Gene Café CBR-301 | First Full Batch Roast
After receiving the Regional Jess (Huila, washed blend), the goal of this roast was simple:
Produce a clean, balanced full-batch roast to replace the earlier sample roast, which was useful for understanding the machine behaviour but not optimal for evaluating the coffee itself.
This roast therefore serves as the first proper full-batch reference for this coffee.
Key Metrics
| Metric | Value |
|---|---|
| Roaster | Gene Café CBR-301 |
| Bean | Colombia Regional Jess (Huila, Washed Blend) |
| Batch size | 250 g |
| Output weight | 213.5 g |
| Weight loss | 14.6% |
| Total roast time | 12:28 |
| Ambient temperature | 21°C |
| Ventilation | Oven extractor hood |
| Time to 200°C | 04:12 |
| Time to 230°C | 06:56 |
| Cooling time | 07:14 |
No preheat was used (standard Gene Café operating procedure).
Roast Objective
This roast aimed to explore a slightly lighter development than the Brazil Santos comfort profile.
Target characteristics:
- clean structure
- moderate acidity
- lighter body
- good drinkability as black coffee
Target weight loss range:
14.6–15.2%
Final result:
14.6%
This places the roast at the lower edge of the intended development window.
Roast Phase Behaviour
Drying Phase
Start → 200°C
04:12
This is extremely consistent with previous cold-start roasts.
Comparison with earlier dataset:
| Roast | Bean | Time to 200°C |
|---|---|---|
| Roast 28 | Brazil Santos | 04:10 |
| Roast 32 | Brazil Santos | 04:31 |
| Roast 36 | Brazil Santos | 04:46 |
| Roast 38 | Jess | 04:12 |
Observation
The Gene Café continues to show remarkably consistent early-phase heating when started cold.
Maillard Phase
200°C → 230°C
04:12 → 06:56
Phase duration:
2:44
This is slightly faster than many Brazilian naturals in previous roasts.
This behaviour aligns with expectations for washed coffees, which often progress slightly faster through Maillard reactions.
Fan Behaviour
The Gene Café automatically shifted airflow:
Fan 2 → Fan 3
At:
04:25 (~202°C)
This is consistent with the pattern observed across many previous roasts.
Your dataset has repeatedly shown this shift occurring at:
~4:05–4:25
This confirms again that the machine’s airflow behaviour is predictable and repeatable.
Development Phase
Total roast time:
12:28
Final weight loss:
14.6%
This sits exactly on the lower boundary of the intended development range.
This roast should therefore produce:
- lighter body
- more noticeable acidity
- clean finish
First Crack Observation
No first crack button was recorded in the roast log.
However, this is consistent with several previous roasts.
Reasons likely include:
- extractor hood noise masking crack sounds
- Gene Café drum noise
- relatively subtle crack onset in washed coffees
As reinforced in earlier project notes:
Crack audibility is not used as a primary roast decision signal in this setup.
Instead, the primary indicators remain:
- time
- aroma
- colour
- weight loss
Smoke Behaviour
Visible smoke appeared late in the roast.
This coincided with:
- toasty / hot bread aromas
- deeper browning of the beans
This timing corresponds with typical development phase chemistry, where caramelisation and sugar breakdown increase volatile compounds.
Roast Colour
The beans finished a medium brown, lighter than most of the Brazil Santos roasts.
This matches expectations for a 14.6% weight loss roast level.
System Behaviour Observations
One important comparison emerges when this roast is placed beside Roast 37.
Roast 37 started with a warm drum temperature of 71°C due to minimal time between roasts.
Roast 38 returned to a true cold start (21°C).
The difference in behaviour reinforces an emerging pattern:
Drum temperature at roast start significantly affects roast progression.
Warm starts compress the roast timeline and accelerate early heating.
Cold starts provide the most consistent and predictable behaviour.
Key Lessons from Roast 38
1. Cold starts remain the most predictable approach
Across the dataset, cold starts consistently produce:
- stable drying phases
- predictable Maillard timing
- repeatable total roast times
2. Washed coffees progress slightly faster than Brazilian naturals
The Jess roast moved through Maillard slightly quicker than Santos roasts.
This behaviour is typical of washed coffees and should be expected in future roasts.
3. Weight loss remains the most reliable roast metric
With crack sound sometimes unclear, weight loss provides the clearest confirmation of roast level.
14.6% weight loss aligns with the desired roast profile.
4. Smoke is a development indicator
The appearance of smoke around the late roast stage coincided with:
- toasted bread aromas
- colour development
This is consistent with expected development chemistry.
Where This Roast Fits in the Project
Roast 38 now becomes the first reference roast for the Regional Jess coffee.
Reference metrics:
| Parameter | Value |
|---|---|
| Batch | 250 g |
| Start temp | ~21°C |
| TRT | 12:28 |
| Weight loss | 14.6% |
Future Jess roasts can now be compared against this baseline.
Next Experiment
The next useful experiment would be a slightly longer roast:
Target:
~12:40 TRT
Expected weight loss:
~15.0–15.2%
This would test whether the coffee benefits from slightly more development and body.
Personal Reflection
One unexpected outcome of the last series of roasts has been a shift in taste preference.
While the Brazil Santos roasts remain very enjoyable, especially for milk drinks, the move toward drinking more coffee black has opened the door to appreciating slightly lighter roasts.
The Jess coffee therefore represents a useful contrast:
- lighter
- cleaner
- more acidity
Not necessarily “better” — just different.
And that difference is part of the learning process.