Internal scorching is kicking my behind. Ideas?

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Vince_in_Montreal
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#1: Post by Vince_in_Montreal »

No matter what I do I can't get rid of it. I have lowered my charge temp from ~400 to 360f (also learned about and implemented Scott Raos warm up procedure and between batch protocols) and the result was far far better coffee and insane aromatics. But even this has some internal scorching which I could taste in the coffee. These coffees are intensely aromatic, good tasting but baked (ROR curve was not ideal, both crashes and flicks at FC but the scorching is what I'm working to get rid of.

Edit: here's a picture of a bean with internal scorching.




Today I tried lowering batch size from 250g to 210g (it's a 350g spec Kaldi machine) and I also lowered charge temps to 330f and even 300f for 1 batch of 180g as it was the end of the bag. The results are very good looking profiles but internal scorching is still present in all batches. At my wits end. Help?

Haven't tasted these as I roasted them today.





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Vince_in_Montreal (original poster)
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#2: Post by Vince_in_Montreal (original poster) »

The lower batch size was an attempt to fix a rapid declining ROR immediately after peak ROR like so:




Mine always peaks and then rapidly loses momentum before leveling off. I noticed most people ROR peaks and declines more evenly and in less of a hurry than mine were.

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keno
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#3: Post by keno »

Maybe try increasing your batch size? Scorching involves transferring too much heat to the bean too quickly. At the start of your roast the thermal mass in your drum is transferred to the bean mass. So increasing the bean mass may help to spread out the load and reduce scorching. Check also that you aren't using too low or too high a drum speed.

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baldheadracing
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#4: Post by baldheadracing »

The article by Boot that you pulled the pics from says interior scorching might be caused by improper drying of the greens. Is this unique to one green?
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Brewzologist
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#5: Post by Brewzologist »

Have you tried a gas-off soak for ~1 min at charge?

Vince_in_Montreal (original poster)
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#6: Post by Vince_in_Montreal (original poster) »

@keno ive been getting the scorching at all batch sizes and charge temps. This is the first time I've charged such a small batch size at such a low charge temp and I see a big improvement in ROR control. The bigger batch size had just as much scorching but the ROR was wonkier. Bigger batch size necessitates more heat which cause more scorching I believe.

@Baldheadracing I am fairly certain that the more moisture in a green, the worse this problem gets. I have a Bolivian with over 12% moisture that gets more internal scorching than my Ethiopian Guji with 10.5%. So moisture levels play a role me thinks.

Also now that I think of it the faster dry time seems to make it worse. On previous roasts I extended dry to 5 - 5:30 and it was better, but still had it. Maybe you're on to something, I can try extending dry to 5:30-6 maybe but that seems very long and I have a hard time controlling ROR with such little gas input.

@Brewzologist I do soak for 1 min for all roasts.

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keno
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#7: Post by keno »

There is an old HB thread on this topic: Roasted coffee beans darker inside than outside

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Vince_in_Montreal (original poster)
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#8: Post by Vince_in_Montreal (original poster) replying to keno »

Yea I read a few threads on the subject including that one, but didn't find a solution. Dry time does get mentioned but not as a definitive solution or details. I will try extending dry with the new batch size but then I have a real hard time with the ROR.

1 problem at a time I guess.

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CarefreeBuzzBuzz
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#9: Post by CarefreeBuzzBuzz »

I may be very off base here, but what if you drop between 1:45 and 2:15 post FCs? Those are very long development times you have. I am thinking the opposite, you aren't getting enough heat to start and you end up baking the beans through and through. Have you asked other Kaldi owners. I think you may want to go the other way to try things out WITH A HIGHER CHARGE TEMP.
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Vince_in_Montreal (original poster)
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#10: Post by Vince_in_Montreal (original poster) »

CarefreeBuzzBuzz wrote:I may be very off base here, but what if you drop between 1:45 and 2:15 post FCs? Those are very long development times you have. I am thinking the opposite, you aren't getting enough heat to start and you end up baking the beans through and through. Have you asked other Kaldi owners. I think you may want to go the other way to try things out.
No not at all thanks for helping. So the reason I extend development times is I much prefer darker roasts. As does my wife who will not touch (MY) coffee if I drop below 390-400f. And actually the coffee we most preferred was dropped 405-415 which is on the verge of second.

If Dry happens at 4ish how much more heat should I give it? My older roasts would hit Dry around 3:30 and first crack like 6:30-7:30 and those were not drinkable.

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