Your Roasting Temperatures Don't Make Sense To Me

[farmroast]

As we're starting to have some handy computer roast softwares to hook probes up to, better probe placement becomes more important. If your readings are too far off from bad bean mass contact with the probe they will also likely be effected nonlinear from different batch sizes, different heat or air profiles. But when all is the same in repeated roasts there should be some decent consistency.

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[Jazz]

I had a post a month or so ago about ambient temp and bean temp. I am wondering if the differences of opinions are because when describing the roasting processs, maybe we should be more clear on whether we are talking ambient or true bean temp. Also my question is, does it make a largr difference where the probe is? Great topic, lets keep it Rollin. There are no dumb questions

[expat]

My roaster measures the drum temperature and the exhaust temp. So possibly that is where the discrepancy lies. Some folks are talking drum temp, others are talking bean temp?

[eldub]

Our drum temp tends to run 40 to 80* above the bean temp until I get up to 370* or so. At that point, I shut down the gas and extend the time between cracks. Its common for our bean temp probe to reach 440* while the drum temp is 10* or so lower than that. However, if I let the bean temp get higher than the drum temp early in the roast, the process will stall out.

[eldub]

Jazz: In the earlier discussion, I was talking about bean temps.

[Jazz]

Very interesting. If you dont mind me asking, how long between cracks would you go on average. I always try to never go beyond 4 min.

[eldub]

I don't have my roasting schedule in front of me but four minutes sounds about right. (Three minutes might be on the acceptable quick side and five on the long.)

[PerfectDayCoffee]

I find the sweet marias temps to be way off I first pop at 375° to 388° F and go to like 415 at a ramp between 10° to 3° per minute for a nice city roast. Their end temps are way high- I stop popping way before 426.

[eldub]

perfectday: What roaster are you using?

I don't go by sweet marias' guide. I go by the roaster manufactures numbers (US Roaster Corp) as well as the guide in "Home Coffee Roasting," by Kenneth Davids. However, all three sources mentioned above cite roughly the same temps for specific stages of the coffee bean roasting process and my personal experience on our machine corresponds closely to those figures given.

[Josh]

No, I'm not making any such claim. I am stating that temperature probe readings will very by machine, placement, and accuracy.

So... if If wikipedia tells me that 2nd crack is at 437f inside the bean, I believe it. However, my machine will read the bean mass probe at 405 when second crack is happening.

As long as my probe is consistent I can track my roast profile and that is what matters.