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End Of Yellowing? or End of Drying?
ciel-007
"End Of Drying" (EOD) is a misnomer:

Roasting coffee involves coaching the beans through 3 critical phases.
Namely: 1) End Of Drying, 2) Ramping, and 3) Development.
Some might argue that "End of Drying" is be the most important phase, and that it is liable for cup sweetness, flavor and mouth feel. Although I do indeed appreciate the importance of this first phase, I am skeptical about the terms that have been used to describe it.

My purpose here is to encourage an exchange about the words chosen to describe the first phase of roasting. I find the phrase "End of Drying" to be both confusing and misleading. Roasters tend to state that EOD occurs when the Bean Mass Temperature (BMT) reaches 300F, or so. However, that is not the case. Empirical evidence shows that when the BMT reaches 300F, the beans have merely begun to dry. What follows is an example.

Some months ago, I conducted an experiment to determine how many grams of moisture were removed from Columbian greens during a typical espresso roast. To accomplish that, I weighed the beans at three critical stages. Namely:
(1) Weight of the greens at room temperature: BMT = 75F
(2) Weight of beans at the End Of Drying (EOD): BMT = 300F, and
(3) Weight of the beans at the end of the roast: BMT = 428F.
(see link on Bean Drying Phase)
http://homeroaste...post_51412
The results showed that only 19% of the moisture had been removed from the beans by the time BMT had reached 300F. The fact that over 80% of the moisture still remained inside the beans at the "End Of Drying" confirmed that EOD is a misnomer. Might there not be a better choice of words to describe the first phase of the intricate roasting process?

Ciel
Ciel... seeking Heaven in my cup with ................................................................................................................. EXPOBAR Brewtus II - MAZZER Mini E - MAHLK�NIG Vario - GeneCafe - RAF-1 Extreme (Modified B-2 HOTTOP) - BellaTaiwan XJ-101
ciel-007
"End Of Yellowing" (EOY) is more accurate

In my experience, the phrase "End Of Yellowing" better reflects what is actually happening during the first phase of the roast. Not only are the words "End Of Yellowing" more precise, they are also more intuitive for the novice roaster.

When the pale green beans are dropped into a hot chamber they immediately begin to absorb heat. In theory, one might expect the moisture inside the greens to vaporize when the surface of the bean reaches 212F. However, that is not actually the case. Given the hardness of the bean, it's density, and the cell structure, the heat requires time to penetrate down into the core before proper evaporation may effectively begin. As the heat advances, the surface of the bean begins to yellow; the roast has barely begun to dry and the initial vapors carry the scent of grass and hay.

The "End Of Yellowing" is at hand when the beans are fully saturated with heat. That's when the color of YELLOW gives way to the TAN complexion; the vapors now carry the bouquet of baking bread. More importantly, the beans have begun to soften; upon closer examination, one can see partial stripes and delicate wrinkles forming on the surface. The roasters from Taiwan have a special name for these emerging patterns: they call them "cat faces". Those partial stripes, delicate wrinkles, and "cat faces" begin to appear when the BMT approaches 330F (165C).

On my BellaTaiwan XJ-101, I find that 6.5 minutes is an ideal amount of time to reach "End Of Yellowing". My typical 1 kg load takes a total time of 13 minutes to complete all three roasting phases before ejecting the beans. In other words, I dedicate half of my total roasting time in order to allow the beans to reach the "End of Yellowing".

Ciel
Ciel... seeking Heaven in my cup with ................................................................................................................. EXPOBAR Brewtus II - MAZZER Mini E - MAHLK�NIG Vario - GeneCafe - RAF-1 Extreme (Modified B-2 HOTTOP) - BellaTaiwan XJ-101
turtle
I am not sure about technical terms but I find drying to occur (at least in my roaster) between 270 and 340 degrees after which I do not find much moisture coming out of the fan. Now this does vary slightly with the bean being roasted but this is my "rule of thumb" when I roast.
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: Behmor 1600 +
Grinders: Modified Super Jolly - Forte BG (x3)
Pour over: Hario - Bee House - Chemex - Kalita - Bodum
Drip: Bunn CWTF15-1 & CW15-TC (commercials)
Espresso: Pasquini Livia 90 auto
Vacuum: Cona - Bodum
Press: Frieling - Bodum Colombia
ciel-007
End Of Yellowing vs End of Drying?

According to my reading of Willem Boot, the beans aren't dry by the time they reach BMT 300F. Boot makes it clear that beans undergo drying throughout the roasting process, all the way up to First Crack (1C); 1C is the moment at which the mounting gas pressure splits open the bean to release nearly 100% of its moisture. I would never suggest that we substitute the phrase "End Of Drying" for the term First Crack. However, I would suggest that we consider discouraging the use of the misnomer "End Of Drying", in light of the fact that over 80% of the moisture still remains at BMT 300F.

In my opinion, HRO is the premier "Home" roasting site on the internet. HRO is the site to which budding roasters flock to learn about roasting, and to hone their skills. Not that long ago (in 2012) I was a newbie at this site. I struggled for some time with the term "End Of Drying", which I hadn't fully grasped until recently. It wasn't until 2014, following a modification to my Hottop RAF-1, that I literally began to "see" just how misleading the term "End Of Drying" really was. (see link on "Venting the Plenum"):
http://homeroaste...post_50706

It should be made much clearer that the main purpose of the first phase of roasting has little to do with actual drying. Rather, the first phase is all about allowing the heat to fully saturate the bean in preparation for phase 2 (Ramping) and phase 3 (Developing). Wouldn't we be doing newcomers to HRO a favor if we were to encourage the phrase "End Of Yellowing" instead of the customary but misleading term, "End of Drying"?

Ciel
Ciel... seeking Heaven in my cup with ................................................................................................................. EXPOBAR Brewtus II - MAZZER Mini E - MAHLK�NIG Vario - GeneCafe - RAF-1 Extreme (Modified B-2 HOTTOP) - BellaTaiwan XJ-101
turtle

Quote

ciel-007 wrote:

End Of Yellowing vs End of Drying?

Wouldn't we be doing newcomers to HRO a favor if we were to encourage the phrase "End Of Yellowing" instead of the customary but misleading term, "End of Drying"?

Ciel


I like the fact that the hottop has such a large view glass in front. It allows me to "see" as well as smell when the beans are releasing gas/moisture.

I stop my fan when I notice the beans moving from yellow to tan in color which comes between 330 and 340 degrees on my BT probe.

Maybe I am doing it all wrong but I do enjoy what comes out when I am done, regardless of whether it is correct or not.

My drying stage consists of adding 50% fan when I notice the beans start to move from green to a paler color... When that color deepens I move to 100% fan up until the beans start to change once again from their yellow to tan.

I keep the burner at 100% through out the roast until I get to the start of first crack which, depending on the beans, comes anywhere from 350 to 360 degrees on my BT probe. Then I cut it down to 50% or less depending on the rate of rise of the BT probe.

If the burner/heater were more responsive the hottop would be a better product but I find the burner does not react to the setting changes quickly. I equate it to a fully loaded 300 car coal train trying to slow down. Hit the breaks and whoa look out..... so I tend to over compensate on the heater settings, dropping it before I think I should

I am looking forward to using the coil heaters in the SF rebuild as from my limited testing on/off - up/down is pretty responsive with those coil type burners as opposed to the rod type used in the hottop
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: Behmor 1600 +
Grinders: Modified Super Jolly - Forte BG (x3)
Pour over: Hario - Bee House - Chemex - Kalita - Bodum
Drip: Bunn CWTF15-1 & CW15-TC (commercials)
Espresso: Pasquini Livia 90 auto
Vacuum: Cona - Bodum
Press: Frieling - Bodum Colombia
lyle
One thing I thought I'd share is that Cafe Imports, in their roast notes in their "Beanologies", usually note three points during the roast: 1) turning point, 2) color change, and 3) first crack.

Example: http://www.cafeim...inpro-2508 (scroll to the bottom).

The point is, it's not unprecedented to use the color change as a marker versus EOD, at least in the professional roasting world.
boar_d_laze
A rose by any other name would smell as sweet.

I use EOD because it's well understood (even if it's not completely accurate), and because it's what Artisan uses.

With most beans I crank the heat at 300F; with a few at the aroma of "baking bread + rum; and with a few others at "cat face" In any case, I mark the moment as EOD on my plot, and make a note for aroma or appearance if necessary.

I like to hit my interval times within 15sec and my Drop temp within 1F. "End of yellowing" is too inexact as a cue to action, so it's not something I bother tracking anymore, although it was a big thing for me before I started real time plotting.

Some other term than EOD might represent the period between Charge and Ramp more accurately, but one way or the other, it doesn't bother me.

Rich
USRC 1lb Roaster, Chemex+Kone, Espro, Various FPs, Royal Siphon Vacuum, Yama Ice Drip Tower, Bunnzilla, La Cimbali M21 Casa, Ceado E92.
CookFoodGood
ciel-007

Quote

boar_d_laze wrote:

... I use EOD because it's well understood (even if it's not completely accurate)...



Rich, thanks for contributing to a topic that is of critical importance in successful roasting. I've read many of your instructive posts on roasting, both here and on other established sites. The insights and expertise that you have generously shared are much appreciated. They have helped me, and many others I'm sure, improve roasting results.

I agree with you that EOD is "not completely accurate". However, I feel that you are being kindhearted when you add that OED is "well understood". The words I posted above advance the contrary thesis. Namely: When it comes to burgeoning roasters, the term EOD is misunderstood precisely because EOD is not an accurate term. If only the above confusion was constrained to newbie or "burgeoning" roasters.

Unfortunately, I have seen fairly experienced roasters (high volume posters) advising others with misguided information about "drying". Examples of that abound in popular discussions about roasting profiles, among others. Perhaps the confusion surrounding the "drying phase" goes well beyond the fact that EOD is simply a misnomer. It would seem that the misnomer itself provides a convenient excuse to shy away from discussing the complex roasting chemistry occurring deep inside the yellowing greens - beans that still contain over 80% of their moisture as their BMT approaches 300F.

Rich, you are a proficient roaster, and you are familiar with the styles and techniques used by some of the top roasters around. In light of the above, might you be in a position to shed light on the origin of the term EOD, and perhaps even provide insights on how this misnomer has managed to find a niche in the parlance of commercial roasting?

Ciel
Ciel... seeking Heaven in my cup with ................................................................................................................. EXPOBAR Brewtus II - MAZZER Mini E - MAHLK�NIG Vario - GeneCafe - RAF-1 Extreme (Modified B-2 HOTTOP) - BellaTaiwan XJ-101
boar_d_laze
I'll give it a shot, but bear in mind that this is highly speculative. My sense of it is that roasting jargon evolved when coffee roasting incorporated electronic telemtry and datalogging.

In the dark ages when everyone roasted without BT telemetry and datalogging software -- until about the turn of the century -- many if not most professional roasters considered the entire interval from charge to 1stCs as "drying." And of course, since it's true that drying continues through the entire roast period, if you ask people (like pros) who've given it a lot of thought, they still think in those terms, even if that isn't how they communicate or mark their logs.

By way of context, there weren't very many amateurs then who were even that sophisticated. We were a few years behind the pros when it came to telemetry.

When good telemetry and datalogging software hit, craft roasters learned to more tightly control profiles by ramping at particular temperatures rather than visual and aromatic milestones.

Then, when Artisan went online, it contained EOD as a descriptor, and everyone started using it to mark the beginning of "Ramp."

With telemetry we were able to anticipate more accruately, too.

So, 300F became "EOD and crank the gas," instead of "yellow cat face (which occurs at around 325F) and crank the gas."

And with better anticipation, realtime logging, and better telemetry we could hit all of our milestones within a few seconds of our ideal plot.

And since roasting on purpose is the idea, that's a good thing. We owe the people who developed the good software -- including Markos, Arpi, and Ira -- a huge debt.

If you want to get a sense of the evolution of roasting vocabulary you should subscribe to Roast and look into the archives, especially at articles by Willem Boot describing how to roast varietals.

Also, talk to people who don't use BT telemetry or realtime plotting and you'll get an entirely different sense of how to conceptualize the roast.

Rich
USRC 1lb Roaster, Chemex+Kone, Espro, Various FPs, Royal Siphon Vacuum, Yama Ice Drip Tower, Bunnzilla, La Cimbali M21 Casa, Ceado E92.
CookFoodGood
RAG
Time to do some experiments but I don't expect to learn anything new as I have learned to trust Ciel's work. I find it perplexing that the 2016 SCAA Expo presentation titled 'The art and Science of Roasting" by the VP of Probat/Burns seems to contradict these findings if I read it correctly.

"300F all free water has been evaporated"

The slide that shows a graph of moisture content vs. bean temperature shows no significant moisture loss until bean core temp reaches about 210C (410f).

I'm glad Ciel's data is not this confusing.
Edited by RAG on 12/23/2016 9:54 AM
oldgearhead
SCCA probably used oven-dry tests instead of batch weight for the data.
I use a %M grain meter to determine the moisture content of a batch of new greens..I have found green beans between 6% and 13% before roasting. A fluid-bed roaster probably drys quicker than a drum because of the higher air-flow rate. In grain drying increasing heat or CFM will affect drying speed.
No oil on my beans...
BenKeith
I guess this old, dumb country boy ain't scientific enough to really understand or care about getting that deep into the technical terms of coffee roasting. I have a couple of basic goals when roasting beans and don't have a clue what you call them, other than roasted coffee beans when I'm done.
If I'm doing a light roast just to the end of FC, my set procedure to start with is I want to see a bean temp of 300F in 4:00 minutes. I want to see the deepest yellow in 5:00 minutes. I want to start seeing tan in 6:00 minutes and FC in 9:30 minute with the end of the roast coming at 11:45 minutes. All of these are very precisely controlled so I can then go back and make adjustments in 15 second intervals to these times when/where I think I need it.
That's the total extent of my technical understanding and approach to roasting coffee beans. People talk about the mallard phase, hell, to me, that's just a duck I like to hunt.
Seeing how I'm the only one I have to please with my coffee, I seem to get away with that approach pretty good, however a lot of people say I make some dang good coffee.
coffeeforblood
BenKeith - I have to agree with you that I am much more of a holistic roaster, meaning, "is the end product good?. Yes. Then let's move on." In my mind life is far too short to spend hours contemplating splitting hairs on what to call a particular phase of roasting, but that's just me. I know some people live for the minutiae, but I have lots of other things on which I would rather spend my time. Could I roast even better coffee if I paid more attention to details? Maybe, but since what I produce right now is pretty good to my palate, I am not going to obsess over the process unless I run out of things to do. I am a scientist and very detail-oriented by nature, but I am also very intuitive (Myers-Briggs ENFP), so I do a lot of things "by feel" rather than by endless collection of data.
BenKeith
Well, I do pay very close attention to the details as for the times and temps at each phase of my roast, and I'm paying close attention to the smell as it's going through these key points. Unlike these professionals that might do a dozen roast a day and stay very tuned in on what the roast is doing, I normally only do a couple of roast a week, so I have to depend on heavily on PID and computer control and my little notes I make during the roast. Then when drinking it, I go to a compass type chart one of the guru's published and see where I need to change it based on something I liked and want to try to enhance, or something I didn't like and want to try getting ride of. I have found 15 seconds makes a noticeable difference. I found I would go right by a specific flavor I wanting to enhance if I tried making 30 second adjustments. Much less than that, and my old dumb taste buds can't tell a difference. Plus, I can't find that many flavors others describe anyway, so I'm usually just working on one area at the time. Earthy flavors from under developed roast is one I can't stand and pretty quick to get rid of.
coffeeforblood
Actually, I depend on what my Chem. E. colleagues call "process validation ". That is, one establishes very firm conditions and maintains those conditions and then the results of the process should be (and typically are) very reproducible. In my case, the geometry of the system is fixed, the air flow is fixed, the bean load is fixed and the inlet air temperature is fixed (to within a couple of degrees). This results in very consistent roasts. Now, bean to bean variation (especially moisture content) will certainly have an impact, but moisture content of green beans should not (at least in theory) have a huge range and can be "adjusted" by storing beans under constant, known humidity conditions if one is so inclined. I can alter the roast profile by changing air flow, inlet temperature and bean load.

I am surprised to hear you say that a 15 second adjustment makes a difference to you. I wouldn't think that the bean mass would react that quickly, but if it makes a difference to you, that's all that matters.
BenKeith
I guess I just thought I had some dumb taste buds. I find a 5-7 degree difference in bean temp enough to make a noticeable change in flavor
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