Hi,
I am running into some problems with my roast profile on my Diedrich IR-12. Below are two15# profile roasts that I have completed and am getting a coffee taste with a flat flavor. Any help from you all would be greatly appreciated.


15# Costa

Drop 415 f – gas @ 80%

After 1 min. drop gas to 50%

Bottom out – 167 f

240 f @ 3:75 – 4:00min

280f – 50/50 air

305f @ 6:00min

370f @ 10:30 – Full air

1st crack 382f @ 11:00

Finish temperature 432f – start of second crack (15:20 min)

Roast development 4:20 min.

Coffee is flat w/o flavor


15# Guat

Drop 415f – gas @ 80%

After 1 min drop gas to 50%

Bottom out – 163f

240f @ 4:00 min

280f @ 5.5 – 6:00 min

280f - 50/50 air

305f @ 7:00 min.

370f @ 10:05 min – Full air

1st crack 381f @ 11:00min

Finish temperature 431f – start of second crack (15:42 min)

Roast development 4.42 min

Coffee is flat w/o flavor


15# El Sal

Drop 415f – gas @ 80%

After 1 min drop gas to 50%

Bottom out – 163f

240f @ 4:00 – 4:30 min

280f @ 5.5 min

280f - 50/50 air

305f @ 6:30 - 7:00 min.

370f @ 10:05 min – Full air

1st crack 376f @ 11:00min

Finish temperature 432f – start of second crack – 15:00 min

Roast development 4:00 min.

Coffee is flat w/o flavor

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I'm surprised about the flame settings.  Are you using 50% flame until you're close to first?  If so, the first thing I'd try would be the increase that.  Should shorten the drying phase a little but the real point is to have more energy stored in the coffee so it'll hold momentum while you're gently guiding it through 1st.

Roasting on an IR-12 as well here.  Most of our batches are ~20 pounds (9kg).  Here are some thoughts, some already mentioned by others:

1. Your turning point temperature seems a bit low to me.  I try to keep mine between 168-175f.

2. Your roast development time seems a bit long to me.  I've had good coffee with long development time on Probat roasters, but on Diedrich, I try to keep them between 2:30 and 3:30.  Past this, I end up with flat coffee as you mention.

My "typical" roast profile is:

1. Drop 415-425f depending on the coffee

2. After 1 minute, I drop gas to 45-55 depending on the coffee

3. Bottom out between 168-175f @ 1:30

4. 240f @ 4:00 -- 4:30 (closer to 4:00)

5. 280f @ 5:00 -- 5:30 (closer to 5:00)

6. 280f - 50/50 airflow

7. 320f @ ~7:00 (yellow stage: uniformly yellow)

8. 340f @ ~8:00

9. 360f -- gas @ 25-30 depending on the coffee

10. 365f @ ~9:00

11. 365f - full airflow

12. 1st crack 390-395f @ ~11:00

13. 405-415f -- gas @ 10-15 depending on the coffee

As mentioned previously, I try to keep my roast development time between 2:30 and 3:30.  For drip coffee, closer to 2:30 - 3:00 and for espresso, closer to 3:30.

Hope this helps!

Martin

Of course, what I'm about to say is personal preference, but I haven't had much luck with faster finishes.  Most of my profiles are full city, so maybe running a little longer than you're going for, but I'm usually going about 5 minutes between FC and SC, and maybe another minute or so before I drop.  For lighter, brighter roasts, I follow essentially the same profile, but just drop right around the SC onset.  The reason I don't like the faster finishes is that they always seem to take on a biting, bitter, tar/phenol sort of flavor that I don't get if I stretch things out a little.

For my tastes, the best way to brighten up your profiles would be to adjust batch sizes and early heat settings to get to FC faster.  My ideal profile is about 9 minutes to FC, although the Diedrich I most recently worked on had a hard time getting there as fast as I wanted.  I would roast some coffees in smaller batches specifically to get the faster ramp to FC and maintain more acidity and aroma.

Below are links to two example profiles I really liked while roasting on a Diedrich IR-24 (despite its implied capacity, I could never get more than about 30lbs to do what I wanted on that machine - 25 or so seemed to be ideal.)

http://www.beowulf-recording.com/download/coffee/Roast%20Data/data%...

http://www.beowulf-recording.com/download/coffee/Roast%20Data/data%...

P.S. If the charts seem a little weird, it's cause I've started graphing all of my roasts with FC as the "0" time mark.  It makes it easier for me to compare the different stages of the roast on various batches.

I figure I'll throw my two cents into the mass of recommendations. I roast on an IR-12 and as someone else stated, temperature and profiles don't translate directly even if on the same roaster. My suggestion would be to get a sooner drop out temperature, if you go any quicker on your drop out time you will probably start to see scorching/tipping. However, if I'm not mistaken, you want to utilize the moisture in the bean to propagate heat evenly from the inside to the outside to produce proper browning reactions. When you heat the outside cellulose matrix of the coffee without using the moisture content inside to your advantage scorching will occur and can flatten out the taste perception of the cup (which I understand you're not having a problem with). However, I have noticed that when profiling a coffee if my drop out temperature happens way below boiling point (any more than 20 degrees) even in lighter roasts dropped just post first crack can produce that flat acidity that you're experiencing. I have found the best results when my drop out temperature is 10-15 degrees before boiling point, on my IR-12 that means 180-190F.

Flat, bland, baked flavors generally (and this is very generally, there are other reasons as well) come from time spent in the roaster given the temperature rise. If minimizing roast characteristic and getting livelier acidity is what you want, I would recommend either using higher airflow (which will have to be counter-acted with lower heat because convectional heating will dry out the bean faster) or hitting first crack sooner (9:00-10:00) still keeping in mind that you don't scorch the coffee.

Hope this helps! Look forward to hearing your progress.

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