{ "id": "washed-process", "url": "https://coffearium.org/entries/washed-process/", "license": "CC-BY-4.0", "title": "Washed process", "summary": "A processing method in which the skin, pulp and mucilage are removed from the coffee seed before it is dried.", "domain": "post-harvest-processing", "kind": "Method", "stage": "process", "topics": [ "sustainability" ], "topicSections": { "sustainability": { "id": "water-and-wastewater", "label": "Water and wastewater" } }, "lang": "en", "status": "verified", "reviewer": "Coffearium verification pass", "lastVerified": "2026-10-08T00:00:00.000Z", "updated": "2026-10-08T00:00:00.000Z", "brief": [ "The skin and pulp are removed mechanically, in the presence of water.1", "The remaining mucilage is broken down – usually by fermentation, sometimes with enzymes or machines – and washed off, leaving parchment coffee.1,3,5", "The parchment coffee is dried until it is safe from fungal damage – below 12.5% moisture (wet basis) according to the Codex code of practice.1" ], "quickFacts": [ { "label": "Fruit removed", "value": "Before drying" }, { "label": "Raw material", "value": "Ripe cherries only" }, { "label": "Fermentation time", "value": "12–36 h (Codex); 12–48 h (2016 review); 6–72 h depending on climate (2023 review) – contested" }, { "label": "pH during fermentation", "value": "From about 6.0–6.5 down to about 4.0" }, { "label": "Water use", "value": "About 40 L/kg conventional; under 1 L/kg with mechanical demucilaging" }, { "label": "Optional soak", "value": "About 12 h (Kenya); overnight to rarely 48 h" }, { "label": "Cherry to green", "value": "About 5–6 kg fresh cherry per kg green coffee" }, { "label": "Dried as", "value": "Parchment coffee" }, { "label": "Safe from fungi", "value": "< 12.5% moisture (wet basis), water activity 0.67–0.70" } ], "aka": [ "Wet process", "Fully washed" ], "linkTerms": [ "wet processing", "washed coffee", "washed coffees", "wet-processed" ], "related": [ "coffee-cherry-anatomy", "natural-process", "mucilage", "fermentation", "microorganisms", "drying", "moisture-and-water-activity", "cherry-to-green-conversion" ], "contested": [ "Typical fermentation time: the Codex code of practice gives 12 to 36 hours1, a 2016 review gives 12 to 48 hours14, and a 2023 review gives 6 to 72 hours, depending on the surrounding climate.2", "Flavour impact of fermentation metabolites: lactic acid, acetic acid and mannitol formed in the mucilage have been found in the seed6, but a 2023 review describes the migration of microbial metabolites into the seed as \"believed\" and their link to flavour as a correlation.2", "Why washed green coffee has less glucose and fructose: a drying study attributes the loss at least in part to metabolic processes, not to leaching – sugars fell while wet-processed (mechanically demucilaged) Arabica dried, with no process water present8 – and an earlier comparison found that the two sugars decrease during wet processing but stay unchanged or rise during dry processing12; a field study links the drop during fermentation to anaerobic sugar consumption by the seed, but adds that during soaking osmotic pressure helped monosaccharides leave the beans.6 A trial in Yunnan found fructose among the most abundant compounds in the soaking water.5" ], "corrections": [], "sources": [ { "id": "s1", "title": "Code of Practice for the Prevention and Reduction of Ochratoxin A Contamination in Coffee (CAC/RCP 69-2009)", "authors": "Codex Alimentarius Commission (FAO/WHO)", "year": 2009, "publisher": "Codex Alimentarius", "url": "https://www.fao.org/input/download/standards/11250/CXP_069e.pdf", "tier": "A", "quote": "In the fermentation process, the mucilage is broken down by fermenting the beans in water at ambient temperature (using microrganisms) for between 12 and 36 hours.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s2", "title": "Coffee fermentation: Expedition from traditional to controlled process and perspectives for industrialization", "authors": "Elhalis, H.; Cox, J.; Zhao, J.", "year": 2023, "publisher": "Applied Food Research 3(1), 100253", "url": "https://www.sciencedirect.com/science/article/pii/S2772502222002086", "doi": "10.1016/j.afres.2022.100253", "tier": "A", "quote": "Studies have shown that desired microbial metabolites were produced during fermentation that is believed to migrate inside coffee seeds and correlated to modulation of the final product flavor, aroma, and sensory quality. … In the wet fermentation process, water conveys the de-pulped beans into a tank filled with water, where the beans are subjected to submerged fermentation for 6-72 h depending on the surrounding climate conditions", "accessed": "2026-10-08T00:00:00.000Z" }, { "id": "s3", "title": "The Harvest and Post-Harvest Management Practices' Impact on Coffee Quality", "authors": "Haile, M.; Kang, W. H.", "year": 2019, "publisher": "Coffee – Production and Research, IntechOpen", "url": "https://www.intechopen.com/chapters/70151", "doi": "10.5772/intechopen.89224", "tier": "B", "quote": "After de-pulping, chemicals mostly enzymes used to remove mucilage or the natural fermentation proceeds depend upon the environmental condition and fruit ripeness.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s4", "title": "Enhancement of Coffee Quality Attributes by Combining Processing Methods and Varieties", "authors": "Teran, E.", "year": 2024, "publisher": "Beverages 10(1), 10", "url": "https://www.mdpi.com/2306-5710/10/1/10", "doi": "10.3390/beverages10010010", "tier": "A", "quote": "specific Arabica varieties, such as Bourbon and Pacamara, enhance flavor when processed using the 'Natural/Dry' method", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s5", "title": "Influence of various processing parameters on the microbial community dynamics, metabolomic profiles, and cup quality during wet coffee processing", "authors": "Zhang, S. J.; De Bruyn, F.; Pothakos, V.; Contreras, G. F.; Cai, Z.; Moccand, C.; Weckx, S.; De Vuyst, L.", "year": 2019, "publisher": "Frontiers in Microbiology 10, 2621", "url": "https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02621/full", "doi": "10.3389/fmicb.2019.02621", "tier": "A", "quote": "For all fermentation variants, the initial pH was approximately 6.0–6.5 and decreased continuously until approximately 4.0.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s6", "title": "Exploring the impacts of postharvest processing on the microbiota and metabolite profiles during green coffee bean production", "authors": "De Bruyn, F.; Zhang, S. J.; Pothakos, V.; Torres, J.; Lambot, C.; Moroni, A. V.; Callanan, M.; Sybesma, W.; Weckx, S.; De Vuyst, L.", "year": 2017, "publisher": "Applied and Environmental Microbiology 83(1), e02398-16", "url": "https://journals.asm.org/doi/10.1128/aem.02398-16", "doi": "10.1128/AEM.02398-16", "tier": "A", "quote": "Several of the metabolites associated with lactic acid bacterial metabolism (e.g., lactic acid, acetic acid, and mannitol) produced in the mucilage were also found in the endosperm.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s7", "title": "Transient occurrence of seed germination processes during coffee post-harvest treatment", "authors": "Bytof, G.; Knopp, S.-E.; Kramer, D.; Breitenstein, B.; Bergervoet, J. H. W.; Groot, S. P. C.; Selmar, D.", "year": 2007, "publisher": "Annals of Botany 100(1), 61–66", "url": "https://academic.oup.com/aob/article/100/1/61/2763338", "doi": "10.1093/aob/mcm068", "tier": "A", "quote": "The highest germination activity occurred 2 d after the onset of wet processing, whereas the corresponding maximum in the course of dry processing appeared about 1 week after the start of post harvest treatment.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s8", "title": "Influence of drying on the content of sugars in wet processed green Arabica coffees", "authors": "Kleinwächter, M.; Selmar, D.", "year": 2010, "publisher": "Food Chemistry 119, 500–504", "url": "https://doi.org/10.1016/j.foodchem.2009.06.048", "doi": "10.1016/j.foodchem.2009.06.048", "tier": "A", "quote": "The contents of fructose and glucose decreased significantly within the first day of drying. This diminution for the first time proves that the lower contents of glucose and fructose generally present in wet processed coffee beans in comparison to dry processed ones are – at least in part – due to metabolic processes and are not related to the leaching of sugars into the process water in the course of wet processing.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s9", "title": "Ecological Processing of Coffee at the Farm Level: An Ecological and Profitable Case", "authors": "Roa, G.; Oliveros, C. E.; Álvarez, J.; Sanz, J. R.; Ramírez, C. A.; Dávila, M. T.; Álvarez, J. R.; Zambrano, D. A.; Puerta, G. I.; Rodríguez, N.", "publisher": "Cenicafé (Colombian Coffee Research Centre)", "url": "https://www.ctahr.hawaii.edu/hawaii/downloads/Low_Water_use_processing.pdf", "tier": "A", "quote": "The conventional process of the coffee might use 40 liters of water per kilogram of dry parchment coffee", "accessed": "2026-10-08T00:00:00.000Z" }, { "id": "s10", "title": "Advances in coffee drying: A comprehensive review of traditional, solar, mechanical, hybrid, and emerging methods", "authors": "Duque-Dussán, E.; Figueroa-Varela, P. A.; Cruz-Ospina, V.; Banout, J.", "year": 2026, "publisher": "Foods 15(10), 1737", "url": "https://www.mdpi.com/2304-8158/15/10/1737", "doi": "10.3390/foods15101737", "tier": "A", "quote": "Controlled drying within the range of 40–50 °C has been shown to best preserve desirable attributes while still achieving microbiological safety", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s11", "title": "Risk Assessment of Coffee Cherry (Cascara) Fruit Products for Flour Replacement and Other Alternative Food Uses", "authors": "Eckhardt, S.; Franke, H.; Schwarz, S.; Lachenmeier, D. W.", "year": 2022, "publisher": "Molecules 27(23), 8435", "url": "https://www.mdpi.com/1420-3049/27/23/8435", "doi": "10.3390/molecules27238435", "tier": "A", "quote": "ripe coffee cherries are separated in flotation tanks, after which a mechanical depulper separates the skin and pulp.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s12", "title": "Influence of processing on the content of sugars in green Arabica coffee beans", "authors": "Knopp, S.; Bytof, G.; Selmar, D.", "year": 2006, "publisher": "European Food Research and Technology 223, 195–201", "url": "https://link.springer.com/article/10.1007/s00217-005-0172-1", "doi": "10.1007/s00217-005-0172-1", "tier": "A", "quote": "While in washed coffee beans (wet processing) only low amounts of these both hexoses were present, those in unwashed coffees (dry processing) were significantly higher.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s13", "title": "Post Harvest Handling and Processing of Coffee in African Countries, Annex 5: Coffee Post Harvest Handling and processing in Kenya", "authors": "Mutua, J.", "year": 2000, "publisher": "FAO", "url": "https://www.fao.org/4/X6939E/X6939e11.htm", "tier": "A", "quote": "Studies in Kenya have shown that soaking of coffee parchment after fermentation for about 12 hours improves the coffee quality both in colour and taste.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s14", "title": "Challenges in Specialty Coffee Processing and Quality Assurance", "authors": "Poltronieri, P.; Rossi, F.", "year": 2016, "publisher": "Challenges 7(2), 19", "url": "https://www.mdpi.com/2078-1547/7/2/19", "doi": "10.3390/challe7020019", "tier": "A", "quote": "After mucilage removal, the parchments are held under water for a period from overnight up to, rarely, 48 h.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s15", "title": "The potential for income improvement and biodiversity conservation via specialty coffee in Ethiopia", "authors": "Schuit, P.; Moat, J.; Gole, T. W.; Challa, Z. K.; Torz, J.; Macatonia, S.; Cruz, G.; Davis, A. P.", "year": 2021, "publisher": "PeerJ 9, e10621", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC7879952/", "doi": "10.7717/peerj.10621", "tier": "A", "quote": "for fresh cherry to clean coffee, via the washed coffee processing method, is often stated to be around 5:1, but in Ethiopia is usually around 6:1", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s16", "title": "The Journey of the Coffee Bean", "authors": "European Coffee Federation", "publisher": "European Coffee Federation", "url": "https://www.ecf-coffee.org/wp-content/uploads/2022/02/Final.-Journey-of-the-bean.pdf", "tier": "B", "quote": "To produce 1 kg of green coffee, 5 to 6 Kg of coffee cherry will be needed.", "accessed": "2026-09-30T00:00:00.000Z" } ], "markdown": "
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What stays on the seed during drying in the three processing families.
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\n\n## How it is done\n\n1. **Selection** – the process needs ripe cherries only, either picked selectively or separated mechanically during processing,1 for example in flotation tanks.11\n2. **Pulping** – a pulping machine removes the skin and pulp in the presence of water.1 The seeds are left covered in slimy mucilage, which pulping does not remove.1 In Kenya, the pulped coffee is then graded by density and size into grades 1 and 2 and \"lights\".13\n3. **Mucilage removal** – the coffee is usually fermented in water at ambient temperature, so that microorganisms break the mucilage down.1 Some producers use enzymes instead.3\n4. **Washing** – the loosened mucilage is washed off. The result is called parchment or washed coffee.3 Some mills add a soak in clean water before the final wash (see below).13,14\n5. **Drying** – the parchment coffee is dried in thin layers of 3–5 cm and turned regularly.1 It is considered safe from fungal damage below 12.5% moisture (wet basis) and a water activity of 0.67–0.70.1\n\n## Soaking and grading\n\n**Soaking.** In some processing chains the washed parchment is held under clean water once more, from overnight up to, rarely, 48 hours.14 This is sometimes called secondary fermentation.14 In Kenya, about 12 hours of soaking after fermentation was found to improve colour and taste; the parchment is then washed again.13 Soaking is used to improve the look of the green bean and give a cleaner cup.5 In a trial in Yunnan, a 24-hour soak evened out the green coffee: it tempered the gains of longer fermentation, whatever had been done before.5 Short soaks do not seem to cause defects unless the water is tainted.14\n\n**Grading by density.** Density sorting starts before pulping, when floating cherries are separated in water.1,11 In Kenya, the pulped coffee is graded again by density and size into grades 1 and 2 and \"lights\".13 The final wash there is done in concrete channels, where the parchment is pushed with wooden paddles against a stream of water.13 In the Yunnan trial, washing was done by passing the beans through a curved water channel.5\n\n## Effect on the cup\n\nWhether coffee is processed wet or dry creates typical differences in quality and flavour.3 The effect is not the same for every coffee: a 2024 analysis of Coffee Quality Institute cupping records found that the effect of processing on flavour scores depended on the variety.4 Within the washed process, fermentation time matters too: in a controlled trial, a longer fermentation gave a fruitier and more acidic cup.5\n\n\n\n## Reference protocol\n\nThe table brings together the parameters reported in the sources. It describes the range found in practice and research, not a single correct recipe.\n\n| Step | Parameter | Value reported | Source |\n|---|---|---|---|\n| Sorting | Ripeness | Ripe cherries only; floaters separated in water | Codex1, Eckhardt et al.11 |\n| Pulping | Method | Mechanical, with water | Codex1 |\n| Fermentation | Medium and temperature | Under water, ambient temperature | Codex1 |\n| Fermentation | Duration | 12–36 h (Codex); 12–48 h (2016 review); 6–72 h depending on climate (2023 review) | Codex1, Poltronieri & Rossi14, Elhalis et al.2 |\n| Fermentation | pH course | Starts at about 6.0–6.5, falls to about 4.0 | Zhang et al.5 |\n| Alternative | Mechanical demucilaging | Cup quality comparable to fermented coffee in one trial | Zhang et al.5 |\n| Grading | Pulped parchment | Grades 1, 2 and lights, by density and size (Kenya) | FAO13 |\n| Soaking | Duration | About 12 h (Kenya); overnight to rarely 48 h; 24 h in one trial | FAO13, Poltronieri & Rossi14, Zhang et al.5 |\n| Washing | Final wash | Concrete channels, parchment pushed against a stream of water (Kenya) | FAO13 |\n| Water | Use per kg dry parchment | About 40 L conventional; under 1 L with the DESLIM mechanical demucilager | Cenicafé9 |\n| Drying | Layer depth | 3–5 cm, turned constantly during the day | Codex1 |\n| Drying | Protection | Parchment can be heaped and covered after one day of drying | Codex1 |\n| Drying | Drying temperature | 40–50 °C recommended; maximum generally considered to be 50 °C | Duque-Dussán et al.10 |\n| End point | Storage safety | < 12.5% moisture (wb), water activity 0.67–0.70 | Codex1 |\n\n
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Fermentation time as reported by the sources of this entry: Codex code of practice1, Poltronieri & Rossi14, Elhalis et al.2, Zhang et al.5 The ranges do not agree (see Contested).
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\n\n## Fermentation: microbiology and chemistry\n\nWet fermentation is dominated by lactic acid bacteria. In a study in Ecuador, *Leuconostoc*, *Lactococcus* and *Lactobacillus* were the most common group, together with enterobacteria and the yeasts *Pichia* and *Starmerella*.6 A 2022 review names *Leuconostoc pseudomesenteroides*, *Lactobacillus vaccinostercus*, *Lactobacillus brevis* and *Lactobacillus plantarum* among the lactic acid bacteria that increase during fermentation.11\n\nTheir activity acidifies the fermentation water: in a trial in Yunnan, China, pH fell from about 6.0–6.5 to about 4.0 in every variant, with the largest drop after 36 hours.5 Lactic acid, acetic acid and mannitol formed in the mucilage were later found inside the seed.6\n\n## The seed's own metabolism\n\nProcessing does not only act on the outside of the seed. The seed is alive, and processing switches on germination processes inside it. In washed coffee, germination activity peaked about two days after processing began – much earlier than in natural coffee.7\n\n## Why washed coffee has less sugar\n\nWashed green coffee holds significantly less glucose and fructose than natural coffee processed in parallel, in a study of Arabica var. Acaiá.12 Two explanations are offered.\n\n**Seed metabolism.** In washed coffee the two sugars fall during processing, while in natural coffee they stay the same or even rise.12 When Arabica that had been mechanically demucilaged and dry-fermented without water was dried under controlled conditions – with no process water present – glucose and fructose fell significantly within the first day.8 The authors concluded that the difference is, at least in part, due to metabolic processes and not to sugars leaching into the process water.8 A field study in Ecuador agrees for the tank stage: fructose, glucose and sucrose in the endosperm fell significantly during fermentation, and the authors put this down to the lack of oxygen under water, which triggered germination and an anaerobic sugar-consumption response in the seed.6\n\n**Loss into the water.** The same Ecuadorian study found that fructose and glucose fell further during a 24-hour soak, and proposed that osmotic pressure helped monosaccharides and fermentation products leave the beans.6 In Yunnan, fructose was among the most abundant compounds in the soaking water at the end of soaking, and glucose and fructose in the beans dropped after washing.5\n\nThe two mechanisms are not exclusive. The evidence points to metabolism during fermentation and drying, with leaching adding to the loss where a soak is used.6,8 No study in this entry has measured how much of the final difference each one explains.\n\n\n\n## Mass balance\n\nProcessing removes most of the cherry's weight. Published conversion factors are rounded rules of thumb.\n\n| Parameter | Value reported | Source |\n|---|---|---|\n| Fresh cherry to green coffee (washed) | About 5:1 often stated; usually about 6:1 in Ethiopia | Schuit et al.15 |\n| Fresh cherry to green coffee | 5–6 kg cherry per kg green | European Coffee Federation16 |\n| Mucilage | About 13% of the cherry's weight; about 22% of pulped coffee | Cenicafé9 |\n| Parchment husk | About 20% of the weight of dry parchment coffee (1.25:1 parchment to green) | Schuit et al.15 |\n\nThe sources opened for this entry give no primary figure for the share of skin and pulp on a fresh-weight basis, so it is left out.\n\n## Water and wastewater\n\nConventional washing can use about 40 litres of water per kilogram of dry parchment coffee.9 The ecological processing developed by Cenicafé in Colombia pulps without water and removes mucilage mechanically; with its DESLIM demucilager, water use fell to under 1 litre per kilogram.9\n\n## Key studies\n\n
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Zhang et al., 2019 – Processing parameters in wet processing. A controlled trial in Yunnan (Catimor) comparing depulped and mechanically demucilaged coffee, standard and extended fermentation, and soaking. Longer fermentation gave a fruitier, more acidic cup; mechanical demucilaging matched the fermented coffee; soaking dampened the fermentation effects.

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Frontiers in Microbiology 10, 2621 · doi:10.3389/fmicb.2019.02621

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De Bruyn et al., 2017 – Microbiota and metabolites in wet and dry processing. Follows Typica coffee in Ecuador from harvest to drying with DNA sequencing and metabolite analysis. Wet processing was dominated by lactic acid bacteria, and several of their metabolites reached the seed.

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Applied and Environmental Microbiology 83(1), e02398-16 · doi:10.1128/AEM.02398-16

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Bytof et al., 2007 – Germination during processing. Measures germination markers in seeds during wet and dry processing and shows that their timing and extent differ between the two methods.

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Annals of Botany 100(1), 61–66 · doi:10.1093/aob/mcm068

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Kleinwächter & Selmar, 2010 – Sugars during drying. Dries Arabica that was mechanically demucilaged and dry-fermented without water, under defined conditions, and shows that glucose and fructose fall within the first day, with no process water present. The authors read this as evidence that metabolic processes, not leaching, explain at least part of the sugar gap between wet- and dry-processed coffees.

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Food Chemistry 119, 500–504 · doi:10.1016/j.foodchem.2009.06.048

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Teran, 2024 – Processing and variety. Analyses Coffee Quality Institute cupping records to see how processing method and variety interact in their effect on sensory scores of Arabica coffee.

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Beverages 10(1), 10 · doi:10.3390/beverages10010010

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" }