Coffee Fermentation Design & Innovation in Coffee Processing using Yeasts   | Interview with Microbiologist Lucia Solis


When we think of innovation in specialty coffee most of us tend to think of equipment—scales, grinders, brewers, roasters, and other mechanical tools that allow us to make coffee better. But, what if there were microorganisms—or living tools—we could use to improve the quality and consistency of what's in our cup? Humans have been cultivating yeast populations for thousands of years and utilizing them as tools to innovate in bread, wine, and beer—is there potential for yeasts to improve the way we process coffee?


This past April, Microbiologist Lucia Solis took the stage at Re;co Symposium in Seattle to give a compelling talk about her research at origin on the benefits of applying yeasts to coffee during processing. With a background in winemaking, Solis has spent the past three years collaborating exclusively with coffee producers, utilizing science, and controlling fermentation to manipulate flavors. Lucia's groundbreaking work as a 'Coffee Fermentation Designer' is both rooted in established science is and at the forefront of innovation in specialty coffee. 


I am delighted to share this interview with Solis where we learn about her path to specialty coffee and dig into the benefits and challenges of adding yeasts to coffee during processing. I hope you will be as fascinated with her work and its potential to transform the specialty coffee industry as I am—


Photo of Lucia Solis by  A. Klass  

Photo of Lucia Solis by A. Klass 


tLBCC: How did you get into specialty coffee?

Lucia Solis: ...Circuitously.

I grew up in northern California and studied Viticulture & Enology at UC Davis. When I graduated, it was a short distance from Napa Valley, so immediately after graduation, I started working in wineries. When I worked in the wine industry I bought yeast and various winemaking supplies from a company called Scott Labs. After being their customer for 6 years and building a good rapport with them, I was offered an opportunity to work with Scott Labs to open up the Mexican wine market. They’d recently started to get involved with exploring the utility of yeast to the coffee industry and due to my background in fermentation, language skills and willingness to travel, I started traveling to different origins and using their yeast in different scenarios. For a while, I was straddling wine and coffee, but ultimately I chose to focus on coffee. Now, I work in coffee full-time as an independent consultant specializing in coffee processing and fermentation design.


Illustration by Lucia Solis

Illustration by Lucia Solis

tLBCC: Most people probably don’t know coffee goes through a fermentation process. Can you tell us a little bit about how this process happens in traditional coffee processing and how we may be using the term fermentation incorrectly?

Lucia Solis: I agree, many people don’t know that coffee is fermented, but due to lack of information, many of the people that do know it’s fermented don’t really know what that means. When we talk about coffee we tend to focus on the bean and it’s easy to forget that it comes from a fruit. Is coffee the seed, or the fruit, or some combination of the two? In the coffee industry fermentation is seen as a mechanical step to remove the fruit pulp and liberate the seed—what we typically refer to as coffee—for drying and roasting.


tLBCC: Since your background is in viticulture and enology, is the fermentation process in wine very different from the microbial demucilagination process in coffee?

Lucia Solis: It’s actually very different, and I caution about making too many comparisons between wine and specialty coffee for this reason. The biggest difference is that wine would not exist without a fermentation—the grape juice must be fermented to create alcohol and our favorite flavors. In coffee, fermentation is optional—it’s just one method to remove the fruit pulp. The mucilage can also be removed by a machine that uses water and friction to liberate the seed from the mucilage, for example. Fermentation is primarily, in current practice, a mechanical—or rather bio-mechanical—process for removing the mucilage. This is why I encourage people to try to use the more accurate term of ‘demucilagination’ because that describes a mechanical process. Fermentation is already defined by scientists as a metabolism. It’s a biological process—not mechanical. If you look at this step as a mechanical process, you miss the opportunity that the microbe’s metabolism can impart desirable flavors to the seed.


Another big difference is that in wine, we directly drink the product of fermentation. In coffee, the fruit mucilage is fermenting around the seed but the seed itself is not transformed. For some who think of coffee as only the seed and coffee flavor should only come from the seed, then technically coffee is not fermented at all.


Illustration by Lucia Solis

Illustration by Lucia Solis

tLBCC: Where do you source yeasts from? And, how exactly do they work their magic on coffee?

Lucia Solis: Currently, I work with yeasts manufactured by a company called Lallemand who's been in the yeast business since in the 1920s, Scott Laboratories is the distributor in the Americas. The yeasts are sourced directly from nature meaning they have been collected from the skin of fruits, isolated, grown in a culture, and then amplified so only a single population is present. The yeasts come packaged in a dried form and need to be rehydrated before use. Once rehydrated, I add them to the tank of freshly-pulped coffee. As a primary function of their metabolism the yeasts consume the sugar in the fruit and produce enzymes that help breakdown the pectin also found in mucilage. But along with the primary function, the yeasts also produce secondary metabolites that are flavor precursors which are absorbed into the seed. That’s how we can add value to the coffee by processing.


ºB = sugar content measured in the liquid from a coffee cherry. Illustration by Lucia Solis

ºB = sugar content measured in the liquid from a coffee cherry. Illustration by Lucia Solis


tLBCC: Where have you been implementing controlled microbial demucilagination?

Lucia Solis: I work primarily in the Americas. I have personally processed coffees in Kona, Mexico, Guatemala, Costa Rica, El Salvador, Nicaragua, Honduras, Panama, and Peru. I recently did my first virtual consultation for coffee processed in Rwanda.


tLBCC: What’s been the most surprising thing you’ve found in all of your yeast experiments at origin?

Lucia Solis: How little understanding there is about processing. I meet so many people knowledgeable in agronomy, and most of the farmers have well cared for and healthy plants, but processing is seen as a neutral step instead of an opportunity to enhance and supplement the hard work done in the field. Most processing techniques and knowledge came from the 1960s, and from what I’ve seen, little has changed for the majority of producers. Most of my work these days doesn’t even involve yeast—it’s just building systems that prioritize quality and uniformity before we can even get there!


tLBCC: What are some of the challenges in implementing systems for microbial demucilagination? In general, are you finding the folks at origin receptive to the idea of controlling fermentation?

Lucia Solis: This one is tough. Coffee farmers are, overall (and understandably), a very risk-averse group. For that reason, I only work with producers who want to work with me. So there is already a level of openness. It’s a self-selecting group. But even the producers that are open enough to invite me to their farms are still very hesitant about some protocols I want to implement because they challenge the historical narrative and traditional methods of coffee processing.


Illustration by Lucia Solis

Illustration by Lucia Solis

tLBCC: Wine is having a moment with wild fermentation right now. Why should the specialty coffee industry embrace the idea of adding specific yeasts to processing to control flavor?

Lucia Solis: Hmm...I think wine in the media may be having a moment with wild fermentations. The 0.05%. But: the broader wine industry is still controlling their fermentations. In other words, it’s a very small percentage that is making a lot of noise. Additionally, there is a long history of using commercial strains in winemaking and a lot of research and information about yeast strains and winemaking. You have to learn the rules first before you can know how to selectively and masterfully break them! I see the wine argument being used in coffee as a way to not have to do the work of learning, and go straight to rule-breaking.


tLBCC: Can adding specific strains of yeast to fermentation tanks affect the roasting process at all?

Lucia Solis: Absolutely! This is also an exciting part. The plant created building blocks which are then transformed by processing into flavor precursors that are then transformed in the roast. Some of my work now is focusing on how to modulate roast curves to bring out even more what is being created in the tank or specifically highlight some of the unique attributes we’re creating. I’ve gotten feedback that the coffees processed using a controlled fermentation roast more uniformly, crack predictably, and were overall easier to control.


The Benefits of Yeast Population Control. Illustration by Lucia Solis

The Benefits of Yeast Population Control. Illustration by Lucia Solis


tLBCC: If a coffee roaster wanted to source beans that have undergone controlled microbial demucilagination, are they accessible right now? If so, what process are they labeled as?

Lucia Solis: At this exact moment, unfortunately not. I would like to work with an exporter or importer who would like to offer this service to the broader market. The closest option is from Aida Batlle. You can get a yeast preparation of her coffees. She, as well as Emilio Lopez from Cuatro M, are early adopters of the process. A few forward-thinking roasters have purchased the yeast and have processed their own lots with the yeast. At this point, this is the only way to go about it. I hope to link to some of those coffees soon via my website so you can try them for yourself.


tLBCC: How many months of the year are you traveling to origin? And when you are not on the road applying yeast strains to at coffee mills what are you busy doing?

Lucia Solis: I think in 2016 I only had 2 months without a trip, May and July—and that’s because I haven’t worked in Colombia or Brazil yet (I see you, 2017...)! It’s fun and I love it, but it definitely takes a toll. There are hidden downsides: constant jet lag, airport meals, bad sleep, the stress of missed or delayed flights... not to mention everything you miss when you’re gone. When I’m not traveling I’m in deep recovery mode. I come home and have trouble doing much else besides catching up on Netflix shows, eating home-cooked meals and reading. This stage of my life is very binary, 100 mph traveling from mill to mill or 0 mph on my couch.


tLBCC:  What excites you about specialty coffee right now?

Lucia Solis: I’m excited to meet more curious people and citizen scientists. There is so much to know about coffee. On one hand it’s mind-boggling how little we know about plant genetics or agronomy or processing of this multi-billion dollar industry, but I try not to think about that too much and instead focus on all the cool work this generation gets to do and all the contributions we can make. It’s exciting that more than ever, we have the opportunity to pool our resources and share, on social media and elsewhere, what we learn so we don’t all make the same mistakes. It empowers us to build on progress more quickly.


tLBCC: If people want to get in touch with you, where can they find you? Do you have any other speaking engagements, workshops or cuppings lined up that we should know about?

Lucia Solis: I just got back from speaking in the first World Coffee Science Summit in El Salvador. It was great to see more resources being made available to producers in origin countries and the level of curiosity amongst producers for more advanced processing techniques. My next speaking engagement is at the Anacafe conference in Guatemala this August—also a producer-heavy audience.

I share photos from all of my fermentation trials on Instagram 

I have several treated coffees vacuum-sealed in my freezer that I would love to get some Q-grader feedback on and create more cuppings like the successful showing in Seattle.
If you have a specific question or problem you want to solve, or process you want to design, shoot me an email me at

Connect with Lucia Solis:  website  |  instagram  |  email:

Listen to Lucia Solis on the Opposites Extract Podcast

All illustrations by Lucia Solis