Roasting Case Study: Venezuela (Washed / Medium-Dark City Roast) · Coffee Roasting with Microwaves

This document is an empirical log recording the roasting of a Venezuelan fully washed green coffee to a medium-dark (City) roast, executed in accordance with the Standard Process Guide.

Roast Date: August 18, 2026

Batch Specifications (Step 0)

Parameter	Set / Measured Value	Notes
Coffee Origin / Lot	Venezuela Mucucay (2024/2025)	-
Variety	Castillo, Monte Claro, Caturra	-
Processing Method	Fully Washed	-
Input Green Bean Weight	144.0g	Standard unit (1kg bag divided into 7 batches)
Washing Water Temp	50°C (Purified water)	Chaff and floater culling
Soaking Solution	50°C water + 15g honey + 20g fructose	30-minute soak
Post-Soak Bean Weight	190.3g	Measured after removing 12.0g of defective floaters
Initial Bean Temp	28.7°C	Infrared reading immediately before roasting
Initial Bed Volume	300–325ml	Visual cylinder reading
Total Weight (incl. container)	459.4g	-

Profile Projection
Consistent with typical washed coffees, the hydrated weight reached 190.3g (near the upper baseline limit). Because the objective is a medium-dark roast (City Roast), the profile was designed to supply sustained thermal energy through the mid-to-late stages.

Detailed Roasting Operations

Steps 1–2: Setup

Secure the lid on the container and place the cylinder vertically on the wooden chopsticks centered on the microwave floor.

Step 3: Initial Uniform Preheating (300W)

No.	Power	Exposure	Agitation Interval	Volume Trend	Operational Notes
1	300W	60s	23s	325ml	Preheating initiated
2	300W	60s	25s	325ml	Steady temperature rise
3	300W	60s	25s	325–350ml	Initial expansion from internal steam pressure
4	300W	60s	52s	-	Interval extended for intermediate weighing

Step 3 Cumulative Heat Input: 72k Ws (300W × 60s × 4 sets)
Step 4 Pre-check Metrics: Outer wall temp 90.2°C / Total weight 456.7g (Moisture loss: 2.7g)
Assessment: An outer wall temperature around 90°C and 2.7g moisture loss align cleanly with standard baseline criteria, indicating low thermal runaway risk. A standard 26- to 27-step profile was deployed.

Step 4: Primary Heating (High + 500W Medium Power)

Applied the "800W + 500W × 50s" alternating cycle designed for higher-moisture batches. The lid was burped (<1s) during each agitation interval.

No.	Power	Exposure	Agitation Interval	Volume Trend	Operational Notes
5	800W	30s	35s	325ml+	Rapid temperature rise
6	500W	50s	30s	325ml	50-second pulse accumulates thermal mass
7	800W	30s	29s	325ml	Thermal boost
8	500W	50s	32s	300–325ml	Volumetric contraction commences with moisture loss

Step 4 Interval Heat: 98k Ws / Cumulative Total: 170k Ws

Step 5: Steady-State Heating (Crack Preparation via Medium Power)

Employed 500W × 50s in the first half to build energy, shifting to 600W × 40s in the second half to enhance thermal uniformity.

No.	Power	Exposure	Agitation Interval	Volume Trend	Operational Notes
9	500W	50s	30s	300–325ml	Continued moisture evaporation
10	500W	50s	26s	300ml	Surface yellowing starts
11	500W	50s	31s	300ml-	Shifting from yellow to light brown
12	600W	40s	22s	275ml+	Switched to 600W
13	600W	40s	28s	275ml	Maximum volumetric contraction phase
14	600W	40s	28s	275ml	Uniform brown color spreading

Step 5 Interval Heat: 147k Ws / Cumulative Total: 317k Ws

Step 6: Thermal Boost Driving into First Crack

Based on bed color and volume dynamics, another round of energy was deemed necessary to cleanly initiate the crack. Instead of the 30-second pulses used for lighter roasts, two sets of 600W × 40s were applied.

No.	Power	Exposure	Agitation Interval	Volume Trend	Operational Notes
15	600W	40s	30s	275ml	Driving temperature upward
16	600W	40s	26s	275ml+	First crack commences (volumetric turning point)

Step 6 Interval Heat: 48k Ws / Cumulative Total: 365k Ws

Step 7: Driving First Crack (800W / 600W Alternating Boost)

To maintain crack momentum and thoroughly transfer heat through to the bean cores, alternating sets of 800W × 20s and 600W × 20s were conducted.

No.	Power	Exposure	Agitation Interval	Volume Trend	Operational Notes
17	800W	20s	29s	275–300ml	Early first crack (isolated pops)
18	600W	20s	30s	275–300ml	Latent heat transfer
19	800W	20s	27s	275–300ml	First crack continuing
20	600W	20s	30s	300ml-	Expansion progressing
21	800W	20s	30s	300–325ml	First crack peak
22	600W	20s	32s	300–325ml	First crack subsiding

Step 7 Interval Heat: 84k Ws / Cumulative Total: 449k Ws

Step 8: Finishing & Second Crack Development

Targeting a medium-dark roast (City to Full City boundary), the roast was taken cleanly into second crack.

No.	Power	Exposure	Agitation Interval	Volume Trend	Operational Notes
23	600W	15s	21s	300–325ml	First crack completely ended
24	600W	15s	25s	300–325ml	Quiet period immediately prior to second crack
25	600W	15s	25s	300ml-	Second crack commences (fine, sharp snaps)
26	600W	15s	0s	-	Second crack peak confirmed; terminated immediately

Step 8 Interval Heat: 36k Ws / Cumulative Total: 485k Ws

Step 9: Discharge and Rapid Cooling

Discharged immediately onto the cooling tray; recorded bean temperature and applied forced air cooling.

Discharge Bean Temperature: 226.9°C
Total Post-Roast Weight: 110.0g (Net yield after 0.8g defect culling: 109.2g)

Roasted Venezuelan coffee in the case study

Roast Summary

Evaluation Metric	Measured Value
Total Steps	26 steps
Net Microwave Exposure Time	15 min 30 sec
Total Elapsed Time (incl. agitation)	27 min 31 sec
Discharge Bean Temperature	226.9°C
Finished Bean Weight	110.0g (76.4% of dry green weight)
Total Cumulative Energy	485k Ws
Time-Normalized Equivalent Energy	1057.54 kW/h

Venezuela roast profile chart, 18 August 2026

Technical Analysis

Completing in 26 steps with 485k Ws cumulative energy and a final discharge temperature of 226.9°C successfully captured the entry into second crack, delivering the intended medium-dark City roast profile with clean body and rich caramelization.

Even with a washed lot requiring substantial latent heat of vaporization, the time-normalized energy metric was 1057.54 kW/h, remarkably close to the empirical standard baseline (approx. 1,060 kW/h). The high reproducibility of this index underscores the reliability of thermal mass management in microwave coffee roasting.