It’s the savor in your miso and the bouquet in your sake, but until recently, you may not have known its name. Aspergillus oryzae, better known by its Japanese name koji, is a microbe that has been prized for thousands of years for its power to ferment. First isolated by the Chinese during the Shang dynasty, koji breaks down cooked grains and beans into stuff that we crave, namely booze and umami. Without it, we would not have mirin or soy sauce. Yet in Western society, koji’s praises remain relatively unsung.
Maybe it’s because koji is a mold and, historically, mold has not been given a lot of respect. Consider penicillin: Sure, it’s useful as an antibiotic, but you don’t often hear anyone wax poetic about its culinary benefits. And yet various strains of penicillin marble Stilton, give a white bloom to a Camembert rind, and are dusted on many an artisanal salami.
For koji, things are about to change. With its nutty, floral, woodsy-sweet fragrance, its creamy, furry looks, and its white truffle–like flavor, this mold’s star is in ascent. What’s more, koji now plays a leading role in a growing number of dishes. It’s not just about soy sauce and miso anymore. Finally. After centuries of patiently laboring behind the scenes, it’s time for koji’s close-up.
Koji belongs to the fungus kingdom, along with mushrooms, truffles, and yeast. Fungi nourish themselves by secreting enzymes that break down their food into simpler sugars (like alcohol) and amino acids (like glutamate). So, like sourdough and yogurt, koji is a living food. Traditionally, the spores of koji are introduced to a grain, usually rice (but sometimes barley) and left to flourish in a warm, humid environment.
Once the rice has developed into a koji-rich culture, it can then be introduced to more grain or legumes to continue its magic. Yes, it ferments soybeans into sauces and miso and breaks down rice into wine, but there are so many more possibilities. Rather than soybeans, how about chickpeas and pistachio nuts? Rather than rice or barley, why not freekeh or quinoa? Rather than rice into sake, why not wheat into whiskey?
To get you started, we have recipes for the two most basic koji marinades. Think of them as koji mother sauces from which you can build. Shio koji is koji fermented with salt (shio). A dash of shio koji elevates a humble stir-fry; when combined with raw vegetables, it yields a bright, fully flavored pickle. It also makes for a killer gravlax and a life-changing marinade for fried chicken. Shoyu koji is koji fermented with soy sauce (shoyu), and it lends its mellow caramel richness to red meats.
For those of you looking for greater koji mastery, we will also teach you how to cultivate your own koji rice. It’s not as daunting as it sounds; it’s all about maintaining an even temperature and working clean. It will take a bit of time but not a lot of work—the whole process takes just over a week, but with very little active time. Just think of the whole world that lies ahead when you become a true master, like Koji-Wan Kenobi. Koji sourdough bread as light as air. Beef “dry-aged” with koji flavor. Koji charcuterie garnished with koji pickles. The possibilities are endless.
Go now, young Padawan … and may the spores be with you.