Phases of roast, Colour changes, how do you interpret them?


#1

I have been thinking hard, and trying to read a bit during Christmas. And, I think it would be good to discuss how we interpret those, where we separate them, and ideally come to a common language and understanding.

For you @deven.patel411 I have this question, as you mentioned many times those distinct phases and clean separation of them - is what you mean by that just that in the process of colour changes all the beans are aproximately of the same colour, or do you mean to create a plateau of the colour extended in time, and then a faster shift into another phase?

For me it is about a gradual changes but most of the time the beans are very close in colour. Yet, its pretty hard for me to say, now its yellow, not its golden or brown … its a gradual change and I not see a sharp point in time to mark as - now this one happened, its all sort of plus minus around here, so thats also a reason why I do not write those numbers down. They are +/- 10s at least where I could put them, depending on what exactly I call brown …


What have I done wrong?
#2

To start off, nothing in the chemical world is like an on/off switch, everything is a gradient. First it starts, then it peaks and ends. and often times the ends and beginnings get blurred. If you look at distilling alcohol (or any purification/distillation through evaporation) there is a window of optimal output. For alcohol its called cutting the head, heart and tail. For coffee its the pale, yellow, brown. We can subdivide this further by making distinctions like calling a certain segment gold, or milk chocolate and dark chocolate, etc. for clarification. But there will always be some parts of the transition that aren’t so clear, a good roast (maybe, maybe not, this is my theory) will minimize the duration of the unclear phases. When I write down my notes even though I list: yellow @330*F, 2:33 (random numbers) that is when the majority of the beans transitions from pale, to yellow and that mark is the beginning of the yellow phase which lasts until I mark the next phase.

If I create a “plateau” (which it’s not, because remember there is a definite differential between the input temp and the bean temp. Meaning the beans are still increasing temp, just slowing down the rate the temp of the bean is increasing). My thinking is that, I am extending the time of the phase I want because more of what that phase produces or reduces will be made available or knocked out for the next phase and end result.
So if I want to extend yellow I am making the final product less acidic. And if I slow the brown, I am trying to break down the starches and cellulose, proteins etc. creating more body. sweetness…When and where all these chemical reactions actually take place and convert to I am unsure yet. But there’s the general gist of it.

EDIT: I mean to say “killing sweetness…”

Then the answer is obvious, you are not able to get a clear visual of the color changes. Yes there is some discrepancy of shades of yellow and there will be a small window of “hard to tell” transition. But for the majority of the phase it should be clearly a color. You should not question what color it is, some beans may be a little light or a little dark but overall you should say it is fairly distinct. To reiterate, I mark the time/temp during the transition between pale and yellow when I feel the majority in that +/-10s window, has turned from pale to yellow, and I call that the beginning of yellow. You can create your own markings too you just have to be clear when relating your information to other people and call it at your markings every time for consistency.

If the end product is uneven and I don’t mean on the outside of one bean (well I do a little), but also mainly for this roaster, if the insides of the beans are really different from one another. Then the beans were not roasted evenly. My guess is because the beans were not able to get enough contact with one another to either, absorb or dissipate the heat it collected from the air or drum wall.


#3

Great, so it seems I was on the right track … if I ignore the phase when I am not sure if it is allready that other colour or not, then there is a moment when I am sure … all the beans are about that colour, its just that a moment before that its also like that, and a moment before that maybe too, its a bit hard for me to,say now! And not think I should have said it 10 s ago :wink:

Also perfectly explained that extending of one or another phase - I just was not sure which of the possible versions are you talking about. Now I know exactly what you mean.

On phase that I am having problems with, is that pale … from my POV the beans are green, and then they are yellow (and then golden/orange, then caramel/lightbrown, then brown) these phases or colour are nicely visible. But I have yet to find what that pale is, and how is it different from the green or yellow. I understand it should be different from both, but … not able to cleanly identify it, even on the long A profile…


#4

If it helps, I’ve noticed a step I call “olive” and it’s right before pale. I think it’s part of the paling process, but when just the edges have started to pale and the center of the bean looks almost darker it’s “olive.” Looks kinda like the color of a green olive. From there, the ikawa does tend to race past the typical white paling stage into yellow. I used to try to hit pale around 1 minute in my popper and the bean temp was around 200 F. I don’t typically stretch that phase out as much on the ikawa and so pale becomes less distinct. Its also a little harder to see and depends on what kind of light you’re using (yellow light, yellow beans). Some say the only effect of the paling stage is reducing moisture content. My guess is that lower initial moisture makes beans slightly easier to roast, like more suceptible to heat, but I don’t know. Anyone have any ideas about the effect of extra paling versus minimal paling?


#5

Yes absolutely! Boot had an article stating as much and I just use the same light every time for consistency.

As for the pale, again I agree with what you said, I think that it is mainly just setting up the bean to absorb heat evenly. I’ve noticed some correlation with a clearer pale and a more even result. (Again more testing required)


#6

Yes, It would help if I had fullspectral source of light for this, but I use strong led headlight, just above the glass. So a lot of light inside, but it has holes in the spectrum as all the leds do.
My plan it to get or make a ring light, and use some camera with fixed whiteballance to get the picture, and do the averaging to see how the colours change.


#7

I accidentally made a new thread and can’t delete it… @Geoff_IKAWA if you would be so kind.

http://community.ikawacoffee.com/t/color-based-on-temp-cooking-based-on-time/240?u=deven.patel411

I have also notice that I can get 1c after 6:00 in the range of 465-485F (240-251F). Has this aligned with everybody else’s observations?


#8

I’m noticing yellowing beginning consistently just past the 200C mark irrespective of time.
I’m assuming it is the end of the drying phase and how long it takes depends on the first stage of the profile.
Do you think the beans have reached different stages of development between a faster and slower start when they get to yellow?
I’ve also noticed FC beginning before 6min at in the 240-250C range depending on the profile.

How long on average does FC last? At what point are you taking it? I’m noticing somewhere around 45sec between the very first and last crack but I have had some longer ones as well.

It might be useful to get an idea of how a profile splits between drying,maillard and post FC development.


#9

I am having usually between 30s and 1:10 between first and last crack of 1st

depends on bean and profile a lot.


#10

Yes that is true, can be pretty variable. Even another batch of the same bean might not crack at precisely the same point.
At what actual time point then is FC on the profile? From the point of saying that the roast had x % post FC development time


#11

Not sure about that - I think its a bit more clear with the big roaster when there is a lot of beans popping, with those 50g it is not so many pops. I started to ignore the first and last one … and I think of the development time as the time after the crack ends (not the last pop but the one before … ) but … not very precise … meh


#12

I would say about the same, I don’t have my notes on me now so I won’t be certain until I look them over.

I agree

yea that pretty much is my conclusion

That’s because most of the roasts are inaccurate, umbrella profiles. Beans will not crack at the same point they will crack at the same(relatively) temperature, how evenly or how well encompassing the profile is suited for the variety of beans being roasted will determine this.

I note first crack when I hear the first one, 1C is always, like in every phase, a range that the phase takes place. Pale, yellow, brown, 1C, 2C all happen over lengths of time and % of entire roast. They are noted as such.

Maybe check out fruit for thought again, not all the articles and stuff are very heavy, I just posted another quote that would help. Fruit for Thought: A Library of Resources


#13

Hey deven, I just deleted the thread you mentioned!


#14

At first I thought you meant “fruit for thought” and my heart almost shattered. But then I realized, so thanks, it is much appreciated.


#15

What temperature ranges do you notice when the phases and color changes take place?