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Fermentation Tales of Koji and Miso 

click to enlarge Richard Wagner holds a piece of barley koji.

Photo by Simona Carini

Richard Wagner holds a piece of barley koji.

"You may be interested in trying this," Richard Wagner told me one Saturday morning in April while I was looking at the produce he had brought to the Arcata Plaza farmers market. He and his wife Lauren run Palmer Creek Farm, a biodiverse farm in Fortuna. "I'm always interested in trying something new," I answered. He placed in my hands a small jar of shoyu koji, which I brought home, together with a substantial amount of curiosity to try its content.

Two weeks later, after another conversation with Wagner, I brought home a 3-year-old green-lentil miso. I knew miso as a fermented soybean paste used in Japanese cuisine, but I'd never dug deeper. It was time I understood the process, which, as every fermentation tale I know, is fascinating.

At the beginning there is a grain — often rice, but also barley, which is what Wagner says he uses — that gets steamed and then inoculated with koji starter, the mold Aspergillus oryzae. The result is called rice koji or barley koji, which is combined with other ingredients and allowed to further ferment to produce the following condiments: shio koji (with water and salt), shoyu koji (with tamari and salt), miso (with cooked legumes, see below). Shio koji is a light-colored, lumpy paste with a mild, sweet miso-like flavor. Shoyu koji is brown, smells salty and mushroom-y, and adds umami to dishes. Both are used for seasoning or marinating.

To produce miso, koji is mixed with salt and mashed, cooked soybeans (most commonly) or other legumes. For example, Wagner has used, among others, green lentils and great northern beans. The combination is placed in a clay vessel under pressure (a layer of tamari forms on the top, which acts as a seal) and fermented for a length of time between a few and many months, depending on the desired flavor profile. The duration of aging and amount of salt produce different types of miso: older miso is darker and stronger. Aging tests the producer's patience. It is one thing to wait for a few days or even a few weeks; waiting years requires discipline.

Wagner's journey in fermented foods started around eight years ago with making kombucha, then yogurt, sour pickles and beer. In 2018 he started experimenting with koji. The steps he took mirror my experience in making cheese: reading resources, connecting with people with the same interest and experimenting.

Now that you know a bit about how these fermented products are made, the question is: How do you use them in the kitchen? Here a few suggestions from my experiments so far, for which I skip the salt in favor of shoyu koji or miso:

Use shoyu koji in salads and to season savory pancakes.

Toward the end of cooking, add miso to vegetables, and to onion and fava bean soup made without stock or broth.

I use great northern bean miso in my oatmeal raisin cookies (recipe likely coming soon) and my brown butter, chocolate chunk cookies ("What-if Cookies," Jan. 13, 2022).

And here are a couple of recipes from Wagner himself, whom you can find at the Palmer Creek Farm's booth at the year-round Saturday farmers market on the Arcata Plaza and the summer one in Fortuna on Tuesdays.

Miso Dijon Salad Dressing 

¼ cup olive oil

1 ½ tablespoons miso

¼ -½ teaspoon Dijon mustard

2 tablespoons rice vinegar

1 garlic clove

Ground black pepper, to taste

Blend ingredients well using an immersion blender and serve.

Miso Glaze

I prefer to use a sweet mustard and go fairly heavy on the dill, as I like the taste. I typically use this glaze for fish — especially salmon.

2 tablespoons miso

1-2 tablespoons honey

1-2 tablespoons mustard of choice

Dill, preferably fresh, to taste

2 garlic cloves

¼ cup olive oil

Blend ingredients well using an immersion blender. Coat the fish with the glaze, marinate for 2 hours, then bake as usual.

Tenderizer for Meat or Vegetables

This uses shio koji or shoyu koji (blended, if needed, to make a smooth paste).

For meat: With a kitchen brush, coat the meat with koji and let rest for a few hours. 

For vegetables: Add 1 tablespoon koji and other spices to cleaned and cut vegetables, and place in a container to rest for an hour or so before cooking.

Curious to learn more? Check out these books and articles (links at

The Art of Fermentation by Sandor Kats

The Noma Guide to Fermentation by René Redzepi and David Zilber

Koji Alchemy: Rediscovering the Magic of Mold-Based Fermentation by Rich Shih and Jeremy Umansky

Miso, Tempeh, Natto & Other Tasty Ferments: A Step-by-Step Guide to Fermenting Grains and Beans by Kirsten K Shockey (Wagner recommends this as easy to follow and doable for beginners.)

"Koji Starter and Koji World in Japan" by Hideyuki Yamashita in the Journal of Fungi

"Fermentation and the microbial community of Japanese koji and miso: A review" by Joanne Allwood, Lara Wakeling and David Bean in the Journal of Food Science

Simona Carini (she/her) also writes about her adventures in the kitchen on her blog and shares photographs on Instagram @simonacarini. She particularly likes to create still lives with produce from the farmers market.

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Simona Carini

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