We spent most of Friday playing with Airflow. The Diedrich roaster has the ability:
- CB: to pull air from the cooling bin (i.e. no air into the roasting barrel),
- 50-50: 50/50 (i.e. half setting to pull some air into the roasting barrel / bin)
- RB: all the air is pulled through the roaster, good for removing chaff
Airflow set to CB
So first we tried a roast only on with air of CB:
With this setting the coffee chaff did not clear, and the coffee did not have a complete taste profile, it was missing something. We were roasting the Sumatran Java and it was not a bright and the roast on full profile.
Airflow set to 50/50
We then roasted with the setting on 50/50:
When checking the roast, the beans appeared a little shrivelled, but once they got past the first crack they seemed to recover. The coffee seemed a little green, almost like the roast had stalled.
Airflow set to RB
We then roasted with airflow setting at Roasting Bin for the full roast.
This tended to result in a baked and dry taste on the coffee.
When then looked at when the Java Sumatra coffee had the best roast, and found that CB until 280F when we moved it to 50%, then at around 340F we moved it to 100%.
This seemed to create a great tasting profile.
Afterwards we played with the 12 kg running automated profiles, and found that charge temperature has to be very stable for the automation to be deadly accurate.
We then said goodbye to Steve and Becky since we were on our way.