Posted Tue Mar 18, 2003, 12:22pm Subject: Roasting Profile ?
I have a Hearthware Precision and I know how to control the temperature of the air entering the roast chamber. (I will share that information if anyone is interested.) What I need to know is what the temperature should be as the roast progresses. So far I have dropped the temp. to the point where first crack is at ~ 5 minutes and second crack is at about 13 - 14 minutes. I think the coffee is more mellow then it was when I got the machine.
A roasting profile isn't the heating temperature, but the graph of bean temperature over the course of the roast.
Since these cannot be measured directly (their surface is a wrinkled insulator that doesn't transfer heat very well), one usually measures air temperature where it has equalized with the beans -- in a drum roaster this is the still air inside the bean mass, in an air roaster it is the flowing air after it has been in contact with the beans longest, usually close to the exhaust point.
I've appended a profile here that includes roasting milestones (I was calibrating my temperature readings to duplicate a Hottop roast for an experiment - results soon).
Roasting profiles vary. Drum roasters take a long time to get to the first crack, and usually finish fairly quickly, in 3 to 5 minutes. Air roasters go quickly to the first crack, and slow down, some more than others, at that point.
I'm currently using a profile that goes to 300F as fast as possible, spends four minutes going to 350F, and finishes in 5 minutes thereafter. I find the slow ramp from 300 to 350 mutes the acidity without toning down the origin flavors as much as my previous profile that slowed down after the first crack was done (ca 410F). Slowing down a lot during the early first crack (375F-400F) is rarely advisable, since it's said to "bake" the beans
Thanks Jim, If I understand corectly, What I should do is place a thermometer in the outlet air. I should use try to get to 300 degrees F as fast as possible then gradually ramp up to 350F gradually over a four minute period at which time the beans should be brown and first crack should be starting. At this point I then ramp the temperature ~20F/minute untill second crack.
Phil
another_jim Said:
A roasting profile isn't the heating temperature, but the graph of bean temperature over the course of the roast.
Since these cannot be measured directly (their surface is a wrinkled insulator that doesn't transfer heat very well), one usually measures air temperature where it has equalized with the beans -- in a drum roaster this is the still air inside the bean mass, in an air roaster it is the flowing air after it has been in contact with the beans longest, usually close to the exhaust point.
I've appended a profile here that includes roasting milestones (I was calibrating my temperature readings to duplicate a Hottop roast for an experiment - results soon).
Roasting profiles vary. Drum roasters take a long time to get to the first crack, and usually finish fairly quickly, in 3 to 5 minutes. Air roasters go quickly to the first crack, and slow down, some more than others, at that point.
I'm currently using a profile that goes to 300F as fast as possible, spends four minutes going to 350F, and finishes in 5 minutes thereafter. I find the slow ramp from 300 to 350 mutes the acidity without toning down the origin flavors as much as my previous profile that slowed down after the first crack was done (ca 410F). Slowing down a lot during the early first crack (375F-400F) is rarely advisable, since it's said to "bake" the beans
Thanks Jim, If I understand corectly, What I should do is place a thermometer in the outlet air. I should use try to get to 300 degrees F as fast as possible then gradually ramp up to 350F gradually over a four minute period at which time the beans should be brown and first crack should be starting. At this point I then ramp the temperature ~20F/minute untill second crack.
I'm not sure what the best place for the Hearthware is. If you find a spot that gets you around 320F when the beans are yellow/tan, 380 at the start of the first crack, and 435 at the first pops of the second, you're golden, and you can follow any published profile you want - check sweetmaria's and htttp://homeroaster.com If you can't find such a spot, it's not a problem, you just have to convert your readings you're getting to the milestones.
I go 350-375-400, then 15f per minute to the finish. However, experiment with your own profiles; I'm making absolutely no guarantee that I'll be sticking with this one :)
It's helpful, when making profile (or any other) changes, to do two lots, one with your existing procedure, one with the tweaked one; and to blind taste the results. It's the only way not to taste exactly what one expects.
I've been reading about your Hottop Profile experiments and have been esperimenting with them in my Rosto as well. Too early to tell for sure, but the last 4-5 roasts have been some of my best ever.
I've tried two variations on your profile:
A fast ramp up to 250, followed by a super slow ramp to 1st Crack (i.e. reaching 1st at 10-12 minutes), and a 2-4 minute ramp to 2nd.
A slow, even ramp to 1st crack, by brining the heating element voltage down to about 90-95 (1st crack at 10-12 minutes) with a 2-4 minute ramp to 2nd. My initial impression is that there was a more even, more well rounded roast flavor when I did a slow and even ramp up to 1st.
Any thoughts?
Bottom line is that I think you've stumbled on something very valuable here to help air roasters to better match a drum roast profile. This is made possible by use of variacs and separating fan and heating elements.
A slow, even ramp to 1st crack, by brining the heating element voltage down to about 90-95 (1st crack at 10-12 minutes) with a 2-4 minute ramp to 2nd. My initial impression is that there was a more even, more well rounded roast flavor when I did a slow and even ramp up to 1st.
When I did the hottop "clone" roasts I did a much slower than usual (for me) ramp to 300. I found the results a little to flat for a standard Guat, but rather nice for a Harar. I also duplicated one of Barry's Diedrich's profiles (appended) for the Harar (basically a straight line from start to finish in 15 minutes), and that was best of all. I'm beginning to think the airroaster profiles (fast start/slow finish) may be good for simple central american coffees, but that the drum profiles bring a better balance to the really complicated coffees
...I also duplicated one of Barry's Diedrich's profiles (appended) for the Harar (basically a straight line from start to finish in 15 minutes), and that was best of all. I'm beginning to think the airroaster profiles (fast start/slow finish) may be good for simple central american coffees, but that the drum profiles bring a better balance to the really complicated coffees
This is quite amazing. I've been so immersed in air roast profiles for so long that I've simply not considered the time before 1st crack as being that important. But, now I'm beginning to think otherwise as well.
Thanks for posting Barry's average roast profile. I'll give this a try.
Have been experimenting with profiles in my Caffe Rosto, and using a resistor - rectifier - switch combination with the thermostat by-passed to drop down to 95% current at times. Getting some absolutely great roasts going by profile instead of the timer.
Have been experimenting with profiles in my Caffe Rosto, and using a resistor - rectifier - switch combination with the thermostat by-passed to drop down to 95% current at times. Getting some absolutely great roasts going by profile instead of the timer.
I am using the variace to modify the heater voltage. However, I've also experimented with using it to control the fan (i.e. boost fan voltage to increase batch size) and running the heater element to the wall outlet. This, of course, results in a more straight-line profile, but I'm still getting excellent results.
I'll have to give your profile a try. I've also bookmarked your page to periodically check for updates.
I am using the variace to modify the heater voltage. However, I've also experimented with using it to control the fan (i.e. boost fan voltage to increase batch size) and running the heater element to the wall outlet. This, of course, results in a more straight-line profile, but I'm still getting excellent results.
I'll have to give your profile a try. I've also bookmarked your page to periodically check for updates.
milnerb1: Yes, belive you are correct to experiment with different voltages for both fan and heater.
My supply voltage always measures 121 vac, so don't have any problem in that area. Also, it will roast different batch sizes, actually did 8 oz by weight, just shake the Rosto some to cause bean rotation until they got light enough to rotate freely by just air flow.
I like my coffee degassed for 24 hours, then use within 72 hours of degassing, so only roast my preference in-with just enough beans to keep them from being blown into the chaf collection chamber which will vary I suppose by fan speed.
Also, a tech note: Blowing Hot Air versus Blowing Cold Air. Hot air weighs less than cold air and places less load on the motor which will effect air flow.
I have now done ten (10) roasts back -to- back with out allowing the Rosto to cool down, dump the beans into a fan ventilated from the bottom stainless steel collander. No problems with the Rosto as modified doing this.
Keep me advised on Rosto results you like - prefer so I can try them.
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