Roasting Ethiopia, Oromia, Nefas Farm
|The FZ-94 ready to get roasting|
I picked up 22.5kg's of Ethiopian Yirgacheffe beans harvested 2015/2016 at 1600m above sea level on Nefas Farm in the Oromia region, 500km from Addis Ababa. The berries were hand picked, washed at a local station, fermented up to 48 hours and dried for 9 to 15 days on elevated drying beds.
On arrival from Giraffe I measured a moisture value of 9.5%, using the Wile Coffee an Cocoa moisture meter.
Taste over time
Since I do not do any cupping, my roast evaluation method takes more time. I let the beans rest for about a week, preferably longer and then taste the espresso over a few days time. At home I use a Compak E8 grinder with the redspeed burrs, and also a Compak R120.
If I use the latter grinder I am single dosing, make sure to first throw a handful of beans through the grinder that I won't use, followed by a single dose, trying the extraction, changing the grind, again first flushing a handful et cetera until I get the best shot I can make. The R120 gives an excellently truthful result, revealing precisely the horrid or the beautiful, whatever was in the bean to extract.
Mostly I use the E8 though, with a well filled hopper to have a consistent downward pressure on the beans towards the burrs.
I also send out batches of beans to fellow home baristas, guys who are each very dedicated to their coffee making. One, Bob, uses a Tidaka grinder and a Bezzera Strega machine, the other, Erik, extracts on a Strietman CT-1 matched with a Eureka Olympus grinder fitted with TiN Mythos burrs. I also took batches to Erik and Edward from Trakteren Cafe here in Amsterdam (Edward won the silver award at the recent Dublin world championship for Aeropress) and one batch went to Bert van Wassenhove and his colleague at Caffenation, also in Amsterdam. All their feedback helps enormously to find out how the beans perform on a spectrum of different machines than my own Londinium L1-P lever machine.
First I will show you the best looking roast profile, roasted today but modelled after the profiles that so far scored best:
|Roast profile for Batch 17|
I warmed up the machine until Drum Temp hit 150ºC, then started the roast. In Artisan, the preprogrammed alarms ensured the correct drum speed, airflow and max DT was set and along the roast, voice alerts prompted for events like checking bean color around 120ºC, and the optional hints for switching off the heating elements. At minute 6, as the actual Bean Temp (BT) closely approached the designed background profile, I switched on the internal software PID of Artisan which then took over control of the airspeed to force the BT to coast exactly along the designed curve.
The Rate of Rise (blue line) gradually declined, with a brief tendency to move up near the onset of FC, then sloping gently down until the End of Roast.
I switched off (grey dots) the first of three elements around 11:15, the second around 12:20, briefly switching it back on around 12:50 and then switched off the last element around 14:30. The airflow, managed by the Artisan software PID, made sure that BT did not overshoot nor lag behind.
Average Rate of Rise for the three stages was 8.1ºC/min, 7.8ºC/min and finally 3.6ºC/minute. Development time was 25% of the total roast at nearly 4 minutes and beans were cooled down in just over a minute.
How did I arrive at this profile design?
Below I share 8 profiles of the previous 16 roasts. I printed the profiles, adding handwritten notes to these when I (or others) tasted the results.
PS on August 21, 4 weeks after roast, Erik writes me "Vandaag weer de B7 in de maler. Crema was wat minder vol maar de smaak was goed. Heerlijk romig, wat pittig maar goed pittig, heel licht zuurtje en de lekkere smaak van een Ethiopië. Zo 2 weken verder een compleet andere smaak en nog steeds erg goed." (Translated: "Today B7 in the grinder again. Crema a little less thick but taste was good. Deliciously creamy, a bit spicy but pleasant, light acidity and the good taste of Ethiopia. Two weeks after the previous tasting, completely different taste and still very good.")
PS on 2 September Erik writes me that B8, after 5 weeks, is pungent, unpleasant. So the lower end temp makes this a very bad bean.
PS on 28 August, almost 4 weeks after roast, Erik (Strietman machine) writes me that he "finally came around to tasting this one. Very good for a slightly darker roast, full bodied and creamy with the typical Ethiopian taste, albeit a little dry in aftertaste."
Then (skipping a few batches) I did the roast that's at the top of this page. A copy / combi of the best profiles so far which also happened to work very well with the Artisan setup and PID driving the roaster.
I will add my findings in a week or so!
PS 27 august 2016
Batch 17 does very well here. I first tried it on the set that I brought along for a short vacation near Rockanje in Zuid-Holland and after my return home last night I could hardly wait to try it on the Londinium. 18.6g in the basket, 33g out in 41s after a 10s pre-infusion (5s of 2 bar, 5s of 3 bar). The espresso is bright, very Ethiopian and sweet, without leaning towards a dry after-taste and also not tasting too dark while still having a creamy mouthfeel and, when swirling the coffee in the wide cup, the syrupy coffee fluid momentarily hangs on to the side of the cupping bowl before slowly flowing back into the rest of the espresso.
So I'll stick to this profile for the remaining few batches and start with that when I go searching for the best roast of the next bean ahead, from Guatemala!