What Is Anaerobic Coffee? A Bit of Sparkle and Funk in Your Cup

Hi! My name is Arne. Having spent years working as a barista I'm now on a mission to bring more good coffee to the people. To that end, my team and I provide you with a broad knowledge base on the subject of coffee.

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Anaerobic, double anaerobic, bio innovation, carbonic maceration, lactic process – these days there are so many names for experimental coffee processing that it’s hard to keep up!

Anaerobic, double anaerobic, bio innovation, carbonic maceration, lactic process – these days there are so many names for experimental coffee processing that it’s hard to keep up!

Today, I’ll just look at one: anaerobic coffee.

Before I get into it, I’ll let you in on a little secret. All the other aforementioned experimental processes are also forms of anaerobic processing. Anaerobic fermentation is so dangflexible that it has many names. Plus, coffee producers can pair it with other techniques to make some unique, out-of-this-world coffee.

But what is anaerobic coffee, anyway? Let’s dive in!

Overview: Traditional Coffee Processing Methods

Anaerobic processing is more of a fermentation technique than a processing method. So, all anaerobic processed coffees also undergo one of the traditional coffee processing methods.

The most common processing methods are dry, honey and washed processes.

Incidentally, all three of these processes involve different methods for removing the coffee cherry and sticky mucilage from the seed, the coffee bean.

During the dry (natural) process, the coffee dries with the cherry still intact. Once it’s fully dry, the cherry and any sticky residue is pulped to reveal the coffee bean. At this point, the green coffee is still enveloped in parchment, like it’s wearing a jacket. That bit is usually hulled off in a dry mill.

Brasilien Kaffeefarm 2022 Kaffeekirschen an Pflanze

Meanwhile, in a honey process, the cherry is removed very early in the drying process. Precisely when this happens all depends on the producer and regional farming techniques. However, the general consensus is that the honey process involves the coffee bean drying with the sticky mucilage still encasing it.

On the other hand, in a washed process the coffee is depulped (cherry is removed) and the sticky mucilage is washed away. The coffee then fully dries in parchment form.

Incidentally, fermentation is generally a key part of all of these processes. Fermentation breaks down the coffee cherry and mucilage, allowing them to be removed from the seed with more ease. This process often occurs in large drums or water tanks.

When producers utilize anaerobic processing, they fine-tune the fermentation step of coffee processing. I’ll get to that soon.

Finally, I’d like to emphasize that these coffee processing methods are just umbrella terms. Within each type of processing method are myriads of different techniques and takes. In other words, the hard work and expertise of coffee producers can really shine through their chosen processing method.

What Is Anaerobic Coffee Processing?

As I mentioned, fermentation is almost always used as a step in every processing method. It helps loosen up and break down the coffee cherry and its mucilage, making it easier to separate the coffee seed from all the sticky and fruity stuff that surrounds it.

At the heart of this process are beneficial yeast and bacteria that break down carbohydrates in the coffee.

But what is anaerobic coffee processing specifically?

Anaerobic coffee processing is fermentation that occurs in a zero- or low-oxygen environment.

When all the other fermentation conditions are right, this process encourages the production of lactic acids, which have a beneficial impact on the ultimate flavor of the coffee. Plus, a low-oxygen environment reduces the likelihood that the coffee will be tarnished by bad bacteria and the build-up of alcohol.

Technically, anaerobic fermentation can occur when the coffee is still in cherry or after it’s been depulped. However, anaerobic fermentation most commonly happens in cherry.

Producers can create an anaerobic environment in many different ways. For example, producers can simply put their cherries in a tightly wrapped plastic bag. This is the most economical method, but it also makes it harder to maintain controlled fermentation conditions.

On the other side of the spectrum, some producers utilize specially designed tanks for their anaerobic coffee. These tanks have a one-way valve so oxygen and other gasses can escape while the coffee ferments. The idea is that there will be no oxygen left in the tank by the end of the fermentation process.

In some cases, coffee producers will flush these tanks with nitrogen or carbon dioxide to ensure that it is a truly anaerobic environment from the get-go.

This process can take several hours, days or even more than a week, depending on the producer’s fermentation technique.

Why Use Anaerobic Fermentation for Coffee?

Coffee Processed in Rwanda

You may be wondering, what’s the point of anaerobic fermentation?

Well, anaerobic fermentation, when done effectively, leads to some pretty great results in the final cup of joe. This is thanks to the anaerobic environment, which allows for a longer, safer fermentation time.

Oxidation is a big no-no in the world of coffee fermentation (and wine, for that matter), since it encourages the growth of the wrong kinds of bacteria, such as acetobacter.

In other forms of fermentation, like vinegar production, acetobacter is great. But who wants a vinegary cup of coffee? Not me!

Acetobacter produces acetic acid, which causes unsavory flavors to emerge in the coffee. What we want instead are bacteria that produce lactic acid. Incidentally, lactic acid bacteria thrive in anaerobic environments.

The yeast Saccharomyces cerevisiae, also known as brewer’s yeast, is another important player in anaerobic fermentation. It ferments sugar into carbon dioxide, helping create that anaerobic environment, while also producing ethanol. The ethanol gives the anaerobic coffee some of its boozy and wine-like character.

Still, a balanced environment is necessary to prevent too much alcohol from building up. Otherwise, the coffee could be too boozy. Plus, without a balanced and anaerobic environment, other fermentation pitfalls could crop up. The worst case would be mold or rot, which could destroy a producer’s whole lot.

Ultimately, the anaerobic process is a complicated bit of science. When it’s executed effectively, it can lead to some delightfully bright, vibrant and fruity coffees, even in varieties that aren’t known for such cup characteristics.

Consequently, more delicious coffee correlates with higher cup scores and higher prices paid to producers. And as I’ve said many times over, expensive coffee is a good thing!

How Does Anaerobic Processing Affect Flavor?

I bet you’ve been waiting for me to get to this point. What does anaerobic coffee taste like?

Of course, the flavor of a cup depends on its origin, variety and processing method.

Still, there are some general cup characteristics in all anaerobic coffee. That said, these characteristics depend on how well the process was carried out.

Brewing Cuban Coffee in Moka

A really good anaerobic coffee will often taste extra fruity, complex and sweet. What’s more, anaerobic coffees tend to have vibrant acidity and a juicy or heavy body. They may even have a body and flavor reminiscent of wine.

However, if the anaerobic fermentation is not successful – this truly is a difficult process to master – there are bad consequences in terms of the cup quality.

Some anaerobic coffees taste very bitter, funky or boozy. In the worst-case scenario, they could have the character of a fruit compost bin. Unfortunately, I’m speaking from personal experience here.

That’s the risk of anaerobic processing. Fermentation can be a messy business, especially if you don’t have the tools to control fermentation time, temperature and pH. Even if you do have the right tools, things could still go wrong. After all, a bin full of delicious coffee cherries is a bacteria’s dream world.

Still, when all the conditions are just right, the flavor of anaerobically fermented coffee is nothing short of world-changing. For the devoted coffee lover, at least.

Anaerobic Coffee: Advantages and Disadvantages

In my book, the biggest advantage of anaerobic coffee is the higher premiums paid to coffee producers. The anaerobic process can result in really terrific and surprising results on the cupping table. Incidentally, this can increase cup scores by one or even two points. If you’re not familiar with Q grading, that is a significant jump in quality and price.

However, this bump only happens when the anaerobic process is carried out successfully. As I mentioned, anaerobic fermentation is difficult and expensive to master. For optimal results, it often requires significant investment in materials like specially designed fermentation tanks. The process is very time and labor intensive too, leading to higher labor costs for producers.

That said, it’s no wonder anaerobic coffee yields a higher price. However, what happens when something goes wrong?

Producers need to be able to control fermentation time, temperature and the pH of the anaerobic environment. Otherwise, the fermenting coffee could develop unsavory flavors or even mold and rot. And it bears repeating that poor results could happen anyway, even if everything is seemingly going swell.

This brings me to the biggest disadvantage in my book: risk to producers at the whim of roasters and consumers.

Anaerobic fermentation can lead to very tasty, exciting cups. At the same time, it’s expensive to carry out and results can be disastrous. Coffee farmers who end up with poor results after putting in all that extra time, money and labor are sure to be disappointed. They may be out a significant chunk of cash, too.

Consequently, some producers may reasonably decide it’s not worth it to invest in the anaerobic process. Plus, there’s the simple fact that specialized processing techniques of any sort are not accessible or affordable for many smaller producers.

The Future of Anaerobic Coffee

I’m interested in experimental coffee processing methods because they showcase the hard work, expertise and innovative spirits of the coffee producers that practice them.

On the other hand, it is troubling when roasters scramble to pay top dollar for a new processing method, and producers consequently invest more in that method, only to have roasters and coffee buyers move on to the next fad in the coming years.

That said, I don’t think this is the case for anaerobic coffee. Anaerobic processing seems to be in the early years of a long and fruitful tenure in the coffee industry.

I encourage you to take this prediction with a grain of salt. I can only speak from my own experience in the coffee industry, and I am not a coffee producer.

However, I can say that in recent years consumers haven’t been able to get enough of anaerobically fermented coffee. Like I said, a good anaerobic coffee is really good.

What’s more, high-quality anaerobic coffee does yield a higher price for producers. In an ideal world, those high prices would stay high even when the process isn’t new and exciting anymore. In a super ideal world, prices would stay high while research and product development make the anaerobic process more reliable and affordable for producers.

Final Thoughts

Coffee Tasting at Home Important Terms

This may have seemed like a deep dive into the world of anaerobic fermentation, but I assure you: there is so much more to learn.

I’ll admit, I’m not a scientist or a coffee producer. If you’re looking for first-hand experience or scientific explanations about anaerobic fermentation, you can definitely find more information online. After all, our global coffee community is a diverse group of intelligent, dedicated and enthusiastic coffee professionals.

Personally, one of my favorite ways to learn about new coffees is to learn with my taste buds. Tasting coffee is not just a joy but a learning experience!

Have you had an anaerobic coffee that you adored (or abhorred)? What do you think of this funky processing method? Let’s discuss in the comments section! 

Anaerobic Coffee FAQ

Anaerobic fermentation is a labor-intensive process that often involves significant investment on the part of a producer. So, it costs more to produce and also often yields higher cup scores and premiums.

Nope, I wouldn’t count on that.

Pretty much all coffee undergoes some level of fermentation, so “fermented” coffee is just as good for you as any other coffee!

This terminology doesn’t seem to be in use by many producers, so I can’t say with certainty. I’ll be sure to update this response if a clear definition emerges!

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Arne Preuss

Hi! My name is Arne. Having spent years working as a barista I'm now on a mission to bring more good coffee to the people. To that end, my team and I provide you with a broad knowledge base on the subject of coffee.

More about Arne Preuss

Hi! My name is Arne. Having spent years working as a barista I'm now on a mission to bring more good coffee to the people. To that end, my team and I provide you with a broad knowledge base on the subject of coffee.

More about Arne Preuss

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