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What You Need to Know about Koji Coffee

Coffee has been the preferred beverage for many people across the globe for at least a century. As a result, there is a constant influx of innovations and trends to elevate the coffee-drinking experience further. With the surge in popularity of gourmet coffee, there has been motivation for coffee producers and masters to experiment. One of the areas they like to try and innovate in is processing.

Processing is an integral part of coffee production. It refers to the stage wherein the coffee beans are prepared for roasting. This, in turn, has a significant impact on the resulting flavor and freshness of the end product. One of the most recent processing trends that have emerged in the coffee scene involves using the koji mold.

What You Need to Know about Koji Coffee

What is the koji process?

The koji mold is a priming agent that is widely used in Japan and Southeast Asia. It is used in the fermentation stage of many products known for their umami element, some of which are miso, amazake, and sake. So popular is it in Japan that it has been dubbed the “National Mold.”

Essentially, koji is a beneficial fungus that has been used since ancient times to saccharify starches. This means turning starch into sugar and dextrin so that it can be used for fermentation. Adding koji to certain food and drink items breaks down the starches in them, helping produce new flavors.

How did the koji coffee process come about?

When coffee producers first started experimenting with koji, they encountered some difficulty since green coffee (unroasted coffee beans) holds very little starch. A sufficient amount of starch is necessary since the mold requires enough to stick to the fermentation medium and grow.

Despite the initial challenge, they found a way to try the process out on green coffee. Unfortunately, it resulted in umami flavors that are not exactly pleasant for the average coffee drinker. They did another experiment with coffee cherries (the actual coffee fruits), and the result was far more palatable. Based on this more successful attempt, a collaboration was initiated to develop the first koji coffee process.

koji coffee

How does koji ferment coffee?

The mold can break down starches into fermentable sugars, producing glutamates and amino acids in the process. When koji does this to coffee, the resulting drink enhances mouthfeel, making it weigh heavier on the tongue. It also turns complex sugars into simple ones, indicating the potential for creating new flavor profiles. Koji fermentation also gives coffee a more fruity aroma by producing esters and aldehydes.

Other processing methods are able to break down about 70 percent of coffee sugars. Still, koji allows the use of more sugars in the succeeding fermentation stages, thereby allowing for further flavor intensification.

Koji was first tried on a Red Bourbon coffee variety, following a natural koji fermentation process. The results were excellent. Instead of creating new flavors in the coffee, Koji ended up enhancing the existing components. It changed the body. For instance, it altered the coffee’s soft structure by making it rounder and creamier.

The koji coffee process was also tried on other coffee varieties, but the Java variety is noted to have had the most favorable response to it. Those who created the method knew that coffee producers could benefit from it; thus, they made it available to the public on an open-source page.

How feasible is the koji process in commercial coffee production?

While koji could add value to their coffee, producers tend to lean towards other more beneficial improvement methods such as selective picking, tank cleaning, etc. Farmers gravitate to the traditional since they can trust it to produce the expected flavor profiles. At the same time, not many people, even those in the coffee market, know about koji coffee, hence the low demand for it.

Koji is also quite challenging to scale and control. The culturing stage requires close attention and much effort spent on meticulous monitoring, especially when it comes to timing and temperature. Once the relevant steps are more efficiently managed, however, the process will be much more straightforward, which will undoubtedly help the product rise toward a premium score. In addition, the koji process doesn’t need much equipment to implement; it just needs a shaded space for storing the coffee while it breeds the koji spores.

Coffee experts believe that the koji process has great potential. Once more people try it and learn about it, the demand will be enough for producers to justify further exploring what it can do.

How can koji be more accessible?

One of the other issues with koji is its cost. Spores can be expensive—around $17 for an ounce. Fortunately, the people behind the koji coffee process have found a way to achieve koji spore growth more affordably through rice koji. Rice is also prolific in areas where coffee is grown, so it’s definitely accessible. Rice koji is made by partially cooking rice with steam and then dispersing koji spores on the rice to culture more mold. This method creates rice koji cakes, which can be pulverized for proper dispersion.

Doing this would significantly make the koji process more practical for producers to implement, addressing both questions of affordability and scalability. Nonetheless, it’s all in the experimentation stage at this point. Koji fermentation still has to be established as an entirely safe process. Part of this is figuring out the right koji strain to use for more expansive commercial production.

What is koji’s future in the coffee industry?


Koji coffee processing is very new, and invested producers are still studying it. It should be noted, however, that it has already been introduced at the World Barista Championships.

As previously mentioned, the potential is great, and for the time being, the surface has merely been scratched. Once research shows how koji coffee production can be efficiently scaled for commercial availability, it’s bound to take off. For now, koji coffee is best represented in competitions. It’s a foot in, however. Once it starts garnering wins, it will be a whole new ballgame for this innovation.

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