The soul of miso


Of all the things he could have done in life, Kenji Tsukamoto has chosen to grow mold for a living. He is a fourth-generation koji-ya, or artisanal “mold maker,” on Sado island on the western coast of Niigata, Japan. It’s rare to find a traditional koji-ya in Japan these days.

In fact, to make ends meet, Tsukamoto derives his income from two other sources: teaching math to children and working as a nature guide. He is as expert on calculus and the native wildflowers of Sado as he is on mold.

“Have you ever left cooked rice out and found a white downy growth on the surface?” he asks. “That’s koji.” Most of us can recount a few encounters with mold growing on a day-old sandwich. These microorganisms live in the natural environment, and some play a beneficial role in the production of food. In Japan, the mold called koji is used for fermenting rice and soybeans to make soy sauce, miso and sake, the three staple ingredients in Japanese cuisine.


Koji’s scientific name is a tongue twister -- Aspergillus oryzae. The Brewing Society of Japan officially named it the “national fungus” in 2006. Tsukamoto’s primary koji-based product is miso, the savory seasoning used most commonly in soups. But to Tsukamoto, miso is more than a seasoning. It is a “living food.”

” Koji is the reason Japanese have the highest life expectancy in the world,” according to the 57-year-old, who goes so far as to suggest that instead of spending money on a doctor, you should spend it on good miso. Maybe it’s because during World War II, being a koji-ya saved his father’s life. Assigned to the bitterly fought-over South Pacific island of Guadalcanal, Tsukamoto’s father was taken off the front line when his commanding officer found that he was a koji-ya, and he was reassigned to watch the general’s horse and make miso. He concocted miso using sea salt, locally grown tropical rice and koji, which he found in food collected from the garbage.

Tsukamoto prepares koji in the muro, a special room in the back of his shop where he also keeps the rice used for growing the mold. On the heavy iron doors of the vault, there are calligraphic writings. The right door says, “One must not expect money and parents to be around forever.” The left door says, “Don’t expect fires and catastrophes can never happen to you.” Sado and the greater Niigata region have been hit with massive tsunamis and earthquakes in the past. The Sadoans don’t take life for granted.

The busiest time of the year for Tsukamoto is after the rice harvest in the fall. First he makes the koji with locally grown Sado rice. Koji mold spores are sprinkled on top of steamed rice to start the incubation.

Temperature control is crucial. The steamed rice is brought down to 96 degrees and the temperature is kept steady. It takes three days and three nights to produce koji. During this period, Tsukamoto gets hardly any sleep. In the wintertime, the room can get down to 36 degrees, but he has a hibachi to keep it warm. “I use binchotan [artisanal oak charcoal made in Wakayama] because it produces gentle heat, he says, making a sound to describe the way the heat travels through the room: “Poh-waaaaaaaaah.” Binchotan charcoal, which is also a favorite of yakitori and unagi (grilled eel) chefs, also produces long-lasting heat and releases no odors or smoke.

When the koji is done -- the word can refer to both the mold and the fermented rice -- it gives off a sweet, ripe apple smell and is safe to eat. The rice kernels are covered with white velvety mold, and it flakes apart. “I eat fresh koji by mouthfuls,” he says, smiling.


The miso is produced in another building, across the street. When you enter the production room, the earthy and sweet aroma of miso hits your nostrils. The miso is kept in old wooden vats measuring 16 feet in diameter and 8 feet in height.

The taste, texture and aroma of miso will vary according to the quality of koji, soybeans or grains, water, salt content, temperature and duration of fermentation. For one type of miso, Tsukamoto uses a ratio of 17 parts koji to 10 parts soybeans. He allows one year for fermentation, including one summer. Some miso makers in the north of Japan allow two years because it takes longer for miso to ferment in colder climates. The mild and sweet saikyo miso from Kyoto in the south contains a lot of koji so it undergoes a short fermentation period of six months. And compared with the red miso Tsukamoto makes, it has a shorter shelf life.

Tsukamoto also offers a premium-grade miso that is made with local seawater.

Tsukamoto climbs on a ladder to reach the large wooden vats, using a long wooden paddle to mix the miso, following the traditional way. Sadly, the artisans that make the wooden vats have disappeared from Sado, and there are only 10 left in Japan. Tsukamoto’s vats are more than 100 years old and still holding.

He has looked into contemporary production methods for koji and miso, such as using stainless steel or concrete vessels, and chemical processes that speed up fermentation. “I can’t imagine putting a living food in a concrete vat,” Tsukamoto says.

The wooden barrels have an essential function in the miso making, he says. “The wooden vats breathe. This helps make good miso. They sweat during the rainy season, helping to adjust the moisture level inside the vats. In the dry season, the vats will take the exterior moisture and bring it inside. Tsukamoto produces about 10 tons of miso a year, half of which gets sold in Tokyo.

There is a large window in the back of the miso factory through which there was once a view of the sea. It was a favorite place for Tsukamoto’s father to stand and look out during his breaks. The sea view is now gone because a building stands in the way. When asked what plans Tsukamoto has for the future, a big smile fills his face. His 29-year-old son, who finished college with a major in science, has returned to the island to become a koji-ya, after spending a year in Germany.


“While living abroad, my son was often asked what his father did for a living but he couldn’t explain it well,” Tsukamoto says. “It motivated him to learn koji-making and share it with the rest of the world.

“There are invisible things in the world like koji that can affect your body and soul in good ways. It’s like love.”


Miso-sake marinade

Total time: 5 minutes, plus marinating time

Servings: Makes 2 cups marinade

Note: This savory miso marinade works for most meats, such as boneless pork chops, beef and chicken, as well as fish fillets such as cod and a variety of raw vegetables. For meat and seafood, try a mild and sweet white miso, such as saikyo. For vegetables, look for red or white miso that contains whole grains, such as moromi, koji or tsubu. The grains give the vegetables another layer of texture and flavor. Mirin and sake are added to the marinade to soften the salinity of the miso. The darker miso tends to be saltier. Let the food marinate for 1 to 3 days. Any longer can make the food too salty, so be careful not to overmarinate. Miso varieties are available at Japanese and general Asian markets.

2 cups (roughly 15 ounces) white or red miso

3 tablespoons sake

3 tablespoons mirin

tablespoon sugar (optional)

1. In a nonreactive container, mix miso, sake, mirin and sugar. The marinade should be smooth enough to spread easily. The basic ration to keep in mind is 10 parts miso to 1 part sake to 1 part mirin. The consistency is softer than peanut butter. If you need to make it softer, add more mirin or sake. Adding mirin will make the marinade sweeter. If you like it firmer and longer-lasting, add less sake and mirin.

This marinade keeps in the refrigerator for about 3 weeks. Don’t marinate meat and vegetables in the same marinade.


2. You can reuse the miso marinade if you wrap the meat or vegetables in cheesecloth before marinating: Double-line a sealable container with the cheesecloth, add the food and wrap the cheesecloth completely around it. Pour the marinade over the top. When you’re ready to cook, open the folds of the cheesecloth and take out the food. If some marinade sticks to the food, you can rinse it off lightly and pat dry with a paper towel.

Each tablespoon: 38 calories; 1 gram protein; 6 grams carbohydrates; 0 fiber; 0 fat; 0 cholesterol; 3 grams sugar; 470 mg. sodium.

Pork chops in miso marinade: Place 4 boneless half- or three-quarter-inch-thick pork chops in the miso-sake marinade and marinate 2 to 3 days. If the pork chops are thicker, marinate 3 to 4 days. Wipe off the excess marinade with a damp paper towel. Broil, grill or pan-fry the pork.

Each pork chop: 320 calories; 36 grams protein; 13 grams carbohydrates; 0 fiber; 12 grams fat; 4 grams saturated fat; 84 mg. cholesterol; 7 grams sugar; 989 mg. sodium.

Vegetables pickled with miso marinade: Rub 2 peeled carrots, ribs of celery (cut in thirds) and 2 unpeeled cucumbers with 1 tablespoon salt (preferably ama-shio -- available at Japanese markets -- which contains a lot of nigari, or magnesium chloride, that is highly soluble in water). Let stand 15 minutes to extract excess moisture from the vegetables to firm them. Wipe off the salt and moisture with a paper towel and put the vegetables in the miso-sake marinade for a day or two (the longer you keep them in, the stronger and saltier the flavor will be). Slice and serve.

Each of 10 servings: 76 calories; 3 grams protein; 14 grams carbohydrates; 1 gram fiber; 1 gram fat; 0 saturated fat; 0 cholesterol; 7 grams sugar; 826 mg. sodium.



Miso soup with clams and chives

Total time: 30 minutes, plus overnight soaking time for the clams

Servings: 4

Note: You can make a second batch of dashi by combining the used bonito flakes and kombu seaweed in a saucepan with 4 cups of water. Bring it to a boil over medium heat and then simmer for about 5 minutes. Strain and discard the bonito flakes and kombu seaweed. Use the dashi for miso soups and seasoning. It will not be as flavorful as the first batch, but it is still good.

1 pound small cherrystone clams (8 to 10 clams)

1 tablespoon salt mixed with 4 cups water

3 1/2 cups prepared dashi (see below)

3 to 3 1/2 tablespoons miso

1 tablespoon sake

Chives for garnish

1. Rinse the clams well. Soak in the salt water overnight.

2. Drain the clams in a strainer.

3. Pour the dashi into a medium-sized saucepan. Add the clams and cook over low heat until one of the clams opens, then increase the heat to high and cook until all the clams are open. Remove from heat. Skim the surface of any foam and discard.

4. Remove the clams from the saucepan and pour the broth through a paper towel-lined strainer, then return it to the saucepan. Remove half the clams from their shells, leaving the other half attached. Discard the empty shells.

5. Thin the miso with one-half cup of the broth. Taste the broth, and add enough of the thinned miso to lend flavor without making the broth too salty (the amount needed will vary depending on the salinity of the dashi and the saltiness of the miso; you might not use all the miso).

6. Stir the sake into the broth, then add the clams (both in and out of the shell). Bring to a simmer.

7. Divide the broth and clams between 4 bowls. Serve, garnished with chives.


1. To make the broth, take 1 (6-inch long) piece of dashi kombu and make several crosswise slits into it using scissors. Steep the kombu in 4 cups water over medium heat, just until the water comes to a rapid simmer (it must not boil).


2. Remove from heat and add one-half cup cold water. Cool the liquid for a couple of minutes, then add 2 cups dried bonito flakes ( katsuobushi). Do not stir. When the bonito flakes have settled near the bottom, after about 3 minutes, strain the mixture using a fine-mesh strainer or a sieve lined with a paper towel and discard the flakes. Do not stir the stock, as it will cloud the dashi, which should have a light golden color. This makes 3 1/2 cups dashi broth.

Each serving: 57 calories; 6 grams protein; 5 grams carbohydrates; 1 gram fiber; 1 gram fat; 0 saturated fat; 11 mg. cholesterol; 1 gram sugar; 713 mg. sodium.



How to make miso at home

I grew up on my mother’s homemade miso, but it wasn’t until this year that I made my own. It’s easier than it appears and incredibly delicious. You can find all the ingredients including domestic or Japanese dry soybeans, koji and sea salt ( ara-jio), at Japanese markets, such as Mitsuwa, Nijiya, Marukai and Granada.

To start, rinse the soybeans and soak them overnight in double the amount of water. The next day, combine sea salt and koji. Set aside.

Drain the soybeans in a strainer. Cook the soybeans in a large pot for five or six hours until they can be squashed with your fingers. Set aside 1 cup of cooking liquid. Drain the soybeans in a strainer.

While the soybeans are still hot (about 100 degrees), mash them with a potato masher or a blender. Alternatively, you can put the cooked soybeans in a plastic bag and mash them with your feet. Combine the mashed soybeans with the salt and koji mixture and mix well, until the consistency becomes even. You can leave 10% to 15% of the soybeans whole if you like.


If the miso mixture feels a little dry, take one-third cup of the reserved cooking liquid and pour it into the mixture. Be careful not to add too much water. Miso will soften naturally as it ferments.

Sprinkle 1 teaspoon of salt over the bottom of a crock. Put the miso mixture into the crock, mashing and pressing the miso with your hand, so there are no empty spaces or air bubbles. Sprinkle the surface of the miso mixture with a thin layer of salt. Cover the mouth of the crock with plastic, then with paper or a cotton cloth, and tie it with kitchen twine to keep out the dust.

Place the crock in a cool place, like the pantry, and allow the miso to age for a minimum of six months, including one full summer.

During the fermentation, do the following:

After one month, take a big wooden paddle and turn the miso. Take what is at the bottom and bring it to the top and mix. Cover the crock as you did before and return it to a cool place. Repeat this step two more times, two and three months later.

The color of the miso will gradually darken from yellow to caramel to brown to reddish brown. The miso will have a sweet, earthy smell. If you see any white mold on top, remove it with a spoon. Remove a month’s supply and refrigerate. Re-cover the crock and return it to a cool place.

Miso tastes best after one year and keeps for 18 months in a cool place.

--Sonoko Sakai