If you melt over miso or salivate for soy sauce, you may be surprised to learn that it’s mold that keeps you and your taste buds coming back for more of that rich umami flavor. More specifically, a mold called koji, which has been used in Japanese cuisine for thousands of years. (It is also a crucial ingredient in sake.)  

Historians have long believed koji originated in China, with evidence suggesting it was first used to cleanse water in a process similar to the fermentation process that produces beer, cider and mead while also eliminating dangerous microbes. However, it is Japan that has made this ingredient essential to its cuisine and food culture. Koji is key to the development of some of the cuisine’s foundational flavours and ingredients. And even now — after thousands of years experimenting with this ancient mold — cooks are finding new ways to innovate, which suggest a new path for Koji.

“Koji is an extremely powerful organic technology that has not only shaped the foods of various peoples, but also … transformed their very cultures,” writes leading koji expert and co-author of the book Koji Alchemy, Rich Shih.

“Actually, virtually every culture that encounters koji or a food made with or from it becomes entranced by its transformative power. The Japanese have declared it their National Mold and have even created comic books in which it features as a cartoon character.”

The mold is created by using a grain, typically rice, that is inoculated with aspergillus oryzae or koji spores. The spores’ life cycles are much like that of a fungus. They start out as spores, which then spread and distribute themselves through the air. If the environmental conditions are right, they will then germinate, creating a dense white fuzzy coating called mycelium. In order to grow koji successfully, the inoculated ingredient is kept in a warm, humid environment until the snow-like coating appears.

Although rice is the grain most commonly used to grow koji, other grains like barley are also used. Even legumes such as soybean are viable, which is a key ingredient in one of the world’s most beloved condiments: soy sauce.

Depending on what they’re making, cooks then turn to one of two enzymes. They’ll use a powerful amylase enzyme to break down starches into sugars when they’re making mirin or sake. Or, they deploy the protease enzyme to break down proteins into amino acids to create umami-rich miso pastes and soy sauces.

This process also produces Glutamate, which represents the G in MSG. This compound naturally occurs in tomatoes and parmesan cheese, and is often added to canned vegetables and soups, processed meats and fast foods to enliven flavours — particularly savoury ones.

Like Koji, however, MSG is widely misunderstood.

MSG is used across many Asian cuisines, and has been demonized in Western culture, falsely associated with causing headaches and fatigue, amongst other phantom symptoms of ‘Chinese Restaurant Syndrome’. However, these symptoms are more a product of racial biases against Asian communities than they are based in science.

Writing in Pit Magazine’s MSG issue 2021, Cheryl Chow describes the unfounded letter published in 1968 in The New England Journal of Medicine, in which a doctor refers to a ‘syndrome’ of headaches and fatigue he experienced following visits to a Chinese restaurant.

“In the weeks that followed, The New England Journal of Medicine published many letters that, without scientific evidence, affirmed the validity of the quick slur of ‘Chinese Restaurant Syndrome’,” Chow writes.

“Chinese restaurant owners raced to plaster giant ‘No MSG’ signs at their storefronts and on their menus, despite extensive scientific research that found no relationship between MSG intake and the so-called ‘syndrome’. On the other hand, Campbell’s canned soups, which contained MSG, were pardoned from this newfound scare. But of course — unlike Chinese-American food, Campbell’s soup was ‘American’.”

While it was already a central part of Japanese, Chinese and Korean cuisines, certain uses of the koji fermentation process began life inauspiciously in the west. But, just as prejudiced beliefs about MSG subside, koji is now finding favour with chefs experimenting with fermentation and non-Asian foods.

Chef and food-science evangelist Jeremy Umansky has been working with koji and the work of its released enzymes for years, using it in a variety of ways in his Eastern European-inspired restaurant, Larder. For instance, he uses koji to speed up and intensify the curing and fermenting processes of meats, cheeses and vegetables. The results of these koji inoculations are digestible, fragrant and intensely flavoured foods.

Umansky, head pastry chef, co-founder and business owner Allie La Valle-Umansky, and business partner Kenny Scott embrace the benefits of koji in nearly all the items on their menu. Breads and pastries, meat and vegetable charcuterie, and their daily cured pastrami all get the koji treatment. By either growing koji directly on the meats and vegetables before hanging them to cure, or bathing them in amazake (liquid koji), Umansky can speed up the curing and aging process. This kind of innovation leaves the possibilities for what else can be harnessed using koji wide open.

“It [koji] can also make the food easier to digest because it produces these enzymes — these types of proteins — and each enzyme does a specific thing: one breaks down starch into sugars, one breaks down proteins into amino acids, one breaks down fats into the things that make them up,” Umansky says.

“Normally we have to let our body do that. But with koji, it does that even before the food enters our system. So, your body doesn’t have to exert as much energy into breaking down these foods because some of the work has already been done.”

The fact that Koji makes food easier to digest matches the prevalence of fermentation in Japanese cuisine and culture. Just as the resulting flavour profile is important, so too does Japanese cuisine prioritize the health benefits of fermentation; a process proven to encourage healthy gut microbes and help maintain good digestive health.

Larder also uses koji to produce vegan charcuterie from whole vegetables such as beets, carrots and squash, which are then treated much like meat (a curing and hanging process) to mimic charcuterie-like textures. Their smoked beet charcuterie is made by boiling beets, which are then smoked, cured with salt, inoculated with koji and hung to dry for 10 to 14 days. The result is a toothsome, salami-like texture, owing to the rapid curing magic of koji.

“The idea is to be on the other end of the spectrum [to] the Impossible Burger. You can see these are slices of whole vegetables. We don’t grind them. We don’t mix them. We’re not hiding the fact it’s a vegetable,” Umansky continues.

“We make all our charcuterie with koji, just in different ways. Some are bathed in amazake (liquid koji), with others we grow it directly on the meat. We’ve done that with a couple of the vegetable charcuteries and with the beef.

“We also make ‘black cheese’ — miso made from locally produced cream cheese, made with the same koji rice used to make blood sausage and the same mold used in shōchū or distilled sake.”

Sandor Ellix Katz writes in the foreword of Shih and Umansky’s book that, “Koji is a mold with great transformative powers”. For thousands of years, koji has helped make water safe, and created beloved foods and foodways ubiquitous with Japanese cuisine, culture and health. Today, it continues to inspire cooks and scientists to further experiment and understand the power of its fermentation process. Koji is a powerful ingredient, a living, breathing, organism tied to long-standing traditions, which sparks curiosity and creates great food. Just as it shaped our food’s past, it could define its future, too.