Stages: drying, Maillard, development
This topic explains the three key stages of coffee roasting—drying, Maillard, and development—what happens chemically and physically in each, and how they shape the final cup profile.
- Coffee Basics Nerds
- 2 min read
Article 2 of 12 in Roasting Fundamentals/
1. Drying Stage
- Timeframe: From charge (bean drop) until ~150°C (300°F).
- Bean condition: Green → yellow; moisture evaporates.
- Chemical processes: Water loss, some enzymatic activity.
- Sensory cues: Grassy, hay-like aromas.
- Importance: Prepares beans for even chemical reactions in later stages.
2. Maillard Stage
- Timeframe: ~150–190°C (300–375°F).
- Bean condition: Yellow → light brown; browning reactions begin.
- Chemical processes:
- Maillard reaction between sugars and amino acids.
- Formation of hundreds of aroma precursors.
- Degradation of chlorogenic acids, formation of melanoidins (color).
- Sensory cues: Bready, nutty, caramelizing aromas.
- Importance: Builds complexity, sweetness, and body.
3. Development Stage (First Crack → End of Roast)
- Timeframe: From ~190°C (375°F) onwards.
- Bean condition: Expansion as water vapor and CO₂ force cell rupture (first crack).
- Chemical processes:
- Caramelization and further Maillard reactions.
- Formation of volatile aroma compounds (floral, fruity, chocolate, roasty).
- Breakdown of acids and sugars, influencing brightness vs bitterness.
- Sensory cues: Cracking sounds, intensified aromas.
- Importance: Final stage that defines balance between acidity, sweetness, and roastiness.
Roast Profile Control
- Drying stage: Controls even heat penetration.
- Maillard stage: Extends or shortens to adjust sweetness and body.
- Development stage: Length influences acidity (shorter = brighter) vs roastiness (longer = darker).
Lasting Importance
The three stages—drying, Maillard, and development—are the core framework of roasting. Mastering their timing and transitions allows roasters to create desired flavor profiles, from bright and fruity to dark and bold, with precision and consistency.