A Fuzzy White Fungus Called Koji Is Taking Over Dallas Restaurants

There is a fungus working its way into Dallas. Thin, fibrous white tendrils that are inoculating some of the finest meals in the metroplex. Fortunately, koji (or aspergillus orzaye, as it is known to scientists) isn’t nearly as sinister as its sounds, and the city’s most inventive chefs are using the fuzzy little fungus to crank out some truly incredible dishes.

But what is koji? When aspergillus oryzae is introduced to rice, it uses the grain as a source of energy and essentially takes over, much in the way that yeasts and other funguses are used to leaven breads and produce beer. In Japan, koji is used to make soy sauce, sake, mirin, and miso. Now, the mold-infested rice has officially made its way stateside, where it’s being used to add a massive punch of flavor to otherwise common dishes.

At Deep Ellum’s Junction Craft Kitchen, Chef Joshua Harmon took matters into his own hands when he couldn’t source koji that met his standards for quality. “One of the best ways to get good ingredients is to get them yourself,” says Harmon, and as such, the chef began experimenting with various types of rice to produce his own. After starting with sushi rice, Harmon eventually settled on medium-grain rice, which is then inoculated with the mold and placed into a warm, moist environment to encourage its transition into Koji.

In Japan, koji is made in massive industrial facilities, but Harmon has created his own contraption, which is about the size of a camping cooler. After a few days of mold growth, the chamber is opened and the rice is mixed up, then formed into long rows which allow the fungus’ tiny fibers to spread across the entire surface. When the koji has reached maturity, it ends up in dishes on the menu at Junction, like koji-crusted meats and Harmon’s housemade kimchi.

Harmon isn’t the only chef in Dallas experimenting with koji, either. At Misti Norris’ Petra and the Beast pop-ups, freshly-made butter cultured with koji is a standard offering. At Tokyo Grill, the chefs allow steak to rest in koji for 24 hours, which results in a slightly dehydrated crust that seasons the meat all the way through. At Japanese spot Nikkei, koji is mixed into the breading for the restaurant’s fried chicken, which results in an even juicier bite than the usual fried bird.

The life of a koji mold is a unique one, and its culinary uses are essentially limitless. If taken in its raw form, koji can be ground to a fine powder, which enhances its funkifying capabilities. The powder can be added to pretty much any meat, where it acts like a rapid curing agent, drawing moisture to the surface and essentially dry-aging a steak in a quarter of the time that traditional method takes. When applied to starchy vegetables, the koji immediately begins feasting on the carrot or potato’s natural sugars, making it easier to produce a perfectly caramelized crust. As koji stays on the product for longer and longer, it becomes less about texture and more about flavor.

If left longer, the koji keeps feeding and producing savory soy sauce flavors that are somewhere between of meaty and rich. Pushed even further than that, koji can start producing alcohols, and a drink similar to sake would eventually form. In its final stages of life vinegars start to be made by the koji, which can then be used to preserve and pickle pretty much anything.

It may be a little bizarre, but molds, fungi, and yeasts have always been part of the world’s most popular foods, and koji is no exception. Go forth, and explore this entirely new world of funky, complex flavors.

Daniel Rockey is a Dallas freelance writer and food scientist.