tags: [] - coffee/roasting aliases: - Coffee roasting - Roasting process - Green to roasted

Roasting¶

Tags: #coffee/roasting Aliases: Coffee roasting, Roasting process, Green to roasted Related: Roasting Methods MOC | Roast Profile | First & Second Crack | Maillard Reaction | Green Coffee Status: ✅ Complete

Overview¶

Roasting is the thermal transformation of green coffee into roasted coffee through the application of heat, converting the pale, dense, grassy-smelling seed into the brown, aromatic, porous bean familiar from café and supermarket shelves. During roasting, hundreds of chemical reactions occur simultaneously: water is driven off, cell structures expand, sugars caramelise, proteins undergo Maillard browning with reducing sugars, chlorogenic acids degrade, and hundreds of volatile aromatic compounds are generated. Roasting is the final manufacturing step before grinding and brewing, and the roast profile — the shape of the temperature-versus-time curve — is the primary determinant of the flavour character of the roasted coffee.

Chemistry of Roasting¶

The major chemical reactions during coffee roasting, in approximate sequence:

Reaction	Temperature range	Product / effect
Moisture evaporation	100–150°C	Bean dries; turns yellow
Strecker degradation	150–170°C	Amino acids + carbonyls → aromatic aldehydes; first aromatic compounds
Maillard reaction	150–200°C	Amino acids + reducing sugars → brown melanoidins; hundreds of aroma compounds
Caramelisation	170–200°C	Sugars → caramel compounds; sweetness and brown colour
First crack	185–200°C	Endosperm fractures; CO₂ release; exothermic; bean expands
Chlorogenic acid degradation	190–230°C	Chlorogenic acids break down; acidity decreases; bitterness increases
Second crack	220–230°C	Cell wall fracture; oils emerge; carbons form; very dark roast
Carbonisation	> 230°C	Excessive burning; loss of all positive aromatics

The Maillard Reaction in Roasting¶

The Maillard reaction is the most important chemical process in coffee roasting. It is a non-enzymatic browning reaction between amino acids and reducing sugars, producing thousands of distinct flavour compounds — including pyrazines, furans, aldehydes, and ketones — that give roasted coffee its characteristic aroma. The degree of Maillard development is a primary determinant of the flavour complexity of the finished coffee.

Roast Levels¶

Roast level	Drop temperature (approx.)	Character
Light	195–210°C	Origin-expressive; bright acidity; light body
Medium-light	205–215°C	Balance of origin and roast character
Medium	215–220°C	Balanced; reduced brightness; chocolate/caramel notes
Medium-dark	218–225°C	Roast character prominent; bittersweet
Dark	225–235°C	Roast-forward; low acidity; heavy body; carbon notes

Roasting Equipment¶

Commercial and specialty coffee is roasted on drum roasters (rotating steel cylinders heated by gas or electric elements) or fluid-bed roasters (hot air fluidises the coffee bed). Drum roasters are the industry standard; fluid-bed roasters are used in sample roasting and by some specialty producers. Sample roasters (50–200 g capacity) are used for evaluating green coffee before purchasing; production roasters range from 1 kg to 200+ kg batch sizes.

Key Facts¶

Roasting transforms green coffee chemically and physically through heat; the Maillard reaction produces most of the aromatic complexity
Major stages: drying → Maillard/browning → first crack → development → (second crack for dark roast)
Roast level (light/medium/dark) is determined by drop temperature and development time after first crack
Drum roasters are the industry standard; profiling software (Cropster, Artisan) enables repeatable, data-driven roasting
Roast profile shape determines flavour outcome; a poorly managed profile can ruin high-quality green coffee

References¶

Changelog¶

Date	Change
2026-04-28	Note created

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