Producer Insights: Anaerobic Fermentation in Coffee Processing

Coffees processed using anaerobic fermentation have been growing in popularity with specialty coffee drinkers and producers all over the world. Anaerobic fermentation can result in coffees with unique cup profiles that can demand a premium price in the specialty market due to their specific processing. However, anaerobic fermentation comes with significant risks for producers, not only in its potential to go awry and cause defects in a batch of coffee being processed, but also in the investment of time, knowledge, and resources needed in order to achieve the high quality potential that this fermentation style has come to be known for. In this article, we’ll hear from members of our sourcing team along with perspectives from some of our Colombian producer partners to explore anaerobic fermentation in coffee processing, its potential, its risks, and what the future may hold for this growing trend.

What is Anaerobic Fermentation in Coffee Processing?

Before we dive too deeply into anaerobic fermentation, it’s important to understand the role of fermentation in coffee processing, and what separates anaerobic fermentation from its more traditional aerobic counterpart. All coffee processing begins with fermentation as natural yeasts and microbes break down sugars in the coffee fruit. Elena Lokteva, Colombia Green Coffee Buyer, explains, “the main purposes of any fermentation [in food products] are food preservation, change of organoleptic profile, and improvement of the nutritional value of the product.” In coffee, this fermentation takes many forms, typically happening in whole cherries or containers like fermentation tanks filled with wet parchment coffee.

Elena Lokteva and Claudia SamboniElena Lokteva (left) and coffee producer Claudia Samboni at Finca Las Nubes in Huila, Colombia

“The reason why we talk about anaerobic fermentation in coffee is to differentiate coffees that have been exposed to an extended fermentation process using sealed [environments] from the rest of coffees, given all coffees undergo a fermentation process to a greater or lesser extent,” Elena continues. These sealed environments create an oxygen-free atmosphere rich in CO2—similar in many ways to Carbonic Maceration, another modern processing technique being adopted by coffee producers—either by having the air removed before sealing, or by allowing the CO2 produced during the fermentation reaction to force the oxygen out through a one-way valve or membrane. This critical difference alters the whole fermentation process, requiring extended fermentation times and resulting in some different chemical products than a typical fermentation completed in an environment with oxygen present. These differences are what contribute to the distinct, complex, and at times bombastic flavor profiles we find in anaerobic coffees.

What Are The Benefits of Anaerobic Fermentation in Coffee?

In a quality-focused industry like specialty coffee, cup profile and flavor still weigh heavily on decision-makers' minds when evaluating coffees for purchase. Producers like Rodrigo Sanchez—owner of Aromas del Sur which includes a dry mill and several farms including Finca Monteblanco and El Progreso in Huila, Colombia—have found that using anaerobic fermentation to process some of their coffees has improved the quality of those lots. Rodrigo says, “controlled fermentation is a next step after understanding how traditional or common-style fermentations work. The main reason we use controlled, extended fermentations is because we can see the improvement in taste, quality of the acidity, and flavor notes.”

Beyond just quality, consistency is crucial for coffee professionals at each stage of the supply chain as well as for the end user: coffee drinkers. Rodrigo also notes that adopting controlled fermentation protocols has bolstered the consistency of his coffee, explaining “another important reason is traceability, which we use to analyze and replicate our successful extended fermentations in order to provide our clients with the same quality and taste profile they are looking for.”

Rodrigo Sanchez pictured at Finca MonteblancoRodrigo Sanchez pictured at Finca Monteblanco

Even in the specialty market, quality alone doesn’t sustain producers’ operations without adequate business acumen to afford the costs of operation and, ideally, find a way to be profitable. This is another place where anaerobic coffees can shine for producers, as Abraham Castro, Central America Green Coffee Buyer, explains. “The anaerobic processes are stronger year after year and I consider that not necessarily because the rate or quality is higher in all cases, but because it is a coffee that has a higher price in the market.

“This year in Costa Rica a large percentage of the samples sent to us were [anaerobic coffees], and the tendency to produce [anaerobic coffees] increased. I think the main reason is that despite having an additional job [needed to produce them], these coffees have a higher profitability if we compare them with other processes such as Washed or Honey. A much smaller harvest was projected than in other years and production costs were increasingly higher. It is to be expected that producers will look for paths where they can achieve greater profitability.”

Adopting Anaerobic Fermentation for Coffee Producers

At its most basic level, processing coffee with anaerobic fermentation requires only an air-tight container with some means of removing oxygen from the environment. Frank Torres Rivas, coffee producer at La Indonesia farm in Nariño, Colombia, notes that there are several options to choose from. “It’s up to each producer which container material they prefer to use for extended fermentation,” he explains, “but it’s important to ensure this recipient is seal locked to prevent oxygen inlet and has either a valve or outbound membrane, like the one of GrainPro, allowing the CO2 that results from microbiome metabolism to be released.”

Frank Torres Rivas at Finca La IndonesiaFrank Torres Rivas at Finca La Indonesia

Beyond fermentation containers, Abraham Castro explains that investing in suitable infrastructure can impact the amount of additional work needed to add anaerobic fermentation into a producer’s business. He says, “the rest that is needed [beyond containers] depends on the comfort you want to work with; some put the barrels up high with an outlet system from below so as not to put too much effort into the process and systematize, and others do everything manually, from putting [coffee] in bags to taking it out with shovels to the different drying areas. In short… you only need the barrel, [but] if you want to make it more efficient [you need] a good system to move it from the barrel to the drying areas. In the end they are all costs.”

While this may seem like a relatively low barrier to entry for producers who want to adopt this style of processing, anaerobic fermentation has several variables that require regular monitoring and adjustment for quality and repeatable results. Diego Samuel Bermudez, coffee producer and partner in Finca El Paraiso in Cauca, Colombia, explains, “The extended anaerobic process could take up to 800 hours, but the longer the fermentation lasts the more control it requires with precise scientific tools and complex infrastructure.” Elena Lokteva expands on this idea, saying “to understand and obtain the same results between fermentations, or improve and modulate organoleptic properties of coffee, it’s important to understand the basics of metabolism and the limits and risks of the important parameters like temperature, pH level, sugar content (degrees brix) and even possible contamination during the process.”

Diego Samuel Bermudez at Finca El Paraiso in Cauca, ColombiaDiego Samuel Bermudez at Finca El Paraiso

The required investment in tools and equipment to monitor variables and adjust the fermentation can be costly and, for some coffee producers, prohibitively expensive. However, as Abraham points out, that hasn’t stopped some producers from working to incorporate anaerobic coffees into their offerings despite the challenges. “When this whole trend started, the producers bought machines to measure the pH, regulate temperature, and even measure the sugar content and they continue to do so to prepare their recipe,” he explains. “Those who carry out all this ritual have to invest in the machines, but I have also found many who just put the coffee in the barrel, count the days and it goes to the drying area without many turns, they only count the days. I don't want to say that it is bad, but I do want to say that the professionalism with which it began to be carried out in these fermentations has been lost a bit.”

What Are The Risks of Anaerobic Fermentation in Coffee?

If anaerobic fermentation can increase quality, consistency, and the price received by producers for their crop, it seems reasonable to think that this trend is poised to become the norm in specialty coffee’s near future. However, beyond the up-front cost of adopting this style of processing, it also carries challenges and risks that must be heavily considered by the coffee producers whose livelihoods rely on receiving a fair return for their skill, knowledge, and labor.

Abraham Castro at Beneficio PalmichalAbraham Castro at Beneficio Palmichal

One of the first challenges to weigh is that, capital costs aside, anaerobic fermentation requires the investment of a critical, finite, and expensive resource: time. Elena Lokteva explains, “the longer the timeframe from the time the cherry is picked to the time the coffee is sold and paid for, the larger the operational cycle and the higher the costs. The producer will need a better financial structure and access to funds in order to pay operational expenses like labor, utilities, and consumables. Their production cycle never stops thus it always requires upfront funding. This puts extra pressure on the final price of this type of coffee, otherwise it should be paid [for] upfront to minimize interest rates on credits producers apply for.”

Another important fact to consider for coffee producers is that, due to its complexities and fickle nature, implementing anaerobic fermentation runs the risk of producing defects and potentially ruining whole lots of coffee. This is especially true for producers who are learning the steps through trial and error, as Nolberto Olaya of Finca La Cinta in Tolima, Colombia explains, “We have started experimenting with anaerobic fermentations with the idea to allow longer time for metabolic reactions and sugar degradation [to gain] complexity for our coffee as we started hearing much about it from exporters or their clients. However, we didn’t have much knowledge about the process and after several trials and failures each of us started investigating and referring to already existing studies on fermentations in wine and food.”

Nolberto Olaya at Finca La CintaNolberto Olaya at Finca La Cinta

Beyond the potential for anaerobic fermentation to go awry and produce defects, even successful anaerobic coffees can carry the risk of lost revenue if the producer doesn't have a clear purchase commitment from a coffee buyer ahead of time. Typically, specialty coffee lots that aren’t purchased by a specialty buyer are sold instead in the origin country’s internal commercial (sometimes called “conventional”) market. However, because of the distinctive and unique cup profile found in anaerobic coffees, they often represent something of an all-or-nothing gamble for coffee producers who have invested in the process seeking profitability. Abraham Castro explains, “…for the conventional market these coffees [offer] nothing more than ‘ferment’ and it is frowned upon. Therefore, if this coffee cannot be sold [to a specialty buyer], it has to find a way [to be sold] as an inferior coffee to the [conventional] market due to the ferment it has. In fact, the inferior coffee that comes out of these lots is very difficult to sell in the national or internal market of Costa Rica.”

What Does the Future Hold for Anaerobic Coffee?

Understanding anaerobic fermentation in coffee processing is complicated, not only because of its many variables but also for the widely varied benefits, challenges, and risks that coffee producers face when adopting this novel process. It’s clear that anaerobic coffees are proving successful in elevating quality scores and sale prices for some producers. It should be equally emphasized however that, during a time of rising production costs, significant market volatility, and the many impacts of climate change on coffee producing regions, adopting anaerobic fermentation presents even greater challenges and higher hurdles to clear for producers hoping to increase their profitability.

As a recent development in the industry, there are still questions to be asked about the staying power of this trend in the specialty market at large. Abraham Castro speaks to these, asking, “how long will the roaster market hold us to buy these types of coffee if each time the countries of origin make more and more? Will prices drop or will there be coffee left to sell?” Certainly as more producers adopt anaerobic fermentation there will be impacts on the supply and demand balance in the industry, but the ultimate effects of its growing popularity are still to be seen.

While we can’t say with certainty what the future holds for anaerobic coffees, we’re excited to be able to offer them as part of our curated selection of lots from around the globe. We’re thrilled to continue finding ways to support our many partners—both those who have geared their businesses to focus on experimentation and innovation as well as those who focus on time-tested and well-practiced methods of production—in their efforts to produce and share their coffee with roasters and coffee drinkers, and to continue finding ways to move coffee forward.

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