“Kōji,” says Jeremy Umansky, “is the most romantic, sensual thing you can bring into your kitchen.”

Umansky, co-chef/owner of Larder Delicatessen & Bakery in Cleveland, Ohio, wears his passion for kōji — Japan’s semiofficial “national mold,” Aspergillus oryzae — on his sleeve. As does Rich Shih, who’s a mechanical engineer by day, kōji “culinary explorer” and food preservation consultant by night. The two had been exploring kōji independently throughout the 2010s, sharing their work on social media before connecting and developing a working relationship that’s culminated in “Koji Alchemy: Rediscovering the Magic of Mold-based Fermentation,” out since May 6 from Chelsea Green Publishing.

Koji Alchemy: Rediscovering The Magic Of Mold-Based Fermentation, by Jeremy Umansky and Rich Shih
352 pages

Fermentation nation

“Koji Alchemy” is a natural extension to the growing compendium of books about home fermentation and preservation. There’s the James Beard Award-winning “The Art of Fermentation: An In-Depth Exploration of Essential Concepts and Processes from Around the World” by Sandor Ellix Katz; “Preserving the Japanese Way” by Nancy Singleton Hachisu; “Miso, Tempeh, Natto & Other Tasty Ferments” by fermentation gurus Kirsten and Christopher Shockey; and the New York Times bestselling “The Noma Guide to Fermentation” by renowned chefs Rene Redzepi and David Zilber. But “Koji Alchemy” is the first English-language publication devoted to the mold behind many of these ferments, taking a deep dive into the history and significance of kōji throughout East Asia, and providing a near encyclopedic overview of its applications. Best of all, it demystifies the methods of culturing and cooking with it at home.

Those already familiar with Japanese food and drink may have some understanding of what kōji is and how it’s traditionally used. But even someone completely unfamiliar with kōji has benefited from its cultivation: Soy sauce, miso, sake, Korean gochujang (fermented chili paste) and Chinese douchi (fermented, salted black soybeans), just to name a few ingredients, all owe their existence to kōji. Umansky goes as far as saying that, as one of the oldest domesticated foods on the planet, kōji “was responsible for the development (of civilization).” The Western world is just several thousand years late to the party.

Nevertheless, despite the growing popularity of home fermentation, and kōji’s appearance on the menus of high-end restaurants around the world, both Umansky and Shih recognize there is a mental hurdle “Koji Alchemy” readers need to overcome: that mold is bad.

“It’s what you grow up with in terms of understanding,” Shih says, explaining that most people’s initial ideas of “mold” are the harmful varieties you find on spoiled food, or the mysterious black gunk you find in your basement.

“General misunderstandings put people off kōji,” Umansky adds.

Thomas Frebel, head chef of the now-closed two-Michelin-star Inua, where kōji is used “like salt” in the menu, agrees. “Most of the time when we look at (fungi)… it’s always a bad thing, it’s always bad molds,” he says. And (we) actually keep forgetting that, you know, Camembert — of course it’s (made with) a different fungus, it’s a different spore, it’s a different mold — but it’s a mold.”

Umansky and Shih take great pains to clear up these misunderstandings, and pave the way for professional chefs and home cooks new to kōji to embrace the ingredient.

“Kōji is an unparalleled seasoning that can be used as simply or complexly as the cook who wields it, no matter the experience level. It’s a true secret sauce,” they write in the book’s introduction. “Welcome to the passionate obsession.”

Starting a kōji conversation


One of the most important tasks Umansky and Shih take on early in the book is establishing a kōji lingua franca based on “an amalgamation of current usage, the strongest influences from the most recognized Asian products and a fundamental understanding of the driver of each different food.”

Though heavily influenced by Japanese vocabulary, thanks to the linguistic influence of William Shurtleff and Akiko Aoyagi’s pioneering “The Book of Miso” (1976), Umansky and Shih lay out and clearly define terms with cross-cultural application: Miso becomes an “amino paste”; soy sauce or Korean ganjang becomes an “amino sauce.” The umbrella terms allow readers to establish a foundation before delving into more culture-specific vocabulary, and experiment with concepts and techniques from the book without treading on or disrespecting cultural sensitivities. They take the same care when explaining how kōji’s enzymes break down starches and allow food to develop flavor to become, as Umansky asserts, “the most delicious it could possibly be.”

But the bulk of the book is, of course, how to culture and work with kōji.

In the chapters “How to Grow Koji” and “Expanding Your Koji Making,” Umansky and Shih walk you through selecting your kōji kin (kōji spores). Kōji production companies like Higuchi Matsunonsuke Shoten Co. commercially supply separate spores for miso, sake, soy sauce and even premium ginjo sake, the two assert a light rice kōji kin will work just fine. The chapters show ways to safely disperse the spores from the packets before delving into the technicalities of inoculation.

They first describe a traditional Japanese method using cedar kōji buta (trays) before exploring so-called “modern” incubation methods, which run the gamut from minimal effort to food science: Do you have the means to set up an insulated water bath? There’s a method for that. Have you got access to a dehydrator or fermentation room (like Inua)? Umansky and Shih have you covered. Not willing to invest much capital, but still want to give it a shot? You can just use your oven.

Once the basics have been covered, subsequent chapters branch out into growing kōji on starches other than rice — popcorn kōji, anyone? — and how to make amino pastes and sauces, cure meats and vegetables. There’s even sweet applications. Scattered throughout the book are mini essays written by various experts in the field, providing complementary perspectives on everything from the importance of pH to cultural appropriation.

“(Kōji) wants to live,” Umansky and Shih write. “You don’t grow the kōji; it grows because it wants to. Think of yourself as a farmer or a shepherd of sorts.”



Despite the wealth of technical information, there are relatively few recipes. Umansky and Shih are both quick to assert that “Koji Alchemy” is not a traditional cookbook, or culinary pop art for the coffee table.

Instead, the goal is to provide a baseline establishment, giving readers numerous techniques and then setting them free to experiment.

“Food is very personal,” Shih says. “(We want) to maintain people’s integrity with food and not change that. We don’t dictate anything beyond what basic procedural things need to happen. It’s the empowerment of (having) a technique to develop the flavors you want on ingredients you’re familiar with.”

“The trick (to finding balance in cookbook writing) is to offer each type of personality what they need to thrive,” says Kirsten Shockey, who, along with her husband, Christopher, got her kōji primer from Umansky; she penned a mini essay on culture and food preferences for the book.

“We try to use science and art. We give measurements and recipes, and some folks need and want that. At the same time, we encourage going freestyle. We think if you know the rules and what the microbes need, you can do whatever you want. We also find that using what is available to you in your location is so much more important than finding very specific hard to find ingredients. We want to see folks take ownership.”

This ownership is why you see “blackened kōji” — barley kōji fermented and slowly caramelized — served with ice cream and wild cherry tree bark-infused oil on the menu at Inua; why chef Ken Fornataro runs Cultures Group on Instagram, facilitating popular workshops on innovations like kōji charcuterie; why #kojibuildscommunity, which Shih first used to share kōji ideas with friends, has since welcomed many others into the kōji fold; and why Koichi Higuchi, seventh-generation head of aforementioned Higuchi Matsunosoku Shoten, one of only six companies still selling kōji spores in Japan, is developing a kōji-fermented coffee and aged egg yolk mayonnaise with Japanese food company Kewpie Group.

“Even with the same kōji fermentation, it surprised me how much the viewpoint changes by region, and even as a kōji pro I get a sense there’s new possibilities,” Higuchi says by email.

“In Japan, I think fermented foods have a healthy image, but people outside of Japan have an image that it draws out umami. Also, Japan is too familiar with kōji, and there’s probably a more conservative influence, but the ideas coming from people abroad are novel and striking.”

Umansky and Shih say they’ve noticed an uptick in experimentation from a wider variety of people during COVID-19, and that the pandemic has been a “blessing in disguise to really tailor our (book) events.” There may even be a second book in the works.

“Seeing #kojibuildscommunity through other people’s eyes,” Shih jumps in, “it’s like ‘I feel stupid for not figuring this out myself, but thank you.’”

“The more we learn, the less we know,” Umansky says.

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