Kenya Coffee School (KCS)
Advanced Roasting Certification
📊 Integrated Calculation Tables & Charts
For inclusion in the Advanced Roasting Handbook
This section provides ready-to-print calculation tables, formulas, and chart models to integrate directly into the KCS 60-Page Certification Handbook. These tools support scientific roasting, production consistency, and sustainability benchmarking.
Aligned with best practices referenced by the Specialty Coffee Association framework and adapted for Kenyan high-density coffees (820–850 g/L).
1️⃣ Development Time Ratio (DTR) Calculation Table
📐 Formula
\textbf{DTR (\%)} = \left( \frac{\text{Development Time}}{\text{Total Roast Time}} \right) \times 100
📊 DTR Reference Table
| Total Roast Time | Dev Time | DTR % | Roast Interpretation |
|---|---|---|---|
| 9:00 | 1:30 | 16.7% | Likely underdeveloped |
| 9:30 | 1:50 | 19.3% | Light, bright |
| 10:00 | 2:00 | 20% | Balanced specialty |
| 10:30 | 2:15 | 21.4% | Sweet, structured |
| 11:00 | 2:45 | 25% | Risk of overdevelopment |
🎯 KCS Target for Kenyan Washed Coffees:
20–23% DTR
2️⃣ Density-to-Charge Temperature Adjustment Chart
High-density Kenyan coffees require calibrated charge temperatures.
📐 Adjustment Formula (Guideline)
\text{Charge Adjustment (°C)} = \frac{(\text{Density} - 800)}{10}
(Base assumption: 800 g/L reference)
📊 Density vs Charge Guide
| Density (g/L) | Recommended Charge Temp (°C) | Adjustment Strategy |
|---|---|---|
| 800 | 185 | Base reference |
| 820 | 187–190 | Slight increase |
| 840 | 190–195 | Moderate increase |
| 850 | 195–198 | High-density control |
| 870 | 198–202 | Risk of scorching |
⚠ Increase airflow proportionally to prevent surface burn.
3️⃣ Roast Weight Loss (Shrinkage) Calculator
📐 Formula
\text{Weight Loss \%} = \left( \frac{\text{Green Weight - Roasted Weight}}{\text{Green Weight}} \right) \times 100
📊 Shrinkage Benchmark Table
| Roast Level | Typical Weight Loss |
|---|---|
| Light | 13–15% |
| Medium | 15–17% |
| Medium-Dark | 17–19% |
| Dark | 19–22% |
🎯 Kenyan Specialty Sweet Spot:
14.5–16.5%
4️⃣ Roast Energy Cost Calculator
📐 Formula
\text{Energy Cost per Kg} = \frac{\text{Total Gas Cost per Batch}}{\text{Kg Roasted}}
📊 Sample Calculation
| Batch Size | Gas Used | Gas Cost | Cost per Kg |
|---|---|---|---|
| 15 kg | 2.5 m³ | KES 300 | KES 20/kg |
| 30 kg | 4.2 m³ | KES 500 | KES 16.6/kg |
Efficiency improves with optimized scaling.
5️⃣ Production Consistency Control Chart
📊 Drop Temperature Control
| Target Drop | Acceptable Range | Action Required |
|---|---|---|
| 202°C | 200–204°C | Acceptable |
| 202°C | 198–199°C | Increase development |
| 202°C | 205–207°C | Reduce gas input |
📉 Visual Control Concept
A line graph should show:
- X-axis: Batch number
- Y-axis: Drop temperature
- Highlighted tolerance band (±2°C)
This can be inserted as a control chart in the handbook.
6️⃣ Rate of Rise (RoR) Stability Chart
🎯 Ideal Pattern
- High at turning point
- Gradual decline
- No flick at first crack
- Smooth decline into drop
📊 RoR Benchmark Table
| Roast Stage | Ideal RoR Range |
|---|---|
| 1:00–3:00 | 15–20°C/min |
| 4:00–6:00 | 10–15°C/min |
| First Crack | 5–8°C/min |
| Development | 3–6°C/min |
7️⃣ Carbon Emission Estimation Model
📐 Formula (Simplified)
\text{CO₂ per Kg} = \frac{\text{Total Gas Used (m³)} \times 2.0}{\text{Kg Roasted}}
(Approximate 2.0 kg CO₂ per m³ LPG equivalent)
📊 Sustainability Benchmark
| Batch Size | Gas Used | CO₂/kg |
|---|---|---|
| 15 kg | 2.5 m³ | 0.33 kg |
| 30 kg | 4.2 m³ | 0.28 kg |
| 60 kg | 7.5 m³ | 0.25 kg |
Lower numbers indicate improved efficiency.
8️⃣ Cost-Per-Kg Full Production Calculator
📐 Formula
\text{Total Cost per Kg} =
\frac{\text{Green Cost + Energy + Labor + Packaging}}{\text{Roasted Kg Output}}
📊 Sample Breakdown
| Component | Cost (KES) |
|---|---|
| Green Coffee (per kg) | 650 |
| Energy | 20 |
| Labor | 35 |
| Packaging | 25 |
| Total | 730 KES/kg |
This enables pricing strategy modeling.
9️⃣ Profile Translation Chart (Sample → Production)
| Parameter | 200g Sample | 15kg Batch Adjustment |
|---|---|---|
| Charge Temp | 190°C | 195°C |
| Total Time | 9:30 | 10:30 |
| Dev Time | 2:00 | 2:15 |
| Airflow | Medium | Medium-High |
Scaling requires increased thermal inertia consideration.
🔟 Sensory Score Weighting Matrix
| Attribute | Weight |
|---|---|
| Aroma | 15% |
| Flavor | 20% |
| Acidity | 15% |
| Sweetness | 15% |
| Balance | 15% |
| Aftertaste | 10% |
| Overall | 10% |
Minimum passing sensory score: 84 specialty equivalent
📈 Recommended Charts to Insert Graphically
- Roast Curve Template (Blank Graph Grid)
- RoR Trend Line Example
- Density vs Charge Scatter Plot
- Energy Efficiency Bar Chart
- Carbon Reduction Progress Chart
- Drop Temperature Control Chart
- DTR Comparison Chart
- Shrinkage vs Roast Level Graph