Kaiserblick Knowledge

Coffee Processing

11 min read

Coffee Processing

Sources: El Arte del Café by Sébastien Racineux & Chung-Leng Tran (Lunwerg, 2017); The Coffee Roaster’s Companion by Scott Rao (2014); Kofio.co (website); SICAFESA (website); Tierra Bendita (website); The Barn (website); Tim Wendelboe (website); Pinhalense (website)

Once harvested, coffee cherries must be processed — dried and depulped — to extract the green bean. The method chosen shapes the flavour profile as fundamentally as origin or variety. (source: El Arte del Café)

The target moisture level for green coffee at the end of processing is 10–12%, which enables good conservation.

Harvest

Picking is predominantly manual. Pickers select only ripe (red or yellow) cherries, leaving over-ripe (dark) and under-ripe (green) ones. Because cherries on the same branch ripen at different rates (due to uneven flowering triggered by rain), multiple selective passes per tree are needed for the best quality. (source: El Arte del Café)

An alternative is strip picking — pulling all cherries off a branch in a single pass. This is faster but compromises quality. Mechanical harvesting (machines that shake branches) is only viable on flat terrain and for varieties whose cherries detach easily.

Cherries should be processed within 8 hours of picking; beyond that, fermentation begins and can produce “stinker” beans.

Method Seco (Natural / Dry Process)

Where used: Regions with a pronounced dry season — Brazil, Ethiopia, Panama, Costa Rica.

Duration: 10–30 days.

Principle: Whole cherries are spread in a thin layer (equivalent to 2 cherries depth) on concrete patios or — better — raised African beds, turned regularly so the cherry ferments uniformly in the air. Covered at night to avoid moisture absorption.

Moisture path: Fresh cherries start at ~70% humidity; dried to 15–30%, then 10–12%.

Cup profile: Intense fruity aromas (explosion in the nose and on the palate), full body. The mouth-feel can be winey; in poor execution, vinegary. Less uniform than washed coffee.

Advantages: Minimal equipment and water investment.

Disadvantages: Requires space to spread cherries; high labour during peak harvest; difficult to achieve washed-coffee consistency.

Método Húmedo (Washed / Wet Process)

Where used: High-humidity regions where dry process is impractical — Ethiopia, Kenya, Rwanda, El Salvador, Colombia, Panama.

Duration: 6–72 hours for fermentation (12–36 hours average) + 4–10 days for drying.

Principle: Invented in 17th-century Java. Cherries are mechanically depulped (skin and most pulp removed), then submerged in water tanks where mucilage fermentation loosens the remaining layer. Beans are washed in channels, then dried.

Process steps:

  1. Cherries enter a water tank — ripe (dense) cherries sink; defective and unripe float and are removed.
  2. Depulping machine removes skin and most pulp.
  3. Beans (still covered in mucilage) submerge in water at max 40°C; stirred regularly; ferment 6–72h.
  4. Beans washed in sluice channels (second density sort: ripe sink, defective float).
  5. Beans dried on African beds or in hot-air drums to 10–12% humidity.

Cup profile: Cleaner than natural, with more pronounced acidity. Mucilage enzyme activity lowers pH below 5, contributing characteristic acidity. Less body than natural.

Note: Uses up to 100 litres of water per kilogram of processed cherries. Wastewater (contaminated with nitrates) requires recycling efforts.

Métodos Híbridos (Hybrid Methods)

Pulped Natural

Developed in Brazil in the 1990s. Combines the selective sorting of wet processing with the dry fermentation of natural.

Process: Ripe cherries are passed through a depulper; beans covered in sticky mucilage are dried on raised African beds in a layer 2.5–5 cm thick, raked regularly for uniform drying.

Duration: 7–12 days.

Cup: Cleaner than natural, more body than washed. Cup closer to naturals.

Advantages: Low water use; good selection; homogeneous result.

Disadvantage: Significant investment in depulping equipment.

Honey Process

The Central American name for pulped natural. The degree of honey refers to how much mucilage remains on the bean during drying. Colour of the bean during drying reflects mucilage level:

GradeMucilage removedDried bean colour
White honey80–90%Pale
Yellow honey50–75%Yellow
Red honey5–50%Red-brown
Black honeyMinimumDark

More mucilage left = darker bean during drying = cup closer to a natural.

Giling Basah (Wet-Hulled)

Where used: Indonesia only — primarily Sumatra and Sulawesi.

Why: High year-round humidity makes fully drying coffee in the endocarp impractical (flowering and harvesting occur throughout the year).

Giling basah means “wet endocarp” in Indonesian.

Process:

  1. Cherries peeled, submerged in water; mucilage loosened by overnight fermentation.
  2. Dried to ~40% humidity only (still in endocarp).
  3. Endocarp removed in a wet huller (creating friction; beans emerge rapidly).
  4. Beans dried quickly to 10–12%.

Cup: Very full body, very low acidity. Distinctive earthy, spiced notes. Characteristic blue-green bean colour.

Kenian Washed Process

A double-fermentation washed method associated with Kenian processing tradition — sometimes called the “Kenya double-washed” or “72-hour washed” approach. Depulped beans undergo a first fermentation in water, are then washed and subjected to a second soak, before final drying. The extended contact with water and extended fermentation time extracts cleaner, more complex flavors with pronounced acidity and berry-like cup notes.

SICAFESA applies the Kenian Washed Process specifically to the SL-34 variety at their La Siberia farm — fitting, as SL-34 itself originated from Scott Agricultural Laboratories in Kenya. Cup result: spicy/floral aroma; black currant, ginger, pepper, clove, lemongrass, green tea flavor; black currant and clove aftertaste. (source: SICAFESA (website))

Carbonic Maceration

A processing technique adapted from winemaking in which whole, intact coffee cherries are placed in sealed tanks filled with carbon dioxide (CO₂). The anaerobic, CO₂-rich environment drives intracellular fermentation — occurring inside the cherry cell walls rather than on the surface — producing intensely fruit-forward, wine-like cups.

Process: Whole cherries (not depulped) loaded into sealed CO₂-purged tanks; fermentation proceeds for hours to days; cherries then dried on raised beds.

Cup profile: Intense fruit, wine-like or spirit-like complexity, high aromatic expression; often polarising — desirable for buyers seeking experimental differentiation, unappealing to those prioritising varietal purity.

At Los Pirineos: Finca Los Pirineos (Diego Baraona, Usulután) offers CM as one of its processing options, but Tim Wendelboe — the farm’s primary buyer since 2010 — does not purchase CM lots, preferring semi-washed and honey processed coffees for cleaner flavour. This illustrates how CM production is market-segment dependent. (source: Tim Wendelboe (website))

Distinction from anaerobic fermentation: Carbonic maceration uses whole cherries and active CO₂ pressurisation, producing intracellular fermentation. Standard anaerobic fermentation typically uses depulped beans in sealed tanks without CO₂ injection. See Carbonic Maceration.

Anaerobic Fermentation

A technique where depulped beans (or whole cherries) are placed in sealed, oxygen-free tanks or vessels, allowing anaerobic bacteria to drive fermentation. Removing oxygen shifts the microbial environment and the resulting flavour compounds, producing coffees with unusual complexity — often intense fruit, fermentation-forward aromas, and winey or tropical notes.

Three main variants (source: Roast Rebels (website)):

  1. Anaerobic natural — whole cherries ferment in sealed tanks; most intense flavour expression
  2. Depulped anaerobic (honey-style) — pulp removed before sealing; intermediate intensity
  3. Washed with anaerobic phase — depulped beans undergo a sealed anaerobic stage before standard washing; cleanest of the three, with controlled complexity added

Cup profile: Typically shows intense fruit notes, syrupy body, high sweetness, and often wine-like or tropical aromas. Quality indicator: well-executed anaerobic lots show coherent complexity; defective lots show sharp acetic (vinegary) or hollow notes. (source: Roast Rebels (website))

Roasting implications: Anaerobic coffees are thermally sensitive during roasting. Too much heat destroys the volatile aromatic compounds that make these coffees distinctive; too little heat produces murkiness and muted expression. A conservative approach — lower charge temperature, careful heat management through the development phase — is recommended. For espresso, the extraction window is narrower than for filter; espresso preparation amplifies any imbalance. (source: Roast Rebels (website))

Geographic leadership: Latin America (Costa Rica, Colombia, Brazil, Peru) leads in volume and experimentation with anaerobic methods. The technique is spreading to El Salvador and other Central American origins. (source: Roast Rebels (website))

Extended Anaerobic Fermentation (72–108 hours): Tierra Bendita’s BioKrop Project uses a controlled anaerobic fermentation window of 72 to 108 hours across its honey and natural lots — a notably wide range that indicates systematic experimentation with fermentation intensity to dial in specific flavour outcomes. (source: Tierra Bendita (website))

Low-Temperature Anaerobic Natural: A more controlled variant in which whole cherries ferment in sealed containers inside a cold chamber for an extended period (commonly 72–96 hours). The cold environment slows fermentation, giving greater control over the process and allowing the development of cleaner, more precise aromatic notes without the off-flavours that can come from warm uncontrolled fermentation. Used by José Antonio Guillén at Finca San Antonio in El Salvador’s Apaneca region (96h cold-chamber protocol), producing a cup described as ripe cherry, dark berries, tropical fruit, toffee, dark chocolate, and a hint of red wine. (source: Main Lane Coffee Roasters (website, 2026-04-28))

Co-fermented: Whole cherries or depulped beans are fermented together with other fruits, juices, or botanicals — imparting additional aromatic compounds into the coffee. Produces intensely fruit-forward cups that can read as artificially flavoured to some palates. Popular on European specialty platforms (source: Kofio.co (website)).

Anaerobic Natural (Volcan Azul, Costa Rica): Whole cherries fermented 48 hours in sealed tanks at an average 16.8°C; Brix, pH, and temperature continuously monitored. Followed by 24 hours of open drying then 78 hours of mechanical drying for exceptional consistency. Cup: raspberry, pomegranate, red grape, jasmine, rooibos. (source: The Barn (website))

Lactic Fermentation

A specialised processing variant where lactic acid bacteria (LAB) are intentionally inoculated or promoted to dominate fermentation — rather than relying on wild ambient yeast and bacteria.

Lactic Honey process (Aroma Nativo, Colombia): After initial anaerobic whole-cherry fermentation, cherries are pulped, then undergo a second fermentation in barrels with lactic bacteria introduced from a previous fermentation batch. Beans then dried for 15 days in a parabolic dryer followed by a 3-month stabilisation period in a temperature-controlled room. Cup: cantaloupe, lychee, lemongrass, elderflower; ripe, creamy body; sparkling acidity. (source: The Barn (website))

Lactic fermentation typically produces softer, rounder acidity and a creamy body compared to standard anaerobic fermentation, because lactic acid is milder than acetic acid. The stabilisation period allows volatile compounds to settle, producing a cleaner and more consistent cup at scale.

Roasting implication: Similar to other honey/natural-adjacent processes — reduced density vs. fully washed; slightly lower charge temperature; watch for premature surface development.

Processing Summary

MethodWater useBodyAcidityAroma characterTypical regions
NaturalLowHighLowFruity, winey, intenseBrazil, Ethiopia, Panama
WashedHighLow–mediumHighClean, bright, floralEl Salvador, Kenya, Ethiopia, Colombia
Pulped naturalLowMediumMediumBetween natural and washedBrazil
HoneyLowMedium–highMediumBetween natural and washedCosta Rica, El Salvador, Nicaragua
Giling basahMediumVery highVery lowEarthy, spicedIndonesia

Roasting Implications by Processing Method

Processing method has direct consequences for how a green coffee should be roasted:

Washed/wet-processed coffees: Denser than natural-processed coffees. Require more aggressive roasting — hotter charge temperatures and higher initial energy. Can tolerate and benefit from higher heat. (source: The Coffee Roaster’s Companion by Scott Rao (2014))

Natural/dry-processed coffees: Less dense; burn more easily. Require lower charge temperatures and lower initial gas settings compared with washed coffees of similar origin. The expanded, less-dense cell structure is more susceptible to surface burning. (source: The Coffee Roaster’s Companion by Scott Rao (2014))

Pre-blend roasting: If blending green coffees of different processing methods before roasting (e.g., mixing a washed and a natural), the difference in density means both cannot be developed evenly in the same roast. Always use beans of the same processing type for pre-blend batches. Post-blending by taste is safer when combining different processing types. See Blending.

Relevance to Kaiserblick

Kaiserblick Specialty Coffee operates wet (washed) processing, which is standard in Apaneca-Ilamatepec given the region’s climate. Wet processing contributes the clean, bright, acidic profiles that suit light roast filter coffee. The honey process is one of three main processing methods used in El Salvador (alongside washed and natural), and is well-suited to the country’s climate. It may be relevant to future Kaiserblick processing experiments. (source: XLIII Coffee (website))

Processing Equipment

The machinery used to execute each processing method is documented in dedicated pages:

  • Wet Milling Equipment — pulpers (EcoPulp zero-water; EcoSuper low-water with pre-pulping green separation), mucilage removers, coffee washer/separators, winowers, and pre-cleaners
  • Mechanical Drying — rotary dryers, divided drum dryers (simultaneous multi-lot), heat exchangers, husk feeders, and the CSP automatic temperature control system
  • Dry Milling Equipment — combined hullers, destoners, gravity separators, size graders, and polishers for export preparation

Primary manufacturer reference: Pinhalense (Brazilian; 75+ years; pioneers of pulped natural processing; present in 100+ countries).

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