{ "id": "pulping", "url": "https://coffearium.org/entries/pulping/", "license": "CC-BY-4.0", "title": "Pulping", "summary": "The first step of wet processing – a machine squeezes the seeds out of the fresh cherry and strips off the skin and pulp, leaving the seeds in their mucilage and parchment.", "domain": "post-harvest-processing", "kind": "Process", "stage": "process", "topics": [ "sustainability", "equipment" ], "topicSections": { "sustainability": { "id": "water-and-pulp", "label": "Water and pulp" } }, "lang": "en", "status": "verified", "reviewer": "Coffearium verification pass", "lastVerified": "2026-10-08T00:00:00.000Z", "updated": "2026-10-08T00:00:00.000Z", "brief": [ "Pulping removes the skin and pulp of the fresh cherry mechanically; the seeds leave the machine still covered in mucilage and parchment.1,2", "Drum and disc pulpers press the cherry against a fixed plate; the seeds are squeezed out and the pulp is torn away.5,6,8", "The gap must be set to the size of the cherry – a badly adjusted pulper nips beans, which count as defects and have been linked to stinkers.3,6,13", "A conventional Colombian wet mill uses 40–50 L of water per kg of dry parchment, about half of it for pulping and for carrying the pulp and the pulped coffee in water; pulping without water removes the use at the pulping stage.11", "Pulp is about 44% of the fresh cherry's weight in Cenicafé's figures and the largest source of pollution from a wet mill.11" ], "quickFacts": [ { "label": "Removes", "value": "Skin and pulp (exocarp and most of the mesocarp)" }, { "label": "Leaves on the seed", "value": "Mucilage and parchment" }, { "label": "Machines", "value": "Drum (horizontal cylinder), disc; horizontal- and vertical-shaft pulpers can work without water" }, { "label": "Performance limits (Philippine standard)", "value": "≥ 95% efficiency, ≤ 3.5% damaged parchment, ≤ 5% unpulped" }, { "label": "Water (conventional pulping + hydraulic transport)", "value": "About half of 40–50 L per kg dry parchment (Cenicafé)" }, { "label": "Pulp share", "value": "About 44% of fresh cherry weight (Cenicafé)" }, { "label": "Time to pulping", "value": "Same day; within 10 h (Kenya)" } ], "aka": [ "Depulping", "Despulpado" ], "linkTerms": [ "pulping station", "pulping machine" ], "related": [ "coffee-cherry-anatomy", "washed-process", "mucilage", "harvesting-and-sorting", "mechanical-demucilaging", "fermentation", "pulped-natural", "honey-process" ], "contested": [ "What pulping removes: the Codex code of practice defines pulping as removing the pulp and \"as much as possible of the mucilage\"1, while Cenicafé treats the mucilage as a layer that stays on the pulped seed (about 22% of the weight of pulped coffee) and is removed in a later step.2", "How soon after picking: Cenicafé advises not to leave harvested cherry more than 6 hours without pulping and processing16; a Kenyan field report sets a limit of 10 hours3; the FAO manual for Lao PDR asks for processing on the day of harvest.13 A Hawaiʻi growers' guide (Tier B copy) allows a longer delay.15", "Pulp share of the cherry: Cenicafé gives about 43.58% of the fresh fruit's weight (wet basis)11; a 2019 by-products review gives a lower share of the cherry without stating the basis.14 The difference may partly be one of fresh versus dry weight (see coffee cherry anatomy for the dry-matter share).", "Pulp's share of the pollution load: 72% in the Cenicafé ecological-processing report2, 73.7% in the 2013 Cenicafé manual.11 The two are close; the second is the more recent figure." ], "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": "Pulping: technological operation used in the wet process to remove the pulp (exocarp) and as much as possible of the mucilage (mesocarp) by mechanical means.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s2", "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": "Studies carried out at CENICAFE (3), demonstrated the possibility to pulp the coffee without water, (Figure 8), using pulpers of horizontal shaft and a vertical one", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s3", "title": "Post Harvest Handling and Processing of Coffee in African Countries, 3.0 Post Harvest Handling and Processing of Green Coffee in African Countries", "authors": "Mutua, J.", "year": 2000, "publisher": "FAO", "url": "https://www.fao.org/4/X6939E/X6939e03.htm", "tier": "A", "quote": "Poor adjustment of the pulping machine may cause broken/nipped beans, which are considered as defects and lowers the quality.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s4", "title": "Post Harvest Handling and Processing of Coffee in African Countries, Annex 10: Pictures", "authors": "Mutua, J.", "year": 2000, "publisher": "FAO", "url": "https://www.fao.org/4/X6939E/X6939e16.htm", "tier": "A", "quote": "wet processing system; showing (1) receiving tank, (2) siphon, (3) pulper, (4) separating screen, (5 and 10) engine/motor, (6) repasser (2nd pulper) (7) fermentation tanks, (9) pump (11) drainage hopper", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s5", "title": "Agro-Industry Profiles: Coffee", "authors": "World Bank, Finance and Agro-Industry Unit", "year": 1985, "publisher": "World Bank", "url": "https://documents1.worldbank.org/curated/en/311271467993475518/pdf/FAU14.pdf", "tier": "A", "quote": "Classification by size before pulping and adjustment of the pulper to the cherry size minimizes damage to the beans.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s6", "title": "Agricultural Machinery – Coffee Pulper – Specifications (PNS/PAES 252:2011)", "authors": "Bureau of Product Standards (Philippines)", "year": 2011, "publisher": "Philippine National Standard / AMTEC, University of the Philippines Los Baños", "url": "https://amtec.uplb.edu.ph/wp-content/uploads/2019/07/pns-paes-252-2011.pdf", "tier": "A", "quote": "Clearance between the rotating disc or cylinder and the fixed cover shall be adjustable. It shall be gradually decreasing in size.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s7", "title": "Design, fabrication and evaluation of small-scale disc and drum pulpers for Arabica (Coffea arabica L.) and Robusta (Coffea canephora L.) coffee", "authors": "Bizimungu, G.; Ahouansou, R. H.; Semassou, G. C.", "year": 2024, "publisher": "Journal of the Saudi Society of Agricultural Sciences 23, 404–414", "url": "https://www.academia.edu/123523069/Design_fabrication_and_evaluation_of_small_scale_disc_and_drum_pulpers_for_Arabica_Coffea_arabica_L_and_Robusta_Coffea_canephora_L_coffee", "doi": "10.1016/j.jssas.2024.04.001", "tier": "A", "quote": "The drum pulper outperformed the disc pulper considering efficiency, the pulping index, and the mass of unpulped cherries.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s8", "title": "Nueva despulpadora para una caficultura competitiva (Avances Técnicos 294)", "authors": "Oliveros T., C. E.; Moya M., N.; Ramírez G., C. A.", "year": 2001, "publisher": "Cenicafé", "url": "https://publicaciones.cenicafe.org/index.php/avances_tecnicos/article/download/1798/5222/3934", "doi": "10.38141/10779/0294", "tier": "A", "quote": "se retira la cáscara o pulpa de los frutos al comprimirlos en el espacio conformado por el pechero y los dientes de la camisa", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s9", "title": "Despulpado de café sin agua (Avances Técnicos 164)", "authors": "Álvarez G., J.", "year": 1991, "publisher": "Cenicafé", "url": "https://biblioteca.cenicafe.org/handle/10778/745", "tier": "A", "quote": "En ensayos realizados, comparando los distintos tipos de despulpadoras, bajo la aplicación o no de agua, se encontró que es posible despulpar el café sin agua con el uso de diferentes modelos de máquinas comerciales de cilindro horizontal.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s10", "title": "Controle los flujos de café y agua en el módulo Becolsub (Avances Técnicos 405)", "authors": "Sanz Uribe, J. R.; Oliveros Tascón, C. E.; Ramírez Gómez, C. A.; López Posada, U.; Velásquez Henao, J.", "year": 2011, "publisher": "Cenicafé", "url": "https://biblioteca.cenicafe.org/bitstream/10778/40/1/avt0405.pdf", "tier": "A", "quote": "el consumo específico de agua debe estar entre 0,7 y 1,0 L/kg de café pergamino seco", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s11", "title": "Manejo y disposición de los subproductos y de las aguas residuales del beneficio del café", "authors": "Rodríguez Valencia, N.; Zambrano Franco, D. A.; Ramírez Gómez, C. A.", "year": 2013, "publisher": "Cenicafé — Manual del cafetero colombiano, Vol. 3", "url": "https://biblioteca.cenicafe.org/bitstream/10778/4347/1/cenbook-0026_31.pdf", "tier": "A", "quote": "Despulpar en seco el fruto de café elimina de raíz el consumo del agua en esta etapa", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s12", "title": "Modeling of Coffee Fruit: An Approach to Simulate the Effects of Compression", "authors": "Pereira, J. S.; Magalhães, R. R.; Santos, F. L.; de Andrade, E. T.; Marques, L. S.", "year": 2023, "publisher": "AgriEngineering 5(4), 2303–2313", "url": "https://www.mdpi.com/2624-7402/5/4/141", "doi": "10.3390/agriengineering5040141", "tier": "A", "quote": "In this study, we analyzed the deformation, strain energy, and von Mises stress of coffee fruits at mature, semi-mature, and immature stages under compression forces.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s13", "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": "Nipped beans causing stinker beans", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s14", "title": "Coffee By-Products: Nowadays and Perspectives", "authors": "Torres-Valenzuela, L. S.; Serna-Jiménez, J. A.; Martínez, K.", "year": 2019, "publisher": "Coffee – Production and Research, IntechOpen", "url": "https://www.intechopen.com/chapters/69900", "doi": "10.5772/intechopen.89508", "tier": "B", "quote": "coffee pulp and husk are the first by-products and account for 29 and 12% of the overall coffee cherry", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s15", "title": "Processing (Hawaiʻi coffee growers' guide)", "authors": "College of Tropical Agriculture and Human Resources, University of Hawaiʻi", "publisher": "CTAHR, University of Hawaiʻi (copy hosted by Sweet Maria's Coffee Library)", "url": "https://library.sweetmarias.com/wp-content/uploads/2020/08/CoffeeProcessingCtahrHawaii.html", "tier": "B", "quote": "Without mucilage, the beans will not slip through the pulper grooves and may be nicked, scratched, or chipped by the rough surface of the pulper drum.", "accessed": "2026-09-30T00:00:00.000Z" }, { "id": "s16", "title": "Cómo garantizar la buena calidad de la bebida del café y evitar los defectos (Avances Técnicos 284)", "authors": "Puerta-Quintero, G. I.", "year": 2001, "publisher": "Cenicafé", "url": "https://biblioteca.cenicafe.org/bitstream/10778/562/1/avt0284.pdf", "tier": "A", "quote": "No deje el café cereza cosechado más de 6 horas sin despulpar y procesar.", "accessed": "2026-09-30T00:00:00.000Z" } ], "markdown": "## What pulping removes\n\nPulping is the mechanical step that opens the wet process. It strips the skin and pulp from the fresh cherry.1 The pulp leaves as a by-product; the seeds leave as the main product, still wrapped in parchment.1 A layer of mucilage stays on them: in Cenicafé's figures it makes up about 22% of the weight of pulped coffee.2 What happens to that mucilage – fermentation, a machine, or drying it on the seed – decides the process that follows.\n\nPulping should happen soon after picking. Delay allows uncontrolled fermentation and affects the final flavour.5 Cenicafé advises not leaving harvested cherry more than 6 hours unpulped;16 a Kenyan field report sets a limit of 10 hours from harvest;3 an FAO manual for Lao PDR asks for same-day processing, without mixing in older cherries.13\n\n## How a pulper works\n\nAll common pulpers do the same thing: they squeeze and tear.5 The cherry is pressed between a moving, roughened surface and a fixed plate. The skin splits, the seeds pop out, and the pulp is dragged away.5,8\n\n- **Drum pulper** – a rotating cylinder with flutes turns inside a fixed plate that carries pulping channels and ribs.6 In the Colombian design the cherry is compressed in the space between the breast plate (*pechero*) and the teeth of the drum sleeve (*camisa*); the pulp is carried off through the space between the teeth and the rib (*vena*) of the breast plate.8 One small drum pulper, built in Benin and tested on Arabica from Rwanda and Robusta from Benin, used a roughened sleeve with punched bulbs 20 mm long, 6 mm wide and 5 mm high.7\n- **Disc pulper** – one or more roughened discs turn against fixed surfaces; the pulp is rubbed off by the disc bulbs and chop rails.6 The tested prototype used two roughened discs 300 mm across, one fixed and one rotating.7\n- **Pulpers that work without water** – Cenicafé found that several commercial horizontal-cylinder pulpers work without added water, fed from a dry hopper, with little difference in capacity.9,2 Its ecological-processing work reports the same for horizontal- and vertical-shaft pulpers.2\n\n
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A: Drum pulper

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    \n
  1. Hopper.
    2. \n
  2. Breast plate (pechero). A fixed plate with channels and a rib.6,8
    3. \n
  3. Cherry. Squeezed in the gap; the skin splits.8
    4. \n
  4. Gap. Narrows gradually; adjustable, the key setting.6
    5. \n
  5. Drum. Sleeve with teeth or bulbs (camisa).7
    6. \n
  6. Seeds out. Seeds in parchment, with their mucilage.
    7. \n
  7. Pulp out. Carried round by the teeth.8
    8. \n
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B: Disc pulper

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  1. Cherries between the discs. The pulp is rubbed off between bulbs and chop rails.6
    2. \n
  2. Fixed disc with chop rails. Drawn dashed: its rails face the rotating disc.6
    3. \n
  3. Rotating disc with bulbs. 6,7
    4. \n
  4. Casing. Pulp and seeds leave by separate outlets.
    5. \n
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A drum pulper (A) and a disc pulper (B). Both squeeze the fruit between a moving rough surface and a fixed one.5 Schematic, not to scale.
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\n\nThe gap between the moving surface and the fixed plate is the main setting. A Philippine national standard requires it to be adjustable and to narrow gradually along the path of the cherry.6 Classifying the cherries by size before pulping, and setting the pulper to that size, reduces damage to the beans.5 Cenicafé's newer design sets the breast-plate gap with steel feeler gauges.8\n\n## The pulping line\n\nA pulper rarely works alone. A typical East African wet mill shows the order: receiving tank, siphon, pulper, separating screen, repasser (a second pulper), then fermentation tanks.4\n\n- **Before the pulper** – cherries are washed and sorted to remove twigs, leaves and other foreign matter.13 Green immature cherries and dried fruits can be removed in a water separator.1 In the East African layout, the siphon sits between the receiving tank and the pulper.4\n- **After the pulper** – a separating screen follows, then a repasser, which is a second pulper.4 The Codex code asks each mill to decide what proportion of unpulped cherries and nipped beans it accepts.1\n- **Green-cherry separation** – where machines harvest the crop, mills can use a classifier-type pulper that separates hard, immature cherries from ripe ones.15\n\n## Water and pulp\n\nConventional Colombian mills use 40–50 litres of water per kilogram of dry parchment coffee; about half of it goes on pulping, carrying the pulp to pits in water and carrying the pulped coffee to the fermentation tanks.11 An earlier Cenicafé report gives about 40 litres per kilogram for the whole conventional process.2 Pulping without water removes the use at this stage entirely, and the pulp can be moved to covered pits without water.11 In the Becolsub module, which combines dry pulping with mechanical demucilaging, the target for the whole process is 0.7–1.0 litres per kilogram.10\n\n
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Water use in litres per kilogram of dry parchment coffee, for the pulping stage and for whole processes, as reported by Cenicafé. The conventional pulping-stage bar is half of the 40–50 L/kg whole-process range and also includes carrying the pulped coffee to the tanks.10,11
\n
\n\nPulp is the largest by-product. Cenicafé puts it at about 43.58% of the fresh fruit's weight, or on average 2.25 tonnes of fresh pulp per hectare per year.11 It carries 73.7% of the mill's potential pollution; the mucilage carries the other 26.3%.11 Composted, the pulp is transformed in about four months; vermicomposting yields 35–40% (wet basis).11 Other uses include animal feed, biogas and cascara drinks.14\n\n\n\n## Mechanics of skin rupture\n\nPulping works because ripe fruit gives way easily and the seed does not. In a compression model of Arabica fruit, built on fruit properties taken from earlier studies, ripe cherries deformed most (mean 2.20 mm/mm) and needed the least strain energy (0.07 mJ) and stress (0.25 MPa).12 Immature fruit needed about five times the strain energy (0.34 mJ) and stress (1.25 MPa).12 The authors conclude that the riper the fruit, the more it deforms and the less energy and stress it takes.12\n\nIn the machine, the cherry enters the narrowing gap, the skin splits under compression, and the seeds are squeezed out while the teeth drag the torn pulp through the space between the teeth and the breast-plate rib.8 The mucilage helps: it lets the seeds slip through the pulper grooves. Seeds without mucilage may be nicked, scratched or chipped by the rough drum.15\n\nThe seed itself tolerates only a small squeeze. Cenicafé reports that seeds deformed by more than 1 mm suffer structural damage that can reduce their commercial value.8 The gap therefore has to be wide enough for the seeds and narrow enough to split the skin – which is why cherry size matters.5,6\n\n## Unripe cherries and pulper performance\n\nUnripe cherries resist compression,12 so they tend to pass through unpulped or to be damaged. Classifier pulpers use this: they separate hard, immature cherries from ripe ones.15 In Kenya, the peak season makes hand sorting before pulping impossible, so all coffee is pulped as it arrives.3\n\nFruit type matters too. In one trial, the same small drum pulper reached about 98% efficiency on Arabica but 85% on Robusta; the disc pulper did better on Robusta (about 88%) than on Arabica (about 76%).7 The test used a smaller gap for Robusta (12 mm) than for Arabica (16 mm).7\n\n## Reference values\n\nThe table brings together values reported in the sources. Machine settings are specific to the machine tested; they are a guide to the range, not a recipe.\n\n| Parameter | Value reported | Source |\n|---|---|---|\n| Time from harvest to pulping | Within 6 h (Cenicafé); within 10 h (Kenya); same day (Lao PDR) | Cenicafé16, FAO3,13 |\n| Gap setting | Adjustable, narrowing gradually | PNS/PAES 2526 |\n| Gap in one prototype test (1,200 rpm) | 16 mm Arabica, 12 mm Robusta | Bizimungu et al.7 |\n| Seed deformation limit | Damage above about 1 mm | Cenicafé8 |\n| Minimum pulping efficiency | 95% | PNS/PAES 2526 |\n| Maximum mechanically damaged parchment | 3.5% | PNS/PAES 2526 |\n| Maximum unpulped cherries | 5% | PNS/PAES 2526 |\n| Cenicafé–Ingesec 300 pulper | 300 kg cherry/h; 232 rpm; drum 14 cm × 22 cm | Cenicafé8 |\n| Cenicafé–Ingesec 300, criteria for correct working | Pulp in the grain < 2%; damage < 1%; unpulped < 1% | Cenicafé8 |\n| Small drum pulper (Arabica) | 872 kg/h; 98.4% efficiency; 0.91% damage | Bizimungu et al.7 |\n| Small disc pulper (Arabica) | 684 kg/h; 75.6% efficiency; 0.15% damage | Bizimungu et al.7 |\n| Medium-sized machine | About 3,000 lb (about 1,360 kg) cherry/h | World Bank5 |\n| Water, conventional pulping + hydraulic transport of pulp and pulped coffee | About half of the whole-process use | Cenicafé11 |\n| Water, whole conventional process | 40–50 L/kg dry parchment; about 40 L/kg in the earlier report | Cenicafé11,2 |\n| Water, dry pulping | None at the pulping stage | Cenicafé9,11 |\n| Water, Becolsub (whole process) | 0.7–1.0 L/kg dry parchment | Cenicafé10 |\n| Water, pulper/demucilager units | About 0.5 L/kg fresh cherry | FAO13 |\n| Pulp share | About 43.58% of fresh fruit weight (wet basis) | Cenicafé11 |\n| Pulp's share of pollution | 72%; 73.7% | Cenicafé2,11 |\n| Pulp composting | About 4 months; vermicompost yield 35–40% (wb) | Cenicafé11 |\n\n
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\n
Order of equipment in a wet-mill pulping line, from receiving tank to fermentation tanks.4 The siphon tank classifies cherries by density;2 the pulp leaves as a by-product.1
\n
\n\n## Risks and defects\n\n- **Nipped and broken beans** – poor adjustment of the pulper causes broken or nipped beans, which count as defects and lower quality.3 The FAO manual for Lao PDR lists nipped beans from poor or poorly adjusted equipment as a cause of stinker beans.13 Physical damage makes coffee more susceptible to contamination and deterioration.1\n- **Unpulped cherries and pulp in the parchment** – these carry fruit into the fermentation tanks; Cenicafé counts its pulper as working correctly with under 2% pulp in the grain and under 1% unpulped fruit.8\n- **Recycled water** – mills that recycle pulping water must keep it free of outside contaminants; the gradual build-up of heat and enzymes in it speeds up the fermentation that follows.5\n- **Delays at peak season** – frequent breakdowns and congestion at pulping stations delay pulping.3\n- **Pollution** – the pulp from one kilogram of cherry, with its mucilage, can use up the dissolved oxygen of 7.4 m³ of clean water.2\n\n## Measurement and maintenance\n\n**Measuring performance.** The Philippine standard defines three figures by weight, in per cent: pulping efficiency (parchment collected at all outlets against cherry fed in), unpulped loss (unpulped cherry against cherry fed in) and mechanically damaged parchment (against the weight of a sample).6 The Codex code suggests mills monitor the quantity of broken, nipped and naked beans and the water used.1\n\n**Maintenance.** Before each season, processing equipment should be cleaned, reassembled, lubricated and checked.1 The Hawaiʻi guide asks for every operating part to be adjusted to avoid bean damage, and for the pulper to be cleaned and overhauled every year.15 Cenicafé built its newer drum teeth in reinforced nylon; they can take a radial force 24.8 times that of copper and 5.5 times that of stainless steel.8\n\n## Open questions\n\n- **Nipped beans and stinkers.** The link appears in a practical manual,13 but no study opened for this entry measures how often a nipped bean becomes a stinker, or through which microbial route.\n- **Gap versus ripeness.** The mechanical data on fruit ripeness12 have not been tied, in the sources opened here, to pulper damage and unpulped rates at different gap settings.\n- **Pulp share.** Published shares of pulp differ and do not always state the basis (fresh or dry weight).11,14\n\n## Key studies\n\n
\n

Bizimungu et al., 2024 – Small drum and disc pulpers. Built and tested small drum and disc pulpers for Arabica (from Rwanda) and Robusta (from Benin). The drum pulper was more efficient on Arabica and left fewer unpulped Arabica cherries; damage stayed below 1% for both machines.

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Journal of the Saudi Society of Agricultural Sciences 23, 404–414 · doi:10.1016/j.jssas.2024.04.001

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Pereira et al., 2023 – Compression of coffee fruit. Modelled ripe, semi-ripe and immature cherries under compression. Ripe fruit deformed more at lower stress and energy – the mechanical reason unripe fruit is harder to pulp.

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AgriEngineering 5(4), 2303–2313 · doi:10.3390/agriengineering5040141

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Oliveros, Moya & Ramírez, 2001 – A new pulper (Cenicafé). Describes a small horizontal-drum pulper with nylon teeth and a gauge-set breast plate, rated at 300 kg of cherry per hour; it counts as working correctly with under 1% damage and under 1% unpulped fruit.

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Avances Técnicos Cenicafé 294 · PDF

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Álvarez, 1991 – Pulping without water (Cenicafé). Compared pulpers run with and without water and showed that commercial horizontal-cylinder machines can pulp dry. This finding underpins Colombia's ecological wet milling.

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Avances Técnicos Cenicafé 164 · Cenicafé repository

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