{ "id": "arabica-or-robusta", "url": "https://coffearium.org/entries/arabica-or-robusta/", "license": "CC-BY-4.0", "title": "Arabica and robusta compared", "summary": "How the two commercial coffee species differ as plants, in their climate needs, in the shape of the bean and in what the seed holds, and how a laboratory tells them apart in green coffee, roast coffee and blends.", "domain": "botany", "kind": "Concept", "stage": "plant", "topics": [ "science" ], "topicSections": {}, "lang": "en", "status": "verified", "reviewer": "Coffearium verification pass", "lastVerified": "2026-10-22T00:00:00.000Z", "updated": "2026-10-22T00:00:00.000Z", "added": "2026-10-22T00:00:00.000Z", "brief": [ "*C. arabica* has 44 chromosomes and mainly fertilises itself; *C. canephora* (robusta) has 22 and is an outcrossing species.1,2", "In East African flora descriptions, canephora has larger leaves and more flowers per leaf axil (8–30 against 2–20 in arabica).3,4", "Robusta seeds hold more caffeine, arabica seeds more sucrose; whether robusta reliably holds more chlorogenic acids is disputed.11,12,13,19", "The diterpene 16-O-methylcafestol (16-OMC) marks robusta; a 2024 European standard specifies how to measure it in green and roast coffee.14,17", "DNA tests on chloroplast markers identify the species and estimate the robusta share in a blend.18" ], "quickFacts": [ { "label": "Chromosomes", "value": "2n = 44 (arabica) · 2n = 22 (canephora)" }, { "label": "Breeding system", "value": "Mainly self-fertilising · outcrossing" }, { "label": "Flowers per leaf axil", "value": "2–20 · 8–30(–48) (Flora of Tropical East Africa)" }, { "label": "Optimum mean annual temperature", "value": "18–21 °C · 22–26 °C (2006 review) or below 20.5 °C (2020 yield study)" }, { "label": "Mean bean size, roasted", "value": "10.95 × 8.25 mm · 10.46 × 8.42 mm (one 2022 study)" }, { "label": "Robusta marker", "value": "16-O-methylcafestol (EN 18003:2024)" } ], "aka": [ "Arabica versus robusta", "Arabica vs robusta", "Difference between arabica and robusta" ], "linkTerms": [ "arabica and robusta compared", "arabica or robusta" ], "related": [ "coffea-arabica", "coffea-canephora", "coffea-genus", "polyploidy-and-the-arabica-genome", "flowering-and-pollination", "fruit-development", "peaberries-and-bean-shapes", "green-coffee-composition", "chlorogenic-acids", "caffeine", "coffee-oil" ], "contested": [ "Chlorogenic acids by species: a 2006 review gives 4–8.4% of dry matter for *C. arabica* and 7–14.4% for *C. canephora*12, and a roasting chemistry chapter calls robusta significantly richer15; a 2021 meta-analysis in a master’s thesis found the chlorogenic acid profiles of the two species extremely similar, with roast level mattering more than species except for total feruloylquinic and dicaffeoylquinic acids, which were highest in green robusta.19", "16-O-methylcafestol in arabica: a 2006 review reports that its absence from arabica beans was confirmed14; a 2018 study detected it in arabica roast coffee and concluded that robusta below about 1% of a blend cannot be detected this way.16", "Optimum temperature of robusta: a 2006 review gives 22–26 °C as the optimum annual mean, or 24–30 °C after another author6; a 2020 study of farm yields in South-East Asia puts it below 20.5 °C.7" ], "corrections": [ { "date": "2026-10-22T00:00:00.000Z", "change": "Corrected the 2022 imaging study throughout (body, figure legend, comparison table, methods table, study card) – the counts 105 and 70 are dishes of 20 roasted beans from 21 arabica and 14 robusta samples, not single beans, and the model classified dishes, not individual beans, using spectral, shape and colour features together.", "reason": "Table 1 and Methods of the full text (PMC9108882) state the sampling unit; the entry had described the means as single-bean measurements." }, { "date": "2026-10-22T00:00:00.000Z", "change": "Replaced the SCA News interview as the source for the meta-analysis view on chlorogenic acids with the author's master's thesis (UC Davis 2021), and restated the view from the thesis (profiles extremely similar; roast level matters more than species except for total feruloylquinic and dicaffeoylquinic acids).", "reason": "The interview is a news item (Tier C-like) and may not stand alone (owner ruling, 22 Oct 2026)." } ], "sources": [ { "id": "s1", "title": "A single polyploidization event at the origin of the tetraploid genome of Coffea arabica is responsible for the extremely low genetic variation in wild and cultivated germplasm", "authors": "Scalabrin, S.; Toniutti, L.; Di Gaspero, G.; et al.; Bertrand, B.", "year": 2020, "publisher": "Scientific Reports 10, 4642", "url": "https://doi.org/10.1038/s41598-020-61216-7", "doi": "10.1038/s41598-020-61216-7", "tier": "A", "quote": "The mating system is primarily based on self-fertilization, although pollinator-mediated outcrossing may occasionally occur.", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s2", "title": "The coffee genome provides insight into the convergent evolution of caffeine biosynthesis", "authors": "Denoeud, F.; Carretero-Paulet, L.; Dereeper, A.; et al.", "year": 2014, "publisher": "Science 345(6201), 1181–1184", "url": "https://pages.uoregon.edu/chendon/coffee_literature/old_literature/2014%20Science,%20Robusta%20genome%20and%20caffeine%20production.pdf", "doi": "10.1126/science.1255274", "tier": "A", "quote": "an outcrossing, highly heterozygous diploid, and one of the parents of C. arabica", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s3", "title": "Coffea arabica L.", "authors": "Royal Botanic Gardens, Kew", "year": 2026, "publisher": "Plants of the World Online (World Checklist of Vascular Plants), description from Flora of Tropical East Africa (Verdcourt 1976)", "url": "https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:747038-1/general-information", "tier": "A", "quote": "Flowers (4–)5(–6)-merous, 2–20 per axil, borne in 1–3(–15) fascicles", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s4", "title": "Coffea canephora Pierre ex A.Froehner", "authors": "Royal Botanic Gardens, Kew", "year": 2026, "publisher": "Plants of the World Online (World Checklist of Vascular Plants), description from Flora of Tropical East Africa (Verdcourt 1976)", "url": "https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:747068-1/general-information", "tier": "A", "tierNote": "The description sits on the general-information tab; the coffea-canephora entry cites the same POWO page without the tab path.", "quote": "8–30(–48) per axil, borne in 1–4(–7) congested fascicles", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s5", "title": "The Coffee Tree – Genetic Diversity and Origin", "authors": "Herrera, J. C.; Lambot, C.", "year": 2017, "publisher": "In: Folmer, B. (ed.), The Craft and Science of Coffee, Academic Press, ch. 1, pp. 1–16", "url": "https://doi.org/10.1016/B978-0-12-803520-7.00001-3", "doi": "10.1016/B978-0-12-803520-7.00001-3", "tier": "B", "quote": "Breeding strategies in Robusta are determined by the strict self-incompatibility of the species and by consequence the objectives will be to select clones vegetatively propagated or clonal hybrids propagated by seeds and obtained under controlled pollination.", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s6", "title": "Impacts of drought and temperature stress on coffee physiology and production: a review", "authors": "DaMatta, F. M.; Ramalho, J. D. C.", "year": 2006, "publisher": "Brazilian Journal of Plant Physiology 18(1), 55–81", "url": "https://www.scielo.br/j/bjpp/a/bDfpJwLr4xLcznSwy4b9zkf/?lang=en", "doi": "10.1590/S1677-04202006000100006", "tier": "A", "quote": "Robusta is much less adaptable to lower temperatures than arabica coffee.", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s7", "title": "Not so robust: robusta coffee production is highly sensitive to temperature", "authors": "Kath, J.; Byrareddy, V. M.; Craparo, A.; Nguyen-Huy, T.; Mushtaq, S.; Cao, L.; Bossolasco, L.", "year": 2020, "publisher": "Global Change Biology 26(6), 3677–3688", "url": "https://research.usq.edu.au/item/q5v20/not-so-robust-robusta-coffee-production-is-highly-sensitive-to-temperature", "doi": "10.1111/gcb.15097", "tier": "A", "quote": "robusta has an optimal temperature below 20.5°C (or a mean minimum/maximum of ≤16.2/24.1°C)", "abstractOnly": true, "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s8", "title": "Flowering and Fruiting of Coffea arabica L.: A Comprehensive Perspective from Phenology", "authors": "Unigarro, C. A.; Cayón Salinas, D. G.; León-Burgos, A. F.; Flórez-Ramos, C. P.", "year": 2025, "publisher": "Plants 14(21), 3396", "url": "https://www.mdpi.com/2223-7747/14/21/3396", "doi": "10.3390/plants14213396", "tier": "A", "quote": "the period from anthesis (BBCH stage 60) to fruit ripening (BBCH stage 88) lasts, on average, between 220 and 243 days", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s9", "title": "From anthesis to harvest: evolution of the fructification of Conilon coffee genotypes grown at a transitional altitude", "authors": "Colodetti, T. V.; Tomaz, M. A.; Sartori, L.; de Salles, R. A.; de Souza, I. V.; Senra, J. F. de B.; Rodrigues, W. N.", "year": 2025, "publisher": "Bragantia 84, e20250028", "url": "https://biblioteca.incaper.es.gov.br/digital/bitstream/item/5042/1/coniloncoffee.pdf", "doi": "10.1590/1678-4499.20250028", "tier": "A", "quote": "averaging from 252 to 308 days among genotypes, from anthesis to harvest", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s10", "title": "The use of multispectral imaging for the discrimination of Arabica and Robusta coffee beans", "authors": "Mihailova, A.; Liebisch, B.; Islam, M. D.; Carstensen, J. M.; Cannavan, A.; Kelly, S. D.", "year": 2022, "publisher": "Food Chemistry: X 14, 100325", "url": "https://doaj.org/article/e8157d1269f841ebaf4ea1b896b145ce", "doi": "10.1016/j.fochx.2022.100325", "tier": "A", "tierNote": "Abstract read on DOAJ; bean dimensions and sampling (21 arabica and 14 robusta samples, five dishes of 20 beans each; Table 1 n = dishes) from the open-access full text (PMC9108882), read via Europe PMC.", "quote": "achieved 100% correct classification of the two coffee species in the test dataset", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s11", "title": "Influence of Various Factors on Caffeine Content in Coffee Brews", "authors": "Olechno, E.; Puścion-Jakubik, A.; Zujko, M. E.; Socha, K.", "year": 2021, "publisher": "Foods 10(6), 1208", "url": "https://mdpi-res.com/d_attachment/foods/foods-10-01208/article_deploy/foods-10-01208.pdf", "doi": "10.3390/foods10061208", "tier": "A", "quote": "Arabica green beans contain, on average, 0.9 to 1.5% dry weight of caffeine.", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s12", "title": "Phenolic compounds in coffee", "authors": "Farah, A.; Donangelo, C. M.", "year": 2006, "publisher": "Brazilian Journal of Plant Physiology 18(1), 23–36", "url": "https://www.scielo.br/j/bjpp/a/cbSqnBPFFvhRTvKFm6WNQWC/?lang=en", "doi": "10.1590/S1677-04202006000100003", "tier": "A", "quote": "may vary from 4 to 8.4 % for Coffea arabica, and from 7 to 14.4 % for Coffea canephora", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s13", "title": "Trigonelline and sucrose diversity in wild Coffea species", "authors": "Campa, C.; Ballester, J. F.; Doulbeau, S.; Dussert, S.; Hamon, S.; Noirot, M.", "year": 2004, "publisher": "Food Chemistry 88(1), 39–43", "url": "https://library.sweetmarias.com/wp-content/uploads/2020/08/Trigonelline-and-sucrose-diversity.pdf", "doi": "10.1016/j.foodchem.2004.01.020", "tier": "A", "tierNote": "Peer-reviewed paper; read in a copy hosted by a coffee retailer (the host adds nothing). Values from Table 2.", "quote": "Contents of these compounds are higher in Coffea arabica than in Coffea canephora green beans", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s14", "title": "The lipid fraction of the coffee bean", "authors": "Speer, K.; Kölling-Speer, I.", "year": 2006, "publisher": "Brazilian Journal of Plant Physiology 18(1), 201–216", "url": "https://www.scielo.br/j/bjpp/a/sLcktB9RbKvXRPMmy4kjtfC/?lang=en", "doi": "10.1590/S1677-04202006000100014", "tier": "A", "quote": "16-OMC has become the ideal quality characteristic for reliably detecting Robusta in Arabica coffee blends.", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s15", "title": "The Chemistry of Roasting – Decoding Flavor Formation", "authors": "Poisson, L.; Blank, I.; Dunkel, A.; Hofmann, T.", "year": 2017, "publisher": "In: Folmer, B. (ed.), The Craft and Science of Coffee, Academic Press, ch. 12, pp. 273–309", "url": "https://doi.org/10.1016/B978-0-12-803520-7.00012-8", "doi": "10.1016/B978-0-12-803520-7.00012-8", "tier": "B", "quote": "Together with the high level of phenols resulting from the CGA degradation, Robusta coffee exhibits their typical smoky, earthy, roasty, and phenolic aroma profile.", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s16", "title": "16-O-methylcafestol is present in ground roast Arabica coffees: Implications for authenticity testing", "authors": "Gunning, Y.; Defernez, M.; Watson, A. D.; Beadman, N.; Colquhoun, I. J.; Le Gall, G.; Philo, M.; Garwood, H.; Williamson, D.; Davis, A. P.; Kemsley, E. K.", "year": 2018, "publisher": "Food Chemistry 248, 52–60", "url": "https://ueaeprints.uea.ac.uk/67696/1/Gunning_etal_2018_FoodChemistry.pdf", "doi": "10.1016/j.foodchem.2017.12.034", "tier": "A", "quote": "Using low-field NMR, robusta in Arabica could be detected at levels of the order of 1–2% w/w.", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s17", "title": "EN 18003:2024 Food authenticity – Determination of 16-O-Methylcafestol content of green and roasted coffee – HPLC-method", "authors": "European Committee for Standardization (CEN); published as BS EN 18003:2024 and DIN EN 18003:2025-01", "year": 2024, "publisher": "BSI Knowledge (product page with scope)", "url": "https://knowledge.bsigroup.com/products/food-authenticity-determination-of-16-o-methylcafestol-content-of-green-and-roasted-coffee-hplc-method", "tier": "A", "tierNote": "A standard, cited for what it specifies (scope and working range); the full text was not opened. That DIN EN 18003:2025-01 replaced DIN 10779:2011-03, now withdrawn, was confirmed on the DIN Media product pages of both standards (dinmedia.de/en/standard/din-en-18003/385133543 and dinmedia.de/en/standard/din-10779/137590328, read 22 Oct 2026).", "quote": "The method is suitable for a content of 40 mg/kg to 1 600 mg/kg", "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s18", "title": "Development of a rapid and efficient DNA-based method to detect and quantify adulterations in coffee (Arabica versus Robusta)", "authors": "Combes, M.-C.; Joët, T.; Lashermes, P.", "year": 2018, "publisher": "Food Control 88, 198–206", "url": "https://www.documentation.ird.fr/hor/fdi:010071469", "doi": "10.1016/j.foodcont.2018.01.014", "tier": "A", "quote": "chloroplastic rather than nuclear genetic variations were targeted between Coffea species.", "abstractOnly": true, "accessed": "2026-10-22T00:00:00.000Z" }, { "id": "s19", "title": "A Meta-Analysis of Acids in Coffee and a Quantification of Coffee Beverage Color", "authors": "Yeager, S. E.", "year": 2021, "publisher": "University of California, Davis (MSc thesis; chapter 2 is the meta-analysis later published by Yeager, Batali, Guinard and Ristenpart in Critical Reviews in Food Science and Nutrition)", "url": "https://www.escholarship.org/uc/item/0w62z1n1", "tier": "B", "tierNote": "Master's thesis (B). Replaces an SCA News interview with the author (news item, Tier C), which may not stand alone.", "quote": "The coffee roast level affects CGA concentrations more than the type of coffee, except for total FQA and total diCQA.", "accessed": "2026-10-22T00:00:00.000Z" } ], "markdown": "## Two species behind one drink\n\nAlmost all coffee comes from two species. *Coffea arabica* gives arabica coffee. *Coffea canephora* gives the coffee traded as robusta. This entry sets the two side by side; each species has its own entry with the detail.\n\nThe deepest difference is in the chromosomes. Arabica has 44, in four sets, because it arose as a hybrid of two species.1 Canephora has 22, in two sets, and it is one of arabica’s two parents.2 How that hybrid arose is told in Polyploidy and the arabica genome.\n\nThe two also reproduce differently. Arabica flowers mainly pollinate themselves; insects only occasionally bring pollen from other plants.1 Canephora is outcrossing.2 According to a coffee science textbook chapter, it is strictly self-incompatible, needing pollen from another plant, so breeders select clones or cross chosen parents.5\n\n## How the plants differ\n\nBotanists describe the two plants in the Flora of Tropical East Africa, quoted by Kew’s Plants of the World Online. Arabica is a bush or tree 2–7 m tall. Canephora is a tree or bush 3.5–8.5 m tall.3,4\n\nThe leaves tell them apart more clearly. Arabica leaf blades are 7–18 cm long and 3–7.5 cm wide.3 Canephora blades are 12–31.5 cm long, sometimes up to 40 cm, and 4.5–12 cm wide.4\n\nFlowers grow in clusters where a leaf meets the branch, the leaf axil. The flora counts 2–20 flowers per axil in arabica. In canephora it counts 8–30, sometimes up to 48.3,4 Both have white flowers and red fruit; cultivated arabica can also bear yellow or purple fruit.3,4 How flowering and fruit set work is covered in Flowering and pollination.\n\nThe fruit takes longer to ripen in canephora, at least in the studies opened for this entry. A 2025 review gives an average of 220–243 days from flowering to ripe fruit for arabica.8 A 2025 Brazilian trial recorded 252–308 days from flowering to harvest for conilon, a form of canephora.9 The sites and methods differ, so the numbers are not a direct comparison.\n\n## Where each grows best\n\nArabica is a highland plant and robusta a plant of warmer lowlands, in the classic view. A 2006 review gives an optimum mean annual temperature of 18–21 °C for arabica and 22–26 °C for robusta.6 The same review states that robusta tolerates cold much less well than arabica.6\n\nThat warm optimum for robusta has been questioned. A 2020 study of yields on 798 farms in South-East Asia found robusta did best below 20.5 °C.7 The two findings are set side by side in Contested.\n\nRain matters too. The 2006 review gives an optimum of 1,200–1,800 mm a year for arabica. It says robusta adapts better than arabica to rainfall above 2,000 mm.6 How growers match a species to a site is covered in Site selection and climate.\n\n## The seeds side by side\n\nThe seeds, the coffee beans, differ in shape. One 2022 study measured roasted beans from 21 arabica and 14 robusta samples with a camera system, in dishes of 20 beans: 105 dishes of arabica and 70 of robusta.10 The arabica beans were longer on average, 10.95 mm against 10.46 mm. The robusta beans were slightly wider, 8.42 mm against 8.25 mm.10\n\nSo robusta beans look rounder and arabica beans more oval. The width-to-length ratio was 0.81 in robusta and 0.76 in arabica.10 The drawing shows both means at the same scale.\n\n
\n
\n
    \n
  1. Arabica bean. Mean 10.95 × 8.25 mm; width-to-length ratio 0.76 (105 dishes of 20 roasted beans).10
    2. \n
  2. Robusta bean. Mean 10.46 × 8.42 mm; width-to-length ratio 0.81 (70 dishes of 20 roasted beans).10
    3. \n
  3. Length. The guides mark the ends of the arabica bean; the robusta bean is about 0.5 mm shorter.10
    4. \n
  4. Width. The robusta bean is slightly wider, by 0.17 mm on average.10
    5. \n
\n
Mean bean outlines from one 2022 imaging study of roasted beans, drawn at the same scale. Shape varies within each species and with growing conditions. Schematic outline, not a photograph.10
\n
\n\nThe study did not test shape alone. Its 100% correct classification came from a model that combined spectral, shape and colour features and sorted dishes of 20 beans, not single beans.10 Bean shapes within one species, such as peaberries, are covered in Peaberries and bean shapes.\n\n## What the seeds hold\n\nThe seeds contain the same classes of compounds in different amounts. Robusta holds more caffeine: a 2021 review gives 0.9–1.5% of dry weight for arabica and 1.2–2.4% for robusta (basis not stated).11 Arabica holds more sucrose. In a 2004 study of wild trees, arabica held 7.99–11.0% sucrose and canephora 5.94–6.47%, on a dry-matter basis.13\n\nLipids are higher in arabica, about 15% on average against about 10% in robusta (basis not stated).14 Chlorogenic acids, a family of phenolic compounds, are usually reported higher in robusta, but a meta-analysis disagrees (see Contested).12,19\n\n
\n
\n
Reported ranges for four constituents of green coffee, by species. Caffeine and chlorogenic acids are review ranges; sucrose spans four wild trees per species; lipids are averages. Bases as the sources state them.11,12,13,14
\n
\n\nThese differences carry into the cup, according to a roasting chemistry chapter. It links arabica’s higher sucrose to more caramel-like and buttery aroma compounds after roasting.15 It describes robusta’s aroma profile as smoky, earthy, roasty and phenolic.15 The whole picture of green coffee chemistry is in Green coffee composition.\n\n\n\n## Comparison table\n\nValues as the sources report them. Where sources differ, both are given; plant measurements come from one flora and describe wild and cultivated plants in East Africa.\n\n| Trait | *C. arabica* | *C. canephora* (robusta) |\n|---|---|---|\n| Chromosomes | 2n = 4x = 44, allopolyploid1 | 2n = 2x = 22, diploid2 |\n| Breeding system | Primarily self-fertilisation; occasional outcrossing by pollinators1 | Outcrossing, highly heterozygous2; strictly self-incompatible (textbook)5 |\n| Habit and height | Bush or tree, 2–7 m3 | Tree or bush, 3.5–8.5 m4 |\n| Leaf blade | 7–18 × 3–7.5 cm3 | 12–31.5(–40) × 4.5–12(–22) cm4 |\n| Flowers per leaf axil | 2–20, in 1–3(–15) clusters; flowers (4–)5(–6)-merous3 | 8–30(–48), in 1–4(–7) dense clusters4 |\n| Corolla lobes | 0.9–1.6 cm long3 | 0.8–1.9 cm long4 |\n| Fruit | Red (yellow or purple in cultivated forms), 1–2 cm long3 | Red, 0.9–1.7 cm long4 |\n| Seed (flora) | 6–7 mm wide3 | 7–13 mm long, 5.5–9.5 mm wide4 |\n| Bean, roasted, mean length × width | 10.95 × 8.25 mm (105 dishes of 20 beans)10 | 10.46 × 8.42 mm (70 dishes of 20 beans)10 |\n| Bean width-to-length ratio | 0.7610 | 0.8110 |\n| Flowering to ripe fruit | 220–243 days on average (review)8 | 252–308 days (conilon, 647 m, Brazil); 216–238 days cited for early genotypes at low altitude9 |\n| Optimum mean annual temperature | 18–21 °C6 | 22–26 °C (2006 review)6; below 20.5 °C (2020 yield study)7 |\n| Rainfall | Optimum 1,200–1,800 mm a year6 | Adapts better to more than 2,000 mm6 |\n| Cold | More tolerant6 | Much less adaptable to low temperatures6 |\n| Caffeine, green | 0.9–1.5% of dry weight11 | 1.2–2.4% (basis not stated)11 |\n| Chlorogenic acids, green | 4–8.4% of dry matter12 | 7–14.4% of dry matter12 (contested) |\n| Sucrose, green | 9.32% mean, 7.99–11.0% dry matter (four wild trees)13 | 6.10% mean, 5.94–6.47% dry matter (four wild trees)13 |\n| Trigonelline, green | 1.13% mean, 0.95–1.29% dry matter13 | 0.82% mean, 0.52–1.06% dry matter13 |\n| Lipids, green (basis not stated) | ≈15% (average)14 | ≈10%14 |\n| 16-O-methylcafestol | Reported absent14; traces found in 201816 | Present; 600–1,800 and 1,204–2,236 mg/kg in roast robusta, in two studies cited in 201816 |\n\nThe online text of the flora gives the arabica seed length as “9–1.2(–1.5) cm”, which looks like a typesetting slip; we do not use it.3 The canephora seed range in the flora (7–13 mm long) brackets the mean bean lengths of the 2022 study, which measured roasted beans of unstated origin.4,10 The longer conilon cycle was measured at 647 m, a transitional altitude; the trial cites 216–238 days for early genotypes at low altitude.9\n\n## Chemistry behind the differences\n\n**Sucrose and trigonelline.** The 2004 study measured 14 wild species and six further taxa, four trees each.13 Arabica had one of the highest sucrose contents in the set, 9.3% on a dry-matter basis. Canephora averaged 6.10%.13 Across all species, sucrose ranged from 3.8% to 10.7% and trigonelline from 0.39% to 1.77%.13 The authors call both compounds aroma precursors and suggest canephora could be improved by crosses with *C. eugenioides*.13\n\n**Caffeine and chlorogenic acids.** The caffeine ranges of the two species overlap at 1.2–1.5%, so on these ranges caffeine alone would not separate every sample.11 The chlorogenic acid ranges of a 2006 review overlap between 7% and 8.4%.12 A 2021 meta-analysis in a master’s thesis found the chlorogenic acid profiles of the two species extremely similar; roast level affected the amounts more than species did, except for total feruloylquinic and dicaffeoylquinic acids.19 Chlorogenic acids treats the dispute in full.\n\n**Lipids and diterpenes.** Arabica lipids average about 15%, robusta about 10%.14 The diterpene 16-O-methylcafestol (16-OMC) is the species-specific one: a 2006 review reports its absence from arabica as confirmed.14 The review calls it the ideal characteristic for detecting robusta in arabica blends.14 The diterpenes as a group are covered in Coffee oil.\n\n**Aroma.** According to the roasting chemistry chapter, robusta’s higher amino acids lead to more pyrazines, and its tryptophan to animal-smelling skatole.15 The same chapter attributes arabica’s higher diketones, furfurals and furaneol to its higher sucrose.15 No sensory study opened for this entry compared the two species under one protocol; cup character here rests on that chapter alone.\n\n## Telling them apart in the lab\n\nA buyer may want to know whether green coffee, a roast coffee or a blend contains robusta. Three kinds of method appear in the sources opened for this entry.\n\n**16-OMC by chromatography.** EN 18003:2024 specifies a high-performance liquid chromatography (HPLC) method for 16-OMC in green and roasted coffee.17 It is suitable for 40–1,600 mg/kg; its collaborative study showed that 20–40 mg/kg can also be analysed, depending on the laboratory equipment.17 The standard leaves compliance assessment out of scope.17 In Germany, DIN EN 18003:2025-01 replaced DIN 10779:2011-03, a method for roasted coffee only.17 A 2006 review states that the older DIN method detects robusta at less than 2% of a blend.14\n\n**16-OMC by NMR.** A 2018 study used low-field nuclear magnetic resonance (NMR) on roast coffee.16 It found 16-OMC and 16-O-methylkahweol in arabica for the first time, at an estimated combined level of at least 10 mg/kg in one sample.16 It detected robusta in arabica at about 1–2% w/w. The trace amounts in arabica set a floor near 1%.16 For comparison, the same study cites 600–1,800 mg/kg and 1,204–2,236 mg/kg of 16-OMC in roast robustas from earlier work.16\n\n**DNA.** A 2018 method from IRD, the French research institute for development, uses high-resolution melting analysis of DNA from green and roasted coffee.18 It targets differences in chloroplast DNA rather than nuclear DNA, to make detection more sensitive. It identifies the species and, in a blend, estimates the percentage of robusta.18\n\n**Imaging.** The 2022 imaging study combined spectral, shape and colour features of roasted beans, averaged over dishes of 20 beans. Its model classified every dish in the test set correctly and predicted the robusta share in mixtures.10 The authors present it as a rapid screening tool.10\n\n| Method | What it detects | Working range or limit | Source |\n|---|---|---|---|\n| HPLC, EN 18003:2024 | 16-OMC in green and roasted coffee | 40–1,600 mg/kg; 20–40 mg/kg depending on equipment | CEN17 |\n| HPLC, DIN 10779 (withdrawn) | 16-OMC in roasted coffee | Robusta below 2% of a blend | Speer & Kölling-Speer14; status DIN17 |\n| Low-field NMR | 16-OMC and 16-O-methylkahweol in roast coffee | Robusta at about 1–2% w/w; not below about 1% | Gunning et al.16 |\n| High-resolution melting of chloroplast DNA | Species identity; robusta share in blends | Range not stated in the abstract | Combes et al.18 |\n| Multispectral imaging of roasted beans | Species of a dish of 20 beans; share in mixtures | 100% correct in the test set | Mihailova et al.10 |\n\n## Open questions\n\n- **Sensory comparison under one protocol.** No study opened for this entry compared arabica and robusta cups with one sensory method; the cup descriptions rest on a textbook chapter.15\n- **Bean shape across origins.** The bean measurements come from one study of roasted beans; how far shape separates the species across origins, grades and green coffee is not established in the sources opened here.10\n- **Detection floor for robusta.** If arabica holds traces of 16-OMC, chemical tests cannot detect robusta much below about 1%; DNA methods avoid that marker, but their limit was not given in the abstract read for this entry.16,18\n- **Robusta’s temperature optimum outside South-East Asia.** The 2020 optimum comes from farms in one region (see Contested).7\n\n## Key studies\n\n
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Campa et al., 2004 – Sucrose and trigonelline in wild coffee species. Measured sucrose and trigonelline in seeds of 14 wild species and six further taxa, four trees each. Arabica held more of both than canephora, with one of the highest sucrose contents of all species tested.

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Food Chemistry 88(1), 39–43 · doi:10.1016/j.foodchem.2004.01.020

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Gunning et al., 2018 – 16-OMC in arabica. Analysed arabica and robusta roast coffees with low-field NMR and other methods. Found 16-O-methylcafestol and 16-O-methylkahweol in arabica for the first time, which limits the detection of robusta in blends to about 1% and above.

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Food Chemistry 248, 52–60 · doi:10.1016/j.foodchem.2017.12.034

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Combes, Joët & Lashermes, 2018 – A DNA test for robusta in arabica. Developed a high-resolution melting method on chloroplast DNA for green and roasted coffee. It identifies the species and estimates the share of robusta in a blend.

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Food Control 88, 198–206 · doi:10.1016/j.foodcont.2018.01.014

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Mihailova et al., 2022 – Imaging roasted beans. Measured spectral, shape and colour features of 3,500 roasted beans from 21 arabica and 14 robusta samples. Robusta beans were shorter and rounder on average, and a model built on selected features classified every dish of 20 beans in the test set correctly.

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Food Chemistry: X 14, 100325 · doi:10.1016/j.fochx.2022.100325

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Kath et al., 2020 – Not so robust. Modelled yields from 798 robusta farms in South-East Asia against temperature. Found an optimum below 20.5 °C, lower than earlier estimates, which questions the view of robusta as a warm-lowland crop.

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Global Change Biology 26(6), 3677–3688 · doi:10.1111/gcb.15097

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