When it comes to coffee production, processing is one of the most important steps. As well as being key for preserving quality, processing can also enhance certain flavours, or create new ones altogether.

In recent years, we have seen more and more producers try a range of different experimental processing techniques. These include aerobic and anaerobic fermentation, carbonic maceration, and lactic fermentation.

So as these processing techniques become more prominent in the specialty coffee sector, which trends can we expect to see in the coming years? And how might they evolve? To find out, I spoke with two coffee professionals at green coffee importer Mercon Specialty and coffee consultancy Brewed Behavior.

You may also like our article exploring naturals, pulped naturals, & honeys.

Understanding traditional processing methods

According to the Coffee Quality Institute: “post-harvest processing has the potential to not only preserve quality and food safety, but to create flavours and add significant value [to coffee]”. 

Ultimately, this means processing is one of the most important aspects of coffee production, so it needs to be carried out carefully and in a controlled manner – especially when it comes to experimental techniques.

But in order for us to understand more about experimental processing, we first need to look at traditional processing methods.

Washed processing

Popular in some parts of Africa (including Rwanda and Kenya) and Central America, as well as Colombia, this processing method involves removing all of the flesh and mucilage from the beans before they are dried.

After harvesting, the cherries are depulped to remove the skin and flesh, and are then typically submerged in water so the remaining mucilage can be washed off. Once the mucilage is removed, the green coffee is then left to dry on raised beds or patios.

Washed coffees are generally brighter and cleaner-tasting than other processing methods. This is because the removal of the cherry allows the inherent, natural characteristics of the coffee to shine through.

Natural coffees

Natural processing is common in regions and countries where access to water is limited, such as Yemen, Ethiopia, and Brazil. 

After the ripe cherries are picked and sorted, they are dried fully intact on patios (including the skin, flesh, and mucilage) and are regularly turned to ensure mould does not form. Once the cherries have reached the optimal moisture level (between 10% and 12%), the beans are removed.

Most natural processed coffees have more fruity flavours and are usually sweeter and fuller-bodied. They can sometimes have some wine-like characteristics and heavier mouthfeels.

Honey processing

Honey processing is popular in some Central American countries, especially Costa Rica, where it was first developed.

Scott McMartin is the Director of Coffee at Mercon Specialty.

“Honey processing became prominent in Costa Rica because of government-enforced water usage regulations [introduced after an earthquake struck the country in 2008],” he explains. 

“Essentially, traditional washed processing was outlawed,” he adds. “This forced farmers to experiment more with processing techniques [which used less water].”

Honey processing involves leaving a particular amount of flesh and mucilage on the coffee as it dries. A similar technique to this is pulped natural processing, which was first developed in Brazil. This method is when the fruit and skin are removed, but the mucilage is left intact as the coffee dries. Ultimately, this helps to reduce the drying time.

“Like many of the newer processing methods, the honey process is a hybrid of traditional and innovative techniques,” Scott tells me.

There are different types of honey processing – including black, yellow, red, pink, and white. These colours are indicative of how much flesh and mucilage is left on the coffee as it dries. 

For instance, black honey processing is similar to natural processed coffee, as the majority of skin, fruit, and mucilage are left on the coffee while it dries. Comparatively, white honey processed coffee is more similar to washed coffee, as most of the flesh and mucilage is removed, giving it an altogether lighter cup profile.

Because of the range of honey processing techniques, these coffees can have a variety of flavours. Generally speaking, Scott says honey processed coffees have more sweet flavours, such as red fruit characteristics, as well as more of an enhanced body and mouthfeel.

What are experimental processing techniques?

“Experimental processing methods are not new to specialty coffee,” Scott says. “In many producing countries, tradition and innovation have coexisted in coffee processing to improve quality and sustainability efforts.”

However, over the past several years, there has been a noticeable increase in the number of more experimental processing methods. These are usually more complex than traditional techniques, as they involve more variables and require farmers to exert more control over the process.

Tracy Allen is the CEO of coffee consultancy Brewed Behavior, which is part of the Mercon organisation. He explains how experimental processing methods can sometimes add more value to coffee.

“These processing methods aim to create different sensory experiences, which can increase both demand and value,” he says.

Aerobic and anaerobic fermentation

Fermentation begins occurring as soon as the coffee cherry is picked, but in recent years, producers have started to leverage it to generate a wider range of exciting new flavours.

Today, aerobic and anaerobic fermentation are two of the most popular labels applied to experimentally fermented coffee lots. There is one main difference between the two – the presence of oxygen.

With aerobic fermentation, oxygen is included in the process, which means the sugars in the coffee beans ferment more quickly. However, when fermentation takes place in an oxygen-free environment (such as in large sealed tanks or plastic barrels) fermentation occurs at a slower rate.

“Natural anaerobic fermentation has become more popular in recent years,” Scott says. “[With this method], the coffees are fermented in hermetically-sealed containers.” 

This process is carried out using whole cherries, which can be fermented for up to 96 hours in some cases. Anaerobic washed coffees, meanwhile, are fermented with no skin, flesh, or mucilage left on the beans.

Because there is no exposure to oxygen with anaerobic fermentation, microorganisms break down the sugars at a much slower rate – which allows for more complex flavours to develop.

“Both honey and anaerobic processing methods result in fruitier-tasting coffees, as well as enhancing the body more, especially when compared to washed processing,” Tracy explains.

Carbonic maceration

Carbonic maceration is similar to anaerobic fermentation, however, this process involves flushing the tanks with carbon dioxide.

“Anaerobic and carbonic macerated coffees are produced in a similar way to techniques used for French Beaujolais wines,” Scott tells me. “Fermentation is carried out in closed or sealed vessels, [which are then flushed with carbon dioxide to remove any oxygen].”

“The resulting flavours are very fruity and wine-like,” Scott adds. Other common tasting notes include herbal and floral flavours, as well as more tropical fruit or boozy notes.

Other experimental processing methods

Alongside these methods, lactic fermentation has become more popular in recent years. This technique is similar to those used for other fermented food products (such as sourdough bread and sauerkraut).

With lactic fermented coffee, producers add lactic acid cultures to the coffee as it ferments. As with anaerobic fermentation, lactic washed and lactic natural coffees are becoming more popular.

This type of fermentation often results in a creamier mouthfeel, with more and yoghurt-like flavours.

Alongside this, we also have something called “double fermentation”, which is a method where coffee is fermented twice, as the name implies. Popular in Kenya, the cherries are depulped and then fermented in water for up to 24 hours. The mucilage is removed, before the second ferment takes place for up to a further 24 hours.

Double fermentation typically results in brighter and cleaner tasting coffees, as higher levels of mucilage are removed.

Are experimental processing methods viable for most producers?

Naturally, there are more risks associated with higher levels of fermentation in coffee processing. This is because if variables aren’t tightly controlled, it can be easy to over-ferment coffees – resulting in undesirable off-flavours.

“When carried out incorrectly, experimental processing can produce flavours of sour milk, rotten fruit, or low-quality wine,” Scott explains.

As a result of this, many farmers who carry out experimental processing do so in smaller batches, which allows for more control. However, this level of quality control can be costly, especially for smallholders.

“Experimental processing techniques can be labour intensive and are therefore more expensive to carry out,” Scott says.

“[From my experience], most producers have a good understanding of their costs of production before they try out riskier – yet potentially more economically-rewarding – processing techniques,” Tracy tells me.

Scott agrees, saying: “Farmers I have spoken with are enthusiastic about any kind of innovation that could potentially result in a higher price for their coffee.

“If producing anaerobic fermented or honey processed coffees, for instance, can provide farmers with more market access then they should consider doing so,” he adds. “However, they shouldn’t stop using more traditional processing methods, too.”

Furthermore, producers should recognise that while this market is growing, it is still relatively small and niche.

“Many of Mercon’s suppliers are interested in innovative processing methods, but only for a small percentage of their overall offerings,” Scott explains. In view of this, producers who are interested in carrying out more fermentation in coffee processing should test in small batches first.

Tracy emphasises that communication between farmers and roasters is essential when purchasing experimentally processed coffees.

“Most roasters sell these coffees as limited editions or more exclusive lots,” he tells me. “Once a farmer tests out a new processing method, they need to commit to doing it for a few years,” he says. “They need to communicate the technique clearly to the roaster so they know how to market and sell the coffee.”

Considering consumer preferences

With more experimental processing techniques resulting in different sensory profiles than washed and natural coffees, how could consumers’ preferences change over the years?

“More traditional coffee drinkers may not appreciate the different flavours as much as other consumers as they may believe they detract from the innate characteristics of the coffee,” Scott says. 

Tracy says more fermented flavour profiles may be an acquired taste for some consumers.

“I use the Scotch whiskey analogy; some of them can be an acquired taste,” he tells me. “It’s the same message for roasters – make sure you understand the target demographic for these coffees before purchasing them.”

However, within the specialty coffee market, there’s no doubt that experimental processing has been gathering speed for some time.

“They result in excitement from baristas and customers alike, although their appeal is somewhat limited,” says Scott. “More traditional consumers may not want a cup of coffee with wine-like qualities or tropical fruit flavours.

“However, for those who do enjoy these coffees, they are usually willing to pay higher prices,” he adds.

While experimental processing only makes up a small percentage of coffee production, there’s no denying that it’s becoming more popular in the specialty coffee sector.

“Experimentally processed coffees can be truly special and bring out new, undiscovered characteristics of coffees,” Scott concludes.

For producers looking to scale in this regard, there is clearly opportunity to do so. However, they should first make sure they have the appropriate resources to experiment, start in small batches, and remember that while this market is growing, it is still small for the time being.

Enjoyed this? Then read our article on coffee roasting & experimental processing methods.

Photo credits: Mercon Coffee Group

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