Koji in the Kitchen

Learn how you can incorporate Koji – a modest, flavor packed, and healthy mold – into your cooking repertoire by exploring some everyday uses.

Shutterstock /Brent Hofacker

In the first article in this series, we opened with a soaring overview of Aspergillus oryzae, or “koji,” covering what it is, why it works, and some of the ways it’s used. In this article, we bring it back to the home countertop and explore everyday uses for koji. You can grow it yourself, but if the process of incubating fungus doesn’t entice you, you can purchase pre-made koji and use its secondary ferments to revolutionize your cooking and preserving.

Incubation Station

If you’re ready to start growing your own koji, you’ll need to settle a few practical matters before getting started. First and foremost, you’ll need to build or assemble an incubator. Koji needs specific conditions to flourish; it prefers a hot and humid environment with adequate airflow. Koji is an aerobic mold, meaning oxygen must be available for it to colonize a substrate.

Most incubators consist of an insulated box that controls the temperature and humidity via external devices. You’ll need to keep the temperatures between 80 and 95 degrees Fahrenheit, and the humidity around 85 to 90 percent. Incubator models range from a lidded plastic container full of water with an aquarium heater, to professional-grade warming cabinets. Next, we share our personal incubator setups to help you devise your own plan.

Meredith’s Big Blue Box

I grow koji on many things, including entire hams. As such, I needed something that would fit large, bulky items while maintaining temperature and airflow. My solution was to build a box from pieces of 2-inch foam board glued together with a food-safe epoxy. Inside the box is an incandescent heat lamp, which is plugged into an external thermostat that can be programmed to the desired temperature. For humidity, a small ultrasonic cool-mist humidifier sits in a bowl at the bottom of the box. The food destined for koji is placed in a tamis (a type of flat-bottomed sieve), covered with a flour sack towel. The tamis is supported by wooden dowels that poke through the foam board on either side. It’s that simple. As with any incubator, it has its idiosyncrasies; humidity tends to build quickly, and in great quantities. Over a roughly 48-hour incubation period of koji, I let the humidifier operate at top capacity, and then I open the incubator lid and leave it slightly ajar for the remainder of the incubation time. As you work with your own incubator design, you’ll learn the idiosyncrasies and needs of your equipment. — Meredith

Photo by Kirsten K. Shockey

8/10/2020 1:35:30 AM

Question: I have made Barley Koji, the colour of the mold is dark-grey, rather than White or greenish. I guess nothing else than Koji kan grow that fast anyway, but it makes me unsure. I made a Mole-version with roasted koji, cream and milk,taste is fine. I also made Shio Koji, it tastes like miso paste. But it both cases the colour is almost black. Do you know what can cause this?



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