Temperature Control¶

Temperature control is critical throughout coffee production, from growing to brewing. Precise temperature management affects flavour development, extraction efficiency, quality preservation, and sensory evaluation accuracy.

Temperature Across the Coffee Chain¶

Growing and Processing¶

Cherry Development: - Optimal growing: 15-24°C - Cooler nights: enhance quality - Frost: catastrophic damage - Heat stress: reduced quality

Fermentation: - Fermentation Temperature: 18-25°C optimal - Too cold: slow, incomplete - Too hot: over-fermentation, defects - Controlled fermentation chambers

Drying: - Target: 35-45°C for optimal - Too hot (>60°C): case hardening - Too slow: mould risk - Final target: 10-12% moisture

Storage¶

Green Coffee: - Storage Conditions: 15-25°C - Stable temperature crucial - Temperature swings: condensation risk - Humidity interaction

Roasted Coffee: - Cool, stable environment - Room temperature acceptable - Avoid heat sources - Freezing for long-term (controversial)

Roasting¶

Critical Points: - Charge temperature: 180-220°C - First Crack: ~196°C - Second Crack: ~224°C - Drop temperature: 195-230°C

Bean Temperature vs. Environmental: - Bean temp (probe) - Drum/environmental temp - Both monitored - Relationship varies by roaster

Development Control: - Rate of Rise management - Temperature curve profiling - Consistent heat application - Avoiding thermal shock

Brewing¶

Extraction Temperature: - Optimal range: 90-96°C - Lower (88-92°C): delicate/light roasts - Higher (94-96°C): darker roasts - Method-dependent variations

Temperature Stability: - Espresso machines: ±0.5°C - Home equipment: wider variance - Temperature surfing techniques - PID controllers

Serving¶

Serving Temperature: - Espresso: 65-70°C - Filter coffee: 65-75°C - Too hot: scalding, flavour masked - Too cold: flavour dull, unpleasant

Holding: - Batch brew: don't let drop below 85°C - Thermal carafes better than hot plates - Time limits (30 minutes ideal)

Sensory Evaluation¶

Cupping Protocol¶

SCA Cupping Protocol: - Water: 93°C ± 1°C - Initial evaluation: ~70°C - Main evaluation: 60-65°C (optimal) - Cool evaluation: 50°C

Why Multiple Temperatures: - Different compounds volatile at different temps - Hot: intensity, volatiles - Warm: true character, balanced - Cool: persistent flavours, defects

Temperature Precision: - Critical for consistency - Reproducible results - Fair comparison - Calibration standard

Flavour Perception¶

Temperature and Flavour: - Hot (>70°C): Aromatics prominent, sweetness masked - Warm (55-65°C): Balanced, optimal evaluation - Cool (<50°C): Acidity sharper, sweetness emerges

Compound Volatility: - Light volatiles: escape when hot - Medium volatiles: optimal at warm - Heavy compounds: persist when cool - Sequential perception

Equipment Temperature Control¶

Roasters¶

Heat Sources: - Gas burners - Electric elements - Infrared heating - Hot air systems

Monitoring: - Bean temperature probes - Environmental temperature - Exhaust temperature - Multiple sensors

Control Systems: - Manual (experience-based) - Semi-automated (profile following) - Fully automated (software control) - Roast Profile Design execution

Espresso Machines¶

Boiler Systems: - Single boiler - Heat exchanger (HX) - Dual boiler - Multi-boiler

Temperature Stability: - PID control: ±0.5°C - Thermostats: ±3-5°C - Thermal mass importance - Pre-infusion effects

Group Head: - Active heating vs. passive - Temperature loss through portafilter - Flush routine importance - Temperature surfing

Brewers¶

Batch Brewers: - SCAA standard: 92-96°C - Spray head consistency - Flow rate effects - Thermal carafe vs. hot plate

Manual Methods: - Kettle temperature - Heat loss during pour - Slurry temperature - Ambient temperature effects

Water Heaters¶

Types: - Boilers - Thermoblocks - Heat exchangers - Instant heating elements

Accuracy: - ±1°C minimum - Digital control better - Calibration essential - Regular verification

Measurement Tools¶

Thermometers¶

Types: - Thermocouple probes - Infrared (non-contact) - Digital instant-read - Analogue dial

Accuracy: - ±0.5°C for professional - ±1-2°C acceptable for home - Calibration critical - Ice bath test (0°C) - Boiling water test (100°C at sea level)

Placement: - Probe position matters - Center of mass - Avoid contact with surfaces - Consistent placement

Calibration¶

Frequency: - Daily check (professional) - Weekly verification - Monthly full calibration - Annual professional service

Methods: - Ice bath (0°C) - Boiling water (100°C, altitude-adjusted) - Reference thermometers - Multi-point calibration

Temperature Effects on Chemistry¶

Roasting Chemistry¶

Maillard Reaction: - Accelerates with temperature - Optimal: 140-165°C - Creates flavour compounds - Temperature-time dependent

Caramelisation: - Begins: ~170°C - Accelerates: 180-200°C - Sweetness development - Colour formation

Pyrolysis: - Significant: >200°C - Structural breakdown - Smoke generation - Bitter compound formation

Extraction Chemistry¶

Solubility: - Higher temp = higher solubility - Affects which compounds extract - Acids extract at lower temps - Bitter compounds at higher temps

Rate: - Temperature increases reaction rate - Q10 rule: ~2x per 10°C - Faster extraction at higher temps - Risk of over-extraction

Troubleshooting¶

Temperature Too Low¶

Symptoms: - Under-extraction - Sour, thin, weak - Slow extraction (espresso) - Insufficient development (roasting)

Solutions: - Increase temperature - Check equipment calibration - Preheat properly - Extend time (compensatory)

Temperature Too High¶

Symptoms: - Over-extraction - Bitter, harsh, burnt - Too fast extraction - Scorching (roasting)

Solutions: - Reduce temperature - Check equipment calibration - Reduce contact time - Improve heat management

Temperature Inconsistency¶

Symptoms: - Batch-to-batch variation - Inconsistent results - Quality unpredictability - Failed cupping comparisons

Solutions: - Equipment service - Calibration - Standard operating procedures - Temperature Control protocols

Best Practices¶

Roasting¶

Preheat adequately: Thermal equilibrium
Monitor all temperatures: Bean, drum, exhaust
Follow profiles precisely: ±2°C tolerance
Document everything: Track variations
Calibrate regularly: Weekly minimum

Brewing¶

Measure water temp: Don't assume
Preheat equipment: Vessels, portafilters
Consistent methodology: Same temp each time
Account for ambient: Summer vs. winter
Serve promptly: Don't let sit

Cupping¶

Precise water temp: 93°C ±1°C
Consistent timing: Same cool-down
Multiple temperatures: Hot, warm, cool
Room temperature: 20-25°C ideal
Document conditions: Reproducibility

Advanced Topics¶

Pressure-Temperature Relationship¶

At Altitude: - Water boils at lower temp - Adjust brewing accordingly - Roasting affected - Cupping standards shift

Under Pressure: - Espresso: water stays liquid >100°C - Affects extraction - Pressure profiling interacts - Complex variables

Heat Transfer¶

Methods: - Conduction (direct contact) - Convection (air/water circulation) - Radiation (infrared) - All three in roasting

Efficiency: - Material thermal conductivity - Surface area - Temperature differential - Time

Thermal Mass¶

Concept: - Object's heat storage capacity - Affects temperature stability - Important in equipment design - Influences heat retention

Applications: - Heavy group heads (espresso) - Thick-walled drums (roasting) - Thermal carafes (serving) - Preheated cups

Temperature Control¶

Temperature Across the Coffee Chain¶

Growing and Processing¶

Storage¶

Roasting¶

Brewing¶

Serving¶

Sensory Evaluation¶

Cupping Protocol¶

Flavour Perception¶

Equipment Temperature Control¶

Roasters¶

Espresso Machines¶

Brewers¶

Water Heaters¶

Measurement Tools¶

Thermometers¶

Calibration¶

Temperature Effects on Chemistry¶

Roasting Chemistry¶

Extraction Chemistry¶

Troubleshooting¶

Temperature Too Low¶

Temperature Too High¶

Temperature Inconsistency¶

Best Practices¶

Roasting¶

Brewing¶

Cupping¶

Advanced Topics¶

Pressure-Temperature Relationship¶

Heat Transfer¶

Thermal Mass¶

See Also¶