Now that I've given in to the importance of steadily declining RoR, it's time to start playing with different RoR curve shapes and see what effect it has.
If I do a "set it and forget it" roast with my roaster I get a concave curve that looks more or less like this:
The RoR rises quickly in the beginning and then quickly drops off. The slope starts to level out before 1C and by the post 1C development segment it can almost flatten out.
I want to try and get a straighter RoR curve, and then maybe try a convex curve.
I went into Artisan Designer and created a dark roast curve. That's what you see in the background. When setting the Designer milestones I took into account my normal turn around time/temp, 300 dry and 390 1C. I get 2C around 430and 1Ce a bit before. I then moved the points horizontally until the RoR flattened out.
In order for this to happen on my roaster I need a lower charge temp and carefully controlled heat till "RoR turnaround", the upside down TP on the RoR curve. Then I have to continually add heat bit by bit to keep RoR from dropping below the line. It's a pain. But I did a roast of my house dark on Wednesday:
and the results were interesting. I'm brewing it in the bar today and while I thought it tasted a bit flat, every one of my dark roast customers likes it better...much better. I will say that it is totally roast defect free. No astringency or roastiness whatsoever. It's almost too smooth, which is why I thought it flat.
But the point for me is that this was very different from usual roast. Although milestones are basically the same, the path to them changed. I think what has to happen to flatten the RoR is the dry needs to be a bit later Maillard a bit shorter. Basically, the flatter the RoR curve, the flatter the BT curve. This might be a round about way of getting to a slow start, fast finish roast, but nowadays I'm think much more in terms ofRoR curve than BT curve.
In order to keep drop within Raos 25% dev time, and get a flat RoR, I redid the designer curves like this:
There is still much to be done, especially with lighter roasted coffees, but the results are promising.I was hoping that was not the case, because it really is much hard for me to roast like this.I need to be on the heat dial right from TP instead of 1C.
I'm not sure if my natural concave RoR curve is a trait of air roasters more than drum.