Fermentation is an important stage in the journey of a coffee from seed to cup. Not only does it remove the coffee’s mucilage after harvesting, it also plays a role in developing its distinct characteristics.
Over the last few years, producers have increasingly experimented with fermentation techniques to derive new and exciting flavours for consumers.
With enough skill, they are able to amplify desirable characteristics, such as sweetness, body, and mouthfeel, often leading to higher quality coffee. In some cases, fermentation was able to improve the SCA grading by as much as eight points.
One technique that has recently caught the attention of those in the specialty coffee sector is koji-fermented processing.
Invented by bioscientist Koichi Higuchi, it involves using koji spores – an ancient mould used to make traditional Japanese fermented foods – to green coffee beans and leaving them to ferment for several days.
In addition to enhancing the coffee’s flavours, this method of processing is also thought to carry significant benefits for farmers, who have the opportunity to demand higher prices for their beans.
So are we about to see a lot more koji-fermented coffees entering the market? Read on to find out more.
What is koji fermentation?
Koji fermentation is a technique that has been used in Asian cuisine for centuries.
Found in everything from sake to soy sauce, it involves using a fungus (Aspergillus oryzae) to break down complex carbohydrates and proteins into amino acids, fatty acids, and simple sugars.
This helps to unlock flavours, reduce acidity, and add greater depth. This has led to it being described as “magical” and a “game-changer” by experts.
“It really changes the game overnight in terms of the flavours you get out of it,” said the co-author of Koji Alchemy in a recent webinar. “It opens up a whole world of possibilities.”
Recognising its value to Asian cuisine, Koichi Higuchi, a bioscientist, decided to apply koji fermentation to coffee.
Having spoken to a friend about kopi luwak, a fermentation technique that relies on the enzymes in the digestive tract of civet cats, Higuichi wondered whether he could find a cleaner, more ethical approach.
To do so, he sprinkled koji spores on green beans and left them to ferment over a few days. When he came to check on them, Higuchi found that the amino acid in the beans had increased by three times after fermentation.
He also noticed that the beans had far less grease on their compared to regular beans, another indication that koji transformed the original composition.
How koji fermentation affects the flavour of coffee
Alongside variety, terroir, and roasting, processing is one of the most influential factors on a coffee’s characteristics.
An experienced producer can use it to unlock certain flavour notes, increase complexity, and enhance or mute qualities such as acidity, body, and mouthfeel.
Such is its importance that some claim it has eclipsed origin, with many consumers now looking more at whether the coffee is washed or natural rather than whether it’s from Colombia or Ethiopia.
This is particularly true of experimental processing techniques, such as carbonic maceration and anaerobic fermentation.
Not only do these coffees regularly fetch the highest prices at auctions, they are increasingly appearing at a competition level. At the 2019 World Barista Championships, no fewer than six of the semi-finalists used a carbonic macerated coffee, for example.
Yet while carbonic maceration creates funky, full-bodied, and fruity characteristics, koji fermentation adds a whole different style of flavour. One of the most notable is the additional sweetness that develops within the beans.
According to Kaapo Paavolainen, the 2021 Finnish Barista Champion who presented a koji-fermented coffee to the judges, this is because koji fermentation exploits the “full potential of the beans”.
“Sugar in beans is responsible for coffee’s inherent sweetness,” he said in a recent Forbes article. “But current [processing] methods extract only about 70% of available sugar.”
As well as tapping into the additional 30% of sugars, koji fermentation can also transform the characteristics of low-quality beans.
In a side-by-side cupping of koji-fermented and unfermented versions of the same beans, the results highlighted considerable differences.
Specifically, the koji-fermented beans were said to be rounder, creamier, and softer with more sweetness.
“The differences are beyond my expectation,” said one of the cuppers. “The regular India’s unpleasant aluminum taste turned to a flavour that reminds me of sesame or BBQ flavour. The regular Mexico’s harshness became rounded and creamy, almost like Swiss Miss.”
How can koji fermentation help coffee farmers?
The transformative effects of koji-fermented coffee go beyond the simple satisfaction of consumers. They could also add value to the beans, which may correspond to higher profits for the farmers.
It is a regular occurrence that the processing method on a coffee farm is dictated by the affluence in its surrounding areas. Natural (or dry) processing is a much cheaper method of processing compared to washed, due to the differing amounts of water needed for each method.
Coffee Talk’s post on “Koji-Fermented Coffee May Bring Sustainable Profits To Impoverished Bean Farmers” takes a closer look at a koji-fermented coffee being presented to judges at the 2021 World Barista Championships in Milan, at the Host coffee exhibition, by Finnish Barista Champion, Kaapo Paavolainen.
They write: “While he did not place in the top six at the competition, he was overjoyed to have introduced the novel method to the world – he had bigger goals than a great cup of coffee in mind. The new method may provide additional opportunities for struggling coffee farms.
“According to Enveritas, 44% of smallholder coffee farmers worldwide live in poverty, while 22% live in extreme poverty.
“Paavolainen’s new invention has the potential to help bean farmers earn more sustainable profits, as he discovered that koji’s unique property can transform ordinary beans into noticeably higher-quality products.”
Without the blessing of being situated in a region where terroir alone makes the coffee stand out and score highly, naturally dictating the price of a coffee, processing methods are an incredibly useful way for coffee producers to raise their SCAA score, making their cops more desirable to the tastes of the modern coffee consumer.
While koji-fermented coffee is still in its nascent stages, the method is already exciting coffee professionals around the world.
Its ability to raise the quality of lower quality beans makes it an interesting option for coffee farmers who have traditionally struggled to improve profit margins. By adding value at origin without the need for expensive equipment, koji fermentation could well be the future of coffee processing.
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