{ "id": "wet-hulled", "url": "https://coffearium.org/entries/wet-hulled/", "license": "CC-BY-4.0", "title": "Wet-hulled (giling basah)", "summary": "An Indonesian process in which pulped, briefly fermented parchment is hulled while still wet, at roughly 35–50% moisture content, and the naked green bean is then dried.", "domain": "post-harvest-processing", "kind": "Method", "stage": "process", "topics": [], "topicSections": {}, "lang": "en", "status": "verified", "reviewer": "Coffearium verification pass", "lastVerified": "2026-10-08T00:00:00.000Z", "updated": "2026-10-08T00:00:00.000Z", "brief": [ "Cherries are pulped, fermented and washed, and the wet parchment is sun-dried only briefly before it changes hands.1,2", "The parchment is hulled while the bean is still wet – at 40–45% moisture in the Mandheling trial, 35–45% or 40–50% in the FAO project report – and the naked bean is then dried to about 12%.1,2", "Humid harvest weather and the need for quick cash are the reasons given for the practice.9,10,11", "The green coffee is dark, opal-green, and the cup is known for low acidity, heavy body and earthy notes.1,8", "Holding wet parchment for days raised mould and musty flavours in an FAO trial, and the naked bean must be dried at once to limit mould; rewetting favours fungal growth and ochratoxin A.2,4" ], "quickFacts": [ { "label": "Where", "value": "Indonesia, above all Sumatra; also Sulawesi" }, { "label": "Fermentation", "value": "Overnight after pulping, then washed" }, { "label": "Partial drying", "value": "Half a day to 1–2 days, in parchment" }, { "label": "Moisture at hulling", "value": "About 35–50% (FAO and trial reports); dry hulling about 12%" }, { "label": "Final moisture", "value": "About 12% (basis not stated in the trial reports)" }, { "label": "Green appearance", "value": "Dark, opal-green; split and crushed ends" }, { "label": "Cup", "value": "Low acidity, heavy body, earthy and spicy" } ], "aka": [ "Giling basah", "Wet hulling", "Wet-hulled process" ], "linkTerms": [ "wet-hulled coffee", "wet hulling", "wet-hulling", "giling basah" ], "related": [ "washed-process", "natural-process", "pulping", "fermentation", "drying", "hulling-and-dry-milling", "moisture-and-water-activity", "microorganisms", "grading-and-sorting" ], "contested": [ "Moisture at hulling: the journal report of a 2004/05 trial in North Sumatra describes hulling at 40–45%1, while the FAO report of the same project gives 35–45% for the modified huller and 40–50% for North Sumatran practice2; a trial in Gayo hulled at a moisture within the range of these reports.3 Trade descriptions disagree more widely: some describe further drying before the huller and give lower values7,12, others give values up to 50%.10,11 None of these reports states the moisture basis. No source opened for this entry tests which moisture gives the least damage or the best cup.", "Mould and storage time in the Mandheling trial: the FAO project report states that mould infection clearly increased with the length of wet storage2, while the journal abstract of the same trial found no clear trend with storage period and attributes the variation mainly to differences between parchment lots.1", "OTA results in the Mandheling storage trial: the journal abstract reports OTA in 5 of 42 samples at 0.17–2.24 ppb1, while the FAO project report of the same trial reports OTA in 7 samples at 0.07–2.24 ppb, four of them from parchment stored wet for 14 days.2 Both agree that all values were low.", "Typical cup: the classic description is low acidity, heavy body and earthy, spicy flavour1,8; one importer describes a carefully processed wet-hulled lot with a vibrant, pineapple-like acidity.10 How far the classic profile comes from the process itself, and how far from defects such as mustiness, is not settled.2" ], "corrections": [], "sources": [ { "id": "s1", "title": "Influence of Storage of Wet Arabica Parchment Prior to Wet Hulling on Moulds Development, Ochratoxin A Contamination, and Cup Quality of Mandheling Coffee", "authors": "Ismayadi, C.; Marsh, A.; Clarke, R.", "year": 2005, "publisher": "Pelita Perkebunan (Coffee and Cocoa Research Journal) 21(2)", "url": "https://www.ccrjournal.com/index.php/ccrj/article/view/20", "doi": "10.22302/iccri.jur.pelitaperkebunan.v21i2.20", "tier": "A", "quote": "Parchment coffees (6 lots) used for this trial were drawn from farmers and collectors in the region.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s2", "title": "Storage of wet Arabica parchment prior to wet hulling including the storage of dry green bean coffee (Project GCP/INT/743/CFC, Annex E.6)", "authors": "Marsh, A.", "publisher": "FAO", "url": "https://www.fao.org/fileadmin/user_upload/agns/pdf/coffee/Annex-E.6.pdf", "tier": "A", "quote": "Wet parchment is hulled at between 35 to 45% moisture content", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s3", "title": "Flavor of arabica coffee grown in Gayo Plateau as affected by varieties and processing techniques", "authors": "Abubakar, Y.; Karim, A.; Fahlufi, F.", "year": 2011, "publisher": "Proceedings of the Annual International Conference, Syiah Kuala University 1(1), 70–75", "url": "https://library.sweetmarias.com/wp-content/uploads/2020/08/Flavor-of-arabica-coffee-grown-in-Gayo-Palteau-as-affected-by-varieties-and-processing-techniques.pdf", "tier": "B", "quote": "Arabica coffee processed with wet hulling technique usually has low acidity with strong body taste.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s4", "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": "Avoid rewetting the beans because it favours rapid fungal growth and the possibility of OTA production.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s5", "title": "Influence of hulling and storage conditions on maintaining coffee quality", "authors": "Abreu, G. F.; Rosa, S. D. V. F.; Coelho, S. V. B.; Pereira, C. C.; Malta, M. R.; Fantazzini, T. B.; Vilela, A. L.", "year": 2023, "publisher": "Anais da Academia Brasileira de Ciências 95(4)", "url": "https://doi.org/10.1590/0001-3765202320190612", "doi": "10.1590/0001-3765202320190612", "tier": "A", "quote": "Mechanical damage caused by hulling, associated with the lack of tissue fruit parts, contributes to reduction hulled coffee quality in storage, regardless of the processing.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s6", "title": "Arabica coffee manual for Lao-PDR", "authors": "Winston, E.; Op de Laak, J.; Marsh, T.; Lempke, H.; Chapman, K.", "year": 2005, "publisher": "FAO Regional Office for Asia and the Pacific, Bangkok", "url": "https://www.fao.org/4/ae939e/ae939e08.htm", "tier": "A", "quote": "Notably this process does not ferment the mucilage as it is mechanically removed by a demucilager.", "accessed": "2026-10-08T00:00:00.000Z" }, { "id": "s7", "title": "Sumatran Coffee Processing: Why You Should Know Giling Basah", "authors": "Owen, T.", "year": 2021, "publisher": "Sweet Maria's Coffee Library", "url": "https://library.sweetmarias.com/why-should-you-know-giling-basah/", "tier": "B", "quote": "The longer you have coffee in your possession, the more money you lose.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s8", "title": "Wet Hulled Process (glossary)", "year": 2019, "publisher": "Sweet Maria's Coffee Library", "url": "https://library.sweetmarias.com/glossary/wet-hulled-process/", "tier": "B", "quote": "results in a dark, opal-green coffee with little silverskin", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s9", "title": "The What, the How and the Why of Indonesian processing methods", "authors": "Foster, D.", "year": 2019, "publisher": "Atlas Coffee Importers", "url": "https://www.atlascoffee.com/encyclopedia/the-what-the-how-and-the-why-of-indonesian-processing-methods/", "tier": "B", "quote": "The miller owns the equipment, specifically the wet-huller, which is needed to remove the parchment from the bean.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s10", "title": "What is Wet Hulled?", "authors": "Haigh, T.", "year": 2024, "publisher": "DRWakefield", "url": "https://drwakefield.com/news-and-views/what-is-wet-hulled/", "tier": "B", "quote": "Producing and selling coffee quickly is an asset during harvest in gaining access to money quickly", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s11", "title": "Wet-Hulled (aka Semi-Washed, Sumatra Process, Giling Basah)", "publisher": "Cafe Imports", "url": "https://www.cafeimports.com/europe/blog/?p=37563", "tier": "B", "quote": "the Wet-Hulled process is a result of a combination of environmental conditions, market access, and traditions found in Indonesia", "accessed": "2026-10-08T00:00:00.000Z" }, { "id": "s12", "title": "Indonesian Wet Hulled Coffee: Your One-Stop Guide", "authors": "Lynch, R.", "year": 2015, "publisher": "Perfect Daily Grind", "url": "https://perfectdailygrind.com/2015/10/indonesian-wet-hulled-coffee-processing/", "tier": "C", "quote": "There’s a high risk that the machinery that hulls the coffee will also split it at the ends, due to the bean’s low density.", "accessed": "2026-09-30T00:00:00.000Z" } ], "markdown": "## What it is\n\nWet hulling – *giling basah* in Indonesian – is a way of processing Arabica in which the parchment is taken off while the bean is still wet, and the naked bean is dried afterwards.1,8 In the washed process and in dry hulling, the parchment coffee is dried first, to about 12%, and only then hulled.1,3 In the trade the process is also called \"semi-washed\"11, but the same term is used elsewhere for other processes: the FAO uses it for coffee whose mucilage is removed by a demucilager straight after pulping, without fermentation6, and the Codex code of practice for green coffee from pulped beans dried within their mucilaginous parchment.4 This entry uses \"wet-hulled\" only.\n\nThe method is used in parts of Indonesia, above all Sumatra.8 Mandheling coffee from the highlands around Lake Toba in North Sumatra is made this way by smallholder farmers.1 It is also used in the Gayo highlands of Aceh3 and in Sulawesi.7,9 One importer reports that some buyers now ask for wet-hulled coffee from places such as Bali and Flores, which did not traditionally use it.7\n\n
\n
\n
Who does what along the wet-hulled chain, with the moisture values reported in trials; the fully washed route is shown for comparison. Roles vary by region. Schematic, not to scale.1,2,7,8,9
\n
\n\n## How it is done\n\n1. **Pulping and fermentation** – the farmer pulps the cherries and ferments the pulped coffee, then washes it the next day.2 Importers describe the fermentation as overnight, in bags, tubs or tanks.7,10 In some areas the pulped seeds are instead held with their mucilage in tanks or sacks until delivery.11\n2. **Brief drying in parchment** – the wet parchment is sun-dried only briefly: half a day in an FAO trial, 1–2 days in North Sumatran practice.1,2\n3. **Sale and holding** – the farmer sells the wet parchment to a collector.2,9 In North Sumatra it may be stored for up to a few weeks before hulling; in a 2004/05 trial2 the stored parchment held 41.74–53.96% moisture.1\n4. **Wet hulling** – a huller, usually owned by the mill, takes off the parchment while the bean is still wet: at 40–45% moisture in the Mandheling trial, 35–45% (huller) or 40–50% (practice) in the FAO report.1,2,9 The bean that comes out is swollen with water and white7 or whitish-green.8\n5. **Drying the naked bean** – the green bean is dried straight after hulling, to limit mould,2 down to about 12% moisture.1,2 It then goes through the usual sorting before export.9\n\n## Why it arose\n\nThe sources give two reasons. The first is climate. Rain and humidity are high in the growing regions, which makes it hard to dry parchment coffee fully; taking the parchment off early reduces the mass and shortens drying.9,10,11 The second is money. Smallholders can sell wet parchment soon after harvest, so cash comes in quickly at every link of the chain.7,9,10 One importer adds market access and local tradition to the list.11\n\nThe structure of the trade follows from this. Farmers process small lots, collectors buy and gather the wet parchment, and the miller owns the wet huller.2,9 In some places collectors also do the pulping and fermentation.9\n\n## Appearance and cup\n\n**Green coffee.** Wet-hulled coffee is dark, opal-green, with little silverskin left on the bean.8 Because the bean is soft when it passes through the huller, many beans come out with crushed or split ends.7\n\n**Cup.** Mandheling coffee is described as low in acidity, with a heavy, complex body and spicy, slightly earthy and fruity flavour.1 A trial in Gayo found the same pattern – low acidity and strong body – and tasters preferred wet-hulled over dry-hulled coffee.3 One importer lists earthy, savoury, herbaceous and dark-chocolate notes11; another treats herbal, mossy and mushroomy notes as signs of faults in processing, though it notes that a slight green-herb note can be pleasant.7 The authors of the North Sumatran trial suggest that the handling itself contributes to this character.1\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 in trials, not a single correct recipe. Moisture values are given as reported; the trial reports do not state the basis, and the FAO trial determined moisture by oven drying (105 °C, 24 h).2\n\n| Parameter | Value reported | Source |\n|---|---|---|\n| Pulping | By the farmer, on the day of harvest (trial Day −1) | FAO trial report2 |\n| Fermentation | After pulping, then washed; described as overnight | FAO2, importers7,10 |\n| Partial drying in parchment | Half a day (trial); 1–2 days of sun (North Sumatra) | FAO2, Ismayadi et al.1 |\n| Moisture of wet parchment in storage | 41.74–53.96% | Ismayadi et al.1 |\n| Storage before hulling | Up to a few weeks in practice; 1, 7 and 14 days tested, in PE sacks in a warehouse | Ismayadi et al.1 |\n| Moisture at hulling | 40–45% (Mandheling trial); 35–45% (FAO, modified huller) and 40–50% (FAO, North Sumatran practice); the Gayo trial's value lies within this range | Ismayadi et al.1, FAO2, Abubakar et al.3 |\n| Huller | Indonesian Kemajuan huller, steel huller bar replaced by a rubber strip | FAO2 |\n| Huller power and speed | Raised from 15 to 25 hp and from 600 to 750 rpm | FAO2 |\n| Huller throughput | About 800 kg of wet green bean per hour | FAO2 |\n| After hulling | Dry immediately | FAO2 |\n| Intermediate holding (trial variant) | Dried to 17%, held 3 weeks, then dried to 12% | Ismayadi et al.1 |\n| Final moisture | 12% | Ismayadi et al.1, FAO2 |\n| Safe for parchment coffee | Moisture < 12.5% (wet basis) and water activity at most 0.67–0.70 | Codex4 |\n| Fully washed control | Fresh parchment dried to 12% before hulling | Ismayadi et al.1 |\n\n
\n
\n
Moisture at each step of the wet-hulled chain as reported in trials (basis not stated), against the fully washed control and the Codex limit for parchment coffee (wet basis).1,2,4
\n
\n\n## Moisture and mechanics of hulling\n\nIn a fully washed chain the parchment comes off at about 12% moisture.1 In wet hulling it comes off at about 35–50%, roughly three to four times the moisture value.1,2 At that point the bean is soft and swollen rather than hard and glassy.7 A standard huller does not work on such coffee without changes: in the FAO project the steel huller bar was replaced by a rubber strip, and the machine was given more power and speed.2\n\nThe price of this is mechanical damage. Soft beans are crushed or split at the ends in the huller.7,12 In a Brazilian study of Arabica hulled after drying, mechanical damage from hulling lowered quality in storage for both natural and washed coffee.5 In the North Sumatran storage trial, the first visible mould was on naked and broken beans, in one lot on day 3.2\n\n## Drying without parchment\n\nAfter wet hulling, the bean dries with no parchment around it.2 Importers note that this leaves it exposed to swings in relative humidity and to contamination from dirt, debris and animals while it dries on tarpaulins.11 Some is dried on patios, on the road or on bare dirt.7,12 The Codex code of practice warns against both: bare soil is not appropriate for drying in rainy areas, and rewetting favours rapid fungal growth and OTA.4\n\n## Moulds and ochratoxin A\n\nThe weakest point of the chain is the wet parchment waiting for the huller. In a 2004/05 trial in North Sumatra, six lots of wet parchment from farmers and collectors were stored for 1, 7 and 14 days in sacks before wet hulling.1,2 When mould became visible, the parchment was spread on a plastic sheet inside the warehouse.1\n\n- **Mould.** The FAO report states that infection clearly increased with storage time2; the journal abstract found no clear trend and points to differences between lots (see Contested).1 Black *Aspergillus* dominated; *Aspergillus ochraceus* was found at a low infection rate of 0–15.3%.1 Ochre-group fungi were found in 5 of the 6 lots stored for two weeks, and not at the shorter storage times.2\n- **OTA.** OTA was found only at low levels, below the European Union limit according to the journal report.1 Most of the positive samples came from parchment stored wet for 14 days.2 The exact counts differ between the two reports of the trial (see Contested).\n- **Cup.** Longer wet storage led to more musty flavours in the green coffee.2 Even so, the cup of many samples stored wet for up to two weeks was better than the authors expected.2\n\n## Chemistry and sensory studies\n\nComparative chemistry is thin. No study opened for this entry measured sugars, acids, lipids or volatile compounds side by side in wet-hulled and fully washed coffee from the same lots. What exists is sensory:\n\n- In the North Sumatran trial, coffee stored wet for one day, hulled fast and dried fast to 12% was most likely to show the Mandheling character, and three of four tasters picked a sample of this kind as having the best Mandheling character.2 All tasters used the term \"fruity/fermented\", which the report expected to be the easiest and commonest negative character to identify.2\n- Tasters also found some trial samples too clean in the cup, with less complex body and too green in colour compared with the traditional Mandheling they expected.2\n- In the Gayo highlands, beans were dried in two stages for wet hulling – partly before hulling, to a moisture within the range given by the North Sumatran reports, and again after it – or dried fully in one stage for dry hulling.3 Wet-hulled coffee scored better in the organoleptic test and was preferred.3\n\n## Open questions\n\n- **Where the flavour comes from.** The authors of the Mandheling trial thought the handling probably contributes to the cup character1, but no source opened for this entry separates the effect of wet hulling itself from wet storage, fermentation, drying on the ground, and defects.\n- **The seed's own metabolism.** Seed metabolism during processing affects sugars in washed coffee (see the washed process entry). No study opened for this entry follows the living seed through wet hulling, when the bean loses its parchment at high moisture.\n- **Best moisture at hulling.** The FAO and trial reports give about 35–50%1,2, and trade descriptions vary more widely, some well below that range.7,12 The trade-off between damage, drying time and mould has not been measured.\n- **History.** The sources opened for this entry do not give a primary, dated account of when wet hulling spread in Indonesia.\n\n## Key studies\n\n
\n

Ismayadi, Marsh & Clarke, 2005 – Wet storage before wet hulling. Stored wet parchment from six North Sumatran lots for 1, 7 and 14 days before wet hulling and compared it with a fully dried control. Black Aspergillus dominated, OTA stayed low, storage period showed no clear trend, and the best cup came from a lot stored wet for one day.

\n

Pelita Perkebunan 21(2) · doi:10.22302/iccri.jur.pelitaperkebunan.v21i2.20

\n
\n\n
\n

Marsh, FAO project report – The same trial in detail. The FAO/CFC/ICO project report gives the day-by-day protocol, the changes made to the huller for wet parchment, and the full mould, OTA and cupping results. It is the most detailed open description of how wet hulling is done.

\n

FAO, Project GCP/INT/743/CFC, Annex E.6 · fao.org (PDF)

\n
\n\n
\n

Abubakar, Karim & Fahlufi, 2011 – Wet vs dry hulling in Gayo. Compared Gayo Arabica varieties processed by wet hulling and by dry hulling. Wet-hulled coffee had lower acidity, stronger body and was preferred by the panel.

\n

Proceedings, Annual International Conference, Syiah Kuala University (peer review not stated) · PDF

\n
\n\n
\n

Abreu et al., 2023 – Hulling damage and storage. Studied how hulling and storage conditions affect green coffee quality. In Brazilian Arabica hulled after drying, mechanical damage from hulling, together with the loss of the fruit layers, lowered quality during storage – relevant to wet hulling, where the bean is hulled soft and then dried and stored naked, though wet hulling itself was not tested.

\n

Anais da Academia Brasileira de Ciências 95(4) · doi:10.1590/0001-3765202320190612

\n
" }