Cooking with Koji – A Time-Honored Japanese Tradition

The process of fermentation can be a frustrating endeavor, something that demands a lot of time and patience.  In the Japanese culinary world, one of the main ingredients, and a staple in many essential products, is koji, a culture that is the basis for much of the fermentation in Japanese cooking.

Koji comes in various forms, from rice to barley, and is an integral part of some of the most common items in Japanese cooking – miso, sake, and shoyu (soy sauce) just to name a few.  The process has been around for hundreds of years, but is really starting to pick up steam, not only in Japan , but also here in the Bay Area.

“Making koji is a natural life process.  And for me, it is like caring for a baby,” said Mariko Grady, founder of San Francisco-based Aedan Fermented.  “2-3 days and you’re done.  But during that short time, it’s a very thorough process.”  Grady was living in Japan and usually bought her fresh koji from the local markets. But following the devastating earthquake and tsunami in 2011, she began to spend more time in the kitchen, selling products to help with fundraising efforts.  Many of her colleagues and friends were so impressed, they suggested it could be a new career – and hence the start of Aedan Fermented.

Photo Credit: Aedan Fermented

Now, Grady has partnered with La Cocina, an organization that helps low income food entrepreneurs, using the commercial kitchen space to make her products, from fresh rice koji to different versions of miso, even a sake kit.  “Koji is full of enzymes and provides a healthy option.  The fermented food product line is meant to help people who cook at home, giving them a quick and easy option, which is not just healthy, but also provides a great deal of umami,” Grady said. 

Along with selling and producing her products, Grady offers classes and workshops, for adults and children alike, something she said she would like to expand on this year.  “Just getting the word out about koji, how simple it is to use, whether it’s marinating a dish or something as basic as miso soup,” she said.  Eventually, Grady said along with selling her products, she would like to own a small space where she can hold events, classes and demonstrations, offering a more hands-on approach to koji.

Along with Aedan Fermented, many San Francisco restaurants now feature koji on their menu - from places like Bar Tartine to Nombe.  But the first spot to really use it in earnest was Izakaya Yuzuki in the Mission District.  Since opening, Owner Yuko Hayashi and Chef Takashi Saito have provided guests with a unique Japanese dining experience.  This is not your normal izakaya-style restaurant;  the menu is finely crafted around seasonal ingredients, with items such as miso and tofu made in-house daily.  Chef Saito said he’s proud to use koji in his restaurant.  “Koji is a seasoning that is indispensable to the daily life of almost everyone living in Japan, but it is not really that well-known.  In reality, the basis of the Japanese food culture is koji,” he said.  “Japanese food is all about beauty and taste, while also being gentle and friendly to the body.”

Kara-age Chicken, marinated w/ salt koji

Both Hayashi and Saito grew up in Japan and at Izakaya Yuzuki, they wanted to bring a traditional experience to the Bay Area.  “Growing up in the country, rather than a big city, vegetables and rice were made daily at home.  We would get our water from the mountain behind our house.  Fish came from the nearby river and dairy from the cattle in the neighborhood,” Saito said.  “There was a Buddhist temple next door and during services, my grandmother would prepare meals, and we would all help.  At that time, I never thought I would have a job as a chef, but it was such a valuable experience for me, learning about these different dishes.  Those memories and tastes remain with me to this day.”

At Izakaya Yuzuki, there are normally a handful of dishes prepared with koji on the menu, from the Kara-age Chicken to the Yaki Surume Ika (“Salt Koji” marinated Hokkaido squid with yuzu mayonnaise). Chef Saito said creating dishes from his childhood memories, while also producing food that is nutritious and healthy for guests.      

At both Izakaya Yuzuki and Aedan Fermented, a generations-old Japanese technique is being accentuated in the Bay Area cooking scene, one that provides a healthy and tasty option in both restaurants and home kitchens.  Expect the use of koji to grow steadily in the coming years.