Coffee Science
Antioxidants in Coffee
Also known as: coffee antioxidants, dietary antioxidants
Coffee contains over 1,000 bioactive compounds, with chlorogenic acids (CGA) being the most prominent polyphenols. During roasting, thermal degradation transforms CGAs into quinic and caffeic acids while producing melanoidins. Together, these compounds provide a significant antioxidant capacity, with a standard serving delivering between 70mg and 350mg of chlorogenic acids.
Key Takeaways
- Coffee contains over 1,000 bioactive compounds, including chlorogenic acids and melanoidins.
- Chlorogenic acids make up 6% to 10% of green Arabica coffee dry weight.
- Thermal roasting degrades chlorogenic acids into quinic acid and caffeic acid.
- These compounds collectively provide the beverage with significant total antioxidant capacity.
Coffee contains over 1,000 bioactive compounds, with chlorogenic acids (CGA) being the most prominent polyphenols. During roasting, thermal degradation transforms CGAs into quinic and caffeic acids while producing melanoidins. Together, these compounds provide a significant antioxidant capacity, with a standard serving delivering between 70mg and 350mg of chlorogenic acids.
This concept is explored in depth in The Complete World of Coffee. Read a free sample chapter.
Definition
Coffee constitutes a complex chemical matrix featuring over 1,000 bioactive compounds. The predominant polyphenols are chlorogenic acids (CGA), specifically 5-O-caffeoylquinic acid, which comprise 6% to 10% of green Arabica coffee’s dry weight and up to 14% in Robusta. During the roasting process, thermal degradation transforms these acids into quinic acid and caffeic acid, while simultaneously initiating the Maillard reaction to produce melanoidins. These high-molecular-weight nitrogenous polymers contribute significantly to the brew's total antioxidant capacity (TAC). A standard 200ml serving of coffee delivers a potent dose of 70mg to 350mg of chlorogenic acids, alongside hydroxycinnamic acids like ferulic and p-coumaric acids. These molecules neutralize reactive oxygen species (ROS) through electron donation, providing a robust defense against cellular oxidative damage.
Why It Matters
<p>Antioxidants in coffee represent the most significant source of dietary polyphenols in Western diets, frequently exceeding the combined intake from fruits and vegetables. This high bioavailability is critical for mitigating systemic inflammation and chronic disease risk. Chlorogenic acids specifically modulate glucose metabolism by inhibiting the enzyme glucose-6-phosphatase, which regulates hepatic glucose production. Clinical data suggests that consistent consumption of these compounds correlates with a 30% reduction in the risk of Type 2 diabetes. Furthermore, the neuroprotective properties of coffee's antioxidant profile, including the ability of caffeic acid to cross the blood-brain barrier, are linked to lower incidences of neurodegenerative conditions. By reducing lipid peroxidation and protecting DNA from oxidative cleavage, coffee's chemical profile acts as a primary preventative agent in metabolic and cardiovascular health.</p><h2>Summary</h2><ul><li>Coffee provides 70mg-350mg of chlorogenic acids per 200ml cup, the primary dietary source for most populations.</li><li>Roasting transforms chlorogenic acids into melanoidins, maintaining high antioxidant capacity even in dark roasts.</li><li>Specific polyphenols like 5-O-caffeoylquinic acid inhibit enzymes involved in glucose production, reducing diabetes risk.</li><li>Caffeic and ferulic acids provide neuroprotective benefits by neutralizing reactive oxygen species in the brain.</li></ul>
Antioxidants in coffee, including chlorogenic acids and melanoidins, help protect against oxidative damage. However, once coffee is roasted and ground, these compounds gradually degrade through oxidation and staling processes that diminish flavor. To understand how oxidation affects coffee freshness over time, explore our guide to Oxidation and Staling.
Frequently Asked Questions
Does the roast profile influence the total antioxidant capacity?
Light and medium roasts contain the highest concentrations of chlorogenic acids, as these molecules begin significant thermal degradation at temperatures exceeding 200°C. However, dark roasts generate increased levels of melanoidins through extended Maillard reactions, which provides a substantial, alternative antioxidant effect that offsets the loss of polyphenols.
Are antioxidants lost during the decaffeination process?
The majority of antioxidant compounds remain intact during decaffeination. Processes like the Swiss Water Method or CO2 extraction are highly selective for caffeine molecules. Analytical studies indicate that decaffeinated coffee retains approximately 85% to 90% of the chlorogenic acid content found in its caffeinated counterparts.
How does the brewing method affect antioxidant extraction?
Extraction efficiency depends on particle size and contact time. Espresso provides the highest concentration of antioxidants per milliliter due to high-pressure extraction. Conversely, drip brewing with paper filters removes diterpenes like cafestol but successfully extracts water-soluble polyphenols, with a 200ml cup offering more total antioxidants than a single shot of espresso due to volume.
What is the specific role of chlorogenic acids in the body?
Chlorogenic acids act as potent free radical scavengers. Once ingested, they inhibit the enzyme glucose-6-phosphatase, which reduces the release of glucose into the bloodstream from the liver. They also demonstrate anti-thrombotic properties by inhibiting platelet aggregation and reducing markers of systemic inflammation such as C-reactive protein.
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Coffee Science
Acids in Coffee
Acids are a primary contributor to coffee's flavor, providing brightness, complexity, and the characteristic liveliness that distinguishes specialty coffee. Coffee contains both organic acids (citric, malic, acetic, quinic) and phenolic acids (chlorogenic acids). The acid content and profile change dramatically during roasting: green coffee is high in chlorogenic and citric acids, while roasted coffee has reduced chlorogenic acids but increased quinic and acetic acids from degradation reactions.
ChemistryLipids and Coffee Oil
Lipids (coffee oil) constitute approximately 10 to 15% of roasted coffee by weight and play a critical role in flavor, body, crema formation, and shelf life. Coffee lipids are primarily triglycerides (75%), followed by diterpenes (cafestol and kahweol, 15 to 19%), free fatty acids, sterols, and tocopherols. The lipid content varies by species (Arabica ~15%, Robusta ~10%) and affects body, mouthfeel, and crema stability in espresso.
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Related Concepts
Chlorogenic Acid
Chlorogenic acid (CGA) is a family of ester compounds formed between caffeic acid and quinic acid, and is one of the most abundant phenolic compounds in coffee. Green Arabica coffee contains approximately 5 to 8 percent CGA by weight. During roasting, CGA degrades into lactones and phenylindanes, which contribute significantly to the bitterness, acidity, and antioxidant capacity of brewed coffee.
Coffee ScienceDecaffeination
Decaffeination is the process of removing caffeine from coffee beans. The four primary methods are the Swiss Water Process, the CO2 Process, the Direct Solvent Method, and the Indirect Solvent Method. All remove 97% or more of caffeine.
RoastingMaillard Reaction in Coffee: Browning & Flavor Science
The Maillard reaction is a non-enzymatic browning reaction between amino acids and reducing sugars that occurs during coffee roasting, beginning at approximately 140°C. Named after French chemist Louis-Camille Maillard, it produces hundreds of flavor and aroma compounds—including pyrazines, furans, and melanoidins—that define the complex taste, aroma, color, and body of roasted coffee. It is one of the most critical chemical processes in coffee roasting.
Coffee ScienceMelanoidin
Melanoidins represent the final structural evolution of coffee chemistry during thermal processing, comprising a diverse group of nitrogenous, brown-colored macromolecules with molecular weights ranging from 10,000 to 100,000 Daltons. Their formation initiates at approximately 160°C (320°F) through the Maillard reaction, where reducing sugars like glucose and fructose react with free amino acids and proteins. This sequence generates reactive intermediates—including furfurals and dehydro-reductones—which subsequently undergo polycondensation. In Arabica coffee, melanoidin concentration increases linearly with roast development, typically accounting for 15% to 25% of the total beverage dry matter in medium-to-dark roasts. These polymers are categorized by solubility; water-soluble melanoidins migrate into the extract, while insoluble variants remain within the cellular matrix of the spent grounds. The incorporation of nitrogen into heterocyclic ring structures, specifically pyrazines and pyrroles, differentiates these pigments from simple caramelization products and dictates the aromatic intensity of the roasted bean.
Coffee ScienceTrigonelline
Summary of Chemical Properties Chemical Formula: C7H7NO2 Melting Point: 218°C (decomposes) Solubility: Highly soluble in water and ethanol Occurrence: ~1.0% in Arabica; ~0.7% in Robusta Primary Metabolite: Nicotinic Acid (Vitamin B3)
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Chaff
<h2>Botanical and Structural Composition</h2><p>The silver skin, or spermoderm, represents the innermost layer of the coffee fruit's integument, tightly encompassing the endosperm. During the developmental stages of the <em>Coffea arabica</em> and <em>Coffea canephora</em> seeds, this cellulosic tissue serves as a protective barrier. Structurally, the silver skin is composed of sclerenchyma cells, providing a fibrous matrix rich in polysaccharides. During the roasting cycle, specifically as the bean internal temperature reaches the range of 130°C to 160°C, the bean undergoes physical expansion. This expansion, coupled with the rapid evaporation of remaining moisture (typically 10-12% in green coffee), causes the silver skin to fracture and detach from the bean surface. In washed (wet-processed) coffees, the mechanical friction of pulping and the fermentation process remove a significant portion of the spermoderm, leaving only the portion trapped within the longitudinal fissure, or center cut. Conversely, natural (dry-processed) coffees retain a higher percentage of the silver skin until the roasting phase, where it is liberated as voluminous, lightweight flakes.</p>
Coffee ScienceChlorogenic Acid
Chlorogenic acid (CGA) is a family of ester compounds formed between caffeic acid and quinic acid, and is one of the most abundant phenolic compounds in coffee. Green Arabica coffee contains approximately 5 to 8 percent CGA by weight. During roasting, CGA degrades into lactones and phenylindanes, which contribute significantly to the bitterness, acidity, and antioxidant capacity of brewed coffee.
Coffee ScienceCoffee Borer Beetle
<h2>Environmental Management and Control</h2><p>Control of <i>H. hampei</i> requires a multi-faceted approach, as the beetle's internal nesting protects it from standard contact insecticides. Biological control often involves the entomopathogenic fungus <i>Beauveria bassiana</i>, which is applied at a concentration of 1x10^9 spores per milliliter. The fungus penetrates the beetle's exoskeleton, leading to mortality within 4 to 7 days. Additionally, the introduction of the parasitoid wasp <i>Cephalonomia stephanoderis</i> has proven effective in Latin American plantations, as the wasp enters the berry to prey upon borer larvae. Post-harvest, meticulous sanitation of processing equipment and the use of GrainPro or hermetic storage bags prevent cross-contamination in the warehouse environment.</p>
Coffee ScienceCoffee Leaf Rust
Hemileia vastatrix belongs to the order Pucciniales and is an obligate biotrophic fungus, meaning it requires living host tissue to survive. The infection cycle begins when urediniospores are deposited on the abaxial (underside) surface of the coffee leaf, typically via wind or rain splash. Germination occurs only in the presence of free water—such as dew or rainfall—within a temperature range of 15°C to 28°C. Upon germination, the fungus enters the leaf through the stomata and establishes a mycelium that colonizes the internal tissue. The visual manifestation of the disease begins as small, chlorotic spots that expand into characteristic orange, powdery pustules. These pustules contain thousands of spores capable of further infection. The physiological impact includes a rapid reduction in photosynthetic capacity and the eventual abscission of the leaf. Severe cases lead to 'dieback,' where the plant's branches wither due to carbohydrate depletion, often resulting in the death of the tree or a total loss of the following year's crop.
Coffee ScienceDecaffeination
Decaffeination is the process of removing caffeine from coffee beans. The four primary methods are the Swiss Water Process, the CO2 Process, the Direct Solvent Method, and the Indirect Solvent Method. All remove 97% or more of caffeine.
Coffee ScienceDefects
Coffee defects are imperfections in green or roasted coffee beans that negatively affect flavor, aroma, or appearance. The SCA Green Coffee Classification limits defects in specialty-grade coffee to a maximum of 5 full defects per 300g.
Parent Topics & Topic Hubs
Related Sub-Topics
Chlorogenic Acid
Chlorogenic acid (CGA) is a family of ester compounds formed between caffeic acid and quinic acid, and is one of the most abundant phenolic compounds in coffee. Green Arabica coffee contains approximately 5 to 8 percent CGA by weight. During roasting, CGA degrades into lactones and phenylindanes, which contribute significantly to the bitterness, acidity, and antioxidant capacity of brewed coffee.
Coffee ScienceCoffee Borer Beetle
<h2>Environmental Management and Control</h2><p>Control of <i>H. hampei</i> requires a multi-faceted approach, as the beetle's internal nesting protects it from standard contact insecticides. Biological control often involves the entomopathogenic fungus <i>Beauveria bassiana</i>, which is applied at a concentration of 1x10^9 spores per milliliter. The fungus penetrates the beetle's exoskeleton, leading to mortality within 4 to 7 days. Additionally, the introduction of the parasitoid wasp <i>Cephalonomia stephanoderis</i> has proven effective in Latin American plantations, as the wasp enters the berry to prey upon borer larvae. Post-harvest, meticulous sanitation of processing equipment and the use of GrainPro or hermetic storage bags prevent cross-contamination in the warehouse environment.</p>
Coffee ScienceCoffee Leaf Rust
Hemileia vastatrix belongs to the order Pucciniales and is an obligate biotrophic fungus, meaning it requires living host tissue to survive. The infection cycle begins when urediniospores are deposited on the abaxial (underside) surface of the coffee leaf, typically via wind or rain splash. Germination occurs only in the presence of free water—such as dew or rainfall—within a temperature range of 15°C to 28°C. Upon germination, the fungus enters the leaf through the stomata and establishes a mycelium that colonizes the internal tissue. The visual manifestation of the disease begins as small, chlorotic spots that expand into characteristic orange, powdery pustules. These pustules contain thousands of spores capable of further infection. The physiological impact includes a rapid reduction in photosynthetic capacity and the eventual abscission of the leaf. Severe cases lead to 'dieback,' where the plant's branches wither due to carbohydrate depletion, often resulting in the death of the tree or a total loss of the following year's crop.
Coffee ScienceDecaffeination
Decaffeination is the process of removing caffeine from coffee beans. The four primary methods are the Swiss Water Process, the CO2 Process, the Direct Solvent Method, and the Indirect Solvent Method. All remove 97% or more of caffeine.
RoastingMaillard Reaction in Coffee: Browning & Flavor Science
The Maillard reaction is a non-enzymatic browning reaction between amino acids and reducing sugars that occurs during coffee roasting, beginning at approximately 140°C. Named after French chemist Louis-Camille Maillard, it produces hundreds of flavor and aroma compounds—including pyrazines, furans, and melanoidins—that define the complex taste, aroma, color, and body of roasted coffee. It is one of the most critical chemical processes in coffee roasting.
Coffee ScienceMelanoidin
Melanoidins represent the final structural evolution of coffee chemistry during thermal processing, comprising a diverse group of nitrogenous, brown-colored macromolecules with molecular weights ranging from 10,000 to 100,000 Daltons. Their formation initiates at approximately 160°C (320°F) through the Maillard reaction, where reducing sugars like glucose and fructose react with free amino acids and proteins. This sequence generates reactive intermediates—including furfurals and dehydro-reductones—which subsequently undergo polycondensation. In Arabica coffee, melanoidin concentration increases linearly with roast development, typically accounting for 15% to 25% of the total beverage dry matter in medium-to-dark roasts. These polymers are categorized by solubility; water-soluble melanoidins migrate into the extract, while insoluble variants remain within the cellular matrix of the spent grounds. The incorporation of nitrogen into heterocyclic ring structures, specifically pyrazines and pyrroles, differentiates these pigments from simple caramelization products and dictates the aromatic intensity of the roasted bean.
Continue Through the Encyclopedia
View the Coffee Science category hub →Book References
- Chapter 8: Coffee and Health
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Editorial Standards & Trust
Keith E. Lyons
Author, Researcher & Coffee Educator
Keith E. Lyons is the author of The Complete World of Coffee and the publisher behind Lyons Den Publishing. A licensed trauma therapist turned specialty coffee writer, Keith blends scientific rigor with genuine passion for the craft of coffee.
Last Reviewed
August 10, 2026
Sources & References
(2)Claims are cited to verifiable sources. Peer-reviewed research is marked.
- 1Coffee Science Foundation
- 2Journal of Nutrition
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- • Fact-checked against peer-reviewed coffee science research and industry standards.
- • Reviewed by the author with documented sources for every factual claim.
- • Updated regularly; the "Last Reviewed" date reflects the most recent verification.
- • Corrections are made promptly when new research or evidence emerges.
Our editorial process prioritizes accuracy, scientific rigor, and practical relevance for coffee enthusiasts and professionals alike.
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Chlorogenic Acid
Chlorogenic acid (CGA) is a family of ester compounds formed between caffeic acid and quinic acid, and is one of the most abundant phenolic compounds in coffee. Green Arabica coffee contains approximately 5 to 8 percent CGA by weight. During roasting, CGA degrades into lactones and phenylindanes, which contribute significantly to the bitterness, acidity, and antioxidant capacity of brewed coffee.
Acids in Coffee
Acids are a primary contributor to coffee's flavor, providing brightness, complexity, and the characteristic liveliness that distinguishes specialty coffee. Coffee contains both organic acids (citric, malic, acetic, quinic) and phenolic acids (chlorogenic acids). The acid content and profile change dramatically during roasting: green coffee is high in chlorogenic and citric acids, while roasted coffee has reduced chlorogenic acids but increased quinic and acetic acids from degradation reactions.
Melanoidin
Melanoidins represent the final structural evolution of coffee chemistry during thermal processing, comprising a diverse group of nitrogenous, brown-colored macromolecules with molecular weights ranging from 10,000 to 100,000 Daltons. Their formation initiates at approximately 160°C (320°F) through the Maillard reaction, where reducing sugars like glucose and fructose react with free amino acids and proteins. This sequence generates reactive intermediates—including furfurals and dehydro-reductones—which subsequently undergo polycondensation. In Arabica coffee, melanoidin concentration increases linearly with roast development, typically accounting for 15% to 25% of the total beverage dry matter in medium-to-dark roasts. These polymers are categorized by solubility; water-soluble melanoidins migrate into the extract, while insoluble variants remain within the cellular matrix of the spent grounds. The incorporation of nitrogen into heterocyclic ring structures, specifically pyrazines and pyrroles, differentiates these pigments from simple caramelization products and dictates the aromatic intensity of the roasted bean.
The Maillard Reaction: Coffee Roasting Chemistry Explained
maillard reaction maillard reaction maillard reaction maillard reaction... the maillard reaction produces compounds that affect extraction: melanoidins are...
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Acids in Coffee
Acids are a primary contributor to coffee's flavor, providing brightness, complexity, and the characteristic liveliness that distinguishes specialty coffee. Coffee contains both organic acids (citric, malic, acetic, quinic) and phenolic acids (chlorogenic acids). The acid content and profile change dramatically during roasting: green coffee is high in chlorogenic and citric acids, while roasted coffee has reduced chlorogenic acids but increased quinic and acetic acids from degradation reactions.
The Maillard Reaction: Coffee Roasting Chemistry Explained
maillard reaction maillard reaction maillard reaction maillard reaction... the maillard reaction produces compounds that affect extraction: melanoidins are...
Roasting Chemistry
Coffee roasting is a complex thermal process that transforms green coffee beans into the aromatic, flavorful brown beans used for brewing. Roasting involves over 1,000 chemical reactions, primarily the Maillard reaction, caramelization, pyrolysis, and Strecker degradation. These reactions create hundreds of new compounds responsible for coffee's characteristic aroma, flavor, body, and color. Understanding roasting chemistry is essential for roasters to control flavor development and consistency.
Lipids and Coffee Oil
Lipids (coffee oil) constitute approximately 10 to 15% of roasted coffee by weight and play a critical role in flavor, body, crema formation, and shelf life. Coffee lipids are primarily triglycerides (75%), followed by diterpenes (cafestol and kahweol, 15 to 19%), free fatty acids, sterols, and tocopherols. The lipid content varies by species (Arabica ~15%, Robusta ~10%) and affects body, mouthfeel, and crema stability in espresso.
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Chlorogenic Acid
Chlorogenic acid (CGA) is a family of ester compounds formed between caffeic acid and quinic acid, and is one of the most abundant phenolic compounds in coffee. Green Arabica coffee contains approximately 5 to 8 percent CGA by weight. During roasting, CGA degrades into lactones and phenylindanes, which contribute significantly to the bitterness, acidity, and antioxidant capacity of brewed coffee.
Melanoidin
Melanoidins represent the final structural evolution of coffee chemistry during thermal processing, comprising a diverse group of nitrogenous, brown-colored macromolecules with molecular weights ranging from 10,000 to 100,000 Daltons. Their formation initiates at approximately 160°C (320°F) through the Maillard reaction, where reducing sugars like glucose and fructose react with free amino acids and proteins. This sequence generates reactive intermediates—including furfurals and dehydro-reductones—which subsequently undergo polycondensation. In Arabica coffee, melanoidin concentration increases linearly with roast development, typically accounting for 15% to 25% of the total beverage dry matter in medium-to-dark roasts. These polymers are categorized by solubility; water-soluble melanoidins migrate into the extract, while insoluble variants remain within the cellular matrix of the spent grounds. The incorporation of nitrogen into heterocyclic ring structures, specifically pyrazines and pyrroles, differentiates these pigments from simple caramelization products and dictates the aromatic intensity of the roasted bean.
Trigonelline
<h2>Summary of Chemical Properties</h2><ul><li><strong>Chemical Formula:</strong> C7H7NO2</li><li><strong>Melting Point:</strong> 218°C (decomposes)</li><li><strong>Solubility:</strong> Highly soluble in water and ethanol</li><li><strong>Occurrence:</strong> ~1.0% in Arabica; ~0.7% in Robusta</li><li><strong>Primary Metabolite:</strong> Nicotinic Acid (Vitamin B3)</li></ul>
Mucilage
Botanically identified as the coffee mesocarp, mucilage is a translucent, pectin-rich hydrogel that encapsulates the endocarp (parchment). It represents approximately 5% to 10% of the total coffee cherry weight depending on the cultivar. Chemically, it comprises 84.2% water, 8.9% protein, 4.1% sugar (primarily glucose and fructose), 0.91% pectic substances, and 0.7% ash. The thickness of this layer is genetically determined; Coffea arabica varieties like Bourbon and Typica typically exhibit a more substantial mucilage layer than Coffea canephora. The pH of fresh mucilage ranges between 5.5 and 6.0, but this acidity increases rapidly during fermentation as microbial activity converts sugars into organic acids. In the honey process, the degree of mucilage removal—ranging from 100% for white honey to 0% for natural—directly dictates the drying duration and final water activity levels.
Recommended Encyclopedia Entries
Reference definitions that complement this page.
Chlorogenic Acid
Chlorogenic acid (CGA) is a family of ester compounds formed between caffeic acid and quinic acid, and is one of the most abundant phenolic compounds in coffee. Green Arabica coffee contains approximately 5 to 8 percent CGA by weight. During roasting, CGA degrades into lactones and phenylindanes, which contribute significantly to the bitterness, acidity, and antioxidant capacity of brewed coffee.
Melanoidin
Melanoidins represent the final structural evolution of coffee chemistry during thermal processing, comprising a diverse group of nitrogenous, brown-colored macromolecules with molecular weights ranging from 10,000 to 100,000 Daltons. Their formation initiates at approximately 160°C (320°F) through the Maillard reaction, where reducing sugars like glucose and fructose react with free amino acids and proteins. This sequence generates reactive intermediates—including furfurals and dehydro-reductones—which subsequently undergo polycondensation. In Arabica coffee, melanoidin concentration increases linearly with roast development, typically accounting for 15% to 25% of the total beverage dry matter in medium-to-dark roasts. These polymers are categorized by solubility; water-soluble melanoidins migrate into the extract, while insoluble variants remain within the cellular matrix of the spent grounds. The incorporation of nitrogen into heterocyclic ring structures, specifically pyrazines and pyrroles, differentiates these pigments from simple caramelization products and dictates the aromatic intensity of the roasted bean.
Maillard Reaction in Coffee: Browning & Flavor Science
The Maillard reaction is a non-enzymatic browning reaction between amino acids and reducing sugars that occurs during coffee roasting, beginning at approximately 140°C. Named after French chemist Louis-Camille Maillard, it produces hundreds of flavor and aroma compounds—including pyrazines, furans, and melanoidins—that define the complex taste, aroma, color, and body of roasted coffee. It is one of the most critical chemical processes in coffee roasting.
Coffee Acidity Guide
Acidity in coffee is governed by chlorogenic, citric, malic, and phosphoric acids. Discover the chemical drivers, origin altitude influences, and sensory evaluation of acidity.