Struggling with roast development on Probat P12/2

Discuss roast levels and profiles for espresso, equipment for roasting coffee.

#1: Post by brown_waterboy »

Hey all. Looking for some advice as I am becoming very frustrated since upgrading my roaster to the Probat.

When I first started commercial roasting I was working on a machine that struggled immensely with airflow. The airflow was insufficient so I learned to roast using very high conductive energy. With the Probat it is entirely the opposite. The airflow in this machine is incredibly high and I am having trouble achieving good development on any coffees I throw through it. Rather than lose lots of time and money on trial & error I was hoping to get some pointers.

My average roast on the Probat uses a 400F charge with 80%gas at the start, 7KG batches
Dry around 4:30 - 5:00
"First crack" typically starts around 8:30 @ ~385F by this point I am typically using 30% gas
Drop anywhere in the ballpark of 395-405. Anything over 405F is darker than I would prefer to roast.

I have yet to achieve a very strong, or rolling first crack & I think this is what is causing my underdevelopment (even with darker roasts). The only option I can think of would be to go into FC with a much higher gas setting, but then I would blow past my end temps in 30sec-1min.


#2: Post by Milligan »

Do you have graphs? Weak first crack can certainly be a momentum issue.


#3: Post by archipelago »

1- Do you have airflow set to minimum? I would
2- Have you tried a 0:45-1:00 soak at the start? Often helps with development
3- how are you marking dry?
4- 30% is pretty low to be coming into crack particularly with high airflow
5- how much development time? nb: what's your roast velocity between start of crack and end of roast?

Higher airflow = requires higher gas to maintain roast environment temps sufficient to support crack. This also means a hotter drum which risks tipping ¯\_(ツ)_/¯

brown_waterboy (original poster)

#4: Post by brown_waterboy (original poster) »

Thanks for the suggestions!

I opted for the roaster without the VFD fan thinking I would not be manipulating airflow throughout the roast so I have only played with opening & closing the damper. I do run it with the damper fairly shut.

I have tried soaks, they do seem somewhat helpful but I am still having issue at the tail end of the roast

I mark dry when I don't spot any green hue in the trier

I have been wanting to try other strategies to go into crack with higher gas without having the temperature completely run away.

A recent roast I had done had a development time of 1:55. Velocity... 10.4F/min? I went into crack with an ror of about 15F/min and ended near 3F/min (I am aware this is very low)

I'm willing to risk some coffee to tipping in an effort to solve my greater problem. That seems like an easier issue to solve.