While natural, washed, and honey methods remain the most widely used, they may not always satisfy those seeking distinctive or unconventional flavor profiles. In response, many producers have adopted anaerobic fermentation as a way to add complexity, stand out in the market, and expand their processing toolkit.

This guide explores how anaerobic fermentation works, the variations it takes, who it’s for, and how it stacks up against other methods—giving you a clearer view of how fermentation-based processing can shape flavor and identity in coffee.

 

What Is Anaerobic Fermentation in Coffee? Process, Flavor & Key Considerations

According to the French specialty coffee importer BELCO, Costa Rican producer Luis Eduardo Campos was one of the first to experiment with anaerobic fermentation in coffee. The method gained broader visibility in 2015, when Australian barista Saša Šestić used anaerobically processed beans to win the World Barista Championship. Since then, the technique has evolved into multiple forms and styles.

Anaerobic fermentation involves placing coffee cherries into sealed tanks, where oxygen is displaced—either naturally, through CO₂ released during fermentation, or actively, by injecting CO₂. This creates a low-oxygen or oxygen-free environment that encourages specific microbes (like lactic acid bacteria and yeasts) to break down sugars and produce lactic acid, alcohols, and aromatic compounds. These fermentation-driven changes influence the seed’s chemistry and can contribute to a more complex and distinctive flavor profile in the final cup.

Importantly, anaerobic fermentation is rarely a standalone processing method. Instead, it is typically paired with existing methods such as natural drying, washing, or honey processing—resulting in variations like anaerobic natural, anaerobic washed, or anaerobic honey. This hybrid approach combines the winey, fermentation-forward notes from anaerobic conditions with the structural clarity or sweetness associated with other processing styles.

Because of its high flavor impact and recognizability, many producers and brands now label “anaerobic” as a distinct step on their packaging to help consumers identify and select these coffees.

That said, anaerobic fermentation is a relatively new approach, and processing techniques can vary significantly between regions and mills—leading to notable flavor differences. If you want to know what to expect in the cup, it’s worth learning about the producer’s background, intent, and process.

In the next section, we’ll take a closer look at how anaerobic fermentation is carried out, what kind of flavors it typically brings, and what its strengths and limitations are.

Processing Steps

  

1. Sealed fermentation: Coffee cherries are placed in an airtight container—typically made of stainless steel or food-grade plastic—to begin fermentation.
2. Oxygen removal: Oxygen may be displaced either by actively injecting CO₂ or by relying on naturally produced CO₂ from the fermentation of the cherries themselves.
3. Variable control: Key conditions such as temperature, pressure, and pH are carefully monitored throughout fermentation to ensure stability and quality.
4. Transition to final process: Once fermentation is complete, the coffee is dried and finished using a natural, washed, or honey method—depending on the desired flavor outcome.

Flavor Profile

Coffees processed with anaerobic fermentation often carry fermentation-driven aromas, most notably winey notes reminiscent of red wine. The breakdown of mucilage in low-oxygen conditions may enhance both perceived sweetness and fruit-forward aromatics, commonly yielding flavors of berries, tropical fruits, and in some cases, rose or jasmine florals.

The acidity tends to be soft and rounded, often described as having a lactic, yogurt-like quality. When fermentation is extended, the cup may develop bolder, more intense flavors, with notes of ripe fruit, preserved plum, or warming spices. Overall, these coffees typically offer a full-bodied and multilayered mouthfeel.

 

What Makes Anaerobic Fermentation Appealing

1. When paired with different processing methods, anaerobic fermentation can create distinct and highly varied flavor profiles.
2. Aromatic compounds produced during fermentation may bind to or diffuse into the seed, adding depth and complexity to the cup.
3. The lactic acidity in many anaerobic lots tends to be mild and rounded, making them more approachable for those sensitive to sharp acidity.
4. As a relatively new technique, anaerobic fermentation offers clear differentiation and can enhance a coffee’s perceived value.
5. The process is often tightly controlled—with close monitoring of temperature, pH, and other variables—helping ensure consistency and quality.

Potential Drawbacks of Anaerobic Fermentation

1. Anaerobic processing requires specialized equipment and technical know-how, which can raise production costs and make it harder for smallholder farmers to implement.
2. Some consumers may find its distinct fermentation flavors—such as winey or preserved-plum notes—too unusual or polarizing.
3. Because processing protocols, environmental conditions, and microbial ecosystems vary between producers and regions, batch-to-batch consistency can be harder to maintain.

Read More: The Ultimate Guide to Coffee Processing Methods: Natural, Washed, Honey Process & More

Four Common Types of Anaerobic Fermentation in Coffee

Anaerobic fermentation is often used as a pre-processing step that’s later combined with natural, washed, or honey methods. Over time, this has given rise to several distinct fermentation styles. Since anaerobic processing is still evolving, methods can vary from one producer to another, and there’s no single standardized approach. What follows are four commonly seen variations currently in use across the coffee industry.

Anaerobic Natural

In this approach, whole coffee cherries undergo anaerobic fermentation first, and are then moved directly into a natural drying process once fermentation is complete.

Coffees processed this way combine the winey, fermentation-forward character of anaerobic methods with the intense sweetness and fruitiness of natural processing. The result is typically a cup with noticeable winey aromas, bold floral and fruit notes, and a rounded, smooth acidity—delivering a rich, full-bodied, and approachable profile.

Anaerobic Washed

In this variation, the coffee cherries first undergo anaerobic fermentation and are then processed using a washed method after fermentation is complete.

Compared to anaerobic naturals, these coffees still carry winey and fermentation-driven aromatics, but the acidity tends to be cleaner and more defined. Sweetness and fruit notes are more restrained, and while the body is slightly lighter, the cup still offers layered complexity.

Double Anaerobic

In a double anaerobic process, the coffee cherries undergo two rounds of anaerobic fermentation. The first fermentation takes place with whole cherries in a sealed, oxygen-limited environment. After that, the skins and pulp are removed, and the seeds go through a second anaerobic fermentation. Finally, the coffee is finished using a natural, washed, or honey method, depending on the desired flavor outcome.

Because each fermentation stage involves different microbial activity and environmental conditions, this method often leads to stronger winey character, higher perceived sweetness, and more layered complexity than a single fermentation. It’s especially appealing to drinkers who enjoy bold, intricate flavor profiles.

Carbonic Maceration

Although often grouped together with anaerobic fermentation, carbonic maceration is a distinct sub-category with notable technical differences.

Anaerobic fermentation is a broad term that refers to any coffee fermentation carried out in low- or no-oxygen environments. Carbonic maceration falls under this umbrella, but involves a stricter application of anaerobic conditions—typically by actively filling sealed tanks with carbon dioxide to ensure the complete displacement of oxygen. This level of control can more precisely guide microbial activity and shape flavor development.

Coffees processed via carbonic maceration often display intense floral and fruity aromatics, along with elevated sweetness and winey character. Acidity tends to lean toward a smooth, lactic profile, and some lots may reveal distinctive notes like creaminess, cinnamon, or spice. Final flavor outcomes depend heavily on variety and fermentation parameters.

 

Who Should Try Anaerobic Fermentation Coffee?

Anaerobically fermented coffees are known for their distinctive flavor profiles and are especially appealing to the following types of coffee drinkers:

• Experienced coffee drinkers: If you’ve explored a wide range of coffee origins and flavor profiles, anaerobic fermentation offers an exciting way to push your palate further. These coffees can introduce you to bold, unfamiliar aromas and new dimensions of complexity. If you’re sensitive to winey or fermenty notes, it’s a good idea to start with lighter, shorter-fermentation lots to ease into the experience.
• Fans of winey or ferment-forward flavors: Anaerobic coffees are known for their distinct wine-like intensity and concentrated fermentation notes. If you’re drawn to adventurous flavor profiles that go beyond the typical fruit-and-acid spectrum, this processing method offers a bold and expressive cup.
• Drinkers who prefer smooth acidity and sweet, round profiles: Most anaerobic coffees tend to have gentle, lactic acidity and a pronounced sweetness, making them a great match for those who find overly bright or sharp coffees overwhelming. These cups often feel rich, mellow, and comforting.

 

Overview: Anaerobic, Washed, Natural, and Honey Processing

 

Washed (Wet Process)

 

Washed coffee is produced by first removing the skin and pulp from the cherry, then fermenting the beans in water to break down the mucilage. After fermentation, the coffee is washed with clean water to remove any remaining residue, then dried and hulled.

This method is less dependent on climate conditions and produces clean, bright, and stable flavor profiles that highlight the coffee’s origin and varietal character. However, it requires significant water resources and specialized infrastructure, making it more common in centralized processing stations than on small farms.

Read More: Understanding Coffee Processing Methods: Natural vs. Washed

Natural (Dry Process)

 

In the natural process, whole coffee cherries are spread out under the sun and dried intact. Throughout the drying period, the fruit must be regularly turned to ensure even moisture loss and prevent over-fermentation or mold. Once fully dried, the outer layers—skin, pulp, and mucilage—are removed, and the beans are hulled.

Because the seed remains in contact with the fruit for an extended period, the beans  take on aromatic compounds during fermentation. The result is typically a rich, fruity cup with pronounced sweetness, floral intensity, and a rounded acidity. Natural-processed coffees often display layered complexity and a heavier body.

This method relies heavily on consistent sun exposure but requires minimal equipment, making it accessible to small producers. It is one of the oldest and most traditional forms of coffee processing.

Honey Process

 

In the honey process, the skin and pulp of the coffee cherry are removed before drying, while varying amounts of mucilage are intentionally left on the seed. The level of mucilage determines the specific “honey” category—typically labeled as black, red, yellow, or white honey—each with distinct flavor characteristics.

Black honey retains the most mucilage, often resulting in intense sweetness and pronounced fruity and floral notes. White honey has the least mucilage, producing a cleaner, brighter cup with more vibrant acidity. Red and yellow honeys fall in between, offering a balance of both qualities.

It’s worth noting that these honey classifications are not globally standardized. Factors such as temperature, humidity, and fermentation conditions can affect the final flavor outcome, even within the same category.

Read More: A Guide to Honey Process Coffee

Comparing Coffee Processing Methods: Anaerobic vs. Washed, Natural & Honey

 

Processing Method	Anaerobic Fermentation	Washed Process	Natural Process	Honey Process
Primary Resource	Oxygen-free or low-oxygen environment	水	Sunlight	Sunlight
Process Overview	Cherries are fermented in sealed, low-oxygen tanks, then proceed to washed, natural, or honey process	Skin and pulp are removed → fermented in water to break down the mucilage→ washed→ dried→ hulled	Whole cherries are sun-dried intact, then de-pulped→ hulled	Skin and pulp removed → varying amounts of mucilage left → dried→ hulled
Flavor Characteristics	Distinct winey and fermented notes	Bright acidity, mild sweetness, clean profile	Rich sweetness, fruity intensity, rounded acidity	More mucilage = more sweetness and fruitness; less mucilage = brighter, cleaner cup
Flavor Consistency	Moderate	Relatively high	Relatively low	Moderate
Advantages	Highly distinctive; can integrate characteristics from other processes	Stable flavor profile; suited for standardized production	Layered complexity; low cost; low tech requirements	Flavor diversity; good for experimentation
Disadvantages	Higher cost and complexity; less consistency across producers	High cost; requires large amounts of water and equipment	Prone to contamination; requires frequent turning and intensive manual labor	High management costs

 

Common Questions About Anaerobic Coffee

How Should Anaerobic Coffee Be Stored?

The best way to store anaerobic coffee is in an airtight, opaque container or in a valve-sealed coffee bag. Avoid exposure to heat, moisture, direct sunlight, and frequent contact with air. These factors can accelerate flavor loss and increase the risk of degradation.

Read More: How Long Do Coffee Beans Last? – Shelf Life, Storage Tips & Spoilage Signs

Does Anaerobic Coffee Tend to Taste Off or Have Defects?

Generally, anaerobic coffee is not prone to off-flavors. One of the main advantages of anaerobic fermentation is its high degree of control, which helps prevent spoilage, mold, or over-fermentation caused by weather changes or microbial imbalances. This significantly reduces the risk of undesirable flavors.

That said, improper storage or keeping the coffee past its optimal consumption window can still lead to flavor deterioration. 

Why a Good Grinder Matters for Anaerobic Coffee

 

Anaerobic coffees are bold, fruity, and often complex—but to really taste what makes them special, you need a grinder that keeps up. That’s where 1Zpresso comes in.

A consistent grind is one of the most underrated factors in brewing great coffee. When your grinder produces even grounds with fewer fines, the result is a cleaner cup, more vibrant flavors, and a better expression of what the beans have to offer.

1Zpresso hand grinders are built for exactly that: solid construction, precise grind adjustments, and burr designs tailored to different brewing needs. Want to dial in jammy fruit notes or highlight that winey aroma? These grinders make it easier.

Whether you’re brewing espresso or pour-over, looking for maximum clarity or a creamy body, there’s a 1Zpresso model designed for your style. And with thoughtful design details—like a smooth crank, ergonomic grip, and easy-to-clean parts—every step feels intuitive.

With a variety of burr designs, 1Zpresso has a model for every brewing preference:

• The J-Ultra is expertly crafted for espresso
• The ZP6 スペシャル is designed for pour-over with its exceptional clarity
• The K-Ultra offers flagship performance for a range of brewing methods

If you’re chasing flavor, start with the right tool. A good grinder won’t just improve your cup—it’ll help you fall in love with your coffee all over again.