For some coffee producers, experimental processing methods are a useful way to elevate coffee flavour and quality. At the same time, more roasters and consumers are increasingly being drawn to these advanced processing techniques, and in turn are being exposed to new ways of experiencing coffee.

One of these methods is lactic fermentation: a process championed by the innovative La Palma y El Tucán in Colombia. Classified as anaerobic fermentation, the process involves creating an ideal environment for the growth of lactobacillus cultures. This usually results in a creamier mouthfeel, as well as more yoghurt-like flavours.

So considering how lactic fermentation can impact sensory profiles, it’s also fair to assume that these coffees need to be roasted and brewed in different ways to highlight their best characteristics.

To find out more, I spoke with Felipe Sardi, co-founder of La Palma y El Tucán, and Christopher Feran, coffee industry consultant and expert. Read on to learn what they had to say.

You may also like our article exploring trends in experimental coffee processing.

What is lactic fermentation?

Although lactic fermentation is a relatively novel processing method in the specialty coffee sector, it’s certainly not new to the food industry. For centuries, professional chefs and home cooks alike have been using fermentation to preserve different foods – or even enhance flavour. Some common lacto-fermented foods include:

• Pickles
• Kimchi
• Sauerkraut
• Yoghurt
• Certain cheeses
• Kombucha
• Sourdough bread
• Specific types of hot sauce

So let’s break down what lactic fermentation is. Essentially, it’s a type of anaerobic fermentation, which means no oxygen is present during the process. The dominant microorganisms are Lactic Acid Bacteria (LAB), which thrive in oxygen-free environments. LAB converts simple carbohydrates into lactic acid – as well as carbon dioxide, ethanol, and sometimes acetic acid.

Felipe Sardi is the co-founder and CEO of La Palma y El Tucán in the mountains of Zipacon, Cundinamarca in Colombia. In 2019, seasoned coffee professional World Barista Champion Jooyeon Jeon used a Sidra coffee from La Palma y El Tucán in her winning routine, which helped to cement its position as a pioneering specialty coffee farm.

He explains how they developed their own lactic fermentation process.

“After depulping the cherries, the coffee is sealed in tanks to remove (or significantly decrease) the presence of oxygen during the fermentation process,” he says. “This allows facultative anaerobic lactic acid bacteria like Leuconostoc mesenteroides – which is naturally present on the beans – to rapidly multiply and consume the sugars in the mucilage. This produces lactic acid. 

“Compared to natural processing, up to 90% of glucose and fructose are removed from the beans,” he adds. “The drop in pH level from the increase in lactic acid also triggers enzymatic reactions, which can impact flavour, too. We closely monitor variables like temperature and pH at multiple stages to control fermentation.”

Finding the best method

In specialty coffee, there are two primary lactic fermentation methods that producers currently use: either inoculating with a specific LAB starter or using a 2-3% salt brine. Both are implemented in a low-oxygen environment under strict control to promote healthy LAB growth. 

Christopher Feran is a coffee consultant, green buyer, roaster, and lapsed Q-grader. He explains in detail how these processes work. 

“LAB are halotolerant or halophilic, which means they grow or thrive in high-saline conditions,” he says. “This obviously gives these bacteria an advantage compared to microbes that are halophobic or require oxygen.

“I believe the best method for lactic fermentation is the one that achieves the desired result in the most reliable, safe, and economical way,” he adds. “In most cases, using a 2% salt brine is sufficient to produce a good cup profile. But for producers who have the resources, inoculation is certainly the most reliable and repeatable method.”

Felipe tells me how La Palma y El Tucán developed its lactic fermentation processing method in a way that highlights the farm’s unique terroir.

“We found that strict anaerobic conditions and extended fermentation times beyond 80 hours produce the best results,” he says. “We also adapted our process based on field observations. For example, lowering temperature will inhibit fungal growth which can create undesirable flavours.”

What’s the impact on coffee flavour and mouthfeel?

When drinking lactic fermented coffees, there are notable differences in flavour and texture. Research has shown that using LAB during processing will produce more distinctive floral, fruity, creamy, and buttery flavour notes, as well as a creamier mouthfeel. 

“Based on our experience, lactic fermentation can create more intense sweetness,” Felipe says. “Lactic fermented coffees also have more notes of chocolate and butter, and a more velvety body. 

“The high lactic acid content contributes directly to the coffee’s sensory profile,” he adds. “These are highly distinctive flavours which aren’t typically found in conventionally processed coffees.”

Christopher, meanwhile, points out that there are many types of lactic fermentation. Each one can influence the final cup profile and overall sensory experience in different ways.

“For example, you can ferment cherries before using a pulped lactic fermentation process, or implement a carbonic maceration-style processing method,” he says. “It’s difficult to generalise lactic fermentation.

“The results vary depending on how you develop your processing technique,” Christopher adds. “Salt-lactic fermentations using dried cherries tend to result in brighter and more complex coffees with a creamier mouthfeel. In comparison, pulped lactic fermentations usually produce brighter and more floral and tropical flavours.”

How to roast & brew lacto-fermented coffees

Roast profile development is based on a wide range of variables, but processing methods are one of the most prominent. 

Felipe believes lactic fermented coffees can benefit from roast profiles which enhance sweetness and chocolate flavours. 

“Pour over brewing methods can also help highlight more of the unique and subtle flavours,” he explains. “Since these processing methods are so novel, leveraging specialist and customised roasting and brewing techniques is useful.”

Why interest in these coffees is increasing

Like other processing methods, lactic fermentation can provide certain benefits to some producers. For instance, one study from 2016 showed that these techniques can improve the fermentation process itself – as well as increase quality and cup score.

“The complex flavours and aromas created during lactic fermentation seem to have the potential to improve quality, but it requires in-depth knowledge and a lot of trial-and-error to achieve desirable results and no defects,” Felipe tells me. “When done properly, we have found that lactic fermentation can increase the quality of coffee which has more unique flavours.

“However, the process may not improve the flavour profile for more traditional coffee drinkers,” he adds.

On another note, Christopher tells me the lactic fermentation process isn’t a be-all and end-all solution to improving coffee quality.

“I don’t believe that processing is a silver bullet,” he says. “If a producer is using other methods, lactic fermentation can be a cleaner and safer alternative, but I would argue that the process differentiates a coffee rather than improves it.”

Will lactic fermented coffees continue to be popular in the future?

Lactic fermentation and other experimental processing methods will undoubtedly continue to progress and evolve. As a result, they are sure to have a positive impact on the specialty coffee sector – and remain popular, too.

“Many lactic fermentations are easy to execute and are lower risk than other advanced processing methods,” Christopher tells me. “Additionally, they require more simple and widely available materials, such as sea salt, so it’s likely they will grow in popularity.”

While Felipe agrees, he adds that lacto-fermented coffees will largely remain a more niche segment of the specialty coffee market.

“As processing techniques improve and consumer awareness increases, lactic coffees certainly seem poised to become more popular among specialty coffee enthusiasts who are looking for new experiences,” he says. “However, given the complexity and the degree of control required, these techniques are likely to be a smaller part of the wider market.

“But for producers who are focused on innovation and creating distinctive flavours, lactic fermentation offers a promising path forward,” he concludes.

It takes plenty of dedication, knowledge, and time to carry out lactic fermentation to the highest standards. But Felipe and Christopher both believe these processing methods are some of the most reliable and economical ways to change coffee flavour and mouthfeel.

When done right, there are clear advantages to implementing such techniques. Without the right resources and level of knowledge, however, producers may struggle to see as much success as they would hope to.

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

Photo credits: La Palma y El Tucan

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