Caffeine

Caffeine is the compound most people think coffee is. It is a bitter, water-soluble alkaloid the coffee plant manufactures in its own seeds, and it is the reason coffee became a global crop rather than a regional fruit.

Two things about it are worth holding onto before any of the detail. First, the plant does not make it for us — it makes it as a pesticide, and the fact that it also wakes humans up is an accident of chemistry. Second, almost every caffeine number in circulation is a range, not a value. Species, variety, growing conditions, dose, grind and brew method all move it, and sources that look like they disagree are usually measuring different things. This note gives the ranges and says where they come from.

What it actually is

Caffeine is an alkaloid — one of a family of bitter, nitrogen-containing plant compounds that includes nicotine, quinine and morphine. Its everyday chemical name is 1,3,7-trimethylxanthine; formally it is 1,3,7-trimethyl-3,7-dihydro-1H-purine-2,6-dione, with a molar mass of about 194.19 g/mol.¹ It sits in the xanthine group, alongside two close relatives that also turn up in plants people drink: theobromine (the dominant one in cacao) and theophylline (in tea).

It was first pulled out of coffee as a pure substance in 1820, by the German chemist Friedlieb Ferdinand Runge — and the beans were a gift from Goethe, who had watched Runge demonstrate an experiment with belladonna in 1819 and handed him coffee with the suggestion “you can also use these in your investigations.” Runge published the result the following year.²

How much is in a bean

This is the number everyone wants and the number that fractures hardest across sources. CIRAD, the French agricultural research body, gives the cleanest institutional statement of it:³

Species	Caffeine in the green bean
Arabica (Coffea arabica)	around 1.5%
Robusta (Coffea canephora)	1.6–2.8%, occasionally up to 3.5%

This wiki’s Arabica vs Robusta and Robusta notes carry a slightly tighter pair of ranges — about 1.2–1.5% for Arabica against 2.2–2.7% for Robusta — sourced independently. The two sets do not match at the edges, but they agree on the thing that matters: Robusta carries roughly twice the caffeine of Arabica. That single fact drives most of what follows, from why Robusta survives in lowland heat to why it tastes harsher.

At the far end of the range sits Laurina, the naturally low-caffeine Bourbon mutation, at roughly 0.6% — about half of ordinary Arabica. Excelsa and Liberica are also described in the trade as low-caffeine species. Breeding rather than processing is the route in both cases, and Brazil’s Instituto Agronômico has been working on near-zero-caffeine Arabica selections for years.

To verify — the green-bean percentages do not reconcile across sources

Four different ranges are in circulation for the same measurement. CIRAD gives Arabica ~1.5% / Robusta 1.6–2.8% (fetched and confirmed).³ This wiki’s existing notes give 1.2–1.5% / 2.2–2.7%. The research report behind this note adds Arabica 0.8–1.5% and Robusta 1.7–4.0% from a World Bank agricultural paper and an American Scientist review, neither of which was fetched.⁴⁵ And a comparative botany table gives Arabica as 0.06–3.2%, a range so wide it is almost certainly measuring different plant parts or using a different analytical basis.⁶ Treat caffeine content as range-based and origin-specific. Any single “true” figure per species is a simplification, and reconciling these tables would require the underlying methods, which none of the sources publish here.

Why the plant bothers

Caffeine is an insecticide the coffee bush makes for itself. It is concentrated in the seed and the young leaves — the tissues most worth defending — and it is toxic or repellent to most insects that would otherwise eat them.⁷

That is the cleanest explanation for the species split. Robusta grows in hot, humid lowlands where pest pressure is far higher than in Arabica’s cool highlands, and its higher caffeine load is part of why it needs less spraying to survive there. The chemistry and the geography are the same story told twice.

The exception proves it. The Coffee berry borer, the beetle that does more damage to world coffee than anything else, gets around the defence by outsourcing it: microbes living in its gut produce an enzyme, caffeine demethylase, that breaks caffeine down. The plant’s poison is the beetle’s dinner.

What it does in the cup

Caffeine is bitter. That is its whole sensory contribution — it adds no aroma, no sweetness, no acidity, and it is not what makes a coffee taste of blackcurrant or bergamot. It is a bitter background note, and the more of it there is, the more of that note you get.

This is the honest, unglamorous link between chemistry and the cupping table. Robusta’s harsher reputation is partly its doubled caffeine load; Laurina’s remarkably low bitterness is a direct consequence of having half the usual amount. But caffeine is only one bitter compound among many in a roasted bean, and no source consulted here quantifies a relationship between caffeine level and a cupping score. Anyone claiming a points-per-percent conversion is inventing it.

Two adjacent myths, both already dismantled elsewhere on this wiki:

• Dark roast is not stronger. Caffeine is thermally stable up to about 200 °C and only decomposes near 285 °C, so roasting barely touches it. Dark beans are less dense, so a scoop of them carries less mass and therefore less caffeine — see Coffee roasting.
• Cold brew is not automatically stronger. A long cold steep extracts more caffeine per volume than a short hot brew, but cold brew is served as a diluted concentrate, so the finished drink depends entirely on how far the café cuts it — see Cold brew coffee.

How much reaches a drinker

Caffeine is highly water-soluble, so it comes out of the grounds early and readily — which is why brew-strength measures like Total dissolved solids and Extraction yield do not track caffeine one-for-one.

Two independent institutional figures for a brewed cup:

Source	Figure
CIRAD	60–120 mg per 100 ml cup, varying by coffee type and preparation3
Wikipedia (medical/chemistry article)	50–175 mg per 6 oz cup1

For espresso, this wiki’s Espresso note records roughly 65 mg in a single shot against about 95 mg in a typical brewed cup — a useful corrective to the assumption that espresso is the strong one. It is concentrated, not large.

Physiologically, caffeine is a central nervous system stimulant that works by blocking adenosine receptors — adenosine being the molecule that accumulates through the day and signals tiredness. Caffeine does not add energy; it masks the signal that you are out of it. CIRAD notes it also stimulates the cardiovascular system, that effects “vary from one person to another,” and recommends not exceeding 600 mg daily.³¹

It is, by a wide margin, the world’s most widely consumed psychoactive drug.¹

Taking it back out

Every commercial decaffeination method strips caffeine at the green bean stage, before roasting — the Swiss Water route using only water, the ethyl acetate route using a naturally occurring solvent, and the supercritical CO₂ route using pressurised gas.⁸ All of them exploit the same property that makes coffee brewable at all: caffeine dissolves easily, and the craft is in taking it without taking the flavour with it.

No decaf is caffeine-free. US rules require 97% removal, EU rules 99.9%. See Decaffeination for the methods, the regulations and the plants that run them.

Caffeine beyond coffee

Coffee is not the most caffeinated plant — it is the most consumed one. On a dry-weight basis, tea leaves carry considerably more:⁶

	Plant	Caffeine, % of dry matter
1	Tea (Camellia sinensis) leaves	4.8–9.3%
2	Kola nut (Cola acuminata) seeds	1.5–2.5%
3	Arabica coffee beans	0.06–3.2% (comparative table; see warning above)

The reason coffee still dominates is dose and habit, not concentration: a tea leaf is steeped once and briefly, a coffee dose is ground fine and fully extracted. Global caffeine consumption runs to roughly 120,000 tonnes a year — about one cup of coffee per day for every person alive — of which coffee supplies about 79%, tea 15%, cocoa 4% and mate 3%.⁶

To verify — the industrial caffeine market and the plant count

The research report behind this note states that 128,127 tons of anhydrous caffeine were exchanged on the global market in 2022, attributing it to Wikipedia’s caffeine article — but that figure did not appear when the article was fetched, so it is unconfirmed here. The same report says caffeine is synthesised by more than 80 plant species, sourced to a science-content blog rather than a botanical database.⁷ Neither figure should be quoted as fact.

To verify — "coffee is the second most traded commodity after oil"

The report repeats this claim, along with a retail value “exceeding US$70 billion” and more than 10 million hectares under coffee across 50+ countries, sourced to a single review article.⁵ This wiki has already examined and rejected the second-most-traded ranking on the C-market note: it is industry convention rather than a standardised statistic, and no primary trade-volume series supporting it has been found. The accompanying value and area figures were not independently verified either. Do not repeat any of them as fact.

Why it matters

Strip the romance away and caffeine is the commercial engine underneath the entire crop. It is why coffee spread out of Ethiopia and Arabia and became one of the most-traded agricultural products on earth; a fruit that tasted this good but did nothing would have stayed regional.

For specialty specifically, it cuts two ways at once. Caffeine is the thing the mass market buys — the reason a commodity Robusta blend sells at all — and it is simultaneously the thing specialty spends most effort managing around: breeding it down in Laurina, engineering it out in decaf, or accepting it as the price of Robusta’s toughness in Fine Robusta. The compound that made the industry is also the one it keeps trying to negotiate with.

And the negotiation is getting more urgent from the other direction. As climate pushes Arabica’s growing bands uphill, the species with the higher caffeine — the one built for lowland heat — gains ground. The chemistry that makes Robusta bitter is the same chemistry that makes it survivable. See Climate change and coffee.

Related

• Arabica vs Robusta — the species comparison caffeine sits at the centre of
• Robusta · Fine Robusta — the high-caffeine species and the standard that grades it
• Laurina · Excelsa · Liberica — the naturally low-caffeine outliers
• Decaffeination — taking it out at the green stage
• Instituto Agronômico — breeding near-zero-caffeine Arabica
• Coffee berry borer — the beetle that digests the plant’s own insecticide
• Coffee roasting — why dark roast is not stronger
• Espresso · Cold brew coffee — per-drink caffeine, and why the comparisons mislead
• Extraction yield · Total dissolved solids — what brew strength does and does not measure
• Coffee cherry — the fruit the caffeinated seed sits inside
• C-market · Specialty coffee — the commodity trade caffeine built, and the trade that grew out of it
• Climate change and coffee — why the high-caffeine species is gaining ground

Official links

Caffeine is a compound, not an organisation, so it has no homepage. These are the institutional sources that publish on it:

• Official site — CIRAD, coffee: plant and uses — the French agricultural research body’s technical page on caffeine content and effects
• Official site — Specialty Coffee Association — publishes the coffee standards and sensory framework caffeine’s bitterness is judged within
• Official site — International Coffee Organization — publishes the world production and trade statistics behind coffee’s share of global caffeine intake

Footnotes

1. Wikipedia — Caffeine — confirmed via WebFetch; source of the IUPAC name, the 194.194 g/mol molar mass, the adenosine-receptor mechanism, the 50–175 mg per 6 oz cup and “the world’s most widely consumed psychoactive drug” ↩ ↩² ↩³ ↩⁴

2. Wikipedia — Friedlieb Ferdinand Runge — confirmed via WebFetch; source of the 1820 isolation, the 1819 Goethe encounter and the quoted remark ↩

3. CIRAD — Coffee: plant and uses — confirmed via WebFetch; source of the Arabica ~1.5% / Robusta 1.6–2.8% (up to 3.5%) green-bean figures, the 60–120 mg per 100 ml cup, the CNS and cardiovascular effects and the 600 mg daily ceiling ↩ ↩² ↩³ ↩⁴

4. World Bank — coffee agricultural sector paper (PDF) — cited via the research report, not fetched; source of the Arabica 0.8–1.5% and Robusta 1.7–4.0% ranges ↩

5. American Scientist — The Rise of Coffee (via USDA ARS, PDF) — cited via the research report, not fetched; source of the regional species split and the disputed trade-ranking and retail-value claims ↩ ↩²

6. IntechOpen — Introductory chapter: caffeine, a major component of coffee — confirmed via WebFetch; source of the 79/15/4/3 intake split, the ~120,000 tonnes per year figure, and the tea, kola and Arabica concentration table ↩ ↩² ↩³

7. ScienceInsights — What plant does caffeine come from? — science-content blog; cited via the research report, not fetched. Source of the insecticidal-defence framing and the “>80 plant species” figure ↩ ↩²

8. Britannica — Coffee: origin, types, uses, history — cited via the research report; source of the green-stage decaffeination point and the method list ↩