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Innovation in the Coffee Industry: The Koji Method

From the beginning, we’ve been excited by experimental coffee processing techniques at Hermanos. As well as allowing coffee producers to make a name for themselves and sell their coffee for higher prices, innovation introduces new energy into the industry — giving consumers a chance to taste unique flavours and profiles.

With that in mind, we were determined to get our hands on some  Koji coffee beans for our customers in the UK. And when we learned our friends at Forest Green (producers of our famous El Fresno coffee bean) were growing them, we knew we had to get an order in. 

What is Koji? 

Koji coffee fermentation method

Koji is not a word that most people recognise, and that’s because its influence thus far has been widely limited to parts of Asia, most notably Japan and China. 

It is an ancient filamentous fungus that has long been used during the fermentation process with particular foods, such as soybeans, sweet potatoes, and rice, to break down starches and impart new and interesting flavours. 

What is most fascinating about Koji is that it was originally found and domesticated from mould that grew on steamed rice. Enzymes present in the mould pulled starch out of the grains of rice and produced amino acids, resulting in aromas that were reminiscent of mango and grapefruit. Years and years later, we’re left with what is known as Koji. 

Koji is known to some as “Japan’s national mould”, for its role in making sake, miso, and other distinctly Japanese food and drink products. Although it may be commonplace in East Asian gastronomy, Koji is still relatively unknown in the global coffee industry.

How the Koji Method Works

Coffee cherries undergoing the koji fermentation method 

Many well-known beverages undergo fermentation processes as part of the journey that makes them recognisable to us, such as wine, beer, or kombucha tea. Coffee is no different. 

Koji can be used to ferment coffee beans by turning complex sugars into simple sugars, and producing amino acids and glutamates, which are responsible for delivering a heavier mouthfeel and body to the final cup of coffee. 

Once the mould has been applied to the coffee cherries, it is left to ferment for approximately 60 hours, ample time for the starches in the bean to break down and for secondary fermentation to occur, all thanks to Koji.

Learn About Coffee Processing

The Unique Flavour of Koji Coffee

Forest Green Coffee, Tolima, Colombia

Coffee that has been made using the Koji process is one of a kind. The mould gives great complexity and body to a coffee, whilst also giving a lighter, less acidic, and slightly sweet flavour. 

We’re incredibly excited to be stocking a Koji coffee, courtesy of the Bayter Brothers, Elias and Shady, at Forest Green Coffee in El Vergel, Tolima. 

Upon tasting the beans, we uncovered a whole host of exciting notes, including prune, blueberry, blood orange, bourbon whiskey, dried pineapple, maple syrup, and liquorice candy. The role of Koji in this coffee was to enhance all of those beautiful aromatic compounds and elevate the quality of the bean to an exceptional level.

Shop Our Koji Coffee Bean


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