ambient temp and bean temp

[Jazz]

farmroastI was wondering if you could explain in detail what you mean. it sounds very importantthank you

 

[eldub]

I'm also interested in understanding farmroast's instructions, but am having difficulty with the abbreviations.

(My guess on the last post is that he's saying more airflow earlier in the roast and less airflow later in the roast allows for a more consistent heat transfer rate throughout the process.)

However, even if I'm correct in my understanding of the above post, it still leaves me in the dark as to the best way to maintain the consistency through convection.

(My guess on that would be he's saying to shut down the airflow in the barrel later in the roast when gas is decreased and beans are coasting to finish.)

 

[farmroast]

I was just answering the concept of the question. Concern of the temp being a little high but liking the speed of the progression of the roast. Air flow is the convection adjustment. The more air flow at the same measured temp. the faster the heat transfer.
Different roasters have different ways air flows through the system. So what exactly can be accomplished with adjustments of air and energy will vary.

ET environmental temp.(wherever in the roaster or stack it's measured)

 

[eldub]

Thanks for the explanation, farmroast.

I'm curious at the difference between backing off on the gas later in the roast compared to dampening the airflow. I'm under the impression that lessening the airflow toward the end will make for a smokier flavor profile in the beans.

 

[farmroast]

Thanks for the explanation, farmroast.

I'm curious at the difference between backing off on the gas later in the roast compared to dampening the airflow. I'm under the impression that lessening the airflow toward the end will make for a smokier flavor profile in the beans.

Dampening the air flow will raise the ET environmental temp unless the energy is lowered also.
Air can be used to manage the environmental moisture level earlier in a roast and to deal with chaff and smoke later in roast. Most roasters will be carrying too much momentum into first crack thus a need to use a combination of increased air and decreased energy. I like about a 3 to 3.5 min finish from start of 1st crack for brewed and about a minute longer for espresso(taming acidity and adding body), whether city or full city+.

 

[Jazz]

Im really enjoying this conversation but a little confused. In the earlier parts of the discussion, it was noted that I should try and get to 300 degrees by 5 minutes. If I dump 20+ Lbs green coffee in at 390 degrees bean temp, it takes me down to 170-180 degrees and climbing back up in 1.5 Min. Now, I have to get to 300 degrees in less than 3.5 min. Thats more than 20 degree per minute climb (that I was told to achieve).Could someone clearify thisThanks

 

[Jazz]

Also, if I.continue at that rate of climb, I will be reaching the point of first crack way before the recommend Ed time of 15 to 18 imin

 

[eldub]

You don't want to drop the ambient temps all the way down to 170* when charging the barrel with beans. 230* is a better goal, imo.

For a full load, (25 lbs.) I get the roaster up to 420*, add beans and give it 2+" of gas. That leads to a drop to about 230* before the temps turn around and start to climb.

For a half-load, I'll set the temp at 360*, drop the beans and just add a small bit of gas to get the beans to the same 230* mark.

Keep in mind that multiple people are giving input in this thread and there different ways to go about a roast. For instance, farmroast likes to raise temps at least 30* per minute and I shoot for 20.

 

[eldub]

As far as time reaching first crack...... The 15-18 minutes you mention above is how long my roast goes until finished. I try to get to first crack by 11 minutes or so. Then I back off the gas and try to coast to the finish line in 15/16 minutes total time.

 

[farmroast]

Im really enjoying this conversation but a little confused. In the earlier parts of the discussion, it was noted that I should try and get to 300 degrees by 5 minutes. If I dump 20+ Lbs green coffee in at 390 degrees bean temp, it takes me down to 170-180 degrees and climbing back up in 1.5 Min. Now, I have to get to 300 degrees in less than 3.5 min. Thats more than 20 degree per minute climb (that I was told to achieve).Could someone clearify thisThanks

I'm in the 30s of bean temp. degrees of rise per min. during drying phase. By the time I hit the maillard reactions around 290-300f I'm then at 20-24 degrees rise/min. with about a 5min + or - drying phase.
I tried to upload a graph, the same as I normally do on other sites but it was called an "invalid file"."

 

[Jazz]

so would you say I need to go a little heavier on the gas in the beginning to get to 300 degrees by 5 minutes and then back off on the gas?

 

[eldub]

I would say you need to raise the starting temp in the roaster so the beans don't make it all the way down to 170* before turn around.

 

[Jazz]

I already start the roast at 390 bean probe temp. Are you saying that maybe I should go beyond 400 degrees bean probe temp at the start? This is most interesting

 

[eldub]

Your beans are dropping the temps too far, imo. It seems to me like you would have to raise the ambient temps WAY up to get on schedule when the beans get down below 200*.

We start a half-load (12 lbs.) at 360* bean probe temp and a full load at 420*. I give it just a touch of gas upon charging the barrel with a half load and 2" of gas from the start of a full load. Using this method, my ambient temps never have to get all the way up to 440* when I do a 440* roast.

 

[Jazz]

I was wondering if you would give me a call so I could explain in more detail and why I cannot reach those ideal numbers. 715 451 5336Im not asking for trade secrets but just some general knowledge to help me solve some questions. I will post any info I gather for all