I noticed that there a few roasts of this coffee from SM/CoffeeShrub. I am having nothing but trouble with this bean and am looking for advice on roasting it on the Bullet. This is the first natural I’ve tried to roast on the Bullet. My first attempt was using my Nordic roast profile for 600g. For a washed coffee this comes out to around Agtron whole/ground of 70/110 or at least in that ballpark. This first attempt went super fast, much faster than the washed coffee I use this profile for:
Note that I dropped this at 211C IBTS, which is far past my target drop temp of 206C to meet my end color target. However, I did not detect first crack until 206C. This roast developed nice fruity and floral notes, but the roastiness detracted from those notes, and acidity and sweetness were very low. Overall, not a well-balanced cup. The beans were also unevenly roasted. Agtron scores were too dark: 65/94.
I tried to slow the roast down, but this next roast cupped even worse and still had an agtron score that was too dark: 64/97
To limit waste, I switched to using the Roest sample roaster. I just received this, so I’m still working on profiles, but this 150g inlet temp profile seemed to work well. Beans were more evenly roasted, acidity and sweetness were better and the cup was more balanced, but overall the cup was no where near the stated 91+ score. Nothing offensive and a very clean cup, but nothing that would wow anyone. Agtron on this roast was near my target: 71/111. I could probably go 5 seconds more of development to push the color just a tad darker. This was a 30 second dev time. I did another at 50 seconds and it was way too dark.
This is probably not a direct answer to your question but for some reason I have found that my roasts on the bullet require longer rest times before the coffee tastes its best.
I was roasting Ethiopian Sidamo natural coffee that used to taste very nice after two weeks on my old Hottop. When I started roasting the same beans on the Aillio, it was tasting very average after 2~3 weeks.
However, after 6 weeks the same coffee is now tasting absolutely divine.
I can’t explain it but I have learned not to judge my roasts on the Aillio too early.
FWIW… my experience with Ethiopian beans (in general) is they do roast faster than other even using same “recipe” and also difficult to hear FC. For 600g IMHO your PH is hot and that might be the reason for the “roastiness”. The last time I roasted a natural is back in Feb with a Yrig Natural Grade 1 Koke Coop I got from Burman. I did a 1lb batch with a PH of 410F Roast World - Cup, grade, and analyze your coffee roasts in depth
Personally I liked it. And you got to let it rest at least a week.
If you want to keep the higher PH temp try adjusting the D to a 7 when you first charge the beans and then change it to your D9 after about 1 min. Rational here (my personal take) is the D9 maybe creating a higher centrifugal force on the beans therefore they “stick” to the hot drum wall more while a D7 won’t as much when the drum rotates and beans is more likely to drop back in as it gets “pushed” up (think of why all the salad leaves is against the bowl in a salad spinner). That’s my two cents…
Ethiopian beans are tricky and due to bean size variation roasts are often uneven, it seems like you possibly missed the real first crack which my have happened earlier than you assumed. I roasted Guji, Sidamo, Yirgachefe and Kiffa …and soon Geicha…i cannot afford to ruin the Geicha will post you on that.
I seem to recall reading an analysis that claimed that even D9 did not have the force to make beans stick to the drum. I’ll have to look that up and see if I can find it again. I typically just do D9, though I wonder how varying drum speed might affect convective vs conductive heating.
I already wrote down that post before coming here. I do have very good results with my naturals. They always turn out the way I want them to. I don’t think it will help you because there are too many outside factors to consider other than the profile, but you can take a peek at my 500g and 1kg profiles. It’s not Guji, but it is an Ethiopian natural.