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)
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:
- Cherries enter a water tank — ripe (dense) cherries sink; defective and unripe float and are removed.
- Depulping machine removes skin and most pulp.
- Beans (still covered in mucilage) submerge in water at max 40°C; stirred regularly; ferment 6–72h.
- Beans washed in sluice channels (second density sort: ripe sink, defective float).
- 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:
| Grade | Mucilage removed | Dried bean colour |
|---|---|---|
| White honey | 80–90% | Pale |
| Yellow honey | 50–75% | Yellow |
| Red honey | 5–50% | Red-brown |
| Black honey | Minimum | Dark |
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:
- Cherries peeled, submerged in water; mucilage loosened by overnight fermentation.
- Dried to ~40% humidity only (still in endocarp).
- Endocarp removed in a wet huller (creating friction; beans emerge rapidly).
- Beans dried quickly to 10–12%.
Cup: Very full body, very low acidity. Distinctive earthy, spiced notes. Characteristic blue-green bean colour.
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.
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)).
Roasting implication: Anaerobic naturals share the lower density of conventional naturals and should be treated similarly — lower charge temperatures, careful management of early heat to avoid surface burning.
Processing Summary
| Method | Water use | Body | Acidity | Aroma character | Typical regions |
|---|---|---|---|---|---|
| Natural | Low | High | Low | Fruity, winey, intense | Brazil, Ethiopia, Panama |
| Washed | High | Low–medium | High | Clean, bright, floral | El Salvador, Kenya, Ethiopia, Colombia |
| Pulped natural | Low | Medium | Medium | Between natural and washed | Brazil |
| Honey | Low | Medium–high | Medium | Between natural and washed | Costa Rica, El Salvador, Nicaragua |
| Giling basah | Medium | Very high | Very low | Earthy, spiced | Indonesia |
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 increasingly used in El Salvador and may be relevant to future processing experiments.