The effect of total roast time on result?

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

Postby maccompatible » Jun 14, 2019, 10:47 am

I've been roasting a lot of coffee over the last few weeks trying to understand the process and what I can improve as much as my Behmor lets me. I understand I'm quite limited on it right now, but I think my question would apply to all types of roasters.
At first, I was using stock profiles on the 1600+ just to get used to it, and then began to manually "profile." Using 200g batches, I was able to get to first crack in 8 minutes, and was cutting the heat to allow it to develop on it's own through the exothermic reaction, and cutting just after 9 minutes. Come to find out later, I was cutting too much heat, first crack was falling off too soon (probably not finishing), and my roasts were all WAY too bright, as well as grassy. Finally I read about Scott Rao's DTR, and how long others said first crack should last (60-90 seconds). After lots of tweaking, I found a way to achieve this ( and was getting WONDERFUL fully developed roasts, but not a single one of them was under a medium roast. I usually prefer lighter roasts.
Today I just tried a smaller batch size to get to 1C sooner with the limited energy output of the behmor, and had success! It got to first crack in 7 minutes 10 seconds, and I cut at 8 minutes 45 seconds, handling the heat the same way as before (cutting drastically to P2 when first crack picks up, then going back up to P3 for the remainder of the 20% DRT for good development). When I got the beans out of the roaster, they looked almost identical to the roast that took over a minute longer, and had lost the same percent of weight. I haven't tasted them side-by-side yet, and I'll update this thread when I do.

So (finally) here's my question. What I WANT is a light coffee without sacrificing development. I thought that by making the roast shorter and thereby giving it less time after first crack the end result would be lighter, but that doesn't seem to be the case. Am I missing something, or do I need to abandon the notion that a well-developed coffee NEEDS 20% of its time after first crack begins? Was I right in theory to get to first crack sooner, but I messed up my smaller batch and just applied too much heat and ended up at the same roast level? Am I just understanding the process wrong and lighter roasts have inherently less development? Or am I simply limited by the Behmor? Should I expect a roast that hit 1C sooner but finished at the same temp and DTR to be different from the one that took longer?

I should add that I read the entirety of the recent thread "what's a light roast?" and perhaps it's as simple as my senses and the agtron definition of "light" disagreeing.
Thanks in advance for helping clear this up for me. :)
"Wait. People drink coffee just for the caffeine??"
LMWDP #628

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Almico

Postby Almico » Jun 14, 2019, 11:14 am

A pretty good rule of thumb for a light roast is 4/3/2. 4:00 to DE, 3 more to 1C and finish in 9 total. Of coarse the coffee needs to be of high enough quality to support such a roast. You can drop at 1:30 post 1C, but from my experience, you need to get a lot of heat in the bean pre-dry to force faster development.

You also don't want to tank the heat suddenly after 1C. Better to reduce the heat slowing after DE and while approaching 1C, don't touch it for the 90s around 1C and then reduce again to finish the roast.

maccompatible

Postby maccompatible » Jun 14, 2019, 11:20 am

If those are the time frames you generally follow/recommend, then I feel like I can achieve that with my 155g charges on the Behmor. In the few months I've had it, every few months I've increased my pre-heat, to the point that I'm now pre-heating to 325. Compared to no pre-heat (which is bafflingly recommended), that almost cuts the roast time in half.
So is that how it's done? I know the coffee doesn't JUST develop during and after first crack, so good light roasts are achieved by just giving it more heat prior to first crack, and if done properly, you can get good developed roasts under 20% DTR? If that's true, I think I'm on my way there. I'll try my 155g charge, aggressive push through drying and yellowing, and cut maybe 15 or 17% instead of 20%?
"Wait. People drink coffee just for the caffeine??"
LMWDP #628

maccompatible

Postby maccompatible » Jun 14, 2019, 12:56 pm

Almico wrote:A pretty good rule of thumb for a light roast is 4/3/2. 4:00 to DE, 3 more to 1C and finish in 9 total. Of coarse the coffee needs to be of high enough quality to support such a roast. You can drop at 1:30 post 1C, but from my experience, you need to get a lot of heat in the bean pre-dry to force faster development.

I just tried this. Yellowing at 4:15, cracking at 7, picking up at 7:25, and completing at 9. The Behmor is weird about its heat, but I believe I kept the RoR trending down (hard to tell without thermometers...)
I had the heat on 100% until it got to the max temp the Behmor allows, then 75% to hold it there. Then I cut it back to 100% when the fans/afterburner kicked on (right after yellowing began), but I think the fans dumping heat keeps the net power at or even below 75%. I cut to 75% again at the 6.5 minute mark, and left it there until 8 minutes, where I decreased to 50% power for the last minute. Keep in mind, once the fans are on, the roaster is losing a lot of heat, so I think this has the effect of reducing RoR at the same time as slightly increasing airflow.
Anyway, this batch is just over 17% DTR, so we'll see how it ends up tasting.

Almico wrote:You also don't want to tank the heat suddenly after 1C. Better to reduce the heat slowing after DE and while approaching 1C, don't touch it for the 90s around 1C and then reduce again to finish the roast.

But now I have another question. If I want a darker roast (and not one that's crashed and flicked like I've probably been doing..), how do I achieve that while still maintaining a good RoR curve? Give longer between heat reductions and longer time overall? Keep the heat reduction the same and just draw out the time with 50% power at the end?
"Wait. People drink coffee just for the caffeine??"
LMWDP #628

crunchybean

Postby crunchybean » Jun 14, 2019, 1:20 pm

It would be easier if you know what flavors you are going for and what bean you are using. So even if I land in the realm of "light" it will still take much different heat applications at different times to get there. There isn't a pants size that fits all.

It mostly revolves around moisture loss. Did you loose enough or keep enough in previous segment to carry through the next.

It's also important to note that the machine your using: it's heat source and the boundaries of the fan.

Generally by region guats need the quickest peak ET in the beginning. And inversely the lowest charge temp. As you move further south towards Brazil the time extends as you max ET. On my setup I have seen as time extends so does the temp needed to get to crack and also increases the risk of burning. So as the 1C temp increases the slower the ROR should be working within a tighter temp range limit. This is based on moisture management: I do not have enough water in the bean left to prevent burning. Conversly if I move super fast I can reach temps well into the burning zone but since I have enough water in the bean, I can get by and the rate of flavor development is increased, so it is also easy to overshoot.

maccompatible

Postby maccompatible » Jun 14, 2019, 2:12 pm

crunchybean wrote:It would be easier if you know what flavors you are going for and what bean you are using. So even if I land in the realm of "light" it will still take much different heat applications at different times to get there. There isn't a pants size that fits all.


I really didn't expect there to be. My attempts to over-simplify it are mostly to keep myself sane through the limits of the Behmor. Basically, I'm going for sweetness and clarity, so I've been gravitating towards wet processed central and south americans, especially Honduras and Peru. They've been consistently my favorites.
Did you discover the differences in profiling each of these regions on your own, or is there a source where I could read about this?
My biggest issue with my current setup is that there's only so much heat I can throw on my beans. If I want to start low and quickly go high, I probably simply can't. I've had to pre-heat the roaster nearly to the point of it's safety shut-off to get anywhere near the time frames I'm looking for.

crunchybean wrote:It mostly revolves around moisture loss. Did you loose enough or keep enough in previous segment to carry through the next.

This is fascinating and explains a lot of why my failed roasts just didn't work. When I first got the Behmor I tried a pound like it advertised it could do. It was a DP yemen, and I started it with a cold roaster. I didn't even get a crack and the whole thing tasted like ash. So it must have lost too much moisture before making it to the crack segment. Very interesting.
"Wait. People drink coffee just for the caffeine??"
LMWDP #628

crunchybean

Postby crunchybean » Jun 14, 2019, 3:07 pm

If you want to keep sweetness and clarity than you should really try and follow perfect numbers and ratios. If flavors are just catalyzed reactions and the bean is the reactor, moving in a harmonious/soft/gradual way is my best advice. I have found interesting results by doing physical math and then trying to map it out in a profile. For instance I wanted to start with a ROR of 50*F/min and I wondered what should be the next ROR segment. I divided 50/1.618 and got 30 and again divided 30/1.618 to finish at 18*F/min. It was a shot in the dark but proved interesting. Unfortunately you will have to map out/profile on your own roaster where the trends are for the style of roasting you want to achieve. Trial and error. Searching HB for other users of the Behmor or reading reviews on Royal Crown's "crown jewel" selection, they do a lot sample roasting with an Ikawa, Behmor and Probatino and I have found it helpful. I have little experience, actually I have no experience when it comes to Honduran and Peruvian coffee's. I'll also suggest to not be bound by a particular philosophy or time limit. Lastly, you can look here for a collage of resources: http://community.ikawacoffee.com/t/frui ... ources/167

Hope that helps.

crunchybean

Postby crunchybean » Jun 16, 2019, 6:47 am

Mill City videos are an excellent resource that I feel needs to be singled out. This video is for an Ethiopian but (like all their vids) are jammed with info that take multiple times to understand and absorb everything. At least I need to rewatch them multiple times.