and beany-sweetness. When it’s ready, store your miso in the fridge for maximum shelf-life. 

While I wish I was in a headspace and apartment-space suitable to make seven pounds of miso at a time, I am not. I halved Nancy’s recipe below with great success.

Nancy Singleton Hachisu’s Miso Recipe

Makes 7 1/2 pounds, or enough miso to last until your next batch is ready 

2 pounds (1 kilogram) best-quality non-GMO dried soybeans
2 teaspoons best-quality organic miso (or previous year’s homemade) to use as seed miso for the new batch
2 pounds (1 kilograms) brown or white rice koji
14 ounces (400 grams) fine white sea salt

1. In a large pot of cold filtered water, soak the soybeans for 18 hours.

2. Drain the beans, return them to the pot, then refill the pot with water to about 5 inches (10 centimeters) above the beans. Bring to a boil over high heat, lower to a simmer, and cook for about 1 1/2 to 2 hours, uncovered, until the beans are soft. The idea here is to simmer the beans in just enough liquid so that they cook through, but that most of the liquid will be boiled off eventually. Alternatively, cook the beans in 20 minute batches in a pressure cooker set to high heat.

3. While the beans are cooking, slowly whisk 1/2 cup of hot water into the seed miso, then allow to cool to room temperature (the solution should be like a very thin miso soup in consistency).

4. Drain the cooked beans and start mashing them into a coarse consistency with a potato masher, through a meat grinder, or by pulsing in a food processor. When the beans are smashed to your satisfaction (chunky or smooth), allow them to cool to room temperature (too hot and it will kill the spores). Pour in the rice koji, then sprinkle in about 80% of the salt, and add in the miso thinned with water. Knead well to distribute the rice koji and salt with the mashed beans.

5. Place a large crockery pot, small wooden barrel, or food-grade plastic vat on the floor. Then, using your hands, form tennis ball–sized spheres of bean mash and throw them into the container with all of your might. Whack! Splot! You are looking for a satisfying splat that sounds like thunk rather than a weak glurp. Or (if you are lazy like me, with stunningly bad aim), you might mash the balls in with your fist and the heel of your hand to ensure that all air pockets have been filled. The bean mash should only fill the container about halfway full. Pat down the surface of the mash with the flat of your palm and sprinkle with the remaining 20% of salt.

6. Smooth a clean muslin or cheesecloth across the surface of the mash and let it drape down over the sides of the container to keep out debris. Place your weight of choice—a pickling weight, wood or plastic drop lid, or baggie of salt— onto the cloth-covered mash surface. Cover with another piece of cloth, and tie it into place. The cloth will act as a mold barrier and will become scarily dusted with green mold spores, so don’t skip or replace with plastic. Carefully remove to wash, or replace, when you stir the miso.

7. Let the young miso sit undisturbed in a dark, cool area. Stir once a month for the first few months. If it is particularly warm where you live, and temperatures reach the upper 90°s, stir every 2 weeks to prevent mold from forming on the top. If you see any mold on the surface, carefully scrape it off. Clean the inside surface walls of the container with a cloth soaked with diluted vinegar, vodka, or shochu.

8. At around month 8 or 9, begin tasting the miso to see if it has mellowed to your liking. Once the miso is done, remove the weights and store it in the fridge for the longest shelf life. 

First photo by James Ransom; all others by Kenji Miura

Will you join our miso-making group? Tell us in the comments!