Anaerobic vs. washed: what is really changing in your cup

First, we have to talk about the cherry

Before talking about fermentation, let's talk about raw material. There is a rule worth remembering: the process does not start in the fermentation tank. It starts on the plant.

All of this shapes the coffee's potential. A perfectly ripe Caturra does not start from the same point as a Gesha. A cherry picked at its optimal ripeness does not have the same potential as a mix of unripe, overripe and damaged fruit.

That's why, when two coffees taste different, we can't automatically attribute the whole difference to the process. Genetics and origin are also speaking.

• Variety.
• Terroir.
• Altitude.
• Climate.
• Ripeness.
• Nutrition.
• Harvest.
• Selection.

What is a washed coffee?

Let's start with the classic method. In a washed process, most of the pulp and mucilage are typically removed from the cherry before drying, using different depulping and washing systems.

Fermentation may be used to help remove the remaining mucilage. Afterward, the coffee is washed and dried.

The result tends to be associated with a cup of greater clarity, defined acidity, less perceptible fermentation, floral notes, citrus, clean fruit and a more transparent sweetness.

But be careful. “Washed” does not automatically mean “clean and delicate.” An excellent washed coffee can be tremendously complex and intense. And a poorly processed washed coffee can carry defects. The process simply sets certain conditions. Quality depends on how they're executed.

Now enter anaerobic

Here the story changes. Broadly speaking, anaerobic fermentation takes place in an environment with limited or no oxygen, usually inside sealed containers or systems designed to control gas exchange.

And this changes the microbial ecosystem. The yeasts and bacteria present in the process work under different conditions.

The producer can control variables such as time, temperature, pH, pressure, sugar concentration, oxygen presence and the microorganisms used. And the more control that exists, the more possibilities there are for steering the process. Though “steering” never means “guaranteeing.”

• Time.
• Temperature.
• pH.
• Pressure.
• Sugar concentration.
• Oxygen presence.
• Microorganisms used.

What actually happens during fermentation?

Here we get to the heart of the story. Coffee cherry contains an enormous amount of compounds: sugars, acids, minerals, aromatic precursors, mucilage and other organic components.

During fermentation, microorganisms metabolize part of these compounds. As a result, different metabolites and volatile compounds are produced. And these can influence the final perception of aroma, flavor, acidity, sweetness, body and aftertaste.

Put simply: changing the fermentation conditions can change the chemistry that ends up in your cup.

So why can an anaerobic coffee taste so different? Here is the fascinating part. When fermentation conditions change, the set of compounds generated or preserved during the process can also change. This can produce sensory profiles associated with tropical fruit, red berries, wine, spice, cacao, flowers, fermentative notes and ripe fruit.

That's why some anaerobics can seem almost “explosive” next to a washed coffee. But intensity does not necessarily mean quality.

• Sugars.
• Acids.
• Minerals.
• Aromatic precursors.
• Mucilage.
• Other organic components.

The big mistake: “more fermentation equals better coffee”

Picture a scale. At one end, insufficient fermentation. At the other, excessive or uncontrolled fermentation.

In between there is a zone where the producer manages to express interesting characteristics without losing balance. If the process runs out of control, you can get excessive volatile acidity, alcoholic flavors, vinegar, solvent, rot, astringency and unpleasant flavors.

And this matters for the buyer: a coffee with very evident fermentation is not necessarily a defective coffee. The question is whether that fermentation is integrated, clean, balanced and pleasant.

• Excessive volatile acidity.
• Alcoholic flavors.
• Vinegar.
• Solvent.
• Rot.
• Astringency.
• Unpleasant flavors.

Washed and anaerobic: two different philosophies

We can think of them as two approaches.

Washed: broadly seeks an expression where the cup can clearly show the coffee's characteristics and its origin. It can offer clarity, acidity, transparency and precision.

Anaerobic: introduces a more controlled or particular fermentation environment that can generate a more intense and differentiated sensory expression. It can offer intensity, complexity, fruit, fermentation and persistence.

But these are tendencies, not absolute rules. A washed coffee can be explosive. An anaerobic coffee can be extremely clean. And that's where it gets interesting.

Variety matters too

Now let's run the thought experiment. Suppose we have Pink Bourbon, and we process part of it as washed and another part through an anaerobic protocol. Will we get exactly the same coffee? No. But we also won't get two completely independent coffees.

The genetics remain the same. The process modifies its expression. That's why it's so interesting to compare same farm, same variety, different processes. It's one of the best ways to understand what fermentation actually contributes.

And what about terroir?

Same story. A coffee grown at high altitude, with particular climatic and soil conditions, carries a specific set of characteristics. Processing can amplify them, modify them, or produce a different sensory expression.

But we shouldn't say “this flavor comes from the terroir” without considering the process. Nor “this flavor comes from the anaerobic process” without considering the variety and origin.

The cup is the result of an interaction: genetics, environment, ripeness, processing, drying, roasting and brewing.

The question a roaster should ask

Here we stop talking like consumers and start talking like buyers. When you taste a spectacular anaerobic coffee, it's tempting to think “I need to buy this coffee.” But a roaster should ask more questions.

Because a spectacular coffee in a cupping session is not necessarily a good coffee for building a commercial line.

• How much volume exists?
• What protocol did they use?
• Can it be repeated?
• What happens during storage?
• How does it respond to roasting?
• Is it stable?
• Does the sample represent the lot?

Roasting completely changes the conversation

Another common mistake: comparing only the green coffee. The process influences the bean's characteristics and how it may behave during roasting. An anaerobic coffee may require a different roast strategy than a washed one.

And then comes the real test: the cup after roasting.

• Density.
• Moisture.
• Water activity.
• Bean structure.
• Aromatic development.
• Reaction speed.
• Sweetness development.
• Retention of volatile compounds.
• Behavior during development.

Which is better?

It's a trick question. It's like asking “which is better, a red wine or a white wine?” It depends.

If you're looking for clarity, defined acidity, florals and transparency, a washed coffee can be extraordinary. If you're looking for intense fruit, complexity, fermentation and a more striking sensory experience, an anaerobic coffee can be especially interesting.

But for a professional buyer there is a third dimension: the business. A coffee can be incredible in the cup and barely viable commercially. Another can be slightly less spectacular but offer greater volume, better consistency, better price, greater availability and simpler logistics. And for a roaster, that can make it the better buy.

• Greater volume.
• Better consistency.
• Better price.
• Greater availability.
• Simpler logistics.

How to compare two coffees correctly

If you're evaluating a washed and an anaerobic coffee, don't start by asking “which one tastes stronger?” Use a matrix that compares, criterion by criterion, clarity, acidity, fruit, perceptible fermentation, complexity, aromatic intensity, consistency, differentiation, competition potential and commercial viability across both processes.

In a washed coffee, clarity and acidity can potentially be high and well-defined, fruit tends to be clean and precise, and perceptible fermentation tends to be low to moderate. In an anaerobic coffee, clarity and acidity are more variable or can be intense, fruit can be very expressive, and perceptible fermentation can be moderate to high. Complexity and competition potential can be high in both cases; aromatic intensity and differentiation tend to be higher in the anaerobic. Consistency depends on the producer for washed, and depends heavily on the protocol for anaerobic. Commercial viability, in both cases, depends on the lot.

The keyword keeps coming up: it depends. Because the name of the process does not replace evaluating the coffee itself.

The real value of anaerobic processing

So why are producers investing so much in these processes? Because they allow for experimentation. And experimentation is expanding coffee's sensory language.

For decades, we talked about chocolate, caramel, citrus and nuts. Now we find coffees described with fermented mango, red wine, stone fruit, pineapple, jasmine, spice and tropical fruit.

Processing is helping expand what we understand as “coffee flavor.”

But washed coffee is far from disappearing

And here's the paradox. The more we experiment with fermentation, the more we also value beautifully executed washed coffees.

Because a good washed coffee can demonstrate something very difficult: precision without the need for artificially perceived intensity. A bright acidity. A delicate flower. A perfectly defined fruit. A clean sweetness. A long aftertaste. Without needing a dominant fermentation.

It's a completely different demonstration of control.

The real battle isn't anaerobic vs. washed

And we reach the conclusion. The question shouldn't be “anaerobic or washed?” The question should be “which process best expresses this coffee's potential?”

For a producer, it means understanding their raw material. For a roaster, it means knowing what profile they need. For a buyer, it means evaluating much more than a single word on a spec sheet.

Because behind every coffee there is a chain: variety, farm, climate, ripeness, harvest, fermentation, drying, storage, roasting and brewing. And every stage leaves its mark.

Next time you have two coffees in front of you, one labeled “washed” and the other “anaerobic,” don't think you're choosing between the traditional and the modern. You're comparing two processing strategies. One may take you toward transparency. The other may take you toward intensity. But both can produce an extraordinary cup. And both can also produce a mediocre one.

Because in the end, the process is not the coffee. It's one of the tools the producer uses to reveal — and transform — everything that was already inside that cherry. And for a professional buyer, that difference changes everything.

The process is not the coffee. It's one of the tools the producer uses to reveal — and transform — everything that was already inside that cherry.