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New Seasoning Shio-Koji Emerging in Japan

Preparing steamed rice to make koji. Credit: Sonoko Sakai

Preparing steamed rice to make koji. Credit: Sonoko Sakai

The city of Saiki on the island of Kyushu in southern Japan is blessed by nature. In the surrounding mountains, farmers grow shiitake mushrooms, prized for their thick meat. The crystal clear sea is abundant with sardines, mackerel, squid and local fish whose names are not familiar to me. I was happily treated to both, though the main purpose of my visit to Saiki was neither mushrooms nor fish but mold. I came to visit Myoho Asari, the ninth-generation proprietor of the 300-year-old Kojiya Honten, whose family has been making koji. The process involves inoculating rice with A. oryzae spores, originally for miso, soy sauce and amazake and more recently for shio-koji, a koji-salt-based seasoning that has become trendy with Japanese cooks and chefs.

Fermented foods form the basis of a Japanese diet

Since ancient times, fermented foods have been the backbone of Japanese cuisine. The practice was developed to preserve food and enhance the flavor and nutrition of foods.

Koji-based foods have served not only as staples in the Japanese diet but also as natural remedies to cure colds, increase stamina, improve digestion, slow down aging and brighten the skin, to name a few good things.

The essential condiments in the Japanese pantry include soy sauce, rice vinegar, miso, sake, mirin, salt and sugar. What is uniquely Japanese is that all these condiments, with the exception of salt and sugar, are fermented foods made with koji. My Japanese kitchen would be incomplete if any single one of these items went missing. But when I heard about this new seasoning, shio-koji, I was curious. There is a Japanese tradition of pickling vegetables with koji, but why is koji salt that appealing to many Japanese consumers?

The visit to Kojiya Honten

Kojiya Honten is on a quiet street on Sendo-machi. Asari greeted me, wearing her signature samui, Japanese worker’s clothes, which she made by altering her mother’s old kimonos. A clean, white collar outlined her neck. Asari revealed to me that the collar was a fake snap-on type, and she was wearing a simple tank top underneath the samui. She laughed about it like a girl. I liked that she was practical and honest. Asari wears the outfit every day, except when she was recently honored by Oita newspaper for her cultural contribution as a koji maker. She wore a silk kimono for that occasion.

The struggle to persist and find a new market for koji

Once there were koji makers in nearly every village. However, in these changing times, it has become a rare profession, with only 1,000 artisanal koji makers left in Japan. When Asari took over the reins to help run her father’s business after her mother passed away in 2007, the business was not doing well because fewer people were making miso and amazake at home, and instead opted for cheaper, commercially made products. To keep the koji business alive, the Asaris supplemented their income, selling bento boxes and ice, and teaching math to local children. Asari researched old texts and cookbooks from the Edo period to see how koji was used in their daily cooking and began developing recipes for modern cooks. It was through hard work and persistence that Asari and other koji makers were able to diversify and expand the market for koji. Now, they are experiencing a resurgence of koji-based foods, particularly shio-koji.

Asari showed me the original muro, the dark and cave-like koji-propagating room made with clay walls and paved with large stones that remain from the days when the area was a loading dock. The steamed rice is inoculated with koji that used to incubate in the muro, but because of the danger of the roof falling from old age, they moved the operations to a modern building next door. The old muro will shortly undergo retrofitting to strengthen the ceiling.

Young and old koji makers work together to maintain tradition

It’s 2 p.m. at Kojiya Honten, and Asari’s 88-year-old father, Koichi Asari, a koji master, is supervising the koji-making. Three college interns from the Tokyo University of Agriculture are turning the steaming rice with large wooden paddles.

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Kojiya Honten proprietor Myoho Asari. Credit: Sonoko Sakai

Ryotoku, Asari’s second son, who is now being groomed to run the business, inoculates the rice with koji powder and gives orders out loud, making sure the bag of steaming hot rice is transported to the koji-propagating room in a timely manner.

Asari’s father, who is the first son born in a century of mostly matriarchal lineage, spent three years in a labor camp in Siberia before he returned to Japan to take over the family business. He says the secret to longevity is to work hard and drink amazake — a koji-based non-alcoholic rice drink — three times a day.

Can shio-koji replace salt?

What I learned from Asari through this visit was not only about the nutritional benefits of Koji but also its versatility as I got to savor many delicious dishes. I learned shio-koji is a natural seasoning made of koji, water and salt. It’s a creamy, white liquid with a grainy consistency that tastes salty and sweet, and it can be made simply at home. When koji is used in cooking, the enzyme proteases break down proteins to produce amino acids, including glutamate. The amino acid is responsible for umami, which enhances the flavor of foods. Another enzyme, amylase, is known for its ability to break down starches into simple sugars, which ensures foods prepared with koji have a rounder and deeper flavor. With 50% less salt content, good flavor and high nutrient content, I can see why some people are swearing by it as the new “salt.” Shio-koji can be used to season and tenderize meat and seafood. Even a tough piece of meat can turn into something quite good. You can also use shio-koji in soups, salad dressings, even in your pancake batter instead of salt. How about ice cream with shio-koji? When I was sitting with Asari, we got to talking about all kinds of ways to use shio-koji, and the possibilities were infinite.  What makes it most interesting for eaters and cooks, though, is that koji is a living food.

In the U.S., koji is available through Cold Mountain, Pacific Mercantile Co. and Gem Cultures.


(From the Kojiya Honten website)


500 grams (17 ounces) koji

170 grams (5.9 ounces) sea salt

650 cubic centimeters water (2¾ cups of water)


1. Put the koji in a bowl and rub with your hands to break up any clumps.

2. Add the salt and mix thoroughly with your hands, rubbing vigorously until the mixture sticks together when squeezed.

3. Add just enough water to cover the mixture, stir and transfer to a clean, covered container. Keep at room temperature.

4. For the first week, stir once a day until the flavor settles. Stir from the bottom to bring air into the mixture. It takes seven to 10 days to reach full flavor, depending on the season. When it is done, the rice kernels are smaller and the fragrance is salty and sweet.

Golden ratio of shio-koji

(From the Kojiya Honten website)

Using this ratio will bring out the best flavor in foods: 1:10 ratio of shio-koji weight to total ingredient weight.

For each 100 grams of ingredients, use 10 grams (1½ teaspoons) of shio-koji.

For each pound of ingredients, use 2½ tablespoons of shio-koji.

For each half-pound of ingredients, use 4 teaspoons shio-koji.

When substituting for salt in a recipe: For each teaspoon of salt, use 2 teaspoons of shio-koji.

Green bean salad with shio-koji

(From the Kojiya Honten website)

The dressing is made with basic seasoning and aromatic ingredients. In our family, when making sesame-dressed vegetables, we use only sesame seeds and shio-koji. The delicious sesame shio-koji blends well with the simple flavors of the vegetables.

Makes two servings


For the salad:

100 grams of green beans

1 tablespoon shio-koji

For the dressing:

1½ teaspoons shio-koji

2 tablespoons ground black sesame seeds (White sesame seeds can also be used.)

Dried hot chili pepper to taste


1. String the green beans and cut into 5-centimeter lengths.

2. Boil water in a saucepan. Add the green beans and 1 tablespoon of shio-koji to the boiling water and blanch.

3. Remove from heat, drain and chill in cold water. Drain again.

4. Mix the dressing ingredients together. Add the green beans and toss.

Photo: Preparing steamed rice to make koji. Credit: Sonoko Sakai

Zester Daily contributor Sonoko Sakai is a Japanese food educator, writer and producer, as well as a mobile Japanese cooking teacher and soba maker, who divides her time between Los Angeles; Tehachapi, Calif.; and Tokyo. She has contributed stories and recipes to the Los Angeles Times, the Chicago Tribune and Saveur. She is passionate about making soba by hand and is the founder of Common Grains. She is currently writing "Rice Craft, Adventures in Onigiri, Japanese Artful Fingerfood" (Chronicle Books -- to be published in fall of 2016).