I’ve been roasting on the R1 (v1.5) for a few years now have consistent difficulty bringing out any prominent fruit notes/characteristics from light roasts - typically Ethiopian Naturals aiming for a City roast
Here’s a chart from one of my latest roasts:
The beans don’t have any apparent defects (no tipping, scorch marks, roasty notes, quakers, etc) but when brewed up via either manual (v60, chemex) or as an espresso shot (typically 2;5:1) the taste can be best described as “pretty good generic coffee flavor” with maybe “the slightest hint of a fruit accent hiding beneath the surface”
This is pretty consistent regardless of bean so I’m assuming there must be something I’m overlooking in the technique for City roasts that I’m hoping people with more experience with this style might be able to catch.
I roasted that bean a couple times and remember good Ethiopian juiciness but nothing more distinct. In general, I would try roasting a little lighter IIWY. I haven’t had an Ethiopian or Kenyan coffee from SM taste vegetal or too sour from going very light (other origins, yes). Still, maybe this is useful:
These are just my thoughts that I think could help. Costs nothing to try. Maybe one batch. Since it’s a natural, I’d go with a lower preheat. Maybe even 240 or 230. Second, I think you’re off on yellowing or, if you’re not, your browning stage goes by too quickly. In fact, the whole roast does. So, if you don’t lower the preheat, try going a little bit easier after yellowing. Being a natural, which means more chaff, you really should try going up with the fan during the roast. First signs of chaff, F3, yellowingF4, and then see what’s what and go from there. Last but not least, drop your beans during first crack, at 10-13% development. Dropping early really makes all the fruity notes pop up. It will land you between medium light or light. Also, here’s a link to my other post about Ethiopean naturals. Maybe you find something useful there. Roasting Ethiopian Guji Gerba (Natural) - #8 by braca19452f9m
Apart from the other feedback provided, I just noticed that you are roasting at relatively slow drum speeds. This is likely resulting in more heat transfer by conduction rather than by convection which is what you want to enhance fruity flavours in the roast.
I would definitely increase the drum speed to D9 if you are after fruity notes.
Just a thought but I am not the most experienced roster here
Great catch and great advice. I don’t even look at drum speeds because I assume people keep it at 9. There was this study that suggests we should decrease the speed near the end, but I’m not convinced.
Welcome!
I struggle with cup quality too. That 265C charge and 500g batch may be a solution as I think you’re super close. And I want to thank @braca19452f9m for the chaff removal strategy - this could be a solution to another one of my issues. Back to you @ahunt…
Personally, I would not change anything except to drop it after about 1 minute as was suggested earlier. You’re getting a substantial flick after 8 minutes that’s probably killing the cup. This is evident in blind cuppings. If its a little under-done cut your heat 1 mark at the start of 1C the next batch for a little less energy.
Yes, an 8 minute roast is on the “fast” side but most current crop high elevation Ethiopian naturals have enough moisture for that.
A question: what method do you mark yellow by? I know that if my Maillard is too long with a natural I’m going to get a lot more caramel/coffee flavoring and body than if its truly in the 35% range +/-. This could be another issue but I would tackle that one simple ending first, knowing that the end is setup by things before it.
Thanks so much for all of the feedback; it’s given me a lot to consider and has helped me make quite a few adjustments to my light roast profile.
I’ve lowered the preheat temperature from 509F/265C to 446F/230C. This has stretched out the drying phase by about 30 seconds, up to about 4:30 now
I’ve added a short period of soak time at the beginning at P6, before increasing to 8
I’ve adjusted the power profile to step down more evenly from 8 at the beginning, to 4, about 30 seconds before first crack, smoothing out the RoR a bit.
I’ve pulled the batch a few degrees earlier - 400F vs 403 before (204c/206c)
I’ve adjusted my lowest power setting from P5 to P4 to extend development time to compensate for the lower end temperature
I’ve increased the drum speed from 4 to 9 taking into consideration gabyritaseek.qiAO’s note about conduction vs convection
The resulting roast:
I had a chance to cup it this morning and it’s a marked improvement over previous results! There are definite notes of fruit trying to make an appearance, although still somewhat muted, so I think there’s still plenty of room for improvement.
Some thoughts for the next iteration:
Fan speed. I forgot to add the increased fan speed changes to the recipe so it remained at 2 throughout the roast. Based on braca19452f9m’s advice I’ll increase to F3 early in the roast, and F4 at yellowing, then assess from there.
Drop Temperature: Want to pull this in another few degrees which would be more closely aligned with the note about 10-13% DT
A couple of other notes
Looking at brian.mchenry.bmrul1’s comments, I’m going to try a test batch using my original profile, but just end it after about 1 min DT (which puts it right at my updated target drop temp anyway - about 397F (~202.6c). It’ll let me do a side-by-side comparison to see whether the improvement is coming from fixing DT, or by all of the finessing of the roast along the way
How I measure Yellow: honestly, it’s partially vibes. When I took my roasting foundation courses years ago there was a point in the drying when we were comfortable eyeballing it and saying “nobody could say this is still showing traces of green”, and that’s stuck with me. For me this typically lines up somewhere near 345F/173C
Since it’s a natural, I’d go with a lower preheat. Maybe even 240 or 230. Second, I think you’re off on yellowing or, if you’re not, your browning stage goes by too quickly. In fact, the whole roast does. So, if you don’t lower the preheat, try going a little bit easier after yellowing. Being a natural, which means more chaff, you really should try going up with the fan during the roast. First signs of chaff, F3, yellowingF4, and then see what’s what and go from there. Last but not least, drop your beans during first crack, at 10-13% development. Dropping early really makes all the fruity notes pop up. It will land you between medium light or light. Also, here’s a link to my other post about Ethiopean naturals. Maybe you find something useful there. 
