Good Beer Hunting

Uppers and Downers

Uppers & Downers — Lactic Acid Fermentation

Just an hour outside of Bogota, Colombia, sits a coffee farm called La Palma y El Tucán. The owners, Elisa Madriñán and Felipe Sardi, moved back to Colombia in 2011 in search of the perfect farm to realize their dream of producing uniquely special and distinct coffees. They worked with the hundreds of small farmers surrounding the region, experimenting with different methods of processing to craft what would become some of the most prized coffees in the world.

In 2017, they sold some of their experimental coffees to Onyx Coffee Labs, a roaster located in Springdale, Arkansas. They, in turn, traveled to Seattle, Washington to compete at the United States Coffee Championships, winning a number of titles with a product that was processed using what they called “lactic-washed coffee,” encouraging the production of lactic acid by placing the coffee in an anaerobic tank for 60 hours. This coffee was purchased for $43.10 per pound. The market commodity price for coffee at the time was $1.22 per pound.

Not bad for a bacterium that makes your food sour.


Welcome to Uppers & Downers, an exploration of the similarities between beer and coffee. Every year, Good Beer Hunting holds the eponymous event—and related smaller U&D events—in places like Chicago, London, Atlanta, Seattle, and elsewhere, showcasing the breadth and potential that the partnership of beer and coffee can produce. Our hope is to keep building on the experiences and education of the events by further delving into this fascinating world. With each article in this series, we’ll take one element that both beverages share, and break down how it’s expressed in each drink. First off, we’re going to tackle the huge and slightly-daunting task of understanding lactic acid fermentation in beer and coffee.

I call it daunting because I come from the coffee industry. After a year of unsuccessfully teaching eighth graders Algebra in New York, I took a job at the first place that'd hire me—a chain coffee shop in Times Square. Flash forward eight years, and I'm now the online editor for Barista Magazine, our industry's leading trade publication. I write about coffee for a living, and sometimes compete in coffee competitions while hosting a podcast about everyone's favorite caffeinated beverage called Boss Barista.

But about that coffee industry. It’s a place where knowledge about lactic acid fermentation, let alone fermentation itself, is convoluted, poorly understood, and difficult to articulate. When you tell consumers that coffee can undergo a fermentation process, many stare and are unable to associate the flavors in coffee with other fermented products like cheese or wine.

On the other end, we’re not doing that much better. Within the coffee industry, the importance of fermentation is only yet to be explored, with scientists and researchers now just studying the effects of different bacteria and yeasts on how coffee tastes.

In fact, when I reach out to coffee experts, many regarded as the leading researchers on the topic of coffee fermentation, most are reluctant to give definitive answers. “Lactic fermentation exists, but right now not much work has been done on coffee with lactic acid bacteria,” says Nathalie Sieczkowski, research director at Lallemand, a supplier of wine yeasts and bacteria in France. “Coffee fermentation is still at the beginning. People have been doing it without necessarily taking precautions and adding selected active dry yeast.”

To give context to fermentation in coffee, we have to start with how coffee is grown. Coffee is a seed of a coffee cherry, which grows on shrubs in places that are generally hot during the day and cool at night—mostly places located close to the equator. To get to the seed, all the layers surrounding the seed must be removed. This is called processing, and most farms process their coffee cherries in different ways. What we’re interested in here is specifically the process to remove the mucilage—the sticky parts outside of a peach pit, for example—from the seed itself.

The mucilage has a lot of sugar, so fermentation generally refers to the process of removing the mucilage by allowing yeasts and bacteria to eat away at this top layer. (There’s another form of fermentation that happens with naturally processed coffees, but that’s another article for another day.) For a long time, no one paid much attention to who or what bacteria and yeasts were at play—they just knew it removed the mucilage and didn’t consider any impact different yeast and bacteria could have on flavor.

In 2012, Peter Guiliano, the Chief Research Officer for the Specialty Coffee Association, conducted an experiment with bacteria during processing on a farm in El Salvador, and found no difference in the quality of coffee, writing, “In this test, microbial treatments didn’t have a strong effect…on the coffee.” Five years ago, we not only had zero understanding of yeasts and bacteria, but we also were dead wrong about its influence on coffee.

Beer, on the other hand, has a huge leg up on us, but not on purpose. People have been brewing beer for centuries—before modern refrigeration, and before we understood the importance of sanitation and what bacteria even really were. Back then, a little funk in your beer was expected. And because folks couldn’t kill off bacteria like Lactobacillus, which is responsible for lactic acid fermentation, almost all beers had some sort of funky tartness to them.

That changed with pasteurization techniques—to a degree. Traditionally “sour” beers like Lambic and Berliner Weisse still forged on, but it wasn’t until the late 1990s that a broader range of brewers started intentionally choosing to make these tart, wild beers. This history, to me, feels anecdotal, with beer writers recounting exact beers and specific brewers when they talk about the history of sour beer. I remember—in my very brief time working in a brewery—that the number one question I got was if we had any sour beers.

“There are a quite a few ways of introducing lactic acid into beer,” shares Sam Gilbert, founder of Temescal Brewing in Oakland, Calif. “You can actually just dump in food grade lactic acid—not uncommon especially with larger brewers looking for control over acidity levels, but frowned upon—but for the most part you introduce lactic acid into the beer by way of lactic acid-producing bacteria. Both Lactobacillus and Pediococcus produce lactic acid, and within those two classes of bacteria, there are many different strains to work with.”

Although there are a number of ways to introduce lactic acid, many brewers don’t even bother messing with these bacteria. “In fact, 99% of breweries out there consider Lacto a spoilage micro-organism,” says Jay Goodwin, co-founder of The Rare Barrel in Berkeley, Calif.

Goodwin and his team focus solely on crafting wild beers, and while they employ practices more commonly used, like adding Brettanomyces yeasts or fruit, Lacto beers have a permanent spot on their menu.

“In our brewery, we coax it to create some of the most unique flavors in any beverage,” Goodwin explains. “Lacto, in combination with wild yeasts and other bacteria, can create a wide range of fruity and floral aromas and flavors without having any fruit or floral ingredients added to the beer.”


When brewers talk about Lacto, they talk about it as an ingredient—a way to build a recipe that can sometimes be unwieldy, but has the potential to create something unique and interesting. “I like to think about recipe formulation as a balancing of components, and sourness is a pretty cool arrow in that quiver. First and foremost, it offsets sweetness, which is something beers need and brewers are always trying to do with bitterness,” Gilbert says. “Done well, lactic sourness creates some of the most refreshing beers I've ever had.”

Coffee experts, on the other hand, are just beginning to talk about the potential bacteria has to influence coffee. “I remember when I first heard about lactic fermentation, I thought it was a gimmick,” says Ria Neri, founder of Four Letter Word Coffee in Chicago. (They also have a coffee roaster and cafe in Burgazada, an island off the coast of Turkey.)

Neri visited La Palma y El Tucan just as they were starting out, and is one of a handful of folks to get their coffees in the United States. “When I describe the coffee to others, I always think tropical and coating, like a pineapple yogurt,” she says.

Perhaps some of Neri’s skepticism comes from the fact that she is the co-founder of Whiner Beer Co., also in Chicago, which specializes in barrel-aged styles—Saison, for instance—commonly found in Belgium and France. “People in these countries have been drinking sour beers for centuries,” says Brian Taylor, Ria’s partner at Whiner, who worked at Goose Island when they released Juliet, a now-popular American Wild Ale that was an early introduction to the world of sour beer.

While the tradition of sour and wild beers has existed for centuries, Taylor is quick to note that it’s still a new phenomenon in the United States. “Back in 2007, when [Goose Island] released the first iteration of Juliet, it took months to sell because people thought it was rancid,” he recalls.

Now, in 2018, almost half of Whiner’s menu is made of sour beers, and many of them are made with Lacto. “You get some of the cleanest sour beers from Lacto,” Taylor says.

Taylor and Neri (who made two sour beers with a Lacto-fermented coffee from La Palma y El Tucan at Uppers and Downers in 2017 as part of the Case Studies series) attribute this growth mostly to consumer education and availability of sour beers, as opposed to a trend or a minor shift that’ll eventually swing back.

“For so long, we were used to drinking light, sometimes-flavorless Lagers,” Neri says. “[Sour beers] are something we like, that sweet-sour flavor, because we’re drawn to extremes,” Taylor adds. “People often think they don’t like sour beers, but that’s just because they haven’t had a good one.”

If sour and wild beers are here to stay, so is lactic acid fermentation in coffee, despite the fact that we still don’t know a ton about it. Even at La Palma y El Tucan, where they refer to their fermentation process as lactic acid fermentation, there’s still not a ton of information about how this process happens. “We know that fermentation processes are extremely complex, and involve innumerable variables that may affect the final result,” says Felipe Sardi, one of the owners of La Palma y El Tucan.

In 2016, Sardi and his team commissioned scientists from the Chemical Engineering Department in the National University of Colombia to analyze their fermentation processes. “In order to establish differences in the dynamics between the Lactic and Acetic processes, each one of the fermentations that compose these processes were monitored by measuring organic acids and sugars, and by monitoring the population of lactic acid bacteria, fungi, and yeasts.”

We believe lactic acid bacteria may contribute to the final product’s quality, but we still need to better understand their roles and how they could be used for good.
— Nathalie Sieczkowski

Right now, educated guesses in the coffee world conclude that bacteria can help improve the overall quality of coffee during the processing stage. “We believe lactic acid bacteria may contribute to the final product’s character, but we still need to better understand their role, which are the ones of interest, and how they could be used for good. There’s still obviously a lot to learn,” Lallemand’s Sieczkowski says.

“In the coffees that I work with, I can change the cup scores 5-6 points,” claims Lucia Solis, a former winemaker and fermentation specialists who works with coffee farmers to improve their processing techniques. Solis is referring to the Coffee Quality Institute’s scale for scoring coffees. Generally, coffees that score above an 80 are considered specialty grade, with every point earned potentially translating into more money for that coffee.

“Usually that happens with lower scores—so I can change a 76 to an 82,” she says.

As much as yeasts and bacteria can change the potential earning power of coffee, Solis notes we’re far behind our colleagues in beer, wine, and other fermented foods because fermentation isn’t a required process in coffee. “Because it’s optional, it has a different historical understanding,” she explains. “The potential of fermentation to affect the coffee is really variable—it can be negligible.”

One of the reasons we don’t know much about the effects of yeasts and bacteria in coffee is because we don’t control enough variables. Coffee goes through so much before it reaches your cup—picking, processing, sorting, shipping, roasting—that it can be difficult for anyone to pinpoint one specific variable that affects the final flavor. While there are a number of variables that could be the culprit for a coffee’s final flavor, Solis points to perhaps the biggest-yet-most-silent offender: water.

In beer, people say that the quality of the water is the most important factor. In coffee, the water isn’t really talked about. It’s what in the river or what rain has fallen.
— Lucia Solis

“In beer, people say that the quality of the water is the most important factor. In coffee, the water isn’t really talked about.” Solis admits, noting that many farmers don’t have a choice as to what water they have access to. “It’s what in the river or what rain has fallen.”

Water serves as a medium for coffee and bacteria to interact, and while not all coffee is soaked in water during fermentation, the majority of coffees you drink use water to remove mucilage—that’s why the process is called the “washed.” And while coffee folks have written about water used in brewing coffee, but there’s not much discussion about water used during the processing stage, which is usually just what’s available and around.

Cleanliness is also a big issue. “Beer facilities are some of the cleanest places you work in. Lower pH and higher alcohol content means you have to be really clean,” Solis says. “Coffee farms are generally dirtier because we roast the finished product.” The assumption is that cleanliness only matters at the end of a coffee’s life—when we brew it and drink it.

Because of this, it can be impossible to determine the effects of ambient yeasts and bacteria on the quality of coffee, even though some folks act like they know. “In coffee, not a lot of people know what strain of yeast is doing the fermentation,” Solis says. “When people say there’s an acetic or lactic reaction happening, it’s not because people are testing the water—people are guessing.”

Solis sees a lot of potential in inoculation, or introducing known yeasts and bacteria strains to a sample of coffee during the processing stage and removing the guesswork. “What’s mostly happening [right now] is that the yeasts that I work with have a protective quality,” she notes. “The moment a coffee is picked, fermentation is happening. There’s yeast and bacteria always present—in the water, in the fermentation tanks, and if you’re not cleaning the tanks well, you don’t know what’s building up.”

When working with farmers, Solis will taste their coffees, determine which characteristics their coffee might be missing, like sweetness or acidity, and pick a strain of commercial yeasts to help bring that trait out.

Inoculation can also protect coffee from common fermentation problems. Imagine a coffee tasting like vinegar or kombucha and you’ll know what I mean. This is a serious issue because a couple of over-fermented or defective beans, over hundreds of bags of coffee, can mean a farmer can’t fetch a competitive price for all of their coffee. And it’s as simple as knowing how yeasts work. “Using yeasts is almost like a medical revolution,” Solis says. “It made a big difference when people started washing their hands—there was no new innovation or idea that changed things.”

And how is yeast protective? By sheer numbers. Although Solis can’t predict how much of any strain of yeasts or bacteria are in fermentation tanks at any given time, when she inoculates, she introduces roughly 6,000 times more yeast colonies than are normally present. While she might not know the exact bacteria or yeasts floating around in those fermentation tanks, her yeasts win by overpowering others. She describes it with an analogy. “Let’s say me and and Arnold Schwarzenegger are in a fight. Of course he’s going to beat me. But if there are a thousand of me? I have to win.”

When inoculating, Solis is able to get her desired outcome because she understands the yeasts she introduces and she makes sure her yeasts win out in competition with other unknown yeasts and bacteria strains. “You protect the coffee by having an army.”


There’s a saying in the coffee world that quality is already in the bean itself—it’s the job of farmers, roasters, and baristas to preserve the flavor. Basically, coffee is ours to try not to mess up. But with the number of things that happen to a coffee after it’s picked, that can be a challenging order. Inoculation provides a tactic for preserving the flavor already present, but that’s not its only limit. Although Solis is using yeasts to protect coffee, she’s also excited about the potential to create new and more interesting flavors. “Through a fermentation process, new flavors can be created that can only happen through the process of fermentation,” she says.

However, we’re still at the early stages of understanding what this means. Solis says she operates mostly based on experience, skill, and intuition. There’s no rulebook yet, and it’ll be difficult to change the practices of fermentation on farms, especially as the C-market price for coffee continues to hover around a dollar a pound. (As of this writing, that price is $0.98 per pound). Although there are examples of how yeasts can morph the flavor of coffee (and make it more valuable), that information is still at its infancy. Farmers like Felipe Sardi are the exception, not the rule.

With beer, on the other hand, yeasts and bacteria present a way to create something better and interesting, and we’ve known that for a long time because it’s intrinsic to the way beer is made. Lactobacillus can almost be thought of as any other common ingredient in a recipe—it can change, morph, and create something better than the sum of its parts. And like any ingredient, some folks may think they dislike what Lacto does to beers. But as many of the brewers we talked to mention, making sour beers isn’t about a gimmick or employing a fun technique—it’s about opening your palate to a wider range of flavors.

With Lacto, the range of possibilities in both beer and coffee is yet to be realized. The conversations we’re having now about the effect of bacteria on both beverages are in their infancy, especially when detailing the differences in how Lacto is used in each. As much as it is being used to introduce new, interesting, and wilder flavors into beer fermentation, Lacto is mostly needed in coffee to add stability to the fermentation process—and that’s still not totally understood.

As research grows, so do the possibilities that these diverging paths could start to cross back over, leaving potential for directly changing coffee flavor through Lacto fermentation or seeing Lacto fermentation used in beer as a way to create a new type of consistency. All of which is to say: while this may be the first real conversation we’re having about Lacto in beer and coffee, it certainly won’t be the last.

Words, Ashley Rodriguez Illustrations by Cooper Foszcz