Meet Koji, Your New Favorite Fungus

It's impossible to imagine Japanese meals without soy sauce, or the umami-rich fermented bean paste called miso, or the rice-based spirit known as sake. Which means that Japanese cuisine depends on the one fungus that enables the fermentation of all these delicious foods: koji. Today, American chefs are discovering what Asian cooks have known for centuries, that koji is a microbial powerhouse with seemingly magical abilities to completely transform food. But how does a mold from a family of microbes known for their toxicity turn salty, mashed beans into sticky, succulent miso? How did koji make its way from Japan to the U.S.? And how might the weird and wonderful ways chefs in the U.S. are now using koji transform the American dinner table, too?

Koji, or, as it's known in scientific circles, Aspergillus oryzae, was domesticated by humans around 9000 years ago. The fungus's closest relatives can be deadly, due to the chemicals they produce to kill off microbial competitors. But, fortunately for our taste buds, a random nontoxic mutation likely landed on some damp leftover grains in Asia, and humans noticed that the fuzzy mold, with its intoxicating scent of grapefruit and flowers, also turned those grains into a literally intoxicating drink. (Our ancestors wouldn't have known that this happened because koji broke down the starch enough to let yeast ferment the newly freed sugars into alcohol, but they'd have enjoyed the results.) Delighted, they probably encouraged the mold to grow on other left-over grains, gradually domesticating it by giving it a cushy home and caring for it over generations.

And they'd soon have realized that koji could could be used for more than making booze. Mixing the koji-furred rice, rich with protein-destroying enzymes, into beans breaks those beans down into the funky, fermented pastes that are staples in both China and Japan. Evolutionary genomicist John Gibbons, who studies koji's domestication at Clark University, told us that as early as the thirteenth century in China, "there are advertisements that are selling what's called moyashi. This is koji. So five, six, seven hundred years ago, before we knew what microorganisms were, we were selling them."

Koji is something of a celebrity in Japan, where fans can buy koji cell phone charms, read koji-focused manga, and celebrate the microbe on October 12, a.k.a. National Fungus Day. But, although it was the subject of the first biotech patent ever granted in the U.S., in 1894, it has not caught on outside of Asian cuisine. Until now. Recently, a small handful of American chefs have discovered koji's superpowers, and are using it to aerate whole-grain bread, transform kitchen scraps into complex sauces, re-invent fried chicken, and even cure meat. Listen in now to find out why koji seems to turn everyone it meets into obsessives, how its journey from East to West involves whiskey, arson, and cherry blossoms, and why it might just be next big thing in American cuisine. You heard it here first!

Episode Notes

Aedan Fermented Foods

Mariko Grady founded Aedan Fermented Foods in the Bay area, selling koji-rice and other koji-related products, such as miso, shio koji, and amazake at farmers markets and stores in and around San Francisco.

Moyasimon: Tales of Agriculture

Only two volumes of this microbial manga have been translated into English, sadly, because it's a really fun read.

John Gibbons

John Gibbons, an evolutionary genomicist at Clark University, is attempting to recreate koji's domestication in the lab.

Joan Bennett

Joan Bennett's side research on Jokichi Takamine has become something of an obsession. She's a distinguished professor of plant biology and pathology at Rutgers University, and she's written and lectured extensively about Takamine, even visiting the one museum in Kanazawa, Japan that houses some of Takamine's possessions.

Jeremy Umansky

Cleveland chef Jeremy Umansky currently spends his time touring the U.S. talking about koji, trying out all sorts of new, weird koji experiments (in one of his latest, he's curing cacao beans with koji to try to create new chocolate flavors), and hosting pop-ups for his future restaurant called Larder. (If you're in Cleveland when he's hosting a Larder pop-up, do check it out!) He's also writing a vinegar cookbook with chef Jonathan Sawyer of Trentina, where Jeremy first learned about koji. Here's a TedX talk he gave about koji in Cleveland.

Kevin Fink, Emmer & Rye

At Kevin Fink's restaurant Emmer & Rye in Austin, Texas, you might easily not realize the varied ways he's used koji to create the incredible flavors in your meal. Kevin makes an egg-white-based koji sauce that tastes like a creamy, nutty soy sauce, as well as various flavors of miso. He even incorporates koji into ice cream. A definite Gastropod recommendation.

Arielle Johnson

Chemist Arielle Johnson got her start working with koji at the Noma R&D lab in Copenhagen. She has now brought her fermentation science to the MIT Media Lab, where she's head of the newly launched Open Fermentation Lab. She and her colleagues are building a sensor-covered koji incubator, inside which specialized environmental conditions can be carefully maintained and monitored, and their impact on the resulting growth and flavors of the microbe studied, in order to create a guide to the full range of koji's deliciousness. She recently published open-source plans for building her "$165 plug-'n-play controlled environment koji incubator" on GitHub, as well as a a scientific paper on the potential of microorganisms as a new culinary tool.

Ben Wolfe

Thanks, as usual, to Gastropod's resident microbiologist, the fabulous Ben Wolfe, of Tufts University, for his thoughtful explanation of the science of koji and why some of the culinary experiments it has inspired definitely require further study.

The Science of Koji

Here's the article that started our obsession: Cynthia wrote about koji for Cook's Science last September. Read on for yet more koji, including a recipe for koji-marinated fried chicken. And, if you want to try marinating fish with shio koji, there are recipes such as this one for koji-marinated salmon available online. Not that Cynthia followed them, which is why one attempt was unbelievable and one was, well, not so great. More experimentation required!