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Underdevelopment vs. RDT

PostPosted: Tue Aug 09, 2011 3:41 am
by Ed Kaufmann
Howdy, I have been working at connecting specific flavors in roasted coffee to certain events in a roast cycle. I know that the rate of the second part of the roast is very important thus it is important to shoot for an acceptable Roast Development Time(RDT). When I taste what I perceive as underdevelopment in coffee, I connect that flavor more to the initial approach and break down of starches in to succrose and the completeness or incompleteness of that process. Heres the question (realizing that every reaction is relative to the one before it): Does underdevelopment and the flavors associated with it have anything to do with the length of the RDT or post-first-crack portion of the roast cycle? Thanks friends. Let's talk about it! Go!


Re: Underdevelopment vs. RDT

PostPosted: Tue Aug 09, 2011 5:01 pm
by Christopher Schooley
Hey Ed,
I asked some similar questions here:

Basically I would say that, yes, underdevelopment is has a lot to do with roast development time after the first crack and that improper development during the drying stage creates "baked" defect.

Re: Underdevelopment vs. RDT

PostPosted: Mon Oct 24, 2011 9:42 am
by Jon Brudvig
I often associate underdeveloped sweetness with a fast drying phase for the reason you mentioned. When a good coffee is leaning towards grainy flavors and just not showing the level of sweetness that I know it should, adding more time to the drying phase often helps. Post 1st-crack time also effects perceived sweetness, of course, but I think most of this is due to reductions in perceived acidity rather than creation of sweetness.

The causes behind underdeveloped aromas seem to be much more variable. For example, in my experience, a lot of powerful Kenyans, including the two I'm roasting right now, need relatively more time after first crack to fully develop the aromas I'm going for (currant, juniper, blackberry, vanilla, etc...), regardless of the overall time. The fruit notes in many dry processed Ethiopians, on the other hand, don't seem to benefit from increased time after first crack. With these coffees, I'm usually more concerned with losing fruity/floral aromatics after 1st.

The portion of the roast that I'm most curious about right now is the time between the yellow stage and first crack. I usually focus my attention on the drying phase and post-1st crack phase, and shape the middle stage so that it allows me to do what I want with the other two.

But, getting back to your question, I agree with Christopher. Underdevelopment can have a lot to do with what is happening after first crack. I think underdevelopment can mean a lot of different things in terms of sweetness, acidity, aroma, etc...

Re: Underdevelopment vs. RDT

PostPosted: Fri Mar 23, 2012 2:24 pm
by Jimmy Oneschuk
I've been thinking about this a lot lately - and also considering the impact of different heat sources during different phases of roasting. Following Jon's comments, the length of the drying phase and sweetness, are you using more conductive heat or convective heat? I've had some fantastic roasts with high intensity flame, high convection up to 300, and likewise with low intensity flame and less convection (more conduction). I roast on an ambex with a perforated drum, though, so I think my results might not be the same as those on Probats.

Re: Underdevelopment vs. RDT

PostPosted: Mon Mar 26, 2012 7:49 am
by MeanJoeBean
First off there is very little conductive heat in today's roasting equipment, keep in mind that airflow is a huge piece of the puzzle in the roasting process. I'm not saying that there is no conductive heat transfer happening, but that convective heat is much more important (especially in the first phase and post first crack).

In my experience, before profile roasting became what we all know it as today, the rule of thumb was fast roast time equaled light roast/high acidity and slow roast time equaled dark roast/low acidity/more body. A couple reasons for this, the most obvious being dark roasts take longer and roasting too dark too fast often resulted in a burnt flavor profile. However, as we have learned more and more about heat application during different stages of the roast process, this school of thought has begun to show some cracks in the foundation and thus we (as roasters) have been able to pull some acidity/sweetness out of darker roasts/faster roast times.

To me the length of first crack plays just as big a role as the time between first crack and drop temp. Too fast and you burn, too slow and you bake. Sometimes it helps to go back to basics in order to move forward.

-Joe Davis

Re: Underdevelopment vs. RDT

PostPosted: Fri Apr 06, 2012 7:54 am
by MeanJoeBean
Damn, didn't know I was such a thread ender.