Anaerobic Fermentation: Distinguishing the Difference in Your Cup

Anaerobic coffee bean processing takes the art and science of coffee making to a whole new level. A variation of natural or washed coffee bean processing, anaerobic coffee processing leads to complex and unique coffee flavors and is gaining new followers every day. So how are anaerobic coffees made and how do they taste? We answer a few basic questions to help you fill in the blanks as you contemplate branching out and adding a new coffee experience.

What is anaerobic fermentation coffee?

Coffee bean fermentation occurs when water, natural yeasts, sugars and biological agents present in beans interact to produce unique organic compounds that influence coffee flavor and strength. All coffee beans are fermented to a certain extent during drying, but anaerobic coffee fermentation is a more intense and carefully controlled fermentation process without oxygen. Only the active components and interactions promoted in a zero oxygen environment engage in anaerobic coffee fermentation. The speed of fermentation is reduced, as well as the diversity and amounts of fermentation compounds produced.

The results produce startlingly different and more complex coffee tastes.

Where to find anaerobic coffee?

Currently, there’s a growing trend floating to the top of specialty coffee menus all across the globe: anaerobically fermented coffee. If you’re anything like me, a specialty coffee nerd and fan of fruity coffees—I found myself intrigued by the term. I began chatting with specialty coffee roasters and coffee farmers from all around the world, asking, “So, what is anaerobic fermentation really?”

On a mission to learn more, I found out what this process looks like and how it translates to your morning pour-over. So, what’s all the hoopla about? Hang on tight, it’s about to get real nerdy.

How is anaerobic coffee made?

In short, anaerobic fermentation is a special style or method of coffee fermentation that’s utilized in order to create a crazy complex, distinctly fruit-forward cup of coffee. Put more simply, if your coffee order tends to include a request for lighter roasts, fruity pour-overs or “a single-origin Ethiopia, if you have it”—then, you may just fall in love with the next anaerobically fermented coffee you try.

Shifting our focus back to the beginning of the coffee life cycle—once the coffee cherries have been harvested, sorted and dried—they are placed in airtight, steel tanks to ferment. This style of fermentation can be done with washed coffees or natural coffees, though many coffee professionals agree, that when the coffee bean is left in the husk of the cherry, something really special happens.

What this means, is that the anaerobic fermentation of a naturally processed coffee creates a distinctly bright, fruit-forward taste — because the bean has spent more time in the coffee fruit or cherry. I’ll expand. Once the coffee enters the steel chamber, it’s kept here anywhere between 40-60 hours, with the intent to remove all oxygen from its tank.

At this point, you may be asking yourself why one might take the time to remove oxygen from these steel tanks, and how does that impact the coffee? Well, the answer lies in the oxidation process. When oxygen is introduced to a coffee, it can age the coffee, speeding up the fermentation timeline.

Conversely, when oxygen is removed, the coffee is allowed to ferment slowly. It’s given space and time to develop a more complex flavor profile, resulting in a punchy explosion of fruity flavors. Though in order to remove the oxygen from these massive steel tanks, something new must be introduced. This something else is Co2, and when pumped into the tanks, it presses the oxygen up and out. Pretty cool, right?

At El Vergel Estate, the Bayter brothers are currently working with a coffee they call Java El Eden. As soon as these beans reach a pH level of 4 to 4.1 in those airtight, steel tanks, this signals that it’s time to take the beans out. Each batch is a little different.

“It can be ten in the morning, or one in the morning when the pH level finally reaches that ideal number — which is just a part of doing specialty coffee,” Elias Bayter chuckled. “Once the alarm sounds, you’ve got to get the beans out.”

As the beans are set in a resting room to dry, and the moisture levels drop, the flavor profiles are developed even more, intensifying the bean’s natural flavors.

“This coffee gets better with time,” Shady Bayter shared. “If you save it and store in the right way, because of this process—this bean just keeps getting better.”

Though all the work that’s put into the green coffee before it arrives at the doors of the roasters could be missed if the beans are burnt or under-roasted during the roasting process. This makes the role of specialty coffee roasters, all over the world, just as integral as the role of sourcing directors and processing directors like Shady and Elias Bayter.

Once the green coffee is shipped out, the farmers entrust the fate of the bean to the roasters entirely. From this point forward, it’s the roaster’s responsibility to bring out the best of that anaerobically fermented coffee’s flavors. It takes several hands to produce a quality coffee experience for customers to enjoy.

Green coffee is a term used to reference coffee before it’s been roasted. Slightly green in appearance, this is the way the coffee beans arrive at the doors of coffee roasters all over the world—like Luke Brugh, head roaster and co-owner of Brugh Coffee in Christiansburg, Va. Luke is one of several specialty coffee roasters who works with the Bayter brothers and the Colombian Coffee Club.

Brugh shared that he chose to utilize a lighter roast for this anaerobically processed coffee, the Java El Eden, in order to showcase its peachy, fruitier notes best. “The taste? It’s kind of funky,” Brugh shared. “I think anybody can enjoy an anaerobically fermented coffee, but I think somebody who’s really into specialty coffee — people who like fruity coffees, like naturally processed Ethiopian—they’re really going to like this. They’re going to ‘nerd out’ when they hear about the fermentation process and everything that goes along with it.”

How does anaerobic coffee taste?

So, with all this in mind—how does it translate to the cup? What do coffee lovers gain from their experience with this new coffee? Well, from the perspective of the sourcing director, you’re going to experience a major bump in fruits like pineapple and orange. It’s sweet with an  emphasis on yellow fruits as opposed to red fruits.

From the perspective of the coffee roaster, the same rings true. This coffee is consistently fruity, even from the time it arrives in burlap sacks at the doors of the roastery—you can actually experience the citrusy, sweet aroma of the beans before they’re even roasted. The slow fermentation process leads to a sweeter, more complex development of the coffee’s natural flavors.This is not the norm for green coffee; it’s aromatically distinct. From the beginning of the bean’s lifecycle all the way to the cup.

So, if you have any adventurous coffee friends—or you yourself are the adventurous coffee connoisseur—this may just be the next coffee you want to check out from your local roaster. It’s different, unique, and as many put it—you just have to try the cup for yourself.

About The Author: 

Emily’s introduction to specialty coffee arrived in the form of a pour-over one unsuspecting Saturday morning in her early 20s. Introduced by a dear friend, she recounts this memory as the moment a distinct shift took place—it was the first time she enjoyed the process of making coffee as much as sipping on it. Flash forward five years and the specialty coffee industry has become an integral part of her community, personal growth, and passion to pursue learning. Today, you can find Emily barista-ing in one of her favorite coffee shops in the Blue Ridge Mountains of Virginia, Brugh Coffee. Outside of coffee, Emily enjoys teaching yoga and teaching in the School of Communication at Virginia Tech.