Roasting Dry Processed Coffees
pan roasted DP coffee in Michiti Ethiopia
Dry processed coffees are becoming fruitier and fruitier. This is mostly because there is a lot more sorting of cherry going on these days in this processing method, both by hand and with equipment designed to wash and sort the cherry before drying on patios or raised beds. The traditionally more rustic and earthy flavors in dry processed coffees are giving way to cleaner and brighter fruits. Even in the "natural" processed coffees of Brazil, there is more and more sorting being done. Yes, many Fazendas still mechanically strip-pick the coffees, but there is intensive sorting going on there as well, and there are more producers working towards more selective picking.
The more earthy and rustic characteristics of the traditional dry processed (DP) coffees required roasting that helped to bring out the sweetness of those coffees, pushing the caramelization more into where there were more bittersweet cocoa notes. In lighter roasts these coffees were rough and gritty, with so much texture in them that you could chew them. These coffees needed roasting that took the edge off of the earthiness. Longer drying times and stretched 1st Cracks, and even some smoothing out post 1st Crack and roasting more into the Full City neighborhood in order to bring out the cocoa.
This approach to roasting had and has a lot to do with the mixed density of the beans. In the traditional dry processing method there is a layer of sorting and separation that is missing and which results in the green coffee having a wide variation in density and bean size. Sorting the green coffee could result in a cup with less "noise" in it, but you could also lose a great deal of the other characteristics of the coffee that you did enjoy in the coffee as well as just adding unnecessary labor. I say "has as lot to do with the mixed density" because even though there is better sorting for defects which add more of the unpleasant characteristics to the cup, the end result still is pretty mixy density wise. This is noticeable in the roast by the way that the coffee seems to drag it's way into the 1st Crack and then in how the 1st Crack doesn't seem to ever stop. Lighter density coffee start popping quietly a little early, and then the more dense beans don't start to pop until most of the rest of the charge has already finished popping. This itself also adds to a lack of clarity in the cup, particularly with the more fruited notes.
One fix to this issue is simply to push a little harder into the 1st Crack just before it starts. At around 365F degrees, depending on your roaster model, changing the air flow or energy input in a way to put more energy on the coffee in order to get more of the charge popping at the same time. If you were to look at an XY axis roast diagram, in most cases you'd see a slight decrease in the rate of rise right at this point as the beans absorb the energy and get ready to pop. In a coffee with a more even density, this wouldn't affect that way that the 1st Crack begins as dramatically as in a DP coffee. In DP brazils you do have to be careful however as the coffees can take off on you at this point if you don't pull back on the energy input soon enough once the 1st Crack is rolling.
You'd still want to pull back on the energy input with DP Ethiopias once the 1st Crack is rolling but it is vital that you don't pull back too early. One of the most common mistakes made with DP coffees is pulling back much too early once the 1st Crack is engaged. This tends to stall out the 1st Crack, or at least drag it out, so that it takes a lot of the vibrancy out of the fruitiness. If you're roasting to really get that fruit to pop, you want a condensed and boisterous 1st Crack. The pops themselves tend to be a little quieter in DP coffees because of density and moisture content issues, but you should still be able to get a boisterous 1st Crack if you're able to get the majority of the beans popping together. There may still be a few stragglers but not nearly as many if you weren't to push into 1st. Dropping the roast just 15 - 30 seconds after the end of the 1st will get you that really snappy tart fruit. The deeper you roast from this point you'll still get some of that fruit with some diminishing but also more roast bitterness as you get into 2nd Crack.
Another approach to roasting DP coffees in a way where the fruited notes will still be clearly stated but where you can also get a sweeter more cocoa focused finish (rather than just the snappy tartness of the fruit turning more towards sharp bitterness) is to stretch out the drying stage. This is a pretty great approach in general when working with earthier coffees, but even in cleaner DP coffees this approach is really helpful in being able to work towards a sweeter finish. A longer drying phase allows more of the mixed density beans to normalize before any browning occurs, which makes building to a more unison 1st Crack a lot easier. You can still push into 1st Crack at this point, but you shouldn't need to push as hard. Just make sure it's a solid boisterous 1st Crack.
I never like to extend the 1st Crack itself because I feel like it just tends to flatten the cup and you really are flirting with baking and stalling caramelization doing this, which in a DP coffee is really extra gross. You can add maybe 15-30 seconds to the 1st at this point to try to add a little more texture to the mouthfeel, but extending it towards a full minute or more is definitely not recommended. You're looking for more of a 1:30 but under 2:00 minute 1st Crack time. With an extended drying phase, it may take some of the punch out of the fruit, but the finishes tend to longer and sweeter. The finish can be more and more syrupy when dropped at the right point after the end of 1st, 30 to even 45 seconds after the end moving closer to the start of 2nd which you can do with this roast without it being too bitter.