Tips on how to eliminate the roasty, bitter smell/flavour from these roasts?

I just don’t understand roasting enough to solve this one on my own, if anyone has any tips that’d be great.




What’s the “problem” you’re trying to solve?

If you’re getting bitter flavors, that can be a brewing issue. Grinding too fine for a filter brew will take brew time past 3.5-4 minutes. That longer brew time will pick up bitter flavors by over-extracting. Just one notch on my grinder can make a 1 minute difference for my brewing method.


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I’m trying to figure out what is causing the burnt, roasty smell and taste.

I cracked open a few beans and noticed some charring that ends up as an unpleasant taste in my pour overs.

I can’t for the love of me figure out if it’s the charge temp or wrongful heat application that’s causing it so I’m hoping someone might see something “obvious” in the curves :rofl:

I was thinking that too first but I’ve tried different grinder settings and along with water temperature fiddling with no success.

I was hoping someone could see my wrongdoing from a mile away and solve my problem in an instant :rofl:

I’ve tried raising fan speeds and dropping earlier but no luck eliminating the charry taste :frowning:

I went to RW to take a closer look at your two profiles above, but I wanted to ask your #81 that also tasted burnt? It didn’t look like it should.

I typically start with a slightly higher PH than you for my 350 or 500g batches but with a lower P at charge, usually a P6 and let it “heat soak” for about a minute before bumping up the P, and then a gradual decrease before FC. Seems to work for me getting to almost end of FC.

I would also suggest taking a look at bradm’s 350g profiles. He was my reference point when I started my journey and he was also very helpful in telling me what worked for him.

Those don’t look too bad. You follow pretty closely to the 45%, 35%, 20% ideal (for some) for each phase of the profile. Nothing stands out as being off but perhaps a crash at the end of your first roast. I don’t believe that would lead to your cupping defects.

So, with all respect, are these fresh new crop beans with adequate moisture levels? If the beans aren’t great to begin with you can’t get good coffee. I have little else to add in addition to the above comments.

Good luck

I’m with @blacklabs - I don’t see temps here that should produce charring/burning. If you were ending the roast over 230°C or if you were preheating to over 275°C for a small batch maybe. But this is a pretty tame roast profile in terms of temps. You even have higher fan speeds than I would use so I can’t point at an issue of not clearing smokey out-gassing.

A couple things-

  • Does the supplier have anything to say about what flavors to expect?
  • Any roasting recommendations?
  • Also: have you roasted these beans to your taste preference in the past? I wonder if this is an issue with a different lot.
  • Or possibly the beans have dried during storage with no vapor barrier, maybe at the supplier storage facility.

And I 2nd the notion to ask @bradm for an opinion. He’s usually got helpful insight. How 'bout it Brad?


ps- Just an aside: I invested in a moisture-content meter and have been disappointed with the results. I went for cheap (at that time- 2 yrs ago; now there are several cheaper offerings). Apparently that isn’t always an appropriate criteria (!). My issue is calibration- I have no idea where to find a standard for meter calibration. The only adjustment is to offset the reading by measuring something of known moisture content and finding the difference. But how does the operator know the moisture content of anything they have access to? It’s a circular issue without a separate calibration standard.

Comparing #79 with one of my natural Guatemala roasts one thing that stands out is the initial BT of 130C at time=0. I preheated exactly 15 minutes at 210C, and my initial BT was closer to 110C. So for some reason you’re starting with more heat than the 190C preheat setting would suggest. That, combined with a long initial interval at P9, makes for a pretty hot start to the roast. Could be some early scorching? Try using the tryer to check the beans at 2;00 or 3:00 and see if the surface looks OK. Rob Hoos mentioned early scorching as a tough problem to identify because it is concealed by browning later in the roast. If that is indeed the problem then try a slower start to the roast - lower preheat and less initial power. Sure do hope this helps…


Yeah #81 had a brunt/char/smoky aftertaste too :frowning: Thanks for the tip about checking out bradm’s profiles, I’ll take a peek.

thanks for taking a look! I have used this vendor for a while and I’ve been buying same beans from them since day1.

But as I have not inspected the beans thoroughly I shall take a look and see if anything there is amiss.

I haven’t talked much with the supplier and I have roasted these somewhat successfully in the past. You and @geoffreych might be on to something with the beans/storage so I’ll take a look

Moisture meter is on my item packed “to buy”-list :sweat_smile:

Thank you for your insight on early scorching! I didn’t know that it was a thing and shall keep an eye out. I will also drop the initial heat setting and in future attempts.

I usually always preheat for 25m before I charge but might revise my strategy as I’m starting to think it’s a bit overkill.

Thank you all for your help! Amazing community!

I’ll try your tips in addition to a good roaster clean! Cheers!

I forgot to add that post-roast storage is important too. The Chiapas I’m roasting does better with about a week rest in the fridge, but I also need to get it out of the fridge a week before I want to use it. Some of that (8 hrs?) is to get the roasted beans to room temp to avoid condensation when opening the bag, but the rest of the 6d 16h is to get the flavors right. I might be able to get past this room temp waiting period by roasting a little darker but I prefer waiting- timing at the end of the roast gets too tricky! And most important for this thread, the flavors I notice that appear from not waiting long enough at room temp are a bit of burned taste. Yours is a lighter roast so this may not be applicable but… ??


I keep my beans in coffee bags with one way vales in dark cool cabinets so hopefully there should be no worries there but I will wait a bit longer before I start drinking to see if the flavour goes away with time.

I did a little roaster clean and a couple of roasts more and suddenly there is no burnt smell/flavour anymore. :confused:

There might have been something “infusing” the beans… but the jury will be out until I do a few more roasts.


Seems odd. Truthfully I would have expected roast temps to rid the drum of whatever came before. Seems odd but you can’t knock success!

Did you clean the IR sensor of the IBTS? If you did and it was dirty, cleaning would have increased the IBTS temp reading (roasting snot on the clear lens of the sensor blocks some of the radiated IR so less IR reaches the sensor). Over all that would mean the actual starting temp for Preheat would lower after cleaning. After Prheat, any difference in IBTS reading may or may not affect the roast depending on whether you use IBTS or Bean Temp to manage the roast after Charge…


Yeah it’s very strange and frustrating because I wasn’t able to find out what was amiss which would have been preferable to save me future headaches.

Thanks for the heads-up regarding the IBTS.
I actually did a very simple wipedown and didn’t go near there because I did a big clean not so long ago. Maybe there was something stuck inside from that time? Who knows.

At least it looks fine for now but I do need to rethink my green bean storage facilities :+1:


I’ve recently switched to using these for green storage:

I typically purchase 20-50lb bags of green, and just roll up the grainpro bags the lots come in as tightly as i can. I just topped off with a 30lb order and broke the lot up into separate 5lb Ecotact bags. Hoping to see good results!

Did you have tried 200g green bean to roast?start with 175℃ preheat、P4、F2、D9, 5min turn to yellow, 8min-8.5min first crack, end at 9-9.5min, and the end temperature within 210℃.

To OP:

I had the exact same in-cup notes as you for several months.

My graphs and time/temp marks looked ok but the coffee was horrible.

I downloaded the Rob Hoos recipe and have been much more successful. The previous post follows a similar method.

I was dropping too hot and have come to believe that not all temperature readings are equal. My finish temps are well below what others report (191-195). Was thinking they should be more standardized but that’s not the case.

The trier helps for visual and smell cues. Good luck and report back

Just wondering where you found it? TIA

It’s a Tips and Tricks posted by Ka Fei, May 23, 2022. The first link is for the article. The second is for the recipe.

Should note that the article is entitled “(very) Small-batch roasting on the Bullet”. Its premise is sample roasting, ie a consistent “clean” profile to reveal bean or processing defects whilst limiting roast influence.

I’m not saying this is the end-all but it sure helped me. The Bullet produces and releases heat much differently than my previous roaster.

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Thanks @brian.mchenry.bmrul1 I took a look at the recipes link… very interesting to see how recipes are “created” since I’ve not used that feature but this is good reference. Thanks!