Anaerobic fermentation of coffee

Anaerobic fermentation of coffee

Did you know that your muscles ferment? Well, maybe they should. When you exercise so intensely (that you feel sore the next day), your muscles produce lactic acid.

Lactic acid is produced by glycolysis: the breakdown of carbohydrates into acids by a fermentation process.

It is the accumulation of this acid that creates the characteristic discomfort of muscle soreness.

In a way, everything ferments, but that doesn't mean fermentation is a bad thing.

Fermentation can be used as a preservation process that has been used in cooking for centuries as a way to preserve food and also changes its organoleptic profile.

Anaerobic coffee fermentation is a process that attempts to create and control a flavor profile that enhances its original qualities .

What is fermentation

Diagram of the lactic acid fermentation process. Photo by Khan Academy . Wikipedia says that fermentation is: a catabolic process of incomplete oxidation, which does not require oxygen , and whose final product is an organic compound. It is characteristic of the metabolism of many microorganisms, and depending on the final products, there are different types of fermentation.

If this sounds like gibberish to you, it did to us the first time we read it, but we'll try to simplify it (under penalty of losing accuracy).

Louis Pasteur, who is credited with discovering this process, described it as la vie sans l'air (life without air).

A very poetic way of saying that there are certain microorganisms (such as bacteria) that transform complex molecules into simpler molecules and generate chemical energy; this way, they can continue to live and develop without the need for oxygen.

The molecule that is transformed is glucose, and the process is called glycolysis . Now think about what doesn't contain some type of glucose? Practically none, so everything is susceptible to fermentation.

Fermentation is an incomplete oxidation process (we discuss coffee oxidation in this post ) since the proliferation of the microorganisms responsible for glycolysis prevents other microorganisms from reproducing and prevents the oxidation process from being completed.

Fermentation in the kitchen

Now, what does fermentation mean in the culinary world? And more specifically, what does anaerobic coffee fermentation mean ?

Cooking somewhat escapes the scientific definition of fermentation and makes it extensible to several similar processes.

In cooking, fermentation is the transformation of certain organic elements in food due to the action of yeast or bacteria.

The microorganisms responsible for fermentation can be found naturally in foods or can be added to create the desired reaction.

This results in the formation of acids or alcohols (e.g., yogurt or wine). The type of fermentation varies depending on the food, the ferment, and the time.

Fermentation is a way to preserve foods (e.g., pickles), change their organoleptic profile (e.g., wine), and improve the nutritional value and effectiveness of proteins (e.g., yogurt).

All fermentation is anaerobic.

Rodolfo Rufatti at Finca El Salvador, where our 48- and 120-hour anaerobic fermentation coffees come from. Talking about anaerobic coffee fermentation is redundant, since all fermentation is, technically, anaerobic . That is, the microorganisms responsible for breaking down glucose molecules into simpler ones always operate in the absence of oxygen.

But just because it's redundant doesn't mean it doesn't make sense to talk about it in the context of coffee processes.

Rodolfo Ruffatti, our direct contact collaborator from Finca El Salvador, speaking about anaerobic fermentation coffees, told us: “ Anaerobic fermentation has been around for a while, but no one had a name for it. It was Sasa Sestic, at the World Barista, who first introduced this method when he said the coffee he won with was carbonic maceration. Some people don't want to use the term 'anaerobic' because all fermentations are .”

The reason we talk about anaerobic fermentation of coffee is to differentiate coffees that have been exposed to an extended fermentation process , usually in sealed tanks, from the rest of the coffees, since all coffees undergo a fermentation process to a greater or lesser extent.

Coffee fermentation

The fermentation process begins as soon as the coffee cherries are harvested. Then, depending on the method used to separate the seeds from the cherries (pulping), the fermentation process will be shorter or longer.

Fermentation is longer in a washed process in which a point of fermentation is deliberately sought (pulping, fermenting, washing and drying) than in a semi-washed process (pulping and drying).

In anaerobic fermentation coffee , the coffee, either with pulp or just the mucilage, is left to ferment for a set number of hours in a sealed tank so that no oxygen enters.

Therefore, we could say that the definition of anaerobic fermentation in coffee, although technically redundant, serves a differentiating function . Furthermore, there are several types of designations for different fermentation methods. These are:

• Anaerobic
• Carbonic
• Lactic acid
• Other experimental processes

Let's see what each one means and how it affects coffee.

Anaerobic fermentation

Coffee beans during the anaerobic fermentation process. Photo: https://www.sabores.co.za/ As we've said, all fermentation is anaerobic. But when we use the term anaerobic fermentation for coffee, we mean that it has been fermented in a sealed tank to keep oxygen out, but with a one-way valve to allow it to escape.

The tank temperature is also usually monitored for a more accurate result.

Rodolfo Ruffatti, in one of our conversations, told us that " this process can be done in tanks, barrels, even Grain-Pro plastic bags. The important thing is that it remains sealed for a period of time without access to air ."

This can be done before the cherries are pulped or after they have been pulped. In both cases, the microorganisms will begin to break down the glucose molecules, a chemical reaction that generates CO2 and heat.

This will cause the oxygen in the tank to be displaced and expelled through the one-way valve.

The bacteria naturally found in the coffee cherry and in the mucilage produce enzymes during this process, which are what lead to the generation of less complex compounds, such as organic acids and alcohol.

Why anaerobic fermentation is used and how it affects coffee

As we've said, all coffee undergoes a fermentation process , usually brief, once it's harvested. This fermentation process, which is deliberately extended in some types of processing, such as honey or natural coffee, is part of the characteristic flavor profile of each coffee .

But despite being an integral part of coffee's flavor profile, it's a process that hasn't been fully controlled. Anaerobic coffee fermentation allows this process to be controlled .

This is done by controlling the pH, with a Brix reading (indication of sugar content) and controlling the temperature inside the tank.

The result of controlling and prolonging the fermentation of coffee is that its chemical composition and therefore its organoleptic profile is altered.

Fermentation can enhance flavors or create different profiles within the same coffee. For example, a coffee fermented for 48 hours will not be the same as the same coffee fermented for 120 hours.

Anaerobic fermentation coffees at Ineffable Coffee

At Ineffable Coffee we have several anaerobic fermentation coffees, such as the short fermentation (48 hours) and another long fermentation (120 hours) that you can try to appreciate the differences.

Both from Finca El Salvador and in direct contact with our collaborator in El Salvador, Rodolfo Ruffatti.

Dr. Britta Folmer in her book The Craft and Science of Coffee , says that “[ removing mucilage through] underwater fermentation is said to bring out acidity and aroma, and rule out some astringency .”

Although fermentation that is too long can have the opposite effect, losing acidity, body and aroma.

Producers seek to find a balance that enhances flavor and aroma without causing the coffee to begin to lose its properties.

Carbonic maceration

​ Diagram of the carbonic maceration process. Image: Sassa Sestic. The basic chemistry of coffee carbonic maceration is the same as that of anaerobic fermentation, as it is a fermentation process, but under different conditions.

The difference is that, in carbonic maceration , once the coffee cherries have been introduced into the sealed tank, carbon dioxide is injected into it, which expels all the oxygen from the tank.

For this reason it is called “carbonic”.

The carbonic maceration process

In the carbonic maceration fermentation process, the coffee cherries are placed in a sealed tank with a one-way valve. Carbon dioxide is then injected, which expels all oxygen from the tank.

The duration of the maceration depends on the coffee grower's desired results, but it can range from a few hours to several days. As with anaerobic fermentation, it's important to control the temperature, pH, and sugar level (Brix).

Cherries can be placed in the tank whole or they can be pulped beforehand.

To obtain a “washed” coffee, the cherries are introduced without pulp, while for a “natural” coffee, they are introduced without pulp and subsequently left to dry on African beds.

Why carbonic maceration is used and how it affects coffee

The reason carbonic maceration is used, rather than anaerobic fermentation, is because injecting carbon dioxide into the tank and removing all the oxygen slows down the fermentation process.

Since there is no oxygen (and therefore no oxidation), glucose decomposition is slower, as is the pH evolution. Furthermore, controlling the different parameters can lead to different results.

Sasa Sestic, world champion barista and pioneer in applying this maceration process from wine to coffee, says that by controlling the temperature you can control both acidity and sweetness .

At low temperatures, acidity is enhanced, while at high temperatures, sweetness is enhanced.

As with anaerobic fermentation, the goal is to improve the coffee's presentation in the cup by enhancing the aroma, improving sweetness and acidity, and obtaining a fuller-bodied coffee.

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Lactic fermentation process and other experimental processes

Alternative fermentation processes, such as kombucha, are being experimented with for coffee. Photo: Tim Oliver Metz. Anaerobic coffee fermentation and carbonic maceration are the two most common processes currently used to enhance the organoleptic qualities of coffee, but they are not the only ones .

There are other processes, some in more experimental phases than others, to achieve these results.

We can talk about lactic fermentation, with the bacteria from the kombucha fungus and with that of water kefir.

Coffee contains various bacteria that carry out the fermentation process, including lactic acid bacteria. These are the same bacteria that carry out the fermentation processes in dairy products.

In the lactic acid fermentation process of coffee, conditions are created, through oxygen regulation, for example, so that these bacteria proliferate and not others (such as aerobic bacteria).

This makes the fermentation process different and different results can be obtained.

Experimental processes

Some experimental processes are attempting to introduce the bacteria responsible for fermentation in kombucha and kefir fungi into the coffee fermentation process.

One way to do this is to let the coffee cherries ferment in the kombucha or water kefir liquid instead of just water.

The reason for this experimentation is to broaden the horizon of tasting notes, acidity, sweetness, body in the cup, etc.

And this is very exciting, it opens up a whole new world of possibilities.

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Where are coffee processes going?

Coffees with 48 and 120 hour anaerobic fermentation from Ineffable Coffee As we have seen in this brief review of the different types of coffee fermentation, coffee processes are maturing , they are becoming adults and are learning from other industries such as wine or beer, where the fermentation process is an indispensable and critical part.

Perhaps not all processes and experiments will yield positive results; some will stay, while others will leave us. Perhaps there are some coffees that are better to continue processing using traditional methods.

But all of this will translate into an exciting sensorial journey and an enhanced coffee-drinking experience. And these processes and innovations may take us to unique and previously unknown places in the world of coffee.

We are eager to be part of this journey, and that's why we've included two anaerobically fermented coffees from Finca El Salvador in our selection. These coffees are the result of the work of the Productor Coffee team under the direction of Rodolfo Ruffatti: one aged for 48 hours, with subtle fruity notes, and another aged for 120 hours, where the intensity of the flavors is magnified.

And you, are you coming with us?