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Roasting · Overview

Green coffee composition

What green coffee is made of – carbohydrates, proteins and amino acids, lipids, acids, alkaloids, minerals and water – how arabica and robusta differ, and which constituents the roast turns into flavour and colour.

Across the chain: Science

Source-checkedby Coffearium verification pass· Last source-checked 20 Oct 2026· Prepared with AI assistance· 16 sources (14 tier A)· 2 contested· Updated 22 Oct 2026
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Contents
  • Carbohydrates make up about 60% of green coffee dry weight; cell-wall polysaccharides alone account for about half of the dry weight.2,3
  • Arabica holds more sucrose and trigonelline, robusta more caffeine; most sources also report more chlorogenic acids in robusta, but a meta-analysis disagrees.7,6,14
  • Green arabica averages about 15% lipids, robusta around 10%; the diterpene 16-O-methylcafestol has long served as a robusta marker.5
  • According to a roasting chemistry chapter, sugars, proteins, free amino acids, trigonelline and chlorogenic acids are the principal flavour precursors.1
  • Composition shifts with growing temperature and processing; unwashed (natural) coffees held significantly more glucose and fructose than washed ones.11,12

What green coffee is made of#

Most of the dry weight of green coffee is carbohydrate: about 60%, according to a 2014 review.2 The rest is a mix of nitrogen compounds, lipids, acids, minerals and water.1

The main groups, as dry weight unless stated:

  • Polysaccharides – long sugar chains that build the cell walls. They make up about 50% of the dry weight.3
  • Sucrose – the main free sugar. A 2000 paper gives 3–8% of green coffee.9 A 2006 review gives 5–12% of dry weight in mature seeds.3
  • Proteins, peptides and free amino acids – together 9–16%.2 The free amino acids are only a small part of this.1
  • Lipids – the coffee oil and a thin surface wax, 8–18% of dry matter according to a 2014 review2; a 2006 review gives 7–17%.5
  • Chlorogenic acids – a family of phenolic acids, 4–8.4% in arabica and 7–14.4% in robusta.6
  • Other acids – citric, malic and quinic acid. All acids together, chlorogenic acids included, make up about 11% of the green bean’s weight.9
  • Alkaloids – caffeine, 0.9–1.5% in arabica and 1.2–2.4% in robusta8, and trigonelline, about 1%.2
  • Minerals and water. The Codex code of practice says moisture should not exceed 12.5% anywhere from the point where the coffee leaves the loading area until it is stored or roasted.15

These numbers are ranges across many samples and methods. A single lot can sit anywhere within them, and sources do not always agree (see Contested).6,14

Arabica and robusta compared#

The two traded species contain the same classes of compounds in different proportions.1 A 2001 study of 38 wild accessions of each species found more trigonelline and sucrose in C. arabica. It found more chlorogenic acids and caffeine in C. canephora.7 Green arabica averages about 15% lipids, robusta around 10%.5

According to a roasting chemistry chapter, arabica is also richer in organic acids such as citric and malic acid. Robusta is richer in free amino acids, ash and transition metals such as iron and copper.1

The chart shows one paired example: one arabica from Honduras and one robusta from India, analysed in the same laboratory.4

05101520253035g per 100 g green coffee (basis not stated)Polymeric sugars · arabica32.24 Polymeric sugars · robusta33.74 Protein · arabica11.684 Protein · robusta12.974 Chlorogenic acids ·arabica6.9724 Chlorogenic acids ·robusta9.3974 Sucrose · arabica7.144 Sucrose · robusta4.494 Caffeine · arabica1.054 Caffeine · robusta2.574
Data table
g per 100 g green coffee (basis not stated)Source
Polymeric sugars · arabica32.24
Polymeric sugars · robusta33.74
Protein · arabica11.684
Protein · robusta12.974
Chlorogenic acids · arabica6.9724
Chlorogenic acids · robusta9.3974
Sucrose · arabica7.144
Sucrose · robusta4.494
Caffeine · arabica1.054
Caffeine · robusta2.574
Main constituents of one green arabica (Honduras) and one green robusta (India), in g per 100 g of green coffee (basis not stated). Polymeric sugars are total sugars minus the glucose present as free glucose and in sucrose; protein is calculated from nitrogen.4 One sample per species, not a species average.

The robusta held less sucrose and more than twice the caffeine.4 Polymeric sugars and protein were close in both.4 Whether robusta reliably holds more chlorogenic acids is disputed. A meta-analysis of many published samples found the difference not statistically significant.14 The Coffea arabica and Coffea canephora entries cover the species themselves.

What each group does in the roast#

Almost every constituent of green coffee is a potential precursor of flavour or colour, or takes part in their formation.1 According to a roasting chemistry chapter, the principal flavour precursors are sugars, proteins, free amino acids, trigonelline and chlorogenic acids.1

1Sucrosesplits into glucose, fructose 1,9 2Free amino acidsused up early 1 3Proteinsbound amino acids, later 1 4Polysaccharidesarabinose from side chains 1,3 5Chlorogenic acidsdegraded later in the roast 1 6Trigonellinepartly degraded 1 Maillard and Streckeraroma volatiles, CO₂ 1 Caramelisationfree sugars alone 1 Aliphatic acidsformic, acetic, glycolic, lactic 9 Melanoidinsbrown polymers 1 Phenols and lactonessmoky notes, bitterness 1 Pyridines, pyrrolesand nicotinic acid 1 7Lipidsmove to the surface; some form aldehydes 1 8Caffeinealmost unchanged 1 9Waterlost early in the roast 1 Schematic, not to scale. Main routes only, not amounts or shares.
Which green coffee constituents feed which roast reactions, mainly according to a roasting chemistry chapter.1,3,9 Schematic, not to scale; main routes only, not amounts.
  • Sucrose and free amino acids react first, because they are immediately available.1 Sucrose splits into glucose and fructose, which then take part in the Maillard reaction and caramelisation.1,9 Sucrose is also the main source of the formic, acetic, glycolic and lactic acid formed in roasting.9
  • Amino acids pair with sugars in the Maillard reaction and its Strecker branch.1 Proteins release bound amino acids more slowly, later in the roast.1
  • Polysaccharides lose their arabinose side chains, which feed browning and melanoidins. Cellulose and mannans remain largely unchanged.1 Their role in body is covered under carbohydrates and body.
  • Chlorogenic acids break down later in the roast, into bitter lactones, quinic acid and smoky phenols.1 Details are in the chlorogenic acids entry.
  • Trigonelline is partly degraded to nicotinic acid, pyridines and pyrroles.1
  • Lipids move to the bean surface and help retain aroma; part of them breaks down to aldehydes.1
  • Caffeine is almost unchanged by roasting, according to the same chapter.1
  • Water is lost in the early drying stage. The starting moisture affects light roasts more than dark ones.1

Species differences carry through to the cup. According to the roasting chemistry chapter, the higher sucrose of arabica explains its higher levels of buttery diketones, furfurals and caramel-like furaneol. Robusta’s higher chlorogenic acids give more smoky phenols.1

What changes the composition#

Species and genotype. Composition varies between accessions within each species, not only between the two species.7 Variation was larger in C. canephora than in C. arabica, except for trigonelline and sucrose.7

Climate. A 2010 study used 16 plots on Réunion Island with a wide range of climates. Chlorogenic acids and fatty acids in the seed depended on the mean air temperature during seed development.11

Ripeness. Chlorogenic acid content and composition change considerably as the fruit matures, according to a 2006 review.6 A 2023 study compared three stages of ripe fruit. Lipids, proteins, alkaloids, total chlorogenic acids and sucrose did not differ; only glucose and fructose varied.13

Processing. In a 2006 study of green arabica, washed coffees held only low amounts of glucose and fructose; unwashed (natural) coffees held significantly more.12 Sucrose was not significantly affected by processing.12 The washed process and natural process entries cover the methods.

Storage. Free fatty acids rose during storage, most in green coffee that had been moistened. In one set of samples they reached almost 4.8 g/kg.5 The authors trace this to lipase, an enzyme that frees fatty acids from oil, and report that cold and dry storage inhibits it.5

Carbohydrates in detail#

Galactomannans are the predominant cell-wall components, accounting for 50% of the polysaccharides.3 They have a backbone of β-1,4-linked mannose with single galactose side units.1 The second main group are type II arabinogalactans, highly branched and covalently linked to protein as arabinogalactan proteins.1,3 Cellulose completes the wall.3

During seed development, the wall changes. Arabinogalactan made up about half of the polysaccharides in early growth and 34% in the mature seed, while mannan synthesis increased towards maturity.3 Sucrose dominates the free sugars from the earliest stages of maturation and is essentially all of them in mature seeds.3

In roasting, the polymers are depolymerised and lose molecular weight even in a light roast. Up to 40% of the polysaccharides were degraded after a long roast.3 The released arabinose is mainly involved in melanoidin formation and may contribute to formic and acetic acid.1,9 Free sugars, by contrast, are lost almost entirely within minutes.1

In the paired samples of 2017, total sugars after hydrolysis were 35.8 g/100 g in the arabica and 36.0 in the robusta. Mannose (16.2 and 15.0), galactose (7.82 and 9.96) and glucose (9.76 and 9.00) dominated, with arabinose at 2.00 and 1.98.4

Lipids and diterpenes#

Most of the lipids, the coffee oil, sit in the endosperm; the surface wax is about 0.2–0.3% of the bean weight.5 Triacylglycerols are the main class.5 Linoleic and palmitic acid are the main fatty acids, according to the roasting chemistry chapter.1

Diterpenes of the kaurene family make up up to 20% of the total lipids.5 Arabica contains cafestol and kahweol. Robusta contains cafestol, small amounts of kahweol and 16-O-methylcafestol (16-OMC).5 The diterpenes occur as fatty acid esters.2 Their behaviour in the brew is covered under coffee oil.

16-OMC as a robusta marker. A 2006 review describes 16-OMC as the ideal characteristic for detecting robusta in arabica blends.5 It cites DIN 10779, a method for roasted coffee that detects robusta at less than 2% of a mixture.5 A 2018 study found 16-OMC and 16-O-methylkahweol in arabica roast coffee for the first time.10 By low-field NMR, it could detect robusta in arabica at about 1–2% w/w, but not below about 1% (see Contested).10

Nitrogen compounds and acids#

Proteins, peptides and free amino acids account for 9–16% of the dry weight.2 According to the roasting chemistry chapter, total protein is similar in both species.1 The main free amino acids are glutamic acid, aspartic acid and asparagine, and almost all are used up in roasting.1 The same chapter links robusta’s higher isoleucine and leucine to more 2- and 3-methylbutanal after roasting, and its tryptophan to animal-like skatole.1

Trigonelline is present at about 1% of dry weight, with slightly higher values in arabica.2 Caffeine stays nearly unchanged through the roast (see Caffeine).1 A 2014 review gives 0.9–1.3% for green arabica and 1.5–2.5% for robusta, close to the 0.9–1.5% and 1.2–2.4% of a 2021 review.2,8

Chlorogenic acids are esters of hydroxycinnamic acids with quinic acid.1 In green coffee, 5-caffeoylquinic acid alone makes up about 56–62% of them, according to a 2006 review.6 In the paired samples, 5-caffeoylquinic acid was 4.353 g/100 g in the arabica and 5.061 in the robusta, of totals of 6.972 and 9.397.4 The roast chemistry of the other acids is covered in acids in coffee.

Reference values#

Values as reported in the sources, for green coffee. They describe ranges found in research, not targets. Bases are given as each source states them.

Constituent Arabica Robusta Source
Carbohydrates, total ≈60% of dry weight (both species) – Ludwig et al.2
Polysaccharides ≈50% of dry weight (both species) – Redgwell & Fischer3
Galactomannans 50% of the polysaccharides – Redgwell & Fischer3
Sucrose, both species 3–8% (basis not stated); 5–12% of dry weight in mature seeds – Ginz et al.9; Redgwell & Fischer3
Sucrose, one paired sample 7.14 g/100 g 4.49 g/100 g Moreira et al.4
Glucose; fructose, one paired sample 0.02; 0.03 g/100 g 0.07; 0.12 g/100 g Moreira et al.4
Proteins, peptides, free amino acids 9–16% of dry weight (both species) – Ludwig et al.2
Protein, one paired sample (nitrogen × 6.25, caffeine N excluded) 11.68 g/100 g 12.97 g/100 g Moreira et al.4
Lipids 8–18% of dry matter (both species); 7–17% (both species); average ≈15% ≈10% Ludwig et al.2; Speer & Kölling-Speer5
Diterpenes Up to 20% of total lipids Up to 20% of total lipids Speer & Kölling-Speer5
Surface wax 0.2–0.3% of bean weight – Speer & Kölling-Speer5
Chlorogenic acids 4–8.4% of dry matter 7–14.4% of dry matter Farah & Donangelo6 (contested)
Chlorogenic acids, one paired sample 6.972 g/100 g 9.397 g/100 g Moreira et al.4
All acids incl. chlorogenic acids ≈11% of green bean weight – Ginz et al.9
Caffeine 0.9–1.5% of dry weight; 0.9–1.3% of dry matter 1.2–2.4%; 1.5–2.5% Olechno et al.8; Ludwig et al.2
Caffeine, one paired sample 1.05 g/100 g 2.57 g/100 g Moreira et al.4
Trigonelline ≈1% of dry weight; slightly higher in arabica Slightly lower Ludwig et al.2
16-O-methylcafestol + 16-O-methylkahweol, arabica roast coffee ≥10 mg/kg (estimate, one sample) – Gunning et al.10
Moisture Not above 12.5% from shipment until storage or roasting (Codex) Same Codex15

No Tier A source opened for this entry gives a range for minerals (ash), so none is listed. The roasting chemistry chapter reports more ash in robusta.1

Measuring composition#

  • Moisture. ISO 6673 heats a test portion of about 10 g at 105 °C for 16 h and reports the loss in mass.16 Results are about 1.0% lower than with the ISO 1446 reference method for water content.16 The moisture and water activity entry covers meters and water activity.
  • Sugars. Free sucrose, glucose and fructose are measured by anion-exchange chromatography. Total sugars, including those in polysaccharides, are measured by gas chromatography after hydrolysis.4
  • Protein. Commonly calculated from total nitrogen. One study subtracted caffeine nitrogen first and multiplied by 6.25.4
  • Alkaloids, sucrose and chlorogenic acids. High-performance liquid chromatography (HPLC) was used in the 2001 study of wild accessions.7
  • 16-OMC. DIN 10779 is a validated method for roasted coffee.5 It has since been withdrawn and replaced by DIN EN 18003 (see Arabica and robusta compared). Low-field NMR is an alternative screening method.10

Two points matter when comparing numbers. First, the basis: dry matter, dry weight or as-is weight, which several sources do not state.4,9 Second, the sample: a range across many accessions is not the same as one commercial lot.7

Open questions#

  • Chlorogenic acids by species. Older ranges and a meta-analysis disagree on whether robusta holds more (see Contested).6,14
  • 16-OMC in arabica. If arabica holds small amounts, the limit for detecting robusta in blends is about 1%.10
  • The insoluble fraction. According to the roasting chemistry chapter, the role of the water-insoluble carbohydrates in roasting is much less understood than that of the soluble fraction.1
  • Minerals. No source opened for this entry measured ash or minerals by species with a stated method.

Key studies#

Ky et al., 2001 – Diversity in wild arabica and robusta. Analysed caffeine, trigonelline, chlorogenic acids and sucrose by HPLC in 38 wild accessions of each species. Arabica held more trigonelline and sucrose, robusta more chlorogenic acids and caffeine, and robusta varied more except in trigonelline and sucrose.

Food Chemistry 75(2), 223–230 · agritrop.cirad.fr/526749

Joët et al., 2010 – Climate and processing. Compared green arabica from 16 plots on Réunion Island with broad climatic variation. Mean air temperature during seed development controlled chlorogenic acids and fatty acids in the seed.

Food Chemistry 118(3), 693–701 · agritrop.cirad.fr/551309

Knopp et al., 2006 – Processing and sugars. Measured sugars in green arabica after washed and unwashed processing. Washed coffees held little glucose and fructose, unwashed coffees significantly more, while sucrose was not significantly affected.

European Food Research and Technology 223, 195–201 · doi:10.1007/s00217-005-0172-1

Gunning et al., 2018–16-OMC in arabica. Used low-field NMR and other methods on roast coffees. Found 16-O-methylcafestol and 16-O-methylkahweol in arabica for the first time, which sets a floor of about 1% for detecting robusta in arabica.

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

Contested
  • Chlorogenic acids by species: a 2006 review gives 4–8.4% of dry matter for arabica and 7–14.4% for robusta6, a 2001 study of wild accessions found more in *C. canephora*7, and one paired sample held 6.972 against 9.397 g/100 g4; according to the lead author of a meta-analysis, the two species tend to have similar levels (except total diCQA), and the difference is not statistically significant over their much larger sample.14
  • 16-O-methylcafestol in arabica: a 2006 review reports that its absence from arabica beans was confirmed and calls it the ideal marker for robusta in arabica blends5; a 2018 study detected 16-O-methylcafestol and 16-O-methylkahweol in arabica roast coffee for the first time, at an estimated combined level of at least 10 mg/kg in one arabica sample, and concluded that robusta below about 1% cannot be detected this way.10
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Change log

  • – Removed two numbers resting only on a textbook chapter (total protein about 10%, caffeoylquinic acids about 80%), replacing the latter with the 5-CQA share from a peer-reviewed review; narrowed the Codex moisture statement to the scope the code states; corrected the definition of polymeric sugars in the chart caption; gave both review ranges for total lipids. Reason: Verification against sources (number rule; Codex CAC/RCP 69-2009 §h; Moreira et al. 2017 Table 3 footnote; Speer & Kölling-Speer 2006 gives 7–17%, not 8–18%).

Sources

  1. BPoisson, L.; Blank, I.; Dunkel, A.; Hofmann, T. (2017). The Chemistry of Roasting – Decoding Flavor Formation. In: Folmer, B. (ed.), The Craft and Science of Coffee, Academic Press, ch. 12, pp. 273–309. doi:10.1016/B978-0-12-803520-7.00012-8 · other copies
  2. ALudwig, I. A.; Clifford, M. N.; Lean, M. E. J.; Ashihara, H.; Crozier, A. (2014). Coffee: biochemistry and potential impact on health. Food & Function 5(8), 1695–1717. doi:10.1039/C4FO00042K · other copies
  3. ARedgwell, R.; Fischer, M. (2006). Coffee carbohydrates. Brazilian Journal of Plant Physiology 18(1), 165–174. doi:10.1590/S1677-04202006000100012 · other copies
  4. AMoreira, A. S. P.; Nunes, F. M.; Simões, C.; Maciel, E.; Domingues, P.; Domingues, M. R. M.; Coimbra, M. A. (2017). Data on coffee composition and mass spectrometry analysis of mixtures of coffee related carbohydrates, phenolic compounds and peptides. Data in Brief 13, 145–161. doi:10.1016/j.dib.2017.05.027 · other copies
  5. ASpeer, K.; Kölling-Speer, I. (2006). The lipid fraction of the coffee bean. Brazilian Journal of Plant Physiology 18(1), 201–216. doi:10.1590/S1677-04202006000100014 · other copies
  6. AFarah, A.; Donangelo, C. M. (2006). Phenolic compounds in coffee. Brazilian Journal of Plant Physiology 18(1), 23–36. doi:10.1590/S1677-04202006000100003 · other copies
  7. AKy, C. L.; Louarn, J.; Dussert, S.; Guyot, B.; Hamon, S.; Noirot, M. (2001). Caffeine, trigonelline, chlorogenic acids and sucrose diversity in wild Coffea arabica L. and Coffea canephora P. accessions. Food Chemistry 75(2), 223–230.
  8. AOlechno, E.; Puścion-Jakubik, A.; Zujko, M. E.; Socha, K. (2021). Influence of Various Factors on Caffeine Content in Coffee Brews. Foods 10(6), 1208. doi:10.3390/foods10061208 · other copies
  9. AGinz, M.; Balzer, H. H.; Bradbury, A. G. W.; Maier, H. G. (2000). Formation of aliphatic acids by carbohydrate degradation during roasting of coffee. European Food Research and Technology 211(6), 404–410. doi:10.1007/s002170000215 · other copies
  10. AGunning, 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. (2018). 16-O-methylcafestol is present in ground roast Arabica coffees: Implications for authenticity testing. Food Chemistry 248, 52–60. doi:10.1016/j.foodchem.2017.12.034 · other copies
  11. AJoët, T.; Laffargue, A.; Descroix, F.; Doulbeau, S.; Bertrand, B.; De Kochko, A.; Dussert, S. (2010). Influence of environmental factors, wet processing and their interactions on the biochemical composition of green Arabica coffee beans. Food Chemistry 118(3), 693–701.
  12. AKnopp, S.; Bytof, G.; Selmar, D. (2006). Influence of processing on the content of sugars in green Arabica coffee beans. European Food Research and Technology 223, 195–201. doi:10.1007/s00217-005-0172-1 · other copies
  13. AOsorio Pérez, V.; Matallana Pérez, L. G.; Fernandez-Alduenda, M. R.; Alvarez Barreto, C. I.; Gallego Agudelo, C. P.; Montoya Restrepo, E. C. (2023). Chemical Composition and Sensory Quality of Coffee Fruits at Different Stages of Maturity. Agronomy 13(2), 341. doi:10.3390/agronomy13020341 · other copies
  14. BGiuliano, P. (interviewer); Yeager, S. E. (2021). Acids in Coffee: A Review of Sensory Measurements and Meta-Analysis of Chemical Composition. Specialty Coffee Association, SCA News (interview with the lead author about the review by Yeager, Batali, Guinard and Ristenpart in Critical Reviews in Food Science and Nutrition).
  15. ACodex Alimentarius Commission (FAO/WHO) (2009). Code of Practice for the Prevention and Reduction of Ochratoxin A Contamination in Coffee (CAC/RCP 69-2009). Codex Alimentarius.
  16. AInternational Organization for Standardization (2003). ISO 6673:2003 Green coffee — Determination of loss in mass at 105 °C. ISO.

Tier A · authoritative · B · trade and expert · C · general. Supporting quotes for every source are in the data version of this entry. If a publisher’s site refuses access, try the doi link or “other copies”.

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