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An overview of roasting stages
JETROASTER
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Posted on 06/15/2015 10:43 AM
best post



I need to put together a good overview of the roasting process for a small team of design and engineer types. The company I'm collaborating with has over 100 years in the industrial incinerator business. They speak our language.
They had some questions, so I figured I'd get some feedback from the good folks at HRO. I know its a broad question, so thanks in advance.
To answer their first question, I've determined that a cubic foot of green coffee weighs in at roughly 40 lbs (if anyone ever wondered)

I'd like to nail down the generally accepted temperature ranges for Drying, Roasting, and cooling. Not for debating purposes, but for a good overview of the various insights from air-roasters and drum roasters. The fact that it varies is useful.

Chaff is an issue, so it would be good to gather peoples experience with respect to where it begins, peaks, and tapers off.

Bean swell? that might be useful

Any insights into times and temperatures as it relates to flavor development and the chaining of sugars would be appreciated.

Actually, I'll take anything people feel would be relevent in the early design stages.

I'd like to think that this thread could also be useful for new homeroasters.

As always, many thanks. -Scott
Edited by ginny on 06/15/2015 7:15 PM
 
boar_d_laze
Top  #2 Print Post
Posted on 06/15/2015 12:05 PM
I'm sure you already know this, but the roasting intervals are usually broken down into three intervals, Drying, Ramp and Development. Other roast events are Charge and Turning Point.

The word "Drying" is something of a misnomer in that moisture is leaving the bean throughout most of the roast.

Bean Mass Temperature aka "BMT":
Since the "bean mass" is not a unitary thing, BMT is an artificial construct. Nevertheless, it's the roast master's best guide as to where the roasting process stands at any given temperature.

The BMT is measured at the point(s) of greatest density in the (fluid dynamic) moving beans, and is usually a combination of beans contacting the probe and air in the roaster. The more its a function of contact, the more representative the reading.

Charge:
When the beans are introduced into the roaster.

Turning Point:
When the roaster is charged, the temperature in the drum, including at the points where Bean Mass Temperature is measured, drops. The moment when BMT begins to rise is called the turning point. It's a function of the thermal mass of the roaster, its retained heat, the mass of the charge, and the amount of agitation.

It's important because readings during the interval when the BMT readings are entirely inaccurate in the sense that the bean mass temperature is not actually dropping, and therefore not useful.

Accurate BMT readings don't begin until the TP, and most roasters give it a minute or so after TP before taking the readings too seriously.

Nevertheless, time to TP tells you something about the consistency of the preheating process.

Drying:
The interval between charge and EOD (end of drying)/beginning of Ramp.

Not too much of chemical significance goes on during Drying.

EOD is typically called artificially at a given temperature (often 300F) or some particular visual or aromatic milestone such as yellowing, cat-face, or bread.

Ramp:
The interval between EOD and the the start of First Crack (1stCs).

Lots of stuff happens here. I'm not going to delve into the chemistry other than to say "Maillard." If you want more insight, I suggest lookingat Illy.

Development:
The interval beginning at 1stCs and ending at Drop. Important stages of Development include, the importat profiling milestones of "Rolling 1st," 1stCe, the "medium" roast" stages of City, City +, Full City and Full City +, and 2dCs and rolling 2d.

References:
Look at the new roasting books by Hoos and Rao; roasting articles by Chris Schooley in the Shrub and Sweet Maria archives; the articles on profiling SOs by Willem Boot in the Roast Magazine archives; and see Illy for the chemistry of roasting.

Hope this helps,
Rich
Edited by boar_d_laze on 06/15/2015 12:16 PM
USRC 1lb Roaster, Chemex+Kone, Espro, Various FPs, Royal Siphon Vacuum, Yama Ice Drip Tower, Bunnzilla, La Cimbali M21 Casa, Ceado E92.
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Ringo
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Posted on 06/15/2015 12:20 PM
Good job Boar De laze, thats a lot of information done well. I also believe in what Boot teaches. I took his three day roasting class and learned a lot.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
 
JETROASTER
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Posted on 06/15/2015 6:53 PM
Very useful and compact. Thank you.
I ran a batch yesterday (fluidbed) and continuously popped off the exhaust pipe. Chaff never completely stopped, but it seemed to peak somewhere around 300?f. Any insights are welcome.
I think they are keen to nail down the approximate cut off points between the phases by BMT.
Thanks again, Scott
 
Ringo
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Posted on 06/15/2015 8:58 PM
On my drum. 220 drop temp
160 turnaround at 1 min 20 secs
300 ends drying at 5 min mark
340 start of carimalzation 8 min mark
400 1 st crack starts at 12 min mark
I stop the roast 2.5 min later
430 if light roast
440 if I want a little darker
I never go to 2 nod crack so do not know where that would be.
I do tweet my times but that's my base roast times.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
 
turtle
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Posted on 06/15/2015 11:18 PM
I put the green beans in the top and they
come out the bottom all hot and brown.

What happens in-between is magic. i1066.photobucket.com/albums/u414/turtle-web/misc/smiley/wizard-smiley_zpsygiwvwu9.gif

That's my story and I am sticking with it. i1066.photobucket.com/albums/u414/turtle-web/misc/smiley/yes-nod-smiley_zpsgrx27imy.gif

.
Mick - "Drinking in life one cup at a time"
"I'd rather be roasting coffee"

Roaster 1: San Franciscan SF-1
Roaster 2: Hottop B-2K+
Roaster 3: 2 kilo Chinese drum
Grinders: Mazzer Major - Forte BG (x3)
Pour over: Hario - Bee House - Chemex - Kalita - Bodum
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Espresso: Pasquini Livia 90 auto
Vacuum: Cona - Bodum
Press: Frieling - Bodum Colombia
 
Koffee Kosmo
Top  #7 Print Post
Posted on 06/16/2015 5:29 PM
You can visit my website and copy my everyday language info I have written on the subject
But make sure you don't claim the info as yours

KK
I home roast and I like it. Designer of the KKTO
Roaster Build information
https://homeroast...ad_id=1142

https://docs.goog...lide=id.i0
Blog - http://koffeekosm...gspot.com/

Bezzera Strega, Mazzer Robur Grinder, Pullman Tamper Convex,
(KKTO) Turbo Oven Home Roaster.
 
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JETROASTER
Top  #8 Print Post
Posted on 06/17/2015 9:31 AM
KK, Thank you Sir. Any use will be credited of course.
Ringo, Thank You as well.
Do you feel that these temperature ranges are roughly consistent with other drum roasters experience?
Rich, Thank you. The chemistry discussion really is too much for an overview. Suffice to say that it falls in "Ramp "
Thank You All (with a little shout out to Chicago John). Very grateful. -Scott
 
coffeeroastersclub
Top  #9 Print Post
Posted on 06/17/2015 9:48 AM
Scott, I did a few batches in my air roaster and noticed that the chaff started coming off the beans at 230 degrees F.

Len
"If this is coffee, please bring me some tea but if this is tea, please bring me some coffee." ~Abraham Lincoln
 
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JETROASTER
Top  #10 Print Post
Posted on 06/18/2015 12:11 PM
Thank you Sir. Did you note a peak or a significant drop off point?
-Scott
 
coffeeroastersclub
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Posted on 06/18/2015 2:25 PM
I'll observe that next time I roast, Scott.

Len
"If this is coffee, please bring me some tea but if this is tea, please bring me some coffee." ~Abraham Lincoln
 
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MrPeaberry
Top  #12 Print Post
Posted on 03/08/2016 3:37 PM

Quote

boar_d_laze wrote:

Since the "bean mass" is not a unitary thing, BMT is an artificial construct. Nevertheless, it's the roast master's best guide as to where the roasting process stands at any given temperature.

The BMT is measured at the point(s) of greatest density in the (fluid dynamic) moving beans, and is usually a combination of beans contacting the probe and air in the roaster. The more its a function of contact, the more representative the reading.

Charge:
When the beans are introduced into the roaster.

Turning Point:
When the roaster is charged, the temperature in the drum, including at the points where Bean Mass Temperature is measured, drops. The moment when BMT begins to rise is called the turning point. It's a function of the thermal mass of the roaster, its retained heat, the mass of the charge, and the amount of agitation.

It's important because readings during the interval when the BMT readings are entirely inaccurate in the sense that the bean mass temperature is not actually dropping, and therefore not useful.

Accurate BMT readings don't begin until the TP, and most roasters give it a minute or so after TP before taking the readings too seriously.

Nevertheless, time to TP tells you something about the consistency of the preheating process.



Hi Rich,

I like that you refer to BMT as an artificial construct. When it comes to temperature probes, ie thermocouples, the process of measuring BMT is even further removed from the actual value of BMT. The use of a thermocouple shield or well, the use of a grounded or non-grounded thermocouple, are choices that affect the recorded versus the actual BMT. You didn't mention, yet I think it is worth pointing out that the registered drop in the recorded BMT is due to the cooling off of the probe itself at charge. If it were possible to design a bean probe that could be inserted into the bean mass at charge, one would not record a temperature drop. Of course the recorded temperature would still be a function of the variables you mentioned, and would provide the best way for tracking what is happening in the roast. Since the value of the variables that affect recorded temperature differ from roaster to roaster, one cannot simply transfer a roast profile from one roaster to another. An experienced roaster would have to use a combination of sight, smell, and recorded temperature to successfully roast a profile for the first time on an unfamiliar machine.

It suddenly occurs to me that coffee professionals who operate espresso machines have a unique name given to them, but that the phrase "coffee roaster" applies both to man and machine. This doesn't seem fair...Shock

Peaberry
pouring
FYI - I suffer from OCD (Obsessive Coffee Disorder), please be kind.
 
JETROASTER
Top  #13 Print Post
Posted on 03/10/2016 1:55 PM
It does seem like we should have a more definitive name. We should coin it quickly, if we don't, it could easily getting put upon us. We could wind up with something right out of the Charbucks lexicon.

As an air roaster, I don't really have to do much from one stage to the next. My machine runs a pretty nice curve with little input from me.
I am curious about the things that drum roasters have to do through the various stages, and how consistent those steps are from one manufacturer to the next.
As always, Thanks for your input. Cheers, Scott
 
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