Roasting: Foundation
#CaffeinatedTraining
#OilSlickCoffee
Presented: November 28th, 2018
Host: 5758 Coffee Lab
Location: Bandung, Indonesia
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Three Burner Types
Atmospheric burner (gas burner)
Electric burner (like toaster oven)
Infrared burner (ceramic plates in BBQ grill)
Heat Transfer Methods
Convective
Conductive
Radiative
Related:
Endothermic
Exothermic
Roasting Plant Safety
Three areas of concern:
Fire
Ventilation
Personal safety
- Create an emergency plan ahead of time
- Discuss the plan with everyone
- Create a cleaning + maintenance plan
- Regularly review procedures and plans
Roaster fires
- Shut off gas (or element if electric)
- Keep drum rotating
- Don’t open roaster doors
- Don’t eject beans
Personal Safety Concerns
Four areas of concern:
- Green coffee storage
- Roasting
- Packaging, production
- Shipping
What are some concerns in these areas?
Fire Classifications
- Class A
Ordinary items (wood, paper, plastic, rags) - Class B
Flammable Liquids - Class C
Electrical equipment
Roaster Cleaning & Maintenance
- Remove chaff often (fuel source for fire)
- Know where chaff collects in your roaster
- At least daily, more for “chaffy” beans
- Keep ducts clear/clean (creosote & chaff)
- Keep moving parts lubricated (food grade grease)
- Follow manufacturer’s manual and recommendations
Physical changes in the bean
- Dries out
- Progressively darkens
- Becomes increasingly brittle
- First Crack
- Size can increase 30 - 100%
- Second crack
- Eventually oil seeps out (especially beyond second crack)
- Sometimes get divots (can be a roast defect)
- Rapid cooling (≤ 4min) to halt chemical reactions (changes)
First Crack and Second Crack
- Every successful roast has a first crack
- First crack is the result of rapid release of pent-up vapor/steam pressure and CO2
- Not all roasts reach second crack (operator’s preference)
- Exothermic flashes as escaping heat affects environment
Roast Data
Measurements that can be collected from green and roasted coffee:
- Green: batch weight
- Green: bulk density
- Green: volume
- Green: screen size
- Green: moisture content (acceptable range for Specialty?)
- Roasted: color
- Roasted: weight*
- Roasted: bulk density*
- Roasted: volume*
Cupping data should be associated with roast profile for post-roast analysis.
*Calculate percent changes for these attributes
Label the following on a typical roast profile
Charge
Turning Point
Color change: green to yellow
First crack
Second crack
Roast End
Roast Progression
Lighter roasts highlight (preserve) acidity, enzymatic flavors/aromas
Darker roasts emphasize chocolatey, nutty, bitter flavors/aromas
Temperature Midway Point ≈ 75 Agtron
- New concept
- Generates easy color to work/train with
- Not meant to be a standard or a sweet spot regarding end product
