Understanding Coffee Processing and Sourcing

Updated: April 7, 2025 by Michael Kahn. Published: April 12, 2016.

Coffee processing is a critical step in transforming ripe coffee cherries into green beans ready for roasting. Each method impacts flavor, aroma, and quality significantly. There are three primary coffee processing methods—washed (wet), honey, and natural, along with emerging techniques.

As an avid coffee drinker, I wanted to reach a better understanding on where my coffee came from. What are the things that happen to coffee before it even reaches the store where I buy the beans? What was the flavor impact of some of these words and terminology I’ve seen on coffee bags?

A Sacramento-local coffee roaster and café, Insight Coffee, hosted a three-part series about coffee, each part held once per month. I decided to attend and learn about sourcing coffee and what happens to coffee before it reaches the warehouse of your local or national coffee roaster. How coffee is grown, where its grown, market dynamics, and processing.

Coffee processing is how coffee is prepared before arriving at the roaster. Surprisingly, there is a huge difference in flavor based on the process, discernible to even the casual coffee drinker.

Five Fun Facts About Coffee

1. Coffee is a fruit.
2. Coffee trees can produce fruit for over 150 years.
3. If coffee cherries float when placed in water, it means they are underripe.
4. The fruit around the seed needs to be removed in every processing method before roasting.
5. Roasting caramelizes the sugars inside of the seed – the amount of sugar impacts the sweetness.

How Coffee Beans Are Harvested and Picked

Coffee fruits must be picked at their peak ripeness. At any given time, a branch usually only has 20% of its fruit being ready for picking. This is a crucial reason why the human element will never be removed from speciality coffee producers and roasters. National coffees are more likely to use mechanical strippers to remove all of the fruit at once. Picking only the perfectly ripe coffee is called selective harvesting.

A veteran coffee picker is more likely to have half the amount of fruit than a newbie coffee picker in the same amount of time, due to experience of knowing how to select the top quality coffee. This is an industry problem, as pickers are often paid based on volume and not quality.

A ripe coffee fruit means more sugar has entered the seed – the part we roast. Roasting the coffee in effect caramelizes the sugar inside the coffee seed, or bean, and shapes some of the flavor.

The primary factors which affect flavor during the sourcing process of coffee are region of the world, altitude trees grow in, processing method, and ripeness level of the seed. Overall the size of the seed doesn’t impact taste, except for the pea berry, which is much sweeter.

Coffee Processing Methods

Coffee beans are not beans at all—they’re seeds inside a fruit called the coffee cherry. Processing involves removing layers of skin, pulp (mucilage), and parchment from the cherry to reveal these seeds. The method chosen influences the final cup’s flavor profile.

There are three methods to processing coffee. When tasting the same coffee, grown at the same location, picked at the same time, roasted the same way, but each batch processed differently, there is a marked difference. Is it good? Is it bad? This depends on your own personal palette.

1. Washed Process – This removes the fruit by way of water and machines.
2. Honey Process – This removes fruit without as much water as washing and requires much more manual labor.
3. Natural Process – Fruit is laid out to dry in the sun, then removed in machines.

In each of these processes, there are a few universal steps which must happen.

Coffee beans are separated by size. This is important for the roaster to ensure continuity and consistency in the quality.

Three layers of the coffee fruit must be removed before it is sent to the roaster. The exocarp (skin), mesocarp (mucilage), and endocarp (parchment).

The coffee needs to be dried. An ideal moisture content in the coffee is 10 to 13%. According to one study (Martin et al. (2009)), the ideal drying includes intermittent drying, with 12 hours of 50º C heated air and 12 hours of rest. A second study (Isquierdo et al. (2011)), found that interrupting the drying process when the moisture content is 24% with a rest period of 2 to 12 days and later drying to 11% moisture content results in lower values of potassium leaching and electrical conductivity and, consequently, greater integrity of the cellular membrane system of the beans compared to coffee subjected to continuous drying to 11%. To sum it up, rushing the drying of beans results in a lower quality coffee. How much of a difference can the average person discern? I have no idea!

Washed Process Coffee

The washed process, also referred to as the wet method, remains one of the most widely employed techniques in specialty coffee production due to its ability to yield clean, vibrant flavors that highlight the intrinsic qualities of the coffee bean. This process involves several stages, each designed to refine the coffee while preserving its clarity and complexity.

The journey begins with the careful sorting of freshly harvested coffee cherries. Producers immerse the cherries in water tanks, where ripe cherries sink due to their density while unripe or defective cherries float to the surface.

This initial step ensures only high-quality cherries proceed, eliminating contaminants such as leaves and twigs.

Once sorted, the cherries undergo de-pulping—a mechanical process that removes the outer skin and pulp from the beans. This step exposes the seeds (coffee beans) encased in a sticky mucilage layer.

The de-pulping machines use pressure and friction to efficiently separate the outer layers while leaving the mucilage intact for subsequent fermentation.

The beans are then transferred to fermentation tanks, where naturally occurring microorganisms—such as yeast and bacteria—break down the mucilage layer.

Fermentation can occur underwater (wet fermentation) or in open-air tanks (dry fermentation), depending on regional practices and environmental conditions. This stage typically lasts 12 to 72 hours, influenced by temperature, humidity, and desired flavor outcomes.

• Purpose of Fermentation: The mucilage surrounding the beans is insoluble in water; fermentation produces enzymes that degrade this sticky layer, allowing for easier removal during washing.
• Variations: Some producers opt for mechanical demucilaging, bypassing traditional fermentation altogether. While faster, this method can slightly alter flavor profiles.

Following fermentation, the beans are thoroughly washed to remove any residual mucilage. This step often involves long washing channels or mechanical scrubbing machines that ensure complete cleanliness.

The result is parchment coffee—beans still encased in their protective parchment layer but free of fruit residues.

Drying is the phase which stabilizes the beans and prevents spoilage. Producers employ one of three drying methods based on climate and available resources:

• Sun Drying: Beans are spread across patios or raised beds under direct sunlight and raked regularly for even drying. This traditional method can take 7–15 days depending on weather conditions.
• Mechanical Drying: In regions with high humidity or inconsistent sunlight, mechanical dryers are used to expedite drying within 18–36 hours.
• Hybrid Approach: Some farms combine sun drying with mechanical methods for optimal results.

Beans are dried until they reach a moisture content of 10–12%, ensuring they are stable enough for storage and transport.

Once dried, the parchment layer is removed through hulling at dry mills, revealing green coffee beans ready for export and roasting.

The washed process is renowned for producing coffees with crisp acidity, refined sweetness, and clean flavor profiles.

By removing all traces of fruit material early in processing, this method allows terroir—the unique characteristics imparted by soil type, altitude, and climate—to shine through unimpeded. Common notes include citrus fruits, red berries, floral tones, and caramel-like sweetness.

The execution of the washed process varies across coffee-growing regions:

In East Africa (primarily Kenya), extended fermentation times enhance acidity and complexity.

In Latin America (primarily Colombia), shorter fermentations balance sweetness with clarity.

In Southeast Asia (primarily Indonesia), producers may incorporate hybrid techniques like wet hulling alongside washing.

Modern advancements such as controlled fermentation have elevated the washed process further:

Controlled Fermentation: Producers use specific microbes or enzymes in tightly monitored environments to tailor flavor development.

Thermal Shock: Alternating hot and cold water treatments during washing enhances flavor penetration while preserving bean integrity.

Honey Process Coffee

The honey process, an innovative intermediary between washed and natural processing methods, involves retaining varying degrees of mucilage—the sugar-rich layer beneath the coffee cherry’s skin—on the beans during drying.

While traditionally characterized by the absence of fermentation, modern iterations have introduced controlled microbial activity to refine flavor development, challenging earlier definitions of the method.

This hybrid approach demands meticulous labor and environmental precision but rewards with a spectrum of flavors unattainable through other techniques.

The process begins with depulping ripe cherries to remove the outer skin, leaving mucilage-coated beans. Unlike washed processing, where fermentation tanks dissolve mucilage enzymatically, honey processing historically bypassed fermentation entirely. 

Contemporary practices in regions like Costa Rica and Honduras incorporate controlled fermentation during drying, particularly in red and black honey variants. 

Beans are dried in greenhouse environments where ambient microbes—primarily Hanseniaspora yeast and Leuconostoc bacteria—metabolize residual sugars, generating volatile compounds such as ethyl acetate (pineapple) and linalool (citrus). 

This saccharolytic activity enhances complexity without the over-fermentation risks inherent to natural processing.

The honey process is categorized by mucilage retention levels, each influencing drying duration and flavor outcomes:

• White/Yellow Honey: 10–50% mucilage retained. Dried rapidly on patios (6–8 days), yielding subtle fruitiness and bright acidity akin to washed coffees.
• Red Honey: 50–75% mucilage. Slow-dried in greenhouses (10–14 days) with periodic agitation, developing balanced sweetness and syrupy body.
• Black Honey: 75–100% mucilage. Requires 15–20 days of shaded drying, often with anaerobic intervals, intensifying caramelized sugars and earthy undertones.

Demucilaging machines enable precise mucilage removal, allowing producers to calibrate retention to climatic conditions—a critical factor in preventing mycotoxin formation.

Originating in Costa Rica as a water-conscious alternative post-earthquake, the method has diverged regionally:

Central America which employs hybrid drying (mechanical + solar) to balance humidity challenges, emphasizing floral and tropical fruit notes.

Brazil merges honey with pulped natural techniques, using mechanical demucilagers for consistency in nutty, chocolate-forward profiles.

Ethiopia integrates spontaneous fermentation with traditional raised beds, yielding wild berry and jasmine nuances.

Water usage remains 60–70% lower than washed processing, aligning with sustainable practices.

The mucilage’s composition—40% sugars, 20% pectin, and 15% proteins—serves as a substrate for microbial metabolism, generating esters, aldehydes, and ketones that permeate the bean. 

Studies using HS-SPME-GC–MS reveal black honey coffees exhibit elevated levels of furaneol (caramel) and β-damascenone (honey), while yellow honeys retain higher citral (lemon) and hexanal (grass). 

Sensory profiles range from:

• White/Yellow: Crisp acidity, tea-like body, bergamot.
• Red: Syrupy mouthfeel, red fruit sweetness, tamarind.
• Black: Molasses depth, fermented plum, tobacco.

The method’s fragility necessitates hourly bean rotation during the first 48 hours to prevent clumping and mold. 

In humid regions, mechanical dryers are employed post-initial sun-drying to stabilize moisture at 10–12%. Even minor deviations—a sudden rainstorm or inadequate airflow—can spoil entire batches, explaining the process’s limited adoption despite its sensory potential.

Dry or Natural Process Coffee

The natural process, also known as dry processing, is one of the oldest and most traditional methods of coffee production. It involves drying coffee cherries with their entire fruit intact, allowing the beans to absorb sugars and flavors from the surrounding pulp during fermentation.

This method is celebrated for producing coffees with bold, fruity profiles and heavy body, but it is also labor-intensive and requires precise environmental conditions to avoid spoilage.

The process begins with harvesting fully ripe coffee cherries, as their sugar content is critical to achieving optimal flavor during fermentation.

After harvest, cherries are sorted using water flotation tanks—ripe cherries sink while defective or unripe ones float. This step ensures uniformity in drying and minimizes defects.

The cherries are spread out in thin layers on patios, raised beds, or tarps to dry under the sun. In some regions, mechanical dryers may be used to supplement sun drying during periods of high humidity or inconsistent weather.

Drying typically takes 15–20 days, depending on climate conditions.

• Sun Drying: Cherries are raked or turned regularly to ensure even drying and prevent mold growth. This manual labor is essential for maintaining quality but adds significant time and effort to the process.
• Fermentation During Drying: As the cherries dry, natural fermentation occurs within the pulp. Microorganisms such as yeast break down sugars in the mucilage, imparting fruity and wine-like flavors to the beans.

Once the cherries reach a moisture content of 10–12%, they are sent through hulling machines that use friction to remove the dried fruit layers (skin, pulp, and parchment).

This reveals the green coffee beans ready for export and roasting.

Natural processed coffees are renowned for their intense fruitiness, heavy body, and complex sweetness.

The prolonged contact between the beans and fruit during drying allows sugars to penetrate deeply into the beans, creating unique flavor profiles often described as berry-like or tropical.

• Common Notes: Strawberry, blueberry, mango, chocolate, molasses.
• Body: Fuller and heavier compared to washed coffees.
• Fragrance: Potent aromas reminiscent of ripe fruit or jam.

This method can also lead to inconsistencies in flavor due to uneven fermentation or drying conditions. Defective beans may introduce undesirable notes like sourness or over-fermentation.

Natural processing is favored in arid regions such as Ethiopia, Yemen, Brazil, and parts of Central America where prolonged sunshine allows for efficient drying without excessive humidity. Its reliance on sunlight rather than water makes it an environmentally sustainable option compared to washed processing methods.

Natural processing uses virtually no water beyond initial sorting, making it ideal for areas with limited access to clean water.The method also allows for reduced reliance on machinery, which in turn lowers energy consumption.

Despite these advantages, natural processing demands significant land area for drying beds and requires constant monitoring to prevent spoilage—factors that limit its scalability in wetter climates.

Humidity poses a major challenge during natural processing. Excess moisture can lead to mold growth or over-fermentation, ruining entire batches of coffee.

Farms must carefully control airflow and temperature during drying to mitigate these risks.

The process requires frequent manual turning of cherries during drying—a labor-intensive task that increases production costs.

Sorting defective cherries before drying is time-consuming but essential for quality control.

Due to its reliance on natural fermentation, this method can produce inconsistent results if not managed properly.

Defective beans may introduce off-flavors such as sourness or earthy notes that detract from overall quality.

Recent research has shed light on how environmental factors influence chemical composition during natural processing:

Elevated temperatures accelerate drying but can degrade volatile compounds like chlorogenic acid that contribute to flavor complexity.

High humidity slows drying and increases microbial activity, which can enhance fruity flavors but also risks over-fermentation.

Excessive exposure to sunlight can compromise bean quality by altering caffeine levels and reducing antioxidant capacity.

Advanced technologies such as environmental sensors and data-driven monitoring systems are now being employed by some farms to optimize drying conditions while preserving desirable flavor characteristics.

Natural processing techniques vary across coffee-growing regions:

• Ethiopia: Known for wild berry flavors and floral aromas due to prolonged sun drying on raised beds.
• Brazil: Often combines natural processing with mechanical drying for consistency in chocolatey profiles.
• Yemen: Traditional methods emphasize slow-drying under shaded conditions for rich molasses notes.

These regional adaptations highlight how terroir interacts with processing methods to create distinct flavor profiles unique to each origin.

New Coffee Processing Techniques

In recent years, coffee producers have embraced innovative processing techniques to explore new flavor profiles, enhance consistency, and adapt to sustainability challenges. These methods often leverage scientific advancements, controlled environments, and unique fermentation processes to create distinctive coffees.

Anaerobic Fermentation

Anaerobic fermentation involves fermenting coffee cherries or beans in sealed, oxygen-free tanks. This controlled environment limits certain bacteria and yeasts while encouraging specific microorganisms to thrive.

Coffee cherries (whole or pulped) are sealed in airtight containers where fermentation occurs without oxygen. Temperature and time are closely monitored.

Coffees processed anaerobically often exhibit bold fruitiness, wine-like acidity, and creamy textures. Common notes include chocolate, cola, blackberry, and floral aromas.

The method requires precise monitoring to prevent over-fermentation or spoilage.

Carbonic Maceration

Borrowed from winemaking, carbonic maceration places whole coffee cherries in tanks filled with carbon dioxide. This creates internal fermentation within the cherries.

Coffee cherries are sealed in CO₂-filled tanks with one-way valves to release pressure. The fruit ferments internally before being dried and hulled.

Coffees processed this way are intensely fruity with tropical or wine-like characteristics, juicy acidity, and complex sweetness.

This method has gained traction in countries like Costa Rica, Ethiopia, and Brazil for its ability to produce vibrant and unique flavors.

Lactic Fermentation

Lactic fermentation encourages the growth of lactic acid bacteria during processing, either naturally occurring or intentionally introduced.

Coffee cherries or beans are fermented in environments conducive to lactic acid production. This often involves cooler temperatures and controlled humidity.

Coffees exhibit creamy textures with smooth acidity and tartness reminiscent of yogurt or buttermilk.

The method enhances body while reducing bitterness.

Thermal Shock

Thermal shock involves exposing coffee cherries to sudden temperature changes during processing to alter their cellular structure and enzymatic activity.

Cherries are immersed in hot water briefly before being cooled rapidly. This manipulation enhances flavor development during drying.

Early results suggest enhanced sweetness, reduced bitterness, and fuller body.

Producers are still refining this method for broader application.

Yeast Fermentation

Yeast fermentation introduces specific strains of yeast during processing to control and enhance flavor development.

Producers add selected yeast strains during fermentation to standardize outcomes and amplify fruity or floral notes.

Coffees often display heightened fruitiness with clean floral characteristics.

This method allows producers to tailor flavors based on desired outcomes.

Hydro Honey Process

A hybrid technique combining elements of the honey process with water immersion during drying.

Cherries are partially submerged during drying to balance mucilage retention with water-based cleanliness.

Balanced sweetness and acidity with honey-like body and clarity.

Reduced water usage compared to fully washed methods.

Cryogenic Processing

Cryogenic processing uses freezing temperatures at certain stages of coffee production to alter chemical composition and enhance flavor retention.

Coffee cherries are frozen at -40°C before undergoing sublimation (direct transition from solid ice to vapor) to preserve delicate flavors.

Vibrant taste characteristics with enhanced sweetness and complexity.

Lightweight beans with stable shelf life post-processing.

Controlled Fermentation

Controlled fermentation uses advanced technology to monitor variables such as temperature, pH levels, and microbial activity during processing.

Coffee is fermented in tightly regulated environments using specific microbes tailored for desired flavor outcomes.

Enhanced fruitiness, acidity, and body with well-developed flavors.

Producers achieve uniform quality by minimizing external risks like weather fluctuations.

Ultrasonic Processing

Ultrasonic processing employs ultrasonic waves to disrupt coffee bean cell walls during fermentation or drying stages.

Ultrasonic waves enhance extraction efficiency by breaking down cellular structures within the beans.

Clean cup profiles with heightened sweetness and clarity.

Reduces processing time while preserving bean integrity.

Coffee Processing Taste Comparison

One of the coffee farms Insight Coffee works with processed the exact same selective picking three different ways, as part of an educational experiment and to allow people to compare the tasting notes of each process. While you can’t taste the difference through this blog post, you can see the difference in color. I found the honey and natural processed coffee to taste much sweeter and similar in taste than the washed process coffee. Justin, our presenter, noted that last batch the Natural was fruitier, and this batch, the Honey was fruitier.

Ecological Impact of Coffee Processing and Water Usage

The amount of water used in processing depends strongly on the type of processing. Wet fully washed processing of the coffee cherries requires the most fresh water, dry processing the least. Sources indicate a wide range in water use. Recycling of water in the de-pulping process can drastically reduce the amount needed. With reuse and improved washing techniques, up to 1 to 6 m³ water per tonne of fresh coffee cherry is achievable; without reuse a consumption of up to 20 m³/tonne is possible.

The fermented waste water from washed coffee is often improperly disposed of, which can be harmful to the surrounding environment.

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Michael Kahn

I strive to paint vivid landscapes with my words, bringing the magic of far-off lands and enchanting aromas to life for my readers. Combine passion for exploration and the art of gastronomy in an unending ode to the senses. When I’m not traversing the globe, I find solace in the earth beneath my fingertips, tending to my garden and working on projects around my verdant oasis. MK Library serves as a beacon, guiding fellow travelers and homebodies alike to embrace sustainability, nurturing both our planet and our souls with purpose. Full Bio.

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