In today’s specialty coffee market, buyers look for coffees that have exotic flavour profiles and high cupping scores. This has motivated coffee producers to innovate in production and processing where possible.

One such example is when producers experiment with processing by fermenting their coffee cherries with other fruits. To learn more about how they do this and the effect it has, I spoke to producers and scientists from Brazil and Colombia. Here’s what they had to say.

Lee este artículo en español Fermentar Café Con Frutas: Una Nueva Tendencia

What Is Fermentation?

Fermentation naturally starts occurring just after a coffee cherry is picked (and sometimes before, if the humidity is high enough). It is when yeast, bacteria, and other microorganisms break down the sugar molecules in the mucilage inside the cherry. This process produces acids and alcohols, which in turn can affect the flavour of the coffee it produces.

Fermentation is a sensitive process that can be sped up or slowed down by changes in the environment, including temperature, humidity, and the presence of oxygen. Poor fermentation can lead to mouldy or undesirable flavours in the coffee, so controlling the process is critical.

In response to the increased consumer demand for unique, complex, and high quality coffees, many specialty coffee producers are experimenting with new and unusual fermentation methods (such as carbonic maceration). 

Juliano Tarabal is an agronomist and the director of Federação dos Cafeicultores do Cerrado Mineiro, an association for coffee producers in Minas Gerais, Brazil. He says: “The recent techniques and new demand in the specialty coffee market for micro-lots have made the producer aim for differentiation in post-harvest processing.”

He adds that over the past decade, fermentation has become a particular area of focus for specialty coffee producers. “Coffee farmers started to invest more and more in post-harvest strategy over the last ten years. 

“Before that, they focused only on high yield as the demand for specialty profiles was smaller. Back then, we did not have the need for differentiation that we do today.

“We used to dry coffee as quickly as possible, either in full sun or in the dryer, and we did not explore fermentation. We tried to reduce humidity levels faster, and stopped exploring the microbial richness that exists in the coffee’s mucilage.” 

Juliano says that controlling fermentation first became popular in Brazil’s Cerrado Mineiro region when producers saw that other producing countries (like Guatemala and Colombia) were using it to control the growth of microorganisms in rainy and humid conditions.

Once farmers experimented with it, they realised it had the potential to deliver a more complex and vibrant coffee.

Felipe Sardi, is the co-founder and General Manager of La Palma & El Tucan Specialty Coffee in Colombia. He says that innovations in coffee fermentation have been taking place since around 2012, and that interest in the field is increasing.

“I’d say that this practice has become much more frequent in Colombia during the last 5 years. We’ve seen a lot of interest around this subject both at origin and abroad.”

You may also like A Producer’s Guide to Choosing a Processing Method

Adding Fruit To Fermentation

Recent experiments have led some producers to include fruit when fermenting coffee. 

One such example is where cherries are fermented in a sealed, airtight tank for anaerobic fermentation along with a pre-established percentage of whole fruits or extracts (often sugar cane juice or citrus fruits). This mixture is then fermented in the tank for a predetermined period of time. The tank’s temperature is tightly regulated throughout this period.

Bruno Souza is a producer at Fazenda Esperança in Minas Gerais, Brazil. He tells me that he has been using citrus fruits in his coffee fermentation since 2017.

Bruno first began experimenting with tangerines. He explains that he placed the fruits in a bag, partially smashed them, and then added them to a tank with a natural processed Icatu coffee at a 1:5 fruit/coffee ratio. After 72 hours, he then continued processing as usual. 

“This coffee gave me the best cupping score I’ve had at the farm, 91 points, with a yield of only 3.5 bags,” Bruno says. “I took it to the 2018 Cup of Excellence, and I got a cupping score of 87. 

“But the thing is: we cannot be sure that this outcome came from the interference [of the tangerine] or if it was all from the coffee bean itself.”

Bruno has now processed two batches of coffee with and without adding tangerines to gauge his results. He is also experimenting with lemons. He notes that he does not always rely on fermentation to improve coffee quality, saying that there are many other variables to consider.

“It seems to be easier to get [higher] quality coffees from fermentation, but this isn’t always true… we have to try to make unique coffee out of what the pure beans can provide us, regardless of fermentation.”

Does Fruit Fermentation Actually Work?

Controlling fermentation is still a relatively new and under researched part of coffee processing. Scientists are just beginning to explore how it impacts a coffee’s final cup profile. Many feel that more research is needed on fermentation in general, before fruit fermentation can even begin to be explored. 

Lucas Louzada is a Q grader and professor at the Federal Institute in Venda Nova do Imigrante in Espirito Santo, Brazil. “All of this is very interesting… everyone wants to find a quick, magic solution, but the path is longer than that,” he says.

“I am sure that even 30 or 40 years from now, we will not have all the answers. We know nothing about coffee fermentation from a scientific perspective; we are still learning.”

Lucas says that while it’s been established that including fruit in fermentation affects the wort (the liquid generated during fermentation), further studies are needed to determine how this affects the flavour profile of a coffee. “Overall, we are closer to implicit knowledge than scientific knowledge,” he says.

Felipe doesn’t include fruit in his coffee processing as he feels that fermentation is complex enough as it is. “It is partially because we’d like to stand on the side of a more purist approach. We want to respect the coffee fruit’s own sugars and the native microbial colonies that thrive on it. 

“It is also because we perceive coffee fermentation as a very complex process. Therefore, we’d like to try and grasp some partial understanding of before we consider throwing in additional variables to deal with.”

Advice For Producers Looking To Experiment With Fruit Fermentation

Before considering experimental fermentation methods (such as fermenting coffee with fruit), producers should consider if there is a market they can access for these more unique coffees.

“Some markets will love this coffee, others will hate it. Farmers must ask themselves who is going to buy and drink the coffee,” Lucas says. 

Producers should keep in mind that the coffee processed this way might not suit everyday consumption. “One cannot drink very exotic coffees every day… these are like rare dessert wines,” Bruno points out.

Furthermore, producers should note that adding fruit to fermentation will increase production costs without a guaranteed positive result. Lucas says, “If we tell the producer to buy fruits… he is adding a cost into his production, and planning when we don’t know what the outcome will be.” 

He also notes that experimental processing methods such as fruit fermentation may cause producers’ expectations of the end product to change, when there is very little data about how this affects the quality of a coffee.

Future research could also render current practices obsolete, and cause producers to feel they have wasted their money. Lucas explains that in the past producers used sugar cane syrup to help break down the mucilage in coffee cherries. However, current research indicates that using a glucose solution achieves better results.

It is possible that research could emerge and show that fermenting coffee with fruit has no tangible benefit – which is something that producers need to be aware of.

Fruit fermentation also requires producers to carefully control all the variables they can, which can be labour-intensive and costly. The microorganisms and sugar molecules must interact in a very specific way to achieve any kind of positive result. If outside variables (such as temperature and oxygen levels) are not monitored, this could create a very expensive coffee that doesn’t taste good.

Overall, producers should proceed with caution and with as much professional support as possible. Lucas says: “The best thing to do is to get a specialist researcher to help the producer with the experiments in a controlled and carefully reported manner until it gets the moment we have a steady protocol for processing [in this way].”

It’s clear that more research into controlled fermentation and its effect on coffee flavour is necessary. However, this doesn’t mean that producers shouldn’t attempt to innovate in search of a better tasting and higher quality coffee. 

Well-documented experimentation and continued research will allow producers to fine-tune their processing and come up with replicable results. By being meticulous and careful, producers will be able to experiment and innovate without risking their financial security or the flavour of their coffee.

Enjoyed this? Then read Café Careers: How To Launch Your Own Specialty Coffee Shop

The author has translated some quotes from Portuguese.

Photo credits: Ana Paula Rosas, Acervo Lucas Louzada, Bruno Souza

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