Roast and Learn Together - March/April 2015 - Page 9

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

#81: Post by robmatic »

endlesscycles wrote: ... You can not scorch the coffee as long as there is agitation and the heat is backed off before the ROR stops descending on it's own.
Wait, when you say "ROR stops descending", is that just a complicated way of saying turning point? Or did you mean "ROR stops ascending"? I'm having trouble picturing exactly what point in the roast you're actually referring to.

jellybones

#82: Post by jellybones »

descending ROR means that the bt on a graph has a convex curve. ascending would be a concave curve. either way, the temp is still rising, ROR just shows how quickly it is doing so.

robmatic

#83: Post by robmatic » replying to jellybones »

The question was not "what does RoR mean?". It was "when does RoR stop descending?" Talking about a change of rate of RoR is the second derivative of BT, and looking at any number of typical roast curves, RoR never stops descending:
  • Between charge and TP, BT falls rapidly at first, then more slowly. So RoR is negative and approaching zero, and hence RoR is ascending
  • After TP, BT rises rapidly, and so RoR is still ascending
  • At some point RoR stops ascending and starts descending
  • RoR continues to descend until the roast ends
Hence my question: what point on the curve is endlesscycles referring to when he says "RoR stops descending"? Which led me to wonder if maybe he instead meant "BT stops descending" or maybe "RoR stops ascending".

User avatar
endlesscycles

#84: Post by endlesscycles »

robmatic wrote:Hence my question: what point on the curve is endlesscycles referring to when he says "RoR stops descending"? Which led me to wonder if maybe he instead meant "BT stops descending" or maybe "RoR stops ascending".

..."stops descending on it's own", which is midway through 1C.
robmatic wrote:...
Between charge and TP, BT falls rapidly at first, then more slowly. So RoR is negative and approaching zero, and hence RoR is ascending
After TP, BT rises rapidly, and so RoR is still ascending
At some point RoR stops ascending and starts descending
RoR continues to descend until the roast ends.
Until 2x TP time, or when ROR hits max, the thermometer is not telling you anything.
-Marshall Hance
Asheville, NC

robmatic

#85: Post by robmatic »

endlesscycles wrote:..."stops descending on its own", which is midway through 1C.
Ah, so you're talking about right after "endothermic flash" where the RoR can sometimes increase? So you're saying that scorching effectively won't happen until at least this point? I have a feeling I'm reading too much into your statement, since obviously (I think) excessive heat before this time can cause all sorts of damage.
endlesscycles wrote:Until 2x TP time, or when ROR hits max, the thermometer is not telling you anything.
On the surface, that is a nonsensical statement, since we only know RoR by watching the thermometer, so obviously we are getting some useful information from it. Do you mean that until max RoR, the thermometer is not a good indicator of bean temp? Or what?

User avatar
endlesscycles

#86: Post by endlesscycles »

I'm reading that you got what I was saying, but I will say it again to confirm.

As long as moisture is coming out of the coffee and agitation is sufficient, it's not possible to scorch. It's best to get heat down in advance of 1C due to variations in the greens. Caveat: Poorly dried (at origin) coffee may be set up for scorching post 1C by overly fast profiles.

The thermometer is catching up to the coffee mass until ROR is seen as a max. Until then, the two are not much correlated. The sooner the ROR maxes out on screen, the better the thermometer and it's placement. Ideally, it's maxed out within a few seconds. I'm happy with 90sec.
-Marshall Hance
Asheville, NC

User avatar
[creative nickname]

#87: Post by [creative nickname] »

I continued to experiment with different profiles over the course of this month, and here is the one I ended up liking the most. It is a bit more gentle than that lightning fast roast I posted up thread, but still faster than what I was used to doing in the past.

--

Roasting Info:

Bean: Gedeo Kochore
Roaster: USRC Sample Roaster
Charge Mass: 400g
Charge Temp: 405F
Dry/Ramp/Development: 2:50/2:50/1:50
FC-start temp: 378F
Finish Temp: 400F
Overall Roast Time: 7:30
Moisture Loss: 13%

Profile Plot:



[BT=Red, Exhaust=Green, Gas=Blue, Fan=Yellow]

Cupping Notes:

Rest: 4 days
Brewer: v60
Grinder: Mini-Bunnzilla
Water: 206F, 300mL
Coffee: 20g, med-fine grind

LMWDP #435