tags: [] - coffee/tasting - coffee/roasting - coffee/green-beans aliases: - CGAs - Chlorogenic acid coffee - Coffee polyphenols - 5-CQA

Chlorogenic Acids¶

Tags: #coffee/tasting #coffee/roasting #coffee/green-beans Aliases: CGAs, Chlorogenic acid coffee, Coffee polyphenols, 5-CQA Related: Coffee Chemistry MOC | Acidity in Coffee | Roast Development | Maillard Reaction | Antioxidants in Coffee Status: ✅ Complete

Overview¶

Chlorogenic acids (CGAs) are a family of phenolic ester compounds present at 5.5–10% of green coffee dry weight, making coffee one of the richest dietary sources of CGAs known. They are formed from the esterification of quinic acid with hydroxycinnamic acids — primarily caffeic acid — and exist as dozens of isomers, of which 5-O-caffeoylquinic acid (5-CQA) is the most abundant. Chlorogenic acids contribute to coffee's acidity, bitterness, astringency, and colour, and break down progressively during roasting into quinic acid and caffeic acid, which influence the cup at every roast level. Their antioxidant and anti-inflammatory properties account for much of the health benefit attributed to coffee consumption.

Chemical Structure¶

CGAs are esters of quinic acid bonded to one or more hydroxycinnamic acids. The major structural families are:

Family	Abbreviation	Hydroxycinnamic component
Caffeoylquinic acids	CQAs	Caffeic acid
Feruloylquinic acids	FQAs	Ferulic acid
Dicaffeoylquinic acids	diCQAs	Two caffeic acid units

Within each family, multiple positional isomers exist (3-, 4-, and 5-substituted). More than 70 individual CGA compounds have been identified in coffee. 5-CQA is the dominant single isomer, comprising approximately half of the total CGA content in Arabica.

Content in Green Coffee¶

Species / Factor	Typical CGA range
Arabica	5.5–8% of dry weight
Robusta	7–10% of dry weight
High-altitude Arabica	Upper end of range
Low-altitude Arabica	Lower end of range

Robusta contains consistently higher CGA concentrations than Arabica, which contributes to its stronger bitterness and harsher flavour profile. Within Arabica, higher altitude correlates with higher CGA content — though the relationship reflects the plant's response to increased UV exposure and pest pressure. Processing method has minimal effect on green CGA concentration; the key variable is roast level.

Changes During Roasting¶

CGAs are heat-labile and degrade progressively as roast temperature increases:

Roast level	Approximate CGAs remaining
Green (unroasted)	100%
Light (City)	60–70%
Medium (City+/Full City)	30–50%
Dark (Vienna)	10–20%
Very dark (French/Italian)	<10%

Degradation accelerates above approximately 170 °C as the first crack range is approached and exceeded. The breakdown products are primarily:

Quinic acid — bitter and astringent; its accumulation at darker roast levels is a major source of roast bitterness and dry mouthfeel
Caffeic acid — mildly bitter; also an antioxidant
Lactones (quinide and caffeolactone) — complex character; some contribute pleasant roasty notes, others harshness
Brown polymers / melanoidins — contribute to colour development alongside Maillard products

CGA breakdown is one reason light-roasted coffees taste brighter and more acidic: they retain higher CGA levels, which are intrinsically acidic compounds. Dark roasts lose most CGAs but accumulate quinic acid and other bitter breakdown compounds.

Role in Brewed Coffee¶

Acidity: CGAs are among the most abundant organic acids in brewed coffee and a primary driver of perceived brightness in light roasts. They lower the pH of the brew and contribute to a lively, clean acidity.

Bitterness: Intact CGAs contribute mild bitterness. At higher extraction yields or with dark roasts, the accumulation of quinic acid from CGA degradation produces a harsher, drying bitterness that is perceptible as astringency.

Extraction behaviour: CGAs are water-soluble and extract readily. At over-extraction temperatures or prolonged brew times, more CGA conversion to quinic acid can occur in the cup, increasing undesirable bitterness in the final beverage.

Freshness indicator: As coffee ages post-roast, residual CGAs continue degrading slowly. Higher quinic acid content in aged coffee contributes to the characteristic stale, harsh bitterness of old roasted beans.

Antioxidant and Health Properties¶

CGAs are potent antioxidants — free radical scavengers — that are absorbed in the small intestine and metabolised systemically. Regular coffee consumption provides 200–550 mg CGAs per 1–3 cups, making coffee the primary dietary source of CGAs for most consumers. Research associations include:

Anti-inflammatory effects
Modest blood pressure reduction
Blood glucose regulation and reduced type 2 diabetes risk
Liver health support
Cardiovascular protection

Decaffeinated coffee retains CGAs in full (caffeine removal does not affect CGA content), meaning the antioxidant and metabolic health benefits of coffee are not dependent on caffeine. Light-roasted coffee provides the highest CGA intake per cup.

Key Facts¶

CGAs are phenolic esters of quinic acid and hydroxycinnamic acids; the dominant isomer is 5-CQA (5-O-caffeoylquinic acid)
Green coffee contains 5.5–10% CGAs by dry weight; Robusta higher than Arabica
Break down progressively during roasting: 60–70% remain at light roast; <10% at very dark roast
Breakdown products include quinic acid (bitter/astringent) and caffeic acid — key drivers of bitterness in dark roasts
Contribute to acidity and brightness in light roasts; their loss in dark roasts is accompanied by rising bitterness from quinic acid accumulation
Major dietary antioxidants; 1–3 cups of coffee provides 200–550 mg CGAs; health benefits include anti-inflammatory, blood glucose regulation, and cardiovascular effects

Coffee Chemistry MOC
Acidity in Coffee
Roast Development
Maillard Reaction
Quinic Acid
Antioxidants in Coffee
Robusta

References¶

Changelog¶

Date	Change
2026-05-02	Compliance review: full rewrite — original had no frontmatter, no metadata block, bold pseudo-headers throughout, no proper section structure, no copyright; restructured as encyclopedia article

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