The launch of Mos Burger’s new limited edition Salt Kōji Burger on May 24 officially confirms that salty mold is now the flavor du jour in Japanese kitchens. Kōji, or to give it its long-winded name, Aspergillus oryzae, is a domesticized fungus that has been used in the production of miso, sake and soy sauce for centuries. Salt kōji, made by mixing salt and kōji with water, then leaving it to ferment, is also a traditional seasoning, but one that had rather fallen out of use until it enjoyed a revival in the latter half of 2011.
According to Yomiuri Online, the craze for salt kōji started off when Komego, a miso store in Fukui Prefecture, started selling it for use as a simple seasoning back in January 2011. Word spread with restaurants around the area using the ingredient, causing it to eventually catch on with the mass media.
It was traditionally used as a seasoning for vegetable and fish dishes, but now cooks are enthusiastically using the ingredient more creatively with meat as well as in soups and sauces. Marinating meat or fish in salt kōji converts the starches and proteins into sugars and amino acids increasing the umami, or savory flavors, of the meat. Though salt kōji can be bought, it’s quite simple to make at home, and plenty of cooking websites have featured instructions (see video) on how to whip up a homemade batch.
Fukui Prefecture, which has been a driving force behind the boom, has now introduced a kōji mascot to highlight the benefits of this versatile ingredient. Kōji-kun is drawn in the image of a grain of rice with some weird stuff growing out of its head, to illustrate the fact that kōji starts out life growing on grains of rice. Kōji is also depicted in cute cartoon form in the manga and subsequent anime of “Moyasimon: Tales of Agriculture” a story about an agricultural student who can see and communicate with bacteria.
If you’d like to try out this taste sensation for yourself at Mos Burger, then you’ll have to hurry as there will only be 1 million Salt Kōji Burgers available. Rather than being used as a marinade for the meat, the salt kōji is mixed into a special mayo sauce for a salad topping of crispy nagaimo and edamame.