does any one have a suggestion for roasting this coffee beans ?
i am new to the raoasting world and idid try one batch but the taste was sour
the green coffee beans color is brown and it is difficult to even till when it is reaching dry face (yellow phase)
this coffee is natural fermented >thanks

I went to your roasts (I think I see 3 since the seasoning roasts- sound right?) and, based upon IBTS readings only, from what I see I believe you may be early on calling 1Cs (1Cs is first crack start in my vernacular- FC is used by most folks here but it also denotes Full City, so I’m trying to avoid ambiguity). If that’s right, the roast didn’t go long enough to complete for even a light City roast. But…

When I look at the curves, especially the BT-RoR, it appears you were right on the call for 1Cs. Perhaps these Colombian beans you’re roasting just need to go a little longer after first crack to finish their roast… ??

That said I have a thought related to IBTS readings- my experience has been to expect 1Cs in the range of IBTS = 385°-400°F. You’re hearing 1Cs at a reading of about IBTS = 370°F- pretty early. I wonder if there might be some contamination on the lens (flat, clear glass of some sort) of the IR sensor… ?? Maybe something left from the mfg process? The problem with something like that is that whatever it is from roasting that degrades the IBTS reading isn’t readily visible. I’ve cleaned the IR sensor many times and have yet to see any sort of contamination on the swab. But I do consistently see a change in IBTS readings at 1Cs on the next roast even though nothing was visible on the cotton swab from cleaning.

So even though your Bullet is brand spanking new you may need to clean the IR sensor. Aillio recommends alcohol on a cotton swab. The roasting ‘stuff’ that gets on everything inside the roaster doesn’t dissolve with alcohol but apparently it does soften a little. So it takes a few passes with several alcohol-wetted swabs (I use Q-Tips) to get the invisible stuff off the sensor. And don’t use that ancient old bottle of isopropyl alcohol from the medicine cabinet- get a fresh bottle that hasn’t had all the alcohol evaporate!

An additional impact from a dirty IR sensor is that it affects Preheat. Contamination blocks some small fraction of the IR the sensor is trying to measure and that has the effect of producing a lower temperature reading from the IBTS than is correct. Since only the IR sensor is used to set drum temp during Preheat, a dirty sensor yields a lower-than-actual reading of temperature (an offset error), so that drum temp is higher than the IBTS thinks it is when it announces Charge. In most cases that isn’t going to be a huge error in temp setting but if my guess is right you have an error of about 15-20F° at 1Cs.

1Cs is hard to hear on the Bullet. Noise from the beans crashing around inside the drum interferes with hearing the crack from the outside. Two suggestions that might help…

  • It’s probably advantageous to not record 1Cs until you hear about the 3rd pop or later which guarantees you haven’t been fooled by an odd bean. (Be consistent in how you record this)
  • I have a problem hearing the sound distinctly from the front of the roaster. I get my ear close to the bean chute then tilt the cover about 45° to hear better. That affects air flow inside the roaster so I wait till it’s about time for 1C to begin and tilt the cover for a few seconds, close it again, then check again few seconds later. Not sure it’s absolutely necessary but it’s what I’ve been doing since the beginning. If you search here on R.W you’ll see that others have even modified stethoscopes as an aid.

Good luck with your new Bullet. In a few weeks you’ll be wondering "what was the big deal? " :slight_smile:


thanks bruce i will try to extend roasting time

idid try longer roasting but it still so sore :confounded: i think the problem in the beans it self this ferminted beans is difficult to roast .
i tried 170 c as Ph and 220 c but both given me almost the same result

It could just be that the coffee is defective, but assuming for now that it isn’t and you have more of it to play with:

  • What IBTS reading do you see for 1C start for other coffees that have come out well, and where the crack is really easy to hear and identify? If it’s also well below 195C, did you clean the IBTS sensor as suggested by @bab? Most folks tend to see FC happen at 198-202C for a wide variety of greens.
  • How much coffee did you use on your most recent 220C PH roast? That preheat may still be too low if you’re roasting a larger batch.
  • Regarding the power/fan profile, consider simplifying and shortening the roast - consider looking at the Aillio first roast guide for ideas. If you’re working with a larger roast, the power levels you’re using are probably also too low.
  • The other thing that could be simplified is your fan speed profile - try starting at F2, increase to F3 a bit into the Maillard phase (175-185C), and maybe once more to F4 as you approach FC. The ROR is going to want to flatten or even increase here, so I start reducing power and increasing fan starting around 180 to maintain a softly declining ROR while not stalling the roast.
  • If you do get a quicker roast with a higher FC start and drop temp, and the coffee still tastes sour, what happens if you grind the coffee finer and/or use a higher water temperature when brewing? Sour coffee could result from underextraction rather than a roast defect.

Have fun, and I hope you’re able to conquer that troublesome coffee!

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it was 500 gm batch
thanks for all that suggestions i will try to apply them next batch