In the global specialty coffee market, experimentally processed coffees are becoming increasingly popular – and for good reason. These coffees can provide a range of unique flavours and sensory experiences for consumers, including profiles which often aren’t possible with more traditional processing methods.

We know that processing methods influence roast profiles, meaning roasters need to tweak some variables in order to get the best results from experimentally processed coffees. But another important question remains – should we also brew these coffees in different ways?

To find out, I spoke with three coffee professionals. Read on to learn more about what they had to say.

You may also like our article on coffee roasting & experimental processing methods.

What is experimental processing?

No matter which processing method is used to process coffee, it will have a huge impact on the final cup profile. For farmers, processing is one of the most important steps in coffee production, and can also add significant value to coffee.

The three most well-known “traditional” processing methods are washed, natural, and honey processing. These methods are used by many producers along the Bean Belt, and result in a variety of different flavours and mouthfeels.

However, in recent years, we have seen more and more producers try a range of different experimental processing techniques – but what exactly are they?

Dan Fellows is a two-time World Coffee in Good Spirits Champion and a UK Barista Champion. He also runs a coffee cocktail-themed YouTube channel.

“Experimental processing methods have a lot of influence over the final flavour profile and characteristics of coffee,” he says. “In many cases, these techniques borrow from other industries, such as wine and gastronomy.

“In doing so, producers can broaden the flavour possibilities of different coffee varieties and species,” he adds.

A large part of creating these flavours is by leveraging the use of fermentation. No matter which processing method is used, fermentation begins as soon as the cherry is picked. However, in recent years, more and more producers have realised that changing the parameters in which fermentation occurs can create a wider range of interesting new flavours.

Sam Corra is the Director of Coffee at ONA Coffee in Sydney, Australia.

“In general, experimental processing is defined by smaller batch sizes and are atypical washed, natural, and honey processes,” he tells me. “For example, anaerobic fermentation is becoming a more standardised method.

“These processing techniques usually focus on changing one variable in order to understand its impact on the coffee, or to enhance a specific aspect of the flavour profile,” he adds. “Experimental processing often involves many different variables, including fermentation time, temperature, and different types of fermentation.”

Different types of experimental coffee processing

Although there are many different kinds of experimental processing methods, some techniques are becoming more prominent in specialty coffee. 

Aerobic and anaerobic fermentation are two of the most popular methods. They are both very similar, but there is one main difference between them – the presence of oxygen.

With aerobic fermentation, the presence of oxygen means the sugars in the coffee beans ferment more slowly. However, when fermentation takes place in an oxygen-free environment (or anaerobically), fermentation can occur more quickly.

With anaerobic fermentation, coffee cherries are usually sealed inside large tanks or barrels to create an oxygen-free environment. Coffees can be fermented for anywhere from 24 to 96 hours – depending on the desired sensory profile.

Some producers are experimenting with a new process called “anaerobic impregnation”, which involves placing fruits or other ingredients into fermentation tanks, which can give a coffee more fruity flavours.

Another prominent method is carbonic maceration. Dan says this was inspired by a similar technique in winemaking, and can often give coffee a more “boozy”, wine-like quality. With carbonic maceration, cherries are placed in sealed containers, before being flushed through with carbon dioxide.

Malic fermentation, meanwhile, is similar to other experimental processing methods, but the key difference is the introduction of malic acid. This is a flavour compound most associated with green apples, and can provide a coffee with a clean, sharp acidity.

One of the newest emerging trends in processing is the use of koji mould as a unique priming agent during fermentation. 

Koji mould is commonly used in the production of sake and miso in order to enhance umami flavours. Koji mould is added to the coffee cherries, which helps complex carbohydrates break down into sugars and dextrins which can be used during fermentation.

Each experimental processing method will have its own unique influence on coffee flavour, ultimately affecting extraction variables.

Elika Liftee is the Director of Education at Onyx Coffee Lab in Bentonville, Arkansas. He is also the 2022 US Brewers Cup Champion. 

“With experimentally processed coffees, you should expect a more prominent mouthfeel and an enhanced, more complex acidity,” he says. “However, over-fermentation can also occur [when these methods are not carried out correctly].

“I think experimental processing methods are beneficial for the specialty coffee industry,” he adds.

Sam, meanwhile, tells me how experimental processing methods can influence coffee quality. 

“With experimentally processed coffees, it can be harder to score them based on clarity, mouthfeel, aftertaste, and balance,” he says. “Because of this, some really high-quality and interesting coffees can sometimes score lower or higher than they should.”

Should you brew these coffees differently?

It’s safe to say that no two coffees are the same, therefore no two cups of coffee will be brewed in exactly the same way. But which factors do we need to take into account when brewing experimentally processed coffees?

Fermentation helps to break down sugars, meaning they can be more easily extracted. As a result of this, the likelihood of overextraction can increase, so we need to take this into consideration with our brewing variables. For example, total brew times should generally be shorter, or we can extract these coffees with water at a lower temperature.

“In general, anaerobic fermented coffee tends to be more soluble, so it will extract at a faster rate than other processing methods,” Elika says. “To reduce the risk of overextraction, I brew experimentally processed coffees with water between 88°C and 93°C (190°F to 200°F).”

Sam explains how lower temperatures can help to enhance certain characteristics when brewing experimentally processed coffees. 

“Lower temperatures throughout the total brew time allow the juicier and brighter aspects of the coffee to shine through,” he says. “Brewing with water which is too hot often leads to more murky, dull, or undesirable flavours dominating the final result. 

“Ultimately, lower temperatures used in the final pours of the brew help to mitigate the extraction of tannins, which can reduce bitterness and dryness,” he adds.

Both Sam and Elika suggest their own recipes for brewing experimentally processed coffees as pour over:

Elika’s recipe (to be used with any brewer)

• 15g of medium-to-fine ground coffee.
• 250ml water at 93°C (200°F).

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1. Pour a 50g bloom and wait for 20 seconds.
2. At 0:20, pour 50g of water.
3. At 0:50, aggressively pour 75g of water.
4. At 1:20, aggressively pour another 75g of water.
5. Total brew time should be between 2:30 and 3:00.

Sam’s V60 recipe (two kettle method)

• 20g of medium-to-fine ground coffee.
• First kettle set at 92°C (197°F).
• Second kettle set at 88°C (190°F).

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1. Pour a 50g bloom and wait for 35 seconds.
2. At 0:35, pour 70g of water from the first kettle.
3. Between 1:00 and 1:10, pour 60g of water from the second kettle.
4. Between 1:25 and 1:40, pour 60g of water from the second kettle.
5. Between 1:45 and 2:10, pour 60g of water from the second kettle.
6. Total brew time should be around no more than 3:00.

Alongside filter coffee, experimentally processed coffees have also become increasingly popular among those making high-quality coffee cocktails – including for the World Coffee in Good Spirits Championship (WCIGS). 

In his winning 2019 WCIGS routine, Dan prepared his beverages using his “Frozen Natural Experiment” cocktail recipe – which uses a coffee processed using a technique called “frozen natural processing”.

“This cocktail recipe includes coffee which has undergone a unique processing technique called the frozen natural method,” he tells me. “Red Pacamara coffee cherries were fully frozen before undergoing natural processing, which helped to increase sweetness, body, and flavour intensity compared to more traditional natural processing.”

In his recipe, Dan adds ice wine (which he says inspired the processing method), blood orange, citrus and floral-flavoured gun, malic acid, and cascara coconut syrup. 

“These ingredients are then shaken over ice and served in a frozen glass on top of a cascara aroma cloud,” he explains.

There’s no doubt that experimental processing techniques are going to remain popular in the coffee industry. In turn, baristas and home brewers need to ensure they are getting the best from these coffees.

“It’s important that we as baristas, bartenders, and consumers, support creativity in processing methods and ensure that the potential for these coffees continues to grow,” Dan concludes.

Enjoyed this? Then read our article on carbonic maceration & biodynamic farming: Experimental coffee processing in Panama.

Photo credits: Dan Fellows

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