Koji

Last summer, I was living communally in Pennsylvania. There was a plethora of farmers markets everywhere I looked, so naturally, I befriended a mushroom farmer. Every few weeks he brought me a new variety of mushroom. Bursting with flavor, the umami-filled fungal bodies found their way into my heart (via my taste buds, like all things).

Mushrooms are the sporocarp of the fungi, which means that they are the structures on which spore producing bodies are formed. They are evolutionarily more closely related to animals than plants. The underground part of a mushroom is called a mycelium. The above ground part of the mushroom, (sometimes edible) is also their reproductive organ. The cap of the mushroom protects the gills of the mushroom, which is the spore-producing part. Spores are the ‘seeds’ of the mushroom that can turn into a new mushroom when they fall off their parent mushroom. The rest of the parts of the mushroom are the stem, hypha (transports water + nutrition), volva and ring (remmants of a membrane protecting the baby mushrooms). This is an oversimplification, and some varieties do not have all of these parts. There are so many kinds of delicious mushrooms that taste drastically different than each other – its very easy to get lost in the world of mycology.

There is a specific fungus variety called koji (taxonomical name Aspergillus Oryzae). Koji molds are widely used to ferment soybeans, to make rice vinegar, and plays an important role in making miso, makgeolli, sake, and soju. Koji is used in mostly Asian cuisine, for now.

Koji molds are made by growing koji spores in a warm, humid place, on top of a substrate (like milled rice). The koji produces many enzymes that break down macromolecules. The resulting simpler molecules serve as nutrition for yeast cultures in later fermentation. And that is why koji is so versatile: it saccharifies (breaks down complex sugars/carbs/starches to simpler sugars) , which ends up being very favorable for fermentation.

The substrate that the koji mold spores (koji-kin) are on top of change their composition because of the koji growth and saccharification. For instance, rice is often used as the substrate for koji, in the production of sake. The starch in the rice is broken down into sugar, and the sugar is used in the fermentation process (by the yeast) for making sake. Different substrates yield different precursors for a variety of drinks (rice substrates are responsible for sake, soju, and makgeolli, among other things).

The resulting substrate-koji culture is again mixed into another product (such as soybeans). The enzymes in the culture help break down the protein and starches in the new mixture, and the easily available sugars render the new mixture fermentable.

Many chefs are conducting experiments regarding more experimental uses of koji as we speak: koji-cured fish, cheese fermented with koji, and aged and fermented cookie dough are a few polazing projects that have gained some media attention recently.  I predict that this will catch on with more inertia in the near future and we will see more instances of experimental products made using koji.

I haven’t tried any of these experimental products yet, but I will. The future is exciting, and will probably be delicious ^^

* Koji  is called kōji in Japanese, qu in Chinese,  and nurukgyun in Korean

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