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Experimental Fermentation: A Guide

Portafilter (Experimental Fermentation)

Table of Contents

Is coffee fermented? That’s a new one. When you think fermentation, you think wine or any other alcohol, but it turns out coffee and its fermentation process has a charm of its own. Welcome to the experimental fermentation tour, where we will debunk myths surrounding flavours and tell you more about how those coffee aromas are produced.

Experimental fermentation has been increasingly popular in the specialty coffee sector recently. We’ve all heard the terms “anaerobic,” “extended,” or even “carbonic maceration” used to describe the more controlled approach favoured by progressive producers. And, based on how often they appear, it would seem that these techniques are gaining popularity.

Let’s take a closer look at the fermentation process and the different types of fermentation for coffee to understand how it operates in the world of coffee aromas. Coffee fermentation normally lasts 12 to 24 hours, which is a very short period compared to other processes like beer, cheese, wine, etc., making time incredibly significant in this equation. 

Understanding experimental fermentation through this blog will give you theoretical knowledge about what goes behind coffee brewing, but getting trained by experts at our Nationally Accredited Barista Training Institute will equip you with all the expertise that you need to flourish as a Barista. 


What Is The Fermentation Process?

Fermentation is a process where various microorganisms break down organic substances. Like yeast and bacteria, these microorganisms convert one organic substance into simpler ones. The sugars and other substances in the fruit and mucilage are digested by these bacteria, resulting in the production of by-products like ethanol and other acids. These waste products are then taken up by the seed’s cellular structure. As a result, we have green coffee beans that are somewhat fermented and are prepared for roasting and brewing. This is where you picture those little guys getting a makeover to produce the best-smelling coffee (Haile and Kang). 


There are two types of coffee fermentation: Aerobic fermentation and anaerobic fermentation. 

Aerobic Fermentation: 

This occurs when there is access to oxygen. Natural coffees are a good illustration of the aerobic fermentation process.

On patios or drying beds, cherries are spread out after being plucked from the trees. The temperature and the length of time it takes for the cherries to dry affect how much fermentation takes place.

They will dry out much more quickly in the sun, which will result in less fermentation and less impact on the coffee.

They will dry out more slowly if you keep them in the shade, giving the bacteria more time to break down the organic substances. The flavour will be more potent the longer the fermentation takes, intensifying the coffee’s aroma.

Anaerobic fermentation: 

This process occurs in an atmosphere devoid of oxygen. This oxygen-free environment could be a water or carbon-dioxide-filled stainless steel tank. Carbonic maceration is a prime illustration of one of these processing techniques.

The entire coffee fruit is placed into a sealed stainless steel tank after harvest. The tank is pumped with carbon dioxide. Oxygen is driven out of the tank through a valve at the top since it is lighter than CO2. The bacteria then get to work and eats away at the sugars to create the product we want.


Why Do We Need To Ferment Coffee? 

As part of post-harvest processing, fermentation has historically been used in coffee to separate the coffee fruit from the seed so it can be roasted and brewed into a beverage.

The use of fermentation as a preparation method was likely accompanied by the development and manipulation of flavours through the fermentation process. 

Although there has been countless research on the subject, there are still very few easily accessible primary sources that include empirical evidence about links between fermentation and taste or quality.

You have now moved from the room where your tour guide has finished explaining the types of fermentation. You are getting more curious about what happens after the fermentation process, and we’re getting very close to it, so buckle up.

According to the experts, all coffee is fermented and the flavours it produces can be varied, even including non-coffee aromas like bubblegum, berry, and passion fruit. Conversely, a producer can create clean coffee, devoid of any flavour, depending on the type of fermentation they use.


Experimental Fermentation Techniques

Experimental Fermentation

The carbonic maceration has gained prominence since Sasa Sestic’s WBC victory in Seattle in 2015 because it was an experimental processing technique he employed to produce his winning coffee.

Although still considered experimental, this process has widespread use as a technique for harvesting and processing wine grapes and offers several chances to break through barriers and extract more flavour from the coffee.

In essence, carbonic maceration is the process of fermenting coffee in an atmosphere that is high in carbon dioxide. Coffee cherries are harvested and then placed into airtight stainless steel barrels.

The coffee cherries are then put inside the barrel, and CO2 is blasted into it, allowing the coffee cherries to break down various amounts of pectin. Typically, this procedure results in bright, wine-like coffees with pronounced red fruit overtones.


Dry Fermentation Flavour Profiles 

Separating the bean from the coffee cherry while maintaining the coffee’s profitability are the dual objectives of coffee processing for growers.

Even if the coffee was selected when it was ripe and the harvest went well, poor coffee processing might result in flaws that lower the coffee’s value. 

Selecting the best processing method can be a significant choice for a coffee grower or producer because some processes involve more time, money, and natural resources than others.

Natural processing, also referred to as the dry process, is the most traditional method of preparing coffee and includes the following steps: 

The coffee cherries are plucked from the coffee trees and spread out to dry in the sun in thin layers.

Depending on the farm or location, the drying stations might vary slightly; some utilise brick patios, while others use special elevated beds that allow air to flow around the cherries, resulting in more even drying.

The cherries are periodically turned to prevent rotting, mould growth or excess fermentation. The skin and dried fruit meat are mechanically removed from the cherries once they have dried completely, and the green coffee is then stored and “rested” before being exported.

Barista opinions are divided when it comes to the coffee aroma produced, as some love them and others hate them. The natural process certainly adds fruity and sweet flavours to the coffee, regardless of which region they are produced in. 

Blueberry, strawberry, tropical fruits, and honey are popular flavour notes for naturally processed coffee, but there can also be wild, fermented flavours and alcohol-like undertones. When compared to washed coffees, natural coffees are frequently said to have flavours similar to red wine. 

The natural processed coffees can be helpful for roasteries and baristas in exhibiting coffee flavour nuances, but they can also be unappealing for drinkers who don’t enjoy fermented and wild flavours in the cup.


Wet Fermentation Flavour Profiles 

Water is used in the wet process to de-skin and de-pulp the coffee cherry fruit. The faulty beans are then separated from the coffee cherries by submerging them in enormous water tanks (those with less density which float on top). 

The mucilage layer, which is still sticky and delicious, is still covering the bean. Mucilage is not soluble in water. The beans need to ferment to get rid of it (usually in large tanks with water). Enzymes found in coffee cherries break down the mucilage during fermentation, turning the sugars into acids, fumes, and/or alcohol.

The other popular method for processing coffee is known as the wet processing method. 

Before the coffee beans are dried, all fruit flesh is mechanically removed from them during the washing process. Removal of the fruit flesh is done with a machine called a de-pulper. 

The remaining fruit meat is removed by fermentation after the beans have been de-pulped and placed in a water tank. Depending on the environment and altitude, fermentation takes a certain period. Fermentation will proceed more quickly in hotter climates and vice versa.

The cup’s bright and acidic flavours result from the washing process. Because of the higher complexity and clearer cup characteristics, roasters and baristas frequently praise it. When compared to natural coffees, many say washed coffees have flavours similar to white wine. 

Many farmers and producers opt for this method as the washed procedure reduces the likelihood of flaws and is a more stable method of processing coffee. This technique uses more water, however, which raises the cost of production.


What Is the Value Add Of Experimental Fermentation?

At auctions, experimental coffees frequently bring quite high bids. A prototype microlot of coffee was sold by Panama-based coffee firm Ninety Plus in 2019 for a then-record-breaking $4,535 per pound.

One of the many factors driving this trend is the onset of exotic varieties like Mocca, Geisha, Sudan Rume and Yellow Bourbon. 

These new varieties arrived from Panama and Ethiopia, carrying distinct characteristics that producers used to distinguish them from other varieties on the international market. However, they also noticed that the washed process wasn’t the only way to unlock their fullest potential, so they decided to experiment further. 

Columbian producers began experimenting with their processing methods by drawing influence from techniques popular in Costa Rica and Brazil, and their goal was to highlight specific qualities in the coffee. 

When word got around, many pros, including competition baristas, started going to Colombia in a quest for unique lots that would make them stand out and impress the judges. Eventually, this contributed to the globalisation of Colombia’s experimental processed coffees.


Unravelling the Flavour Conundrum:

Adding extra flavours to coffee beans raises concerns about altering the natural essence, potentially misleading coffee graders.

Some argue that enhancing beans with non-native flavours unfairly influences coffee competition. This critique stems from the lack of transparency in flavouring practices within the coffee industry.

This lack of transparency can damage a coffee producer’s credibility. It’s crucial to address this issue for a more trustworthy coffee trade.

The exploration of experimental fermentation in coffee is primarily undertaken by financially robust large-scale farmers. These farms are categorised into three tiers based on their practices.

Level one: Growers focus on implementing top-tier agricultural practices to ensure the highest quality coffee.

Level two: Farmers employ traditional methods and produce high-quality washed coffee.

Level three: These farms delve into anaerobic fermentation, honey, natural, or carbonic maceration.

About 70% of coffee farmers operate at the first level, while the remaining 30% fall into the second and third tiers.

Medium to large farms, known as ‘estate farms,’ often adopt advanced processing techniques like anaerobic fermentation and carbonic maceration. These methods require substantial resources and infrastructure.

Companies pursue these approaches due to their ability to invest in trials, employ specialists, and standardise procedures. The question of fairness in mass production begs consideration.


Final Thoughts

We encourage you to reflect on this while savouring a cup of flavoured coffee.

Congratulations on completing this international coffee aroma tour, where we’ve delved into processes, benefits, and the potential future of this trend. We trust you’ve gained some useful insights!

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