Traditionally, coffee is processed using washed, natural, and honey processing methods. In certain Asian countries, other processing methods such as wet hulling (or Giling Basah) and Monsoon Malabar have also been in use for decades.

However, now more than ever, there are a seemingly endless number of ways to process coffee. From anaerobic fermentation to carbonic maceration, these experimental processing methods help to enhance coffee flavour – and even create new ones.

Flavoured and infused coffees are also part of this conversation. This is when producers purposefully introduce other ingredients when processing coffee so that the green beans absorb or take on certain sensory attributes.

But as part of the broader discussion on how these coffees can fit into the specialty sector, it’s important that we differentiate between the two. To learn more, I spoke with three coffee professionals. Read on to find out what they had to say.

You may also like our article on issues with infused coffees.

What are flavoured and infused coffees?

It can be difficult to define exactly what infused and flavoured coffees are. There are no formal industry terms for these coffees, so definitions are largely down to personal opinions.

Nanelle Newbom is the Sales West representative at Equal Exchange. She is also a roaster and green buyer at Torque Coffees. She explains what she considers to be a flavoured coffee.

“It’s when you add other separate ingredients to either green or roasted coffee in order to create a new flavour,” she says. “In my opinion, altering the flavour of a coffee by adding yeast strains or controlling the levels of oxygen during processing doesn’t create a flavoured coffee.

“However, I think adding certain ingredients, such as cinnamon sticks, to the fermentation tank during processing results in a flavoured coffee,” she adds.

Another important point that Nanelle raises is whether the ingredients added are natural or artificial.

“For many coffee professionals, the difference between adding natural and artificial ingredients is more of a sliding scale,” she explains. “The answer is not always so clear because what we define as a flavoured coffee can differ greatly, it doesn’t necessarily make a conflicting opinion incorrect.”

Comparisons to infused coffees

Saša Šestić is the founder of ONA Coffee and Project Origin. He is also the 2015 World Barista Champion and an expert in fermentation processing techniques – particularly carbonic maceration. In 2021, Saša wrote two articles for Perfect Daily Grind: one about issues with infused coffees and the other answering common questions about infused coffees.

Saša explains his definition of an infused coffee. 

“It’s the addition of particular ingredients and flavourings,” he tells me. “These could be essential oils, spices, acids, herbs, fruits, vegetables, or any other ingredient. We must be able to detect the presence of these ingredients or flavourings in the final beverage.

“Infusion can happen during fermentation, when the coffee is drying on patios, during storage, or in barrels,” he adds. “Coffee can be infused when it’s green, or after roasting, or even once the coffee is ground.”

Nanelle, meanwhile, believes that infused coffees are mainly created when you add ingredients or flavourings during processing.

What about barrel aged coffee?

Barrel aged coffee is another form of flavoured coffee. This involves placing green coffee inside of barrels which have been used to manufacture beverages such as whiskey, wine, rum, and other alcoholic drinks.

Steven Restrepo is the Head of Coffee at Café de Colita. He explains the purpose of barrel ageing coffee.

“You want the green coffee to absorb some of the flavours of the barrel,” he tells me.

As green coffee is highly susceptible to a number of environmental conditions, the wood of the barrel will influence the flavours in the coffee. Typically, this practice results in fruity, fermented and more “funky” flavour notes which are often indicative of the product which was previously made in the barrel.

“I roasted a few batches of barrel aged coffee a few years ago,” Nanelle says. “People were really interested in it, and it sold very well as both retail bags and by the cup.

“Personally, I prefer smelling this coffee over drinking it, but it certainly generated a lot of interest,” she adds.

So what are the differences between infused and flavoured coffees?

The definitions of both flavoured and infused coffees largely rely on the opinions of coffee professionals. In turn, gaining a clear understanding of the key differences between the two is difficult.

“Flavoured coffees are those which have been modulated using fermentation and the addition of yeasts and bacteria, as well as by adding artificial flavours,” Steven says. 

While Saša believes that infusion can happen at any stage of the supply chain, Steven thinks otherwise.

“Infused coffees are ones which have been infused with artificial flavours after roasting,” he explains.

Nanelle, meanwhile, provides another perspective.

“There are many coffees which include added supplements like CBD or collagen, for example,” she tells me. “These are often referred to as ‘infused’ coffees, but whether they are infused after roasting to avoid denaturing or otherwise destroying the additional supplement is relatively unknown.”

However, Nanelle further explains that the line between infusing and flavouring coffee can be blurred.

“For example, you can add yeast used for beer production into the fermentation tank, which I consider to be controlling the fermentation process, but not infusing the coffee,” she says. “But, I would consider adding hops during processing to result in infused coffee.

“People can also add different fruits, which blurs the line even further,” she adds. “Fruit is fermentable and produces different sugars which yeast strains feed on, but fruit also imparts its own flavours, so I would say it results in infused coffees.”

It’s clear that there are many challenges when it comes to defining the difference between infused and flavoured coffees. However, Saša expects that this will change in the future.

“I anticipate that as we learn more about the complexities of infused and flavoured coffees, the definitions will change and evolve,” he says.

Are these coffees beneficial to the specialty sector?

There is certainly an argument that infused and flavoured coffees can cause a number of issues, especially when it comes to a lack of transparency.

Nanelle says that ultimately, it comes down to whether or not the addition of flavour adds value.

“Any flavour or infusion added once the coffee reaches its export destination takes away value from producers,” she says. “It removes all the intrinsic value of terroir, farming best practices, and processing.

“Instead, it adds value for roasters by removing it from producers,” she adds.

Steven, meanwhile, says infused and flavoured coffees allow producers, traders, and roasters to offer a new kind of product.

“You can enhance flavour profiles without adding any ingredient to the roasted coffee,” he explains. “Our clients ask for personalised, unique products, so why not support farmers to achieve this? 

“As long as there is demand for these types of coffee, we will create them,” he adds.

Is there a market for these coffees?

Although opinions and preferences on flavoured and infused coffees are divided among industry professionals, Steven says that there is clearly a market for these types of coffees.

“What started our journey into fermentation processing techniques was our clients in China asking us to look into whisky-infused coffees,” he tells me.

After initial success, Steven explains he experimented with adding different ingredients.

“We used apple, orange, strawberry, chocolate, chewing gum, and lemon,” he adds. “But our best-selling infused and flavoured coffees are passion fruit and cinnamon.”

In addition to these coffees, Steven believes there is significant demand for extended fermentation processing techniques.

“Prolonged, controlled, or newer fermentation processing methods are all the rage in specialty coffee – demand is high and continues to increase,” he says. “China, South Korea, Japan, and Saudi Arabia are some of the leading markets for these coffees.”

Nanelle agrees, saying that demand from roasters and consumers alike is growing.

“Some of these coffees are more targeted towards the end customer, while some are geared more towards roasters,” she explains. “Even small or relatively newer roasters want to drive innovation and want to differentiate themselves.

“This puts producers in a strong position to market a newly expanding range of products – potentially at a higher price, too,” she adds.

Transparency is key

Many coffee professionals are in agreement that in order to obtain the most value from these coffees, there needs to be complete transparency about how they are flavoured or infused.

“For instance, if a roaster uses additives to flavour or infuse the coffee, then there needs to be open communication about this process so that no value is stripped from producers,” Nanelle explains.

Steven agrees, saying: “In my experience, some people aren’t transparent enough about their flavoured or infused coffees.

“We are open to sharing our techniques because it takes years to learn how to do it successfully – and even longer to master them.”

However, he emphasises that complete transparency about flavouring and infusion processes would be beneficial to the coffee sector.

“People who don’t fully understand the work that goes into these procedures – and thereby the uniqueness of these coffees – can often be quite negative about them,” he says. “But it’s a labour of love – you can’t create these coffees just to make money.”

While the coffee industry could certainly benefit from outlining a clear definition for both “infused” and “flavoured” coffees, it’s also evident that we need to understand more about both to assess their future in the coffee sector.

“Establishing clear industry standards is helpful, so as to not defame or devalue these coffees,” Nanelle concludes. “Moreover, we can increase people’s awareness of the coffees they are buying, selling, and consuming.”

Enjoyed this? Then read our article on answering some common questions about infused coffees.

Photo credits: Steven Restrepo

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However, as with any newly emerging coffee processing technique, farmers need to take great care when manipulating fermentation to process coffee. By tightly controlling a range of variables, producers can create some truly wonderful flavours in their coffees and increase final cup scores.

But how can farmers do this in a way which balances success and profitability? To find out, I spoke with four industry experts to understand more about the process. Read on for more of their insight on fermentation and coffee flavour and quality.

You may also like our article on how to ensure consistency in coffee fermentation & processing.

What is fermentation?

Despite its recent growth in popularity in the specialty coffee sector, fermentation has long been a part of coffee production. 

All coffee undergoes some level of fermentation. As soon as cherries are harvested, the sugars and acids contained within the mucilage of the coffee fruit (a sticky, translucent substance which surrounds the seeds) begin to break down. This is largely where the sweetness in coffee derives from.

With washed coffee processing, farmers soak depulped cherries in water for several hours to remove any remaining flesh and mucilage. This usually results in a cleaner-tasting and brighter flavour profile, and can highlight more of the coffee’s acidity.

However, over the past few years, there has been an increasing focus on controlling fermentation during processing, as well as using selected microbes to facilitate fermentation. These methods can have a number of benefits, which include enhancing flavours and preserving them for longer. 

When we talk about fermentation, however, we must differentiate between the two main ways by which it takes place. These are anaerobic and aerobic fermentation – which are different due to the presence or absence of oxygen.

When including selected yeasts in coffee processing, the presence or absence of oxygen triggers various reactions, namely the growth or breakdown of a number of substrates. These substrates produce various chemical and volatile compounds, such as acids and alcohol.

In general, anaerobic fermentation is most common, whether the cherries are in sealed or open tanks. With open tanks, generally speaking, only the surface is exposed to oxygen, which means anaerobic fermentation occurs further down the tank. This allows the sugars to break down over a longer period of time, creating sweeter and more complex flavours.

In theory, the longer the duration of fermentation is, the more intense the flavours in the coffee will be. This is because more flavour compounds are created and transferred into the coffee beans over longer periods. However, it’s important that this process is controlled to facilitate the transfer of desirable flavours.

In order to carry out fermentation successfully, farmers can add selected microorganisms (which include yeasts and bacteria) to better facilitate fermentation. One of the most commonly used yeasts in the coffee industry is Saccharomyces cerevisiae, which is also widely used to make bread, wine, and beer. 

However, in recent years, many coffee farmers have started to branch out and use different microorganisms, which can result in a number of different sensory profiles.

Camille Duez is the Coffee and Cocoa Fermentation Global Technical Support specialist at Lalcafé, a company which specialises in the development, production, and marketing of yeasts and bacteria.

“We develop and produce yeasts which are known to result in desirable flavour profiles in coffee,” she says. “Many of the flavours you perceive in fermented coffee are a result of the strain of yeast used in the process,” she explains. 

How can yeast inoculation affect coffee flavour and quality?

Although it’s often said that fermentation can help to enhance coffee quality and flavour, producers need to understand more about how the process works in order to carry it out successfully.

Dr. Renaud Boulanger is the coordinator of the Sensory Quality of Fresh and Processed Products department at the Mixt Research Unit at CIRAD, a French agronomic research institute.

“During fermentation, the breakdown of sugars and acids by the yeast produces aromatic and volatile compounds,” he says. “These compounds are then secreted into the water (also known as the fermentative medium) and are absorbed by the green coffee beans.”

Renaud explains that there are two ways this can happen.

“One way is through passive transfer,” he says. “Because of the difference in compound concentration between the water and the green coffee, the aromatic compounds move from the most concentrated area to the least concentrated.

“Active transfer, meanwhile, is when specific proteins allow the green coffee to absorb the aromatic compounds,” he adds.

But understanding which aromatic compounds are transferred from the yeast to green coffee beans is also equally important.

In a 2020 study entitled Transfer kinetics of labelled aroma compounds from liquid media into coffee beans during simulated wet processing conditions, the transfer of three compounds from yeast to green coffee was measured. 

The study analysed four different coffee samples, all of which had various amounts of pulp attached, including depulped cherries with no mucilage and parchment, as well as depulped cherries with only parchment.

The three compounds measured in the study were butanal, 2-phenylethanol, and isoamyl acetate. 

“We chose these compounds because they often result in more herbaceous, floral, and fruity flavours in coffee,” Renaud tells me. 

Specifically, butanal is responsible for apple, chocolate, and bread-like flavours in coffee, while the presence of 2-phenylethanol creates more floral notes. Isoamyl acetate, meanwhile, can produce more tropical flavour notes, such as banana.

The study found that out of all three compounds, the transfer of 2-phenylethanol was by far the highest at all levels of pulp attachment. However, all compounds produced by yeasts can transfer to green coffee, albeit at different rates and concentrations.

How can producers control the transfer of flavour?

In essence, the 2020 study indicates that using different yeasts during fermentation can exacerbate and heighten different flavours in coffee. This means producers can select different yeasts dependent on the sensory profile they want to create for a specific coffee.

Lalcafé produces six different yeast strains, which have different fermentative properties that in turn enhance a variety of flavour compounds in coffee. Ultimately, this means farmers can create a more diverse range of flavour profiles.

Jean Faleiros is the owner of Fazenda El Dorado in Alta Mogiana, Brazil. He tells me how he selects certain strains of yeast to create specific flavours in his coffee.

“If I want to create a more fruity flavour profile, with notes of red fruits, I use the Lalcafé Intenso yeast strain,” he says. “If I want to produce a more exotic sensory profile, I use the Lalcafé Oro strain. 

“For a more clean and bright coffee, I use the Lalcafé BSC yeast strain,” he adds, explaining that this Lalcafé strain helps to break down the mucilage on coffee cherries more quickly.

With regards to improving coffee quality, lactic acid bacteria are becoming more commonly used by producers to result in cleaner and brighter coffees, sometimes used alongside yeasts. 

“When using yeast, the body, flavours, sweetness, and complexity of a coffee can increase,” Camille explains. “When you also add lactic acid bacteria, such as Lalcafé Bactifresh product, you can also enhance the brightness and clarity of a coffee.”

Jean tells me: “In my experience, controlled fermentation using yeasts helped to improve the quality of my coffee, as well as creating flavour profiles that were previously impossible to produce without using inoculation.”

Ultimately, controlling the transfer of flavour during fermentation comes down to which types of flavours the farmer is looking to produce in a coffee. 

This is especially beneficial for producers as they can create more unique sensory experiences for a range of different markets – helping to differentiate their product and potentially meaning they can receive a higher price per pound for each lot.

“I know which flavour profile each of my customers prefers,” Jean says. “Each market has its own preferences, and using yeast helps me to create more specific and repeatable flavour profiles.”

However, it is important to note that many other variables will also influence coffee flavour and quality – such as coffee variety, altitude, and the nutrient content of the soil, for example. This means producers need to also keep these factors in mind when carrying out fermentation.

Moreover, as yeasts are living microorganisms, producers need to be mindful when using them.

“Yeasts are living single-celled microorganisms,” Camille says. “Essentially, this means it’s not easy to control everything during the fermentation process. 

“There are also a number of other factors which affect the final cup profile, including terroir, climatic conditions (such as temperature), cherry ripeness, and the quality of water used to grow and process coffee,” she adds.

Other considerations

Alongside influencing coffee quality and flavour, producers also need to take into account a number of other factors when using yeasts during fermentation.

“When carrying out anaerobic fermentation, for example, we need to control temperature, pressure, pH, and several other variables,” Jean says.

Furthermore, many producers also focus on the total fermentation time.

In theory, the longer the fermentation time, the more aromatic and volatile compounds will be absorbed by the green coffee.

In the Transfer kinetics of labelled aroma compounds from liquid media into coffee beans during simulated wet processing conditions study, the concentration of the 2-phenylethanol compound increased throughout fermentation when using Lalcafé’s Oro, Cima, and Intenso yeast strains.

However, the concentration of other compounds, namely isoamyl acetate, peaked at 24 hours and then began to steadily decline past this point during fermentation – meaning controlling total fermentation time has a significant effect on flavour.

Other processes also take place during fermentation, such as germination. This results in the degradation of certain flavour compounds, or even a reverse transfer of them. There has to be a balance – which is why fermentation duration is so key.

As well as fermentation time, the amount of pulp retained on the coffee cherries is also important to consider.

The results of the study also found that green coffee containing parchment (a paper-like skin covering the beans) absorbed less aromatic compounds created by the yeast. This is because parchment can act as a molecular filter, meaning producers may need to take this into account when fermenting their coffee.

With the exception of wet hull processing, parchment is kept on the coffee beans as they are processed. Removing the parchment could prove to unveil a range of new flavour profiles – but producers should be mindful that this could impact the roasting process, too.

Roasting fermented coffees

While producers certainly need to understand how fermentation affects coffee quality and flavour, roasters also have to know so they can optimise their roast profiles.

Pedro and João Foster are the co-owners of Fuzz Cafés in Rio de Janeiro. They have purchased coffee from Jean for some time.

“We have been roasting the Abacaxi ‘pineapple’ coffee for around three years now,” says Pedro.

João tells me how the coffee’s flavour profile has developed over the years.

“In the first harvest year, we tasted pineapple and flavours similar to black pepper,” he explains. “In the second year, there were more lemon notes, as well as pineapple, and the coffee scored 90 points. 

“It can be difficult to maintain such a consistent flavour profile, but it shows how useful it can be to predict flavour profiles,” he adds.

However, certain factors need to be taken into account when roasting fermented coffees.

“Traditional Brazilian fermented green coffees will stay fresh for up to four months, and the more delicate flavours will deteriorate more quickly,” João says. “But we recently roasted robusta, which had been fermented with Lalcafé’s Cima yeast strain, 18 months after harvest and it was still bright and clean-tasting.”

Pedro offers some advice when roasting yeast inoculated coffees. 

“We often roast with a higher air flow, so it’s more similar to convection roasting,” he explains. “This can help to highlight the more subtle fruity and floral flavours.”

There’s no denying the growing popularity of experimentally processed coffee among roasters and baristas in the specialty coffee sector, and it’s likely that demand will continue to increase.

For farmers looking to produce these coffees, investing in the right equipment and resources beforehand is essential – as is being prepared to experiment slowly and work your way up towards processing like this on a larger scale.

And while experimental processing may not be viable for some producers, it’s certainly clear that controlled fermentation can have a number of benefits when it is leveraged effectively.

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

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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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One of the most important steps in coffee production is the primary processing stage. This is because the margin of error is small; one mistake at this juncture can result in a substantial loss of quality.

In the Kenyan coffee sector, primary processing largely takes place at washing stations. Washing stations are found in countries across the entire Bean Belt, but Kenya in particular has many of them, as much of the country’s coffee is washed. 

I spoke with two Kenyan coffee professionals to understand how typical Kenyan washing stations operate, as well as some of the challenges that coffee farmers face when using them. Read on to find out what they said.

You might also like our article on renewing generational interest in Kenyan coffee production.

What is a washing station?

David Gitonga manages a washing station in Kenya. He explains that in the country, these stations are actually often referred to as factories.

“Washing stations are found in all parts of Kenya where coffee is grown,” he says. “Almost all of the coffee that is produced in the country is sent to these factories for wet processing.”

Apart from large estates which typically own wet mills, most coffee is collectively processed at dedicated washing stations.

“However, there are a few individual producers who own pulping machines and therefore do not need to send their coffee to washing stations,” he adds.

Once cherries are delivered to the stations by producers, the first step is to sort them. Most factories have officials who oversee sorting; their role is mainly to ensure that all foreign objects (such as small stones or sticks) are removed from the cherry.

The coffee is then weighed by another official who records the weight of the delivered cherry on a slip. However, at some more modern washing stations, there are digital scales which automatically generate delivery slips.

After weighing, the coffee is then taken to cherry hoppers. This is where coffee from several farms is combined for the first time. After being poured into these giant hoppers, the sorted cherry is transported for pulping.

During peak season, this process can go on for days at a time.

Sarah Wambui is an agribusiness expert and washing station manager based in Kiambu County, Kenya.

“Sometimes you can stay at the factory for two consecutive days,” she says.

After the cherries are pulped, the seeds are then soaked in water to remove the mucilage. At many stations, there are large tanks which are capable of holding the parchment coffee.

However, it is currently illegal in Kenya for buyers to purchase parchment directly from farmers, so many are instead paid for cherry. Individuals are also not allowed to deal directly with farmers, and must instead buy through co-operatives.

This is partly because in Kenya, the farmers’ involvement in the coffee supply chain ends once the cherry is delivered to washing stations. Farmers then have to wait for payment, which happens on an annual basis.

David explains that washing stations determine the dates and times for farmers to deliver cherry to buyers. They typically publish this information on posters or bulletin boards in local shops or places close to these stations.

Considering location and design

Many washing stations in Kenya are built on river banks. This is so they can have easy access to water that is used for washing and pulping the coffee.

However, the topography of the land can make this difficult. To resolve this issue, some washing stations invest in pump systems, building them on the riverbank and running the pump through to large storage tanks.

Sarah emphasises the importance of keeping water nearby when establishing washing stations. 

“If possible, factories should border rivers,” she says. “This way, you don’t have to invest in pumps or large reservoirs, which saves a lot of time and money.”

Washing stations can be designed differently, but they generally function in similar ways. Depending on the level of investment in the station, some of them have more modern infrastructure and machinery. 

In more remote areas, washing stations have more basic equipment, but David tells me that as a general rule, all stations require a pulper, fermentation tanks, and storage facilities.

Typically, the headquarters or head offices of local co-operatives are located at one of the member’s washing stations. 

“Co-operatives and washing stations are separate entities,” David explains. “Even if the head office is in the compound, the station runs independently.”

Operational structure at Kenyan washing stations

In Kenya, washing stations are generally owned by farmer co-operative societies (FCS). Every individual station must also register with the relevant local or regional authority. 

Most co-operative societies operate several stations, which are individually owned by the respective co-operatives. However, co-operative members rarely oversee or manage activity at these stations. 

“The co-operative acts as more of a guide over activity at a washing station,” David explains. “The final decisions still lie with employees at the factory, whereas the decisions made by the co-op can be applied to all stations in every co-op society.”

Most management teams in washing stations include a factory manager, a treasurer, a chairman, a secretary, and support staff. The manager, treasurer, and chairman positions are often re-elected every few years.

The factory manager is responsible for all activity at washing stations and oversees all staff members. As part of quality control, these stations sometimes employ qualified professionals to manage the fermentation stage. This is because maintaining coffee quality at this point in the supply chain is particularly important.

Washing station membership is voluntary. Each member – usually a producer – receives their own membership number in exchange for a small registration fee. They will then be able to process their cherries at a station once they are delivered.

Members are also responsible for electing their leaders. The washing station, meanwhile, is responsible for choosing its own mill agent and marketing agent, who are elected every year.

Addressing challenges in Kenya’s washing stations

In Kenya, many washing stations still use traditional disk pulpers. Although these machines are reliable, they generally have been used for extensive periods of time, meaning they usually require more maintenance than newer pulpers.

Some modern factories are now investing in eco-pulpers which have in-built demucilagers, meaning that the parchment doesn’t require further fermentation. This can reduce processing time, costs, and water usage. 

Once the fermentation stage is complete, the parchment is taken to raised drying beds. All washing stations have their own drying beds, but many are abandoned because of fluctuating coffee prices and recent reduction in volumes of Kenyan coffee production.

Many drying beds are constructed from wood, which means that they are highly susceptible to rot and termite damage. This has led some stations to invest in metal drying beds, which are less vulnerable to weather and pest damage.

Most washing stations in Kenya have “conditioning” bins in large store rooms. These are used to contain parchment after the coffee is moved from the drying beds, so that the coffee’s moisture content is stable before it’s transported to dry mills.

Parchment stores at washing stations are usually also guarded. This is because if parchment is lost or stolen, farmers will not receive money for the cherry they delivered – making them vulnerable while the coffee is stored there.

Some washing stations in the country are in the process of becoming 4C and Fair Trade certified. While this can be a lengthy and costly process, there is potential for farmers to receive higher prices as a result of these certifications.

In recent years, it’s become clearer that more and more washing stations in Kenya are starting to modernise, investing in metal drying beds, newer pulpers, and other key technology.

And despite the challenges that washing stations sometimes face, Sarah tells me that she thinks there is potential for producers to overcome them.

“The future looks bright for Kenya’s washing stations,” she concludes. “With increasing payout rates, the farmers can be optimistic about the future.”

Enjoyed this? Then try our article exploring popular Kenyan coffee varieties.

Photo credits: Peter Gakuo, NICE Coffee

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Around the world, producers use a number of different types of mills for these steps, which vary from washing stations and large commercial mills to micro mills. Micro mills are small-scale operations which are often family or community-owned.

So, how do micro mills operate and what do they mean for coffee-growing communities? To find out more, I spoke with two coffee professionals based in Africa.

You may also like our article on how micro mills can help producers improve their economic independence.

The stages of coffee processing

There are two main types of coffee milling: wet and dry.

Wet milling covers the removal of the seeds from the flesh of the coffee cherry. The flesh includes the outer skin and the pulp, which are removed using a depulper.

Meanwhile, dry milling covers removing the parchment from the beans, after which they are graded and sorted, packaged, and exported.

After coffee is harvested, it is delivered by farmers to wet mills.

For washed coffees, the cherries are pulped and then fermented in vats or tanks. They are then cleaned to remove any mucilage (a sticky, sugary substance which surrounds the seeds), before being pre-graded and dried.

Alternatively, for honey processing, coffee can be sent directly to drying beds or patios after it has been depulped. Once the beans reach the correct moisture level (between 8% to 12.5%, according to guidelines from the International Coffee Organisation), the beans are dry milled. This is when the husk (the dry skin on parchment coffee) is separated from the green coffee. 

Natural processed coffees, meanwhile, undergo no depulping. Instead, the cherries are delivered straight to drying beds or patios where they are left to reach optimal moisture levels. Producers turn the cherries regularly to avoid mould or overfermentation. 

For any processing method, however, coffee must be destoned and hulled. Destoning machines help to remove small stones and other physical contaminants which can be picked up during harvesting. 

Hulling machines remove the parchment, or in the case of honey or natural processing, the dried cherry as well. This results in green coffee which can then be exported and roasted.

The beans are then polished by removing the silverskin: a thin, papery layer which is difficult to fully remove. This is followed by grading, where the beans are separated according to size and density.

How do micro mills work?

Essentially, micro mills are facilities which process coffee for a small number of producers. They are mainly owned by either a single producer or a group of farmers who use similar processing and quality control methods. 

For a group of coffee producers to set up a micro mill, they will usually form a small co-operative and purchase land on which to build the facility. This way, the farmers can collectively have more control over the harvesting, processing, and trade of their coffees. 

The machinery used in micro wet mills has also significantly improved recently. Previously, large and bulky machines were used, whereas now, farmers have more access to smaller, more modern motorised or handheld pulpers. 

This means it’s possible for smallholder producers to process coffee without having to travel as far from the farm, so they can potentially carry out more experimental processing. However, these lots will usually be small. Handheld pulpers are also useful for farmers living in remote rural areas, who may have little to no access to diesel or electricity.

Peterson Kimathi is the quality control manager for Mai Shayi roasters in Nigeria. He tells me why micro mills can sometimes be appealing for individual producers or small co-ops.

“When smallholder producers have access to a micro mill, they don’t have to pay the charges to commercial millers,” he says. “At Mai Shayi, we have a small mill that carries out the hulling, but grading has to be done elsewhere.”

James Ndegwa is the Secretary Manager for one of the largest coffee farmer co-operatives in Kenya.

“Our co-operative is large, with many washing stations,” he says. “Our mill processes the parchment from all 19 members of local washing stations.”

James explains that micro mills are often appealing to co-operatives who own or operate only one washing station.

“They would need a micro mill that could cater to their needs,” he tells me. “That way, the co-op will be able to control all quality control procedures right from wet milling.”

Micro mills also have benefits for farmers who know their customers want high levels of traceability in their coffees. This is because their coffees can be processed separately from coffees sent from other washing stations, keeping them as individual lots.

Conversely, at larger facilities, cherries from co-operatives can often end up being grouped together to be milled and harvested. This can then affect traceability, as it becomes more difficult to identify which lot belongs to which individual producer. 

Criticisms of the model

There’s no denying that with micro mills, smallholder farmers can gain more independence and freedom when it comes to how much control they have over their coffees. By controlling their own production schedules and timelines, smallholder producers can focus more on maintaining or improving coffee quality if they wish to do so.

However, there are criticisms of the model. Firstly, they require a significant investment in equipment as well as needing land to be built on. They may not always necessarily be economically sustainable in the long term, as you’re effectively banking on improved quality control balancing out the cost of establishing the mill itself.

It’s also worth noting that dry mills are notably more difficult and expensive to establish than wet mills. This is because they require more machinery, such as cleaners, destoners, hullers, polishers, and graders.

Milling also has an environmental impact, and at smaller facilities, managing this impact can be a lot more difficult; larger and commercial mills often have access to the supply chain and infrastructure to responsibly dispose of waste.

Wet mills also create coffee wastewater, which is difficult to properly dispose of; if it ends up making its way back into the soil, it can even be detrimental to soil health and affect productivity or quality all over again.

Micro mills can make it much easier to process micro and nano lots separately to larger harvests, as well as testing out experimental processing techniques (which may not be possible at larger mills).

However, this is only relevant for a small percentage of coffee farmers, who serve as an exception to the rule. Furthermore, while smaller and more experimental coffee lots can be profitable, they often don’t provide the same kind of scale as far as income is concerned.

Generally speaking, micro mills do have their appeal, but it is important to note that at scale, the model can become much more difficult and complex. With greater volumes of coffee, it can be easier to simply outsource milling to a commercial operation.

Will micro mills become more common at origin?

By definition, micro mills are designed to be used on a small scale. But could more farmers and co-ops be able to operate their own?

“The cost of buying, installing, maintaining, and eventually upgrading the milling equipment has to be accounted for,” James tells me. “Servicing is important for the smooth operation of the mills.

“You can have various options, such as an in-house engineer or a supplier who can visit at scheduled times.”

Micro dry mills in particular need to be affordable for co-operative and smallholder farmers to operate. In order to maintain coffee quality, micro dry mills must also have grading machinery, which can be costly. This is because grading usually requires skilled labour that might not be available at the mill. 

“Before buying a grading machine, farmers should consider how long it will take for them to recoup their investment,” Peterson tells me. “The farmers will save on transport and milling costs, as well as on time.” 

Peterson points out that through operating their own micro dry mills, farmers would have more access to coffee by products, such as husk. This is usually left at dry mills, but it can be repurposed for a number of other uses.

“After dry milling, we have what is referred to as milling loss,” he says. “This is the percentage of green coffee left after hulling, which is the husk.

“The husks can be reused for various purposes, including fuel, compost, or animal feed. When a farmer has their own mill, this is all left with them.”

Ultimately, micro dry mills are likely to be more suitable for groups of smallholder producers or co-operatives who can justify the capital investment, rather than individual farmers.

Nonetheless, there are still concerns that the model is not sustainable for operating at scale, and it’s worth noting that in many cases, working with the larger mills can have benefits for the farmer.

It ultimately depends on how much capital the farmer or co-operative in question has, and exactly what they are planning to do with their operation in the medium and long term.

Milling equipment, as it is specialist machinery, can be an expensive initial investment. However, by bringing it closer to the farm, producers gain more control over the process. But as much as this might sound positive, it is arguably not a solution for everyone.

Ultimately, micro mills are a complex concept. They might be suited to some producers, and arguably won’t work for many others. Before making any kind of investment in milling equipment, it’s worth looking at the medium and long term plan for your farm, and understanding whether or not it really makes sense for you.

Enjoyed this? Then read our article on centralised vs in-farm coffee mills: what are the differences?

Photo credits: Peter Gakuo

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In recent years, experimental processing methods which leverage the power of fermentation (such as anaerobic fermentation and carbonic maceration) have become increasingly common. However, there is still room for further innovation in coffee processing.

One of the newest emerging trends in processing is using something called “koji mould” as a unique priming agent during the fermentation stage. This new method is commonly referred to as “koji coffee,” “oryzae coffee”, or “koji supernatural processing”.

To understand this process, I spoke with several coffee professionals who helped design it. Read on to learn more about koji mould and its effects on coffee flavour.

You may also like our article on how microorganisms affect fermentation & the sensory profile of coffee.

Koji: Japan’s national mould

Koji (Aspergillus oryzae) has been widely used across southeast Asia for centuries. It’s perhaps most notably used in Japan to make sake, amazake, miso, and other umami products – granting it the title of “Japan’s national mould”.

Kaapo Paavolainen is the founder of One Day Coffee Co. and the 2021 Finnish Barista Champion. Kaapo used a koji processed coffee in his performance at the 2021 World Barista Championships in Milan.

“Koji is an ancient, beneficial fungus which is used to saccharify starches,” he tells me. 

Saccharification is the process by which enzymes turn starches into sugars and dextrins to be used during fermentation. 

When added to certain food and beverage ingredients (including rice, sweet potato, barley, and soybeans) the enzymes in koji mould break down starches, which helps to develop new flavours.

Over the past few decades, the use of koji mould in cooking has become increasingly prominent in western cultures, too. Author of Koji Alchemy and chef Jeremy Umanski opened the delicatessen Larder in Ohio to showcase the new flavours that can be created by using koji mould.

So, if it works so well in the fermentation process for other food and beverage products, what about coffee? 

Christopher Feran is the Director of Coffee for Phoenix Coffee Co. and an independent coffee consultant. He tells me about some of the initial challenges with using koji mould during fermentation.

“It’s difficult to do successfully because there is very little starch available in green coffee for the koji to grow,” he says. “You have to find some way to make the mould stick to the fermentation medium.”

Christopher tells me that to support with this, he reached out to Koichi Higuchi of Higuchi Matsunosuke Shoten. The Osaka company provides koji fermentation starters to manufacturers of traditionally fermented foods.

Christopher requested Koichi’s assistance and expertise for the preliminary koji coffee processing trials. Koji mould was directly applied to the green coffee as part of this. 

The initial results created prominent umami flavours, which aren’t considered desirable to most coffee drinkers. However, when koji spores were applied to the coffee cherries, the results were much more promising. 

After achieving these results, Christopher and Kaapo collaborated with Elias Bayter Montenegro – Head of Processing at El Vergel Estate in Colombia – to develop the first formal koji coffee process.

Fermenting coffee cherries with koji

“Coffee is almost always fermented at origin because you need to extract the seed from the fruit,” Christopher tells me. “Traditionally, this is done using yeast or bacteria – similar to how you would when producing wine or beer.”

When making beer or wine, the grains or grapes produce sugars, which live microorganisms consume. This produces alcohol, as well as carbonating the beverage and creating other compounds which create the flavours we associate with beer and wine.

“Koji mould breaks down larger starches into fermentable sugars, as well as producing amino acids and glutamates,” he continues. “This makes the coffee feel heavier on your tongue and enhances the mouthfeel.

“Koji also produces esters and aldehydes, which increase the fruity aromas in coffee.”

Kaapo explains that koji helps to break down complex sugars into simpler ones, which has great potential for new flavour profiles.

“Around 70% of the sugars in coffee are broken down in other processing methods – from washed to carbonic maceration and anaerobics,” he tells me. “However, koji allows us to use more sugars in the following fermentation stages, so we are able to intensify the flavours in coffee.”

So, how did Kaapo, Christopher, and Elias achieve these results?

Kaapo says: “We first tried it with a Red Bourbon. We created a natural koji fermentation process as outlined in our processing manual and compared it against a classic natural processed coffee of the same variety. 

“We then sent an A-B test to Japan, the US, Netherlands, and Finland and we all cupped the samples blind,” he adds. “The koji processed coffee scored higher, and had more body, more aftertaste, and a better and more refined acidity.”

Elias agrees, saying that “the results were outstanding”. 

He adds that the koji doesn’t necessarily create new flavours, but rather that it enhances the existing complex components of the coffee.

“The main change was in the body,” he says. “The structure of the coffee changed a lot. For example, a soft body became more creamy and well-rounded.”

Following the success of this experiment, El Vergel has added koji to many other different varieties, including Geisha, Bourbon, Caturra, and Java. Elias emphasises that each varietal had promising results, but says that Java in particular responded especially well to koji processing.

What are the implications for producers?

When asking Christopher if koji could provide added value for fermented coffee, he remains cautious.

“Taking an 85-point coffee to 87 points might be compelling for producers who want to receive a premium for their coffee,” he says. “However, coffee farmers producing 82 or 83-point coffees are likely to see less benefit with koji in comparison to other, more intensive improvements (such as selective picking, sorting, and tank cleaning, for instance).”

Elias points out that scaling the koji fermentation process is also a challenge. In Colombia, he says most coffee farmers are more used to traditional processing methods, which result in more traditional flavour profiles. Moreover, consumer demand for koji coffee remains minimal, as it is largely unknown.

Furthermore, he notes that controlling the koji culturing stage can be difficult, as it requires paying close attention to time and temperature.

“However, once you learn how to manage these steps, it’s a simple process that can help to increase scores by one to two points,” he says. “Farmers don’t need a lot of equipment, mainly just a shaded area to store the coffee where they can spread the koji spores.”

Elias adds: “The most difficult part will be changing people’s perceptions about growing koji and using it in fermentation.”

However, Kaapo believes that koji mould has great potential for coffee producers around the world. 

“The reason we created this processing method is because we knew it was possible and we wanted to test it,” he says. “We noticed it is beneficial for coffee producers, which is why we made the information available on an open-source basis in both English and Spanish.”

Making koji more accessible

Whether or not farmers use koji to increase the scores of their coffee or to attain more premium prices, there’s no denying its potential. But that doesn’t mean that there aren’t challenges in adopting these more experimental techniques.

“Cost is going to be the biggest issue,” Christopher says. “It’s expensive to buy the koji spores. The spores we used for Kaapo’s competition coffee cost around US $17 for 30g.

“We were dosing 2g per 1kg of cherry, so 1kg of cherry might yield between 18g to 20g of green coffee.”

However, Christopher explains that El Vergel attempted to create a more affordable method of growing koji spores.

“We were growing what is called rice koji,” he tells me. “You partially cook rice by steaming it.

“You can then disperse the koji spores on the rice and culture more koji mould, which makes these ‘cakes’. You can then pulverise these cakes and disperse them accordingly.”

Christopher says this can significantly increase the amount of koji mould available to producers.

“From 30g of koji starter you can produce about 240kg of rice koji. Ultimately, this could address some barriers in terms of scalability and affordability.

“But we are still making sure that koji fermentation is a fully safe process and that we are selecting the right strain of koji for broader commercial use,” Christopher adds.

“Rice grows in many places along the Bean Belt, so hopefully koji will become a more accessible ingredient for coffee fermentation.”

What might the future hold?

“Koji processing is still so new,” Kaapo says. “No one has really established a new processing method since Saša Šestić pioneered the carbonic maceration method in 2015.

“We’re still experimenting with the method at El Vergel for my 2022 Finnish Barista Championships coffee,” he tells me. “In addition to koji mould, we’re also using a pre-process technique to increase the sugar content for subsequent processing.”

Elias, meanwhile, says that more research is needed to identify the sugars present in the process, as well as experiments with other varieties and processing methods to explore the full potential of koji fermentation.

“There are a lot more things we can do with koji; we are just scratching the surface of this new processing method,” he says.

Christopher, Elias, and Kaapo are all also focusing on how koji cultivation and fermentation can be scaled for commercial use. Christopher, however, underlines the importance of “starting small”.

“It’s a matter of convincing two or three farmers to produce enough koji coffee that it can be exported and served to consumers to start increasing demand,” he says.

For now, he believes koji coffee will be more prevalent in competitions than coffee shops, but Elias hopes that this will help to boost demand in time. 

“When koji coffees start to win competitions, that’s when the word will spread,” Elias concludes.

As of now, the practice of koji fermentation remains prevalent only on a handful of farms in coffee-producing countries. El Vergel currently only sells pre-orders of its koji coffee through Forest Coffee, a Colombian wholesale platform.

There is potential for the demand for koji fermentation to grow over the next few years, but the only way this will happen for sure is if consumers try it. If you happen to come across koji coffee, take the opportunity to try this rare processing method – it might just become your new favourite.

Enjoyed this? Then read our article on how to ensure consistency in coffee fermentation & processing. 

Photo credits: One Day Coffee Co., El Vergel Estate

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Typically, robusta is treated differently to arabica when roasted. This is mainly because the cell structure of robusta beans is more rigid than arabica, so roasters need to take greater care with it.

The same attention to detail should be accounted for during the processing of robusta, especially as it’s estimated that post-harvest activities can be responsible for up to 60% of final coffee quality.

To learn more, I spoke to George Mhlanga from Bioroots and Lisbeth Ankersen from Innova Consult about developing standardised and high-quality processing methods for commodity robusta. Read on to learn more about what they said.

You may also like our article on exploring robusta coffee’s genetic diversity.

Robusta processing: An overview

Processing removes the layers – including the skin, fruit, mucilage, and parchment – which surround the coffee bean. It is a post-harvest activity which is ultimately necessary for the coffee to be roasted and subsequently ground and brewed.

George Mhlanga is a microbiologist and agronomist. He is also the owner of Bioroots ApS in Copenhagen, Denmark. He tells me that Bioroots has developed a unique processing method to improve the cup quality of robusta.

“There are several processing techniques used for robusta, which depend on the region and factors such as water availability, infrastructure, weather, moisture measurement, and storage,” he tells me.

While robusta originated in Africa, today most of it is grown in Vietnam, which accounts for some 40% of global robusta exports. Brazil is also well known for its robusta production, as are India and Indonesia.

Most robusta produced globally is processed naturally, as this technique is typically more affordable for smallholder farmers. 

With natural processing, the harvested coffee cherries are laid out to dry on patios or raised beds – with the skin, fruit, and mucilage left intact. This adds to overall sweetness and fruit flavours as the sugars are able to fully develop.

Alternative processing methods for robusta include the wet hulling process (also known as “giling basah”), which is frequently used in Indonesia.

This is where the coffee is washed and ferments to remove the pulp and skin (similar to washed processing), but is only dried to around 20% to 24% moisture. At this point, while the beans are still soft, they are hulled using a special machine, before then being dried to 10% to 13%.

Lisbeth Ankersen is the Director of InnovaConsult ApS, which specialises in examining and describing flavours in food – including coffee. She describes some of the common tasting notes found in robusta.

“The flavour notes typically found in robusta coffee are woody, earthy, and sour,” she says. “However, it’s not the presence of individual compounds that creates the overall flavour of coffee, but the combination of several compounds.”

Broadly speaking, these flavour notes are not considered to be desirable in coffee. However, as there is less interest in robusta quality worldwide, producers often don’t account for the difference in general flavour profile throughout post-harvest.

How does processing influence coffee quality?

Lisbeth takes me through the numerous phases of processing, all of which have an impact on final cup quality.

“There are different steps we go through with post-harvest for coffee beans, and they all affect quality and flavour,” she says. “We start with harvesting, sorting, pulping, and fermenting, before moving onto drying, storing, milling (hulling and polishing), and grading.”

At each stage, best practices and standards should be followed in order to produce coffee of the highest quality – much like with roasting and brewing. But as robusta is generally perceived to be of lower quality, it commonly receives less care throughout these stages.

George tells me that because robusta is inherently different to arabica, it should therefore be treated differently throughout processing.

“Robusta’s genetic composition means that it has higher levels of caffeine, chlorogenic acids, and other chemical compounds than arabica, all of which contribute to a more bitter taste.”

Processing and post-harvest should therefore account for these differences, and attempt to balance this inherent bitterness with sweetness and acidity. 

Ultimately, when robusta is grown and processed to higher standards, farmers can produce fine robusta: an industry term used to define high-quality robusta. 

To be considered “fine”, robusta must be free of primary defects and display characteristics which are unique to its origin. 

“Handpicking robusta ensures only the ripe beans are picked, resulting in higher cup quality,” George explains. 

“Sorting also affects the flavour of the beans,” Lisbeth adds. “Various defects can generate different off-notes in the coffee.”

In recognition of the rising quality of fine robusta, the Coffee Quality Institute and Uganda Coffee Development Authority have co-developed guidance for producing it. This is known as the Fine Robusta Standards and Protocols, which includes a list of common defects found in robusta coffee. 

To be classified as fine robusta, beans should have no primary defects, including fungus or mould damage. 

The coffee beans should also have no more than five secondary defects, which include broken or cut beans, small levels of insect damage, and floaters (a sign of unripe coffee beans).

George points out that any coffee can suffer from low quality when there is lack of consistency and attention to detail with processing, irrespective of its species. “Poor processing can also affect the quality of arabica coffee, just as it often has done with robusta.”

However, by the same token, Lisbeth notes that in the future, processing could allow robusta producers to potentially improve the cup quality of their crop.

“Processing has the ability to change the flavour profile of ordinary robusta, and increase the consumer’s overall enjoyment of it.”

Improving robusta processing methods

Washed processing is a common technique used to remove all skin, fruit, and mucilage from beans. It produces a cleaner tasting coffee; for arabica, it often yields a brighter cup profile with more noticeable acidity.

However, washed processing is more difficult to carry out for robusta. This is because robusta beans have thicker layers of mucilage than arabica, which increases the risk of overfermentation. Robusta mucilage is also stickier than arabica mucilage.

To avoid overfermentation, producers usually have to wash their robusta for more than 72 hours. In addition, the lower the elevation the robusta is grown at, the greater the risk that it will overferment. 

Too much fermentation can lead to off-flavours, such as strong notes of alcohol or medicine, or even cause mould and bad bacteria to develop. 

So, how can producers improve robusta quality while minimising this risk?

“For more than five years, Bioroots has worked to develop a process that can help to achieve a higher-quality robusta coffee,” George says. He adds that this process is easy to use at scale, and works for farms of all sizes.

Lisbeth starts by talking about how the proprietary Bioroots processing method uses fermentation.

“The first step of fermentation, which occurs as soon as the cherry is picked, is responsible for generating many of the 900 different flavour compounds found in coffee,” she tells me. “We have then added a second step for the Bioroots process.

“In this second step, the specific enzymes of the fermentation microorganisms digest some of the carbohydrates in coffee and transform them into desirable flavour molecules.”

George explains how this changes the flavour profile of the coffee.

“The process produces robusta coffee with flavour profiles that can be similar to that of arabica coffee, with notes of chocolate and bell pepper,” George says. “These results have been noted through several cupping tests by established institutions in different countries, which have also provided sensory profiles for Bioroots robusta.

“The process is also designed to work in batches, which makes quality control easier,” he adds. “This means it is more cost-effective. It is also natural, and does not use chemicals.”

However, improving robusta quality doesn’t just end at processing – it carries on to roasting and brewing.

“Since developing this processing method, we have worked with several roasters to create a roast profile that takes into account the lower levels of acidity in robusta,” George explains. “The profile has been tailored to fit the Bioroots robusta’s requirements, and seeks to preserve the acidity, leading to a brighter, fresher cup.

“Using the process, we can definitely create two different robusta coffees with unique and distinctive flavours, and it is possible that we will create a third,” he adds. “We’re now ready to use it at scale with partners, and in my opinion, I think these coffees could change people’s perception of robusta being inherently inferior to arabica.”

How can this benefit farmers?

“The use of robusta coffee beans is limited in the wider coffee industry,” George says. “Only 20% of all robusta produced is used in blends with arabica, and even then, the purpose of these blends is to mainly dilute the cost of arabica.”

George adds that because robusta relies on cross-pollination to breed, it is incredibly genetically diverse, but this can be detrimental if not monitored carefully.

“The challenge with robusta hybrids and cultivars is that it’s difficult to trace genetic histories of certain hybrid varieties,” he says. “This makes it difficult to grow a variety of recognised quality.”

However, as robusta comprises 30 to 40% of all coffee exports, improving its quality more broadly could have major implications for the wider coffee sector.

“Robusta can be grown in some areas where arabica cannot grow,” Lisbeth explains. “The possibility of high-quality robusta creates new possibilities for producers seeking higher prices.”

Robusta is generally more resilient than arabica, meaning it can grow at lower altitudes. It is also more resistant to a wider variety of pests and diseases. Furthermore, with recent research indicating that major coffee-growing regions could become much less productive by 2050 due to climate change, the need for more hardy coffee varieties and species is becoming more necessary.

“The market for robusta coffee beans is limited, but it could be increased,” George says. “If we were to do this, we would have a plentiful supply, because robusta plants have higher yields.”

It’s estimated that 1ha of robusta plants can produce around 6,000kg of coffee – significantly more than even the most productive arabica varieties. It’s yields like these that ultimately led to Brazilian robusta exports increasing by a staggering 59.5% between 2018 and 2019. If the market scales, farmers could see their margins and income change dramatically.

But it’s not just producers that could benefit from improving robusta quality. Lisbeth notes that in time, continued focus on robusta quality could lead to more consumers regularly drinking it.

“In our consumer test, we found that a sample of the Bioroots double fermented robusta coffee was preferred over a sample of arabica coffee,” Lisbeth says. “However, a combination of the two was ultimately preferred by most.”

Although growing, harvesting, and processing can help to improve robusta quality, to maintain these improvements, we need consistency down the supply chain.

George concludes: “In order to change the perceptions of robusta as a lower quality coffee, more effort must be made to educate and inform baristas about the potential flavour profiles of fine robusta coffee.”

Enjoyed this? Then read our article on roasting robusta coffee.

Photo credits: George Mhlanga

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Ethiopia, Kenya, Uganda, Rwanda, Burundi, and Tanzania are all established origins in the coffee industry, and between them they hold a significant share of the global market. But how is their coffee processed?

As the two main established methods in the global coffee sector, washed and natural coffee processing are both present in the region. But which is more popular? And what about experimental coffee processing? Are there any barriers to that, and is it growing in popularity here, as it is in Latin America?

To learn more, I spoke to four coffee insiders based in the region. They told me more about processing in East Africa, and how stakeholders can drive a focus on experimentation. Read on to learn more.

You might also like our article on the origins of coffee in Africa.

Processing techniques used in East Africa

In East Africa, prominent coffee producing countries include Ethiopia, Kenya, Tanzania, Uganda, Rwanda, and Burundi. Let’s take a look at each in turn.

Ethiopia

Ethiopia is the birthplace of coffee. Today, it is the fifth-largest coffee producer in the world by volume, and is renowned among specialty coffee lovers for its thousands of wild heirloom varieties.

Historically, Ethiopian coffee processing was driven by co-operatives. Groups of two or more co-operatives formed unions, which then assisted with processing, as well as hulling, polishing, and packaging.

However, in recent years, with legislative changes to the Ethiopian Coffee Exchange (ECX), some coffee farmers have started to move away from this model. As vertical integration has been permitted since 2017, some producers have opted to process their coffee individually.

Private washing stations are also becoming increasingly popular, representing another transition away from the co-operative union model.

Ethiopia is known for both washed and natural coffees, but the ratio and popularity of certain processing methods varies depending on the region in question. For instance, around 60% of Sidamo coffee is washed. 

At a nationwide level, however, research indicates that some 29% of Ethiopian coffee is washed, while almost all of the remaining is natural processed. Washed Ethiopian coffees are known for their delicate floral and citrus notes, while natural coffees from the coffee are “funkier”, with a sweeter, bolder flavour.

Experimental processing methods are becoming increasingly popular with Ethiopian farmers, too. Some of these have come to be used in tandem with new or emerging varieties, which often start as heirloom cultivars before becoming more prominent.

The highly acclaimed Wush Wush, for example, has been subjected to various fermentation techniques in an attempt to amplify its distinctive fruity characteristics.

Rwanda

Almost all coffee grown in Rwanda is arabica, and most of that is washed. Coffee cherries sourced from multiple Rwandan farmers are first sorted in water, before being pulped.

After pulping, the cherries are graded, putting them in one of three categories: A1, A2, or Grade C. Later, the first two categories then undergo waterless fermentation. In very rare instances, some Rwandan coffee is honey processed for special markets.

There is also still some natural processing in the country, but the scale is low. For some farmers, higher yields are favoured over quality.

Tanzania

William Peters is a Tanzanian coffee processing and trading expert. He says that around 90% of Tanzanian arabica is washed; internally, it is described as “mild arabica”. However, he adds that a small percentage is subjected to natural processing, too. 

“After harvesting, the coffee is spread on drying areas [for natural processing],” he says. “This process is similar to the robusta one. Arabica processed this way is referred to as hard arabica.”

Most of the robusta coffee produced in this region is natural processed in this way. Although William believes this is slowly changing, he says that without adequate knowledge and access to the market, the washing and fermentation of robusta remains uncommon.

Organically grown coffee is also being grown in Tanzania, but it still undergoes conventional processing methods.

Uganda

Rogers Sserubombwe is a coffee professional at Kibinge Coffee in Uganda. Here, he says, robusta hardly ever undergoes washed processing, much like in Tanzania.

“After harvesting, the coffee is dried on dry surfaces or tarpaulins and later delivered to the hulling factory after drying,” he explains. “There are other organisations that use the wet process, but mainly it’s just natural sun drying.”

Joe Hage-Chahine is the Managing Director of Ugacof (Sucafina Uganda). He says that while robusta isn’t washed, Uganda is also known for its fully washed arabica.

He explains: “Though the region produces incredible naturals, fully washed is the emblematic taste consumers tend to expect from East Africa, with its acidity, complexity, and floral tones. 

“It’s the processing method that best highlights the full potential of East African coffees.”

However, he says that some individual producers who own processing stations are trying new methods. Some of these methods include the natural processing of arabicas and honey processing, among others. 

Furthermore, there are some experimenting with fermentation techniques. Methods such as carbonic maceration and anaerobic fermentation are gaining interest in the region.

Kenya

In Kenya, it is rare to find co-operatives or smallholder farmers using anything other than washed processing. One of the potential reasons for this is that farmers are bound to the methods dictated by co-operatives, who handle all processing responsibilities. 

Farmers deliver their coffee to the co-operatives, and in many cases, that is the end of their involvement. Because washed processing is seen as a compromise between cost efficiency and quality, it’s widely used.

Burundi

Coffee in Burundi is predominantly washed (somewhere between 70 and 80%). It is grown between 1,250 and 2,000 m.a.s.l., and is largely of the Bourbon variety.

Altogether, this means coffee in Burundi is renowned for its brightness and florality, with berry notes. There is however, also some natural processed coffee in the country, which has a jammier and creamier flavour. 

Co-operatives & processing in East Africa

While this is not a blanket rule, co-operatives in East Africa often handle processing for smallholder farmers at a central location. For example, William says that almost all processing in Tanzania is undertaken at what are known as CPUs (central pulping units). 

These are owned by the co-operatives, and they generally handle all the pulping, fermentation, and washing of coffee supplied by individual farmers.

“These small producers do not know who will buy their coffee from the auction,” William says. “They do not have control of it, so they just take it to the co-operatives, and that’s it. 

“They just want their coffee processed in whichever way, so that they can get paid.”

However, this can at times be a barrier for experimentation with processing in the region. As CPUs in places like Tanzania deal with large volumes of coffee from massive areas and dozens of different farmers, experimenting is not always an easy prospect.

For starters, it requires knowledge of new processing methods as well as the infrastructure and space to carry them out, which is not always readily available.

Barriers for developments in processing

According to William, the Tanzanian Coffee Board has been conducting education aimed at improving and scaling coffee production, rather than exploring new or alternative coffee processing methods.

The board sees coffee production as the more urgent issue, as many farmers have already uprooted their coffee plants. Yields and production numbers are the priority.

“The farmers got disappointed by the low prices paid for their coffee and most of them eventually cut down their trees for other cash crops such as bananas,” William explains. 

“It is really difficult to convince the same farmers to now come and invest in other processes. To them, that is an added cost that is too much.”

For large farms, he says, it is a similar story. With an established market, there is already demand for coffee processed using a certain technique or method. 

It’s a similar story in Burundi, William says. Co-operatives are keen to sell processed coffee as quickly as possible, as farmers often operate at a subsistence level.

“The farmers are not willing to wait forever before getting paid,” he explains. “With some of these processing methods, the coffee takes too long to be ready for sale. Farmers are not willing to wait that long.”

Rogers agrees that funding is one of the major obstacles to improving processing or using alternative techniques. Often, co-operatives have more pressing concerns.

“In our case, we are a growing co-operative, and the aim is to maintain that growth,” he adds. “The funds are a major factor.”

However, this broad trend is by no means true for every farm in the region. In Kenya, for instance, there are large farms starting to invest in new methods like carbonic maceration and aerobic/anaerobic fermentation, as are some producers in Ethiopia.

The owners and directors of these estates explain that they are able to invest in these methods because there is already a market for the coffee. They say it is expensive to establish the facilities, but once set up, this coffee attracts higher prices. 

This makes it difficult for anyone but the larger farms to break in, and even then, there’s no guarantee of a sale at a price premium.

Joe adds: “[In Uganda], we’ve experimented with honey and yeast-fermented robusta recently. The coffees tasted great, but it is often difficult for roasters to justify the high cost associated with these niche products. 

“Experimental production methods add more value when linked to yield or productivity increases, especially in the case of robusta, since it is mostly a volume driven product.”

Is change important? And how can it be achieved?

Joe adds that it is important to have a variety of processing methods, as this gives farmers and cooperatives more flexibility.

He says: “Consumer trends shift constantly, and variety in processing methods allows producers to respond to this demand and remain resilient to market changes and evolution, both at the individual and country level.”

If done at the correct scale and with the right procedures in place, he says, shifting to other processing methods can be a sensible move. 

He explains: “Processing techniques and technologies can be expensive without adding a lot of value or fetching the premium that is expected from these processes.

“The key is to implement best practices diligently, at every step of the chain, in order to capture and preserve the most value from each bean. Only then would it become sustainably profitable.”

Meanwhile, Rogers believes that with more time and access to new information, new methods will be put into action at a co-operative level.

“After we have established ourselves, we shall invest in new methods that will also help with increasing quality,” he says.

All of our interviewees believe that East African coffee farmers would benefit from improving their coffee processing, whether that means a focus on quality in the processing itself, or a full switch to a new method. 

However, these practices should be sustainable and sensible when implemented, given that any kind of change will require a lot of investment.

It remains to be seen how long it will take for producers in East Africa to innovate in processing on a wider scale. However, most of the professionals I spoke to are optimistic that with proper education, the right investment plans, and improving market access, it’s certainly possible.

Enjoyed this? Then try our article on ensuring consistency in coffee fermentation and processing.

Photo credits: Peter Gakuo

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However, it can also be argued that continued creativity and innovation from Panamanian producers has contributed to the country’s profile as a coffee producer. Over the years, Panama has repeatedly broken auction price records for its coffees. The country currently holds the record for the most expensive coffee per pound, sold at the Best of Panama (BOP) auction in 2020.

Today, not just Geisha, but other varieties grown in Panama are receiving high cup scores and fetching astronomically high prices. This is partially because producers in the country are tweaking their processing methods and trying new and unusual techniques to improve the quality of their coffees. 

To learn more about experimental processing methods in Panama, I spoke with four producers from the country. Read on to find out what they said.  

You might also like our guide to specialty coffee in Panama.

Carbonic maceration and biodynamic farms 

Jamison Savage is a producer at Savage Coffees, which includes Finca Deborah and Morgan Estate. “We acquire cherries from other producers and process those cherries to our standards, as well as producing award-winning coffees through Savage Coffees,” he tells me. “It’s a collaboration with several producers here in both Boquete and Volcan.”

Jamison explains that the farm is recognised, among other things, for two main techniques: carbonic maceration and biodynamic agriculture.

Carbonic maceration is similar to anaerobic fermentation, but has one fundamental difference: the use of carbon dioxide. CO2 is flushed into sealed, airtight tanks full of cherries to remove residual oxygen. The microorganisms in the tank break down the sugars in the cherries more slowly, resulting in coffees with complex flavours that are often described as bright and winey.

Jamison tells me that the goal is to enhance certain attributes of a coffee’s flavour and “guide” the fermentation towards that. 

Jamison tells me that Saša Šestić, who won the 2015 Barista Championship using a carbonic macerated Sudan Rume, shared an overview of the method with him in the same year.

He adds: “From there, I just expanded that process into many other alternative processes.

“In 2016, I began experimenting with carbonic maceration. I was the first to do it with a Geisha successfully and to continue down that road, which was the spark that ignited the alternative processing that we see so widely.”

He explains that this level of control enables him to guide the flavours more precisely. “I have a complete recipe book on how to dial in certain flavours, acidity, or brightness.

“This means I can tailor coffees to some of my clients’ specific needs. If a competitor wants a very bright coffee, a highly aromatic coffee, or a sweeter coffee, for instance, I can magnify or enhance those specific characteristics.”

Jamison also notes that biodynamic agriculture has been key in developing these experimental, high-scoring lots.

“Biodynamics focuses on a holistic approach to agronomy,” he tells me. “This is where the applications or the preparations [for the crop] are completely natural. It is organic in the sense that no industrial products are used. No pesticides are ever applied. It’s a way to embrace the ecology and get back to nature on the production side.

Currently, Finca Deborah produces both washed and natural carbonic macerated biodynamic coffees. “Those are the only two processes being done at this time because of the size of the area.

“There is a difference in the flavour profile. It’s more layered and more complex, with elevated acidity, more aromatics… it changes just about everything.”

Using the “juices” from coffee cherries in anaerobic tanks

Wilford Lamastus is a third-generation producer at Lamastus Family Estates. The farm has grown coffee since 1918, and has broken auction price records at BOP on several different occasions. This includes two in a row in 2018 and 2019, which secured prices of US $803/lb and US $1,029/lb respectively.

Wilford explains that the farm uses many different processing methods. Alongside washed, natural, and honey processing, it also uses anaerobic fermentation and a method known as anaerobic slow dry (ASD). ASD processed coffee is fermented in a tank for 120 hours, and then dried on raised, shaded beds.

For this harvest season, he adds that they have started experimenting by adding the juices generated by coffee cherries to fermentation tanks, which modifies the flavour of the coffee.

“We put the cherries in the ASD tank. These fruits generate bright red juices, which usually remain at the bottom of the tank. In that lower part, the flavour of the fruits is more concentrated.

“We extract those juices and pour them into other tanks that have just arrived from the field. This changes the flavor of the coffee. We have done it with washed coffees, natural, honey, all of them.”

Wilford tells me that having three farms in close proximity with unique climatic conditions allows him to experiment with this method. 

“For example, we can use the coffee cherry juices from Elida Estate and place them in tanks with El Burro Estate coffees or vice versa,” he says. “There you get other microorganisms, bacteria, and yeasts typical of each area and use them on the other coffees.

“We label those lots with the word ‘dose’ – for instance, an Elida Geisha Natural Torre ASD Dose.”

He says that while it doesn’t dramatically alter the flavour, it does add something subtle: a characteristic sweetness unlike both natural and anaerobic coffees. 

Drying coffee in dark rooms 

Ratibor Hartmann is a producer from Finca Hartmann, a third-generation family farm based in Renacimiento. He is also a producer at Mi Finquita and Guarumo Coffee Farm, both of which are renowned for producing innovative, high-quality coffees for specific customers.

Ratibor says that, for him, the most serious “problem” in coffee production around the world is drying. To this end, he says he has been studying new coffee drying techniques.

“Most people have the idea that coffee drying has to be at high temperatures. That is false,” he says. “In fact, high temperatures are generally loaded with humidity.”

To this end, Ratibor explains that he doesn’t use a rotary dryer or dry coffee on beds; instead, he says he dries his coffee in dark rooms. 

“I dry in total darkness,” he tells me. “I do not dry with sunlight, or at high temperatures. I do this because there is only one bacteria that can grow in the dark; all the others die due to the lack of light. This gives me full control over the bacteria, meaning that I can eliminate those that I don’t want in the coffee.

“We put the coffee inside drawers in the room. Then we extract the relative humidity with a large dehumidifier, and circulate the air into and out of the room using fans.”

Ratibor says that this method also minimises how much the coffee is moved and disrupted. It has been successful: the Geisha Black Jaguar Natural Limited from Guarumo Coffee Farm was dried using this method, and went on to win best natural Geisha coffee at BOP 2020.

“We have experimented with this for almost ten years, and have mastered the technique in the last three,” Ratibor says. “Experience, trial, and error are what have led us on the right path.

“For me, the most important thing is that it becomes an alternative, especially for small producers, who do not have space for traditional drying or the budget to buy [rotary dryers].”

Temperature control in fermentation tanks

Jean-Paul Langenstein is the General Manager at Carmen Estate in Volcan, Chiriquí. He tells me that the most important part of conducting an experiment is being able to replicate it. 

He tells me that when using anaerobic fermentation, it is essential to have a stable temperature, or else the coffee will develop undesirable “off-flavours”. Therefore, at Carmen Estate, Jean-Paul says they have been looking for alternatives to give them more control.

“You could have a temperature at the edge of the tank that is different than at the center, for example,” he tells me. “You have to figure out how to keep it even. That’s why this year we brought in some beer tanks, and the company we bought them from adapted them to our specifications.

“We now do slow fermentation, where we control the temperature and apply the correct drying method for this type of processing.”

Jean Paul tells me that when coffee is harvested, it immediately starts to ferment as the sugars in the cherry break down. This is called lactic fermentation. He says: “We aim to maintain a temperature range of 15°C to 20°C within the tanks. This results in sweeter lactic fermentation.”

However, he notes that there is no exact guide for this, because fermentation doesn’t work the same for different coffees. “The needs are different, the varieties are different, and the coffee will not act the same,” he says. 

By controlling the temperature, he says you can achieve a cleaner taste in a washed coffee, for example, but with a little more sweetness and a more complex flavour thanks to the slow fermentation.

“It has worked enormously for us without using external agents, such as yeasts, enzymes, bacteria, fungi, or acids, among others.

“At Carmen Estate, we would like to maintain that what you are drinking is the expression of coffee itself. This is why we try to keep on making coffee that shows its true potential by just keeping control of the temperature.” 

Processing is one of the most important aspects of coffee production, and has an effect on the flavour, aroma, and cup quality of a coffee. This is why many producers seek to improve their processing in search of higher-scoring coffees and more complex flavour profiles.

The wider specialty coffee industry is driven by innovation and competition. For these producers in Panama, experimentation helps them not just to add more value to their crop, but also supports the country’s position as a high-quality origin.

Enjoyed this? Then try our coffee tasting exercises to improve your palate.

Photo credits: Carmen Estate, Lamastus Family Estates, Finca Hartmann, Savage Coffees

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Whenever fermentation is involved, producers and scientists experiment with various microorganisms, and examine how their unique relationship with the process can affect a coffee’s sensory profile and cup score.

To further examine how microorganisms affect fermentation and a coffee’s sensory profile, I spoke with a producer, a Q grader, a professor, and a roaster, all involved with the Nucoffee Artisans project in Brazil. I asked them about how tailoring and pairing unique microorganisms can affect coffee fermentation and improve cup profile. Read on to find out what they said.

You may also like How Does Fermentation Affect Coffee Flavour Development?

Fermentation, microorganisms, and controlled fermentation

Coffee fermentation is a naturally occurring process that starts to occur as soon as a coffee cherry is picked. It occurs as the water, sugar, and starches within the cherry begin to naturally break down into acids and alcohols. 

Fermentation typically occurs in one of two main ways: aerobic (an oxygen-rich environment) or anaerobic (an environment with no oxygen). Both fermentation styles can be controlled in different ways.

Whenever fermentation occurs, microorganisms are responsible for converting these sugars and starches into acids and alcohols. There are thousands of microorganisms that have been identified in fermentation, but some of the most common include yeasts (such as saccharomyces cerevisiae), bacteria (such as lactobacillus), and fungi. 

Each individual microorganism affects fermentation (and therefore coffee flavour) in an acutely different way. While we understand that some (in particular saccharomyces cerevisiae and lactobacillus) affect the smell, colour, and pH of a coffee, the effects that other microorganisms have on fermentation are still being studied.

Rosane Schwan is a professor at Universidade Federal de Lavras in Lavras, Minas Gerais. She tells me more about how microorganisms affect fermentation. 

“The main microbial groups of coffee include bacteria, yeast, and filamentous fungi,” Rosane says. “Particular microbial genera/species vary among coffee-producing areas, probably due to environmental conditions, coffee varieties, and processing methods. [They consequently affect] cup quality [differently].

“Processing methods will vary from farm to farm, depending on climate conditions, fruit maturation, capital availability, machinery, and technology.”

More recently, controlled fermentation has been adopted across the coffee sector to offer increased security for producers who experiment with coffee processing. By monitoring and controlling variables such as temperature and time, producers can more effectively manage the flavours of their coffee, and subsequently manipulate its sensory profile. 

Furthermore, it’s important to note that uncontrolled fermentation is still not fully understood, and could (in worst case scenarios) end up being potentially harmful to the end consumer.

Natural fermentation and starter cultures

In comparison to beverage sectors where fermentation has been used for thousands of years (such as beer and wine), fermentation in coffee is still in a relatively early stage of understanding.

However, we know for certain that fermentation can occur both naturally, without external input from the producer, or through the deliberate use of “starter cultures”.

Natural fermentation relies on the microorganisms that are already present in and around a coffee cherry to break down the sugars and starches within. Using starter cultures, however, is like adding a new “ingredient” that kickstarts and guides fermentation in a certain way.

Rosane explains that each starter culture is unique. As a result, they can lead to a variety of final outcomes in terms of the flavour profile of a coffee. “The production of specific [flavour] compounds is due to culture starters’ different fermentation pathways during the complex fermentation process.”

She says that while natural fermentation can often be unpredictable and have an unusual impact on cup profile, “the Nucoffee Artisans [project] has selected culture starters that enhance coffee quality”. 

“Our research at UFLA proposed technological alternatives for greater control over fermentation. This involves a standardised process that guarantees the production of novel coffee flavours and [fosters the development of] desirable sensory profiles.

“In general, microbial performance was improved by the use of anaerobic conditions in closed batches. It also helped by inhibiting [the presence of] undesirable fungi and bacteria.”

Microorganisms and fermentation

The Nucoffee Artisans project has been the product of a development partnership between Syngenta-Nucoffee, UFLA, and Rosane. It has studied controlled fermentation and its relationship with a variety of microorganisms.

By isolating selected microorganisms, the project set out to “transform” the chemistry of coffee fermentation and generate new flavour and aroma precursors.

Jorge Fernando Naimeg, from Cerrado Mineiro, Minas Gerais, was one of the producers involved in the project. He says: “[The project] uses isolated yeasts from the coffee itself that are purified and multiplied.”

Producers then use these microorganisms in controlled fermentation. They carefully monitor temperature, pH, and time to improve consistency.

Jorge adds that this project also studies how different microorganisms react with different coffee varieties. He describes the results as “interesting”.

“[Even across] different varieties, altitudes, and processes, we all had similar sensory profiles.” Effectively, by controlling fermentation with the chosen microorganisms, producers were able to make their sensory profiles more consistent. 

Results have been tested for four years across major Brazilian growing regions, and have delivered the same flavour profile year after year at each farm. The idea is that when a green coffee buyer or roaster partners with a producer using these processes, they can be guaranteed the same level of quality on a regular basis, without seasonal fluctuation.

He adds that this project also supported producers to “trust” the technologies and research behind fermentation through its demonstrated results.

Finally, he notes that a well-communicated, thorough fermentation protocol gave producers a list of instructions to follow throughout the fermentation process. This, he says, helped them to understand and feel more confident about their results.

Changes in flavour

With more than 20 years of research in different microorganisms and fermentation methods, Nucoffee Artisans experts studied more than 3,000 different microorganisms with a focus on how they influenced fermentation and coffee flavour. In 2020 alone, the project passed on 383 microorganism kits to 323 producers (each enough to produce approximately 20 bags).

Jorge says the project allowed producers to isolate microorganisms which were beneficial for coffee fermentation. “This new innovative technology was able to reach the producer at an affordable cost,” he tells me. “It was relatively simple, and opened a new range of possibilities for us producers.”

This new range of possibilities is perhaps best explored in the unusual flavour profiles that these new fermentation techniques produce.

Brazil is the largest producer of coffee in the world. The vast majority of coffee grown in the country is natural or pulped natural processed. Often, Brazilian beans have a full body, low acidity, and sweet, chocolatey notes. 

However, by using these techniques, Brazilian producers can alter the flavour profile of their coffees. This helps them set themselves apart from others on the market.

As part of the Artisans project, producers have been trained to use the techniques, and have subsequently produced more than 1,000 lots scoring between 80 and 90 points.

Silvio Leite is a Q grader at Agricoffee. He says: “The flavours from [this project] can be simplified into three distinct groups… firstly predominantly sweet flavours (notes of brown sugar, lemongrass).

“After that, we have fruity coffees, tasting either of dried fruits (raisin, dates), or the ‘cooler side’ (such as mango, cherries, strawberries).”

Silvio also notes that the third group was characterised by an aftertaste of sourness that he described as “not pleasurable”, but noted that this was evidence where the “processes must be adjusted”.

Michal Socha is the head roaster at Single Origin in Poland. He tells me that the coffees he has sourced from this project are “very original and unusual” and described “very noticeable strawberry notes”.

“The development of such a culture of bacteria and yeast also inhibits the multiplication of pathogenic fungi,” Michal adds. “This positively affects the sensory quality of the coffee.”

Both concluded that altogether, thanks to the use of these unique microorganisms in controlled fermentation settings, the diverse range of flavours that were produced were unusual (and in some cases unknown) for Brazilian coffee. 

Using controlled fermentation to improve producer incomes

Using this project as a benchmark, we can conclude that experimenting with microorganisms in controlled fermentation has the opportunity to improve cup quality and consistency for the producer.

One of the main opportunities for producers is the effect that controlled fermentation has in terms of adding value. Normally, value is predominantly added in consuming countries by roasters. By leveraging fermentation processes to improve flavour and increase quality, producers can diversify what they’re able to offer and be more competitive in the marketplace.

Silvio says: “[By using] these possibilities and processes, producers may have what could be called a ‘new menu’ of coffee flavours on offer.

“This could serve a [much broader] range of buyers, such as those who like a very sweet or super fruity profile, [or even floral flavours].”

Additionally, Jorge says that by using microorganisms to improve consistency, as with the Nucoffee Artisans project, producers can offer buyers a more stable flavour profile.

“The controlled fermentation allows for the repetition of sensory profiles, and [can] boost the aroma, flavour, and acidity of coffees. 

“This allows different varieties to reach a similar flavour profile, yet with different nuances and intensities.”

Roaster & consumer interest

Across the global specialty coffee sector, there is an ever-increasing demand for fermentation. This is because it provides roasters and consumers with the opportunity to experience new and unique flavour profiles.

“I see it as a new market,” Jorge tells me. “[Especially] for consumers that seek new experiences and surprising cup profiles. This then [benefits the producers financially].

“As the process is handcrafted, very technical, and demands a lot of care, the consumers, I believe, will be willing to pay more for the coffee.”

This has been reflected in the results from the project. During International Coffee Week, the producers were recognised with a ranking of the top 50 lots. Today, there are more than 2,000 bags in stock scoring between 86 and 90 points.

Michal adds that these experimental coffees give roasteries unique opportunities to work with high-quality coffees with exotic flavor profiles. He also explains that these coffees in particular are also suitable for both filter and espresso. 

“Both we, as a roaster, and our customers, brewed this coffee using various methods, filter and espresso. With both methods, the coffee is fantastic.”

To seek out new markets for these coffees, Nucoffee have started conducting virtual cuppings in the US and Europe with the hope of generating further interest. For producers, the project has set out the aim of “stimulating the production of new coffee profiles” in the weeks and months to come. 

The Nucoffee platform works with more than 2,000 coffee growers, and the company believes that it is possible to introduce new technologies across a range of Brazilian farms to unlock new market opportunities and new flavours.

While controlled fermentation and microorganisms are still the subject of continuous research in the coffee sector, this project shows that there is considerable opportunity for producers, roasters, and consumers. The potential for producers to leverage these production methods to unlock new sensory profiles is massive. 

Enjoyed this? Then read Coffee Fermentation: What Is It & How Can It Improve Coffee Quality?

Photo credits: Nucoffee, AP Central Farm, Pantano Farm, Armadilllo Sitio, 

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The post How do microorganisms affect fermentation & the sensory profile of coffee? appeared first on Perfect Daily Grind.