Ethiopian Struggle


Struggling to get a good profile for this Ethiopian bean. Very dense bean. Any suggestions for a different control strategy? What’s with the massive dip at 9 min, even at P6?

Maybe it’s because it’s roasting well? I wonder what the roasted coffee beans were like

The dip is to be expected just after/coincidental with 1Cs. You need to power up just ahead of that so that power is increasing as the beans give off more heat than the absorb (the Maillard process becomes exothermic at 1Cs). You’ll still get a bit of a dip (well, I still get a bit of a dip) but not as bad and I’m reluctant to hit it with P9 as it means getting rid of more heat faster as the exothermic stage passes unless the timing is perfect.


In this roast the Recipe anticipates 1Cs at 397°F and increases power from P6 to P8, then at (as I recall!) 407°F it reduces power to P7 then P4. The P8 change may be a little early but the timing isn’t bad. This is a much darker roast than you’re doing with the Ethiopian so just ignore all the stuff coming after.

Bruce

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I’m not a pro. I’m not going to pretend to be a pro. As a matter of fact, I’ve been roasting coffee for less than a year. I’m just going to spit out something I’ve heard and let you figure it out. The bean temp sensor/IBTS are not necessarily indicative of what’s occurring within the bean. We know that First Crack is pressure and moisture escaping the bean. The moisture release contributes to evaporative cooling on the surface of the bean and also inside the drum (water absorbs energy as it changes from liquid to gas). At the time of First Crack, our RoR is probably not accurately depicting what the interior of the bean is doing.

As I’m approaching FC, I leave the power setting alone and usually slightly increase the fan setting. Doing this seems to stretch FC for me, so that my beans gradually crack, and spread that evaporative cooling out a bit. I personally feel that it stabilizes my roasts a little bit. I tried turning the power up to sort of “punch through” first crack, but the effect of all the beans cracking in unison couldn’t be corrected in a way that worked for me.

But back to my point, a gradually sloping RoR is not a huge concern to me; because I think that the RoR around FC is typically unrepresentative of what’s really happening inside the bean, where it matters. Whats wrong with the taste? Whats right with the taste? What do you wish it had more of?

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A few observations:

The idea that the sharp dip inside 1C is not necessarily indicative of actual development inside the bean is a really interesting one.

I find that if I care to counter the dip to make the ROR chart pretty, I keep one eye on the instantaneous IBTS ROR reading at the top of the display. When I see that start to plummet about 30-45 sec after the 1C start I bump power up to P7-P8 and keep it there until the instantaneous reading starts to trend back upward toward 5C/min. Then I begin rolling the power back to prevent the flick.

Does this yield a better result in the cup? I’m not really sure. I get decent results with good repeatability if I use this approach, but I’ve never compared that profile side by side with one where I don’t nanny the power in that way.

Regarding the cracks happening all at once, I happen to be working my way through the Coffee Navigated podcast and in the Gesha episodes the talk about that variety, along with the dense high quality Ethiopians having the property of all going off in 1C at once, and this uniformity being a sign that the beans are well grown and processed. So in that light trying to “stretch out” the audible cracking might not be as useful as simply figuring out how long and how steep you want to roast past 1C start.

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Thanks for all the thoughts. Definitely worthwhile to hear all the different perspectives. I have listened to all the Coffee Navigate podcasts, they are excellent, I certainly learned a lot from them, so I know what is meant by the Gesha’s all cracking simultaneously.
The coffee tasted good as a pour-over, but not amazing. Just lacking clarity of flavours, but no obvious defects to my palate. Perhaps just bit over-roasted. I will take the learnings and suggestions for the next time I roast it and see if I can improve it. I have done lots of side by side tastings of different profiles, but not with this one. I think that will be necessary.
Thanks all!