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Drying Phase Curve
allenb
best post

I'm sure most of you seasoned roasting vets are well aware of the right and wrong way to take your coffee through the ambient to 300 first phase of the roast but for the new to roasting folks I thought I'd give a couple of pointers.

During the so-called drying phase of the roast we're trying to take the beans from room temperature to around the 300 F mark (150 C) in somewhere between 4 and 5 minutes. During this phase we're trying to rid the beans of as much free H20 as possible so that during the roasting phase we're not ending up with a well done outer layer and rare interior which would give us that undesirable grassy taste.

Unfortunately there's more than one way to get the beans from room temp to 300F and some ways are detrimental to proper development. As many have pointed out over the years, there's not much happening prior to the beans hitting over 200F and more like 225 to 250F.

Lets say we don't hit 225 till minute 4 and then pour on the heat trying to get to 300 by minute 5? With this curve we've preheated the beans for 4 minutes but only allowed real effective moisture removal for 1 minute. This is not the way to dry. We want to pour on the heat at the start so we're getting to 200F around the 2 minute mark which will give us a rate of rise of around 50 to 65 degrees/min. At this point we want a slightly slower rate of rise getting to 250F and taper off from there to allow hitting 300F between minute 4 and 5 depending on your preference.

If your roaster isn't capable of achieving a bean temp of 200F by around 2 minutes then I would suggest stretching the drying phase longer allowing more time at temperatures capable of real drying.

I want to note that none of this is carved in stone and depending on your roaster, altitude, bean moisture content etc. might require variations of what I've posted above.

Allen
Edited by John Despres on 02/04/2013 6:53 PM
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
snwcmpr
Thank you Allen
--------------
Backwoods Roaster
"I wish I could taste as well as I wish I could roast."

As Abraham Lincoln said "Do not trust everything you read on the internet".
Lylabrown
Thanks for this Allen.
I've been tinkering with this phase of the roast recently. The best results in-the-cup seem to correspond with the beans undergoing the color change from yellow to amber at the 5min mark. Which is around 320*f "E" temperature on my roaster.

Have you noticed a specific bean color at 4-5 min that yields better results in the cup?

Russ
allenb
Howdy Russ,

No I haven't really paid that much attention to the shift in color other than when it goes from deep green to yellow which is around the 5 minute mark for me. I'll keep tabs on it from now on for the yellow to amber and see what the BT is.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
oldgearhead
I treat drying green coffee just like drying 28% corn;
Take to 230F (BMT) with good air flow and hold it there for 2 minutes...
No oil on my beans...
Gregman
This is the single best thread I have read recently.

That is a very helpful parameter for the drying phase.
I had always thought the intent of the beginning of the roast
to be gentle or light on the bean and then end high.
But that curve suggests higher at the beginning than throttle down for drying.
Then race to first crack.

Of course on a GC its different than you suggest Allen.
My GC does not have the power to go from green to yellow in 5 min.

I tried this idea today and it seemed to work very well.
For the longest time ive had these sour/grassy flavors in my roasts.
I think you just solved my problem!
Greg-
Well now........ that's not suppose to happen!
smico
Thank you Allen. Your drying targets concide with mine. 2 minutes for high grown and 3 for lower grown.
I was struggling with occasional green taste until I started dropping beans at higher temperatures in my Hottop. During first two minutes most of the heat transfer is from hot drum to beans. Due to only 650 W only other way to achieve such ROR is to lower batch.
Miroslav
Hottop B2 + HTC, Cremina 83, OE Pharos, Brewtus IIIR, Baratza Vario
Steve Egge
Thanks for the great explanation of this phase of roasting. . I have been wary of using too high of temps at first but now realizng how much the bean temp lags behing the reading I'm getting of the average temperature applied to the bean in the Gene Cafe. I stopped my roast drying phase on some beans I had bought to take temps on and not roast (cheap beans) after 300 x 5 minutes and the temp of the beans with a thermoprobe was 217. Think I'll try a higher drying temp next and try to nail this phase down as you have set forth.

Steve
Santoker Rev 500, Baratza Vario-W, HG-One, Bunn Trifecta MB, AeroPress, Londinium I
John Despres
It's interesting that after all this time no one has really addressed this subject.

We grow.

Thank you, Allen!

John
Respect the bean.
John Despres
Fresh Roast 8, Gene Cafe, JYTT 1k, Quest M3, Mazzer Mini, Technivorm, various size presses and many more brewers.
allenb
Everyone thanks for the thanks!

An additional note on this subject,

While the curve I've posted can probably help quite a few who are dealing with under-development issues, I want to also say that there are certain roasters that cannot and do not need to move this quickly to a bean temp of 300F and have no problems achieving excellent roasts. I have personally had awesome coffee from roasters that didn't hit the 300's till 8 + minutes so there's no hard/fast rules here.

Keep experimenting and as John say's have fun! BBQ grill

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
jedovaty
A frustration I'm experiencing is how some beans hit 300F more or less quickly than others, and small tweaks seem to have no affect on this.

Once you know which way it goes, what is the first variable to try to change: heat applied, or start temp in the roasting chamber? (assuming solid drum roaster)
Gregman
That's exactly what I have been experiencing Allen.
My beans will not hit yellow until way after 5 min.
However the resulting coffee smells and tastes miles better!

Before I would do a 3 min (premature drying) then crank the heat and had
the beans change light brown by 8- 10 min. But the resulting coffee was not great, still good but not GREAT. So what's the point of that?

We roast at home because it's better. If that ever stops I'm going to buy my beans and coffee at the local roaster.

Greg-
Well now........ that's not suppose to happen!
allenb

Quote

jedovaty wrote:

A frustration I'm experiencing is how some beans hit 300F more or less quickly than others, and small tweaks seem to have no affect on this.

Once you know which way it goes, what is the first variable to try to change: heat applied, or start temp in the roasting chamber? (assuming solid drum roaster)


In my experience with drum roasters, raising the start temp alone will only speed up the rate of rise during the first minute or so. When I've had trouble getting some dry processed coffees to hit the 300 F area in around 5 min I usually up the power level. Of course there's a limit to how much additional power you can apply without scorching or causing other damage to the beans exterior. I used to think that my dry processed beans that required pedal to the metal was due only to higher than normal moisture content but one of the ones i'm remembering was slow to climb even 4 months later when I'm sure it had dropped in moisture content substantially. I would try a little of both but if it's only a 30 second variance or so I don't know if it would need to be corrected for and if it would be noticed in the cup.
Just another one of those coffee mysteries!

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
allenb

Quote

Gregman wrote:

That's exactly what I have been experiencing Allen.
My beans will not hit yellow until way after 5 min.
However the resulting coffee smells and tastes miles better!

Before I would do a 3 min (premature drying) then crank the heat and had
the beans change light brown by 8- 10 min. But the resulting coffee was not great, still good but not GREAT. So what's the point of that?

We roast at home because it's better. If that ever stops I'm going to buy my beans and coffee at the local roaster.

Greg-


So are you now extending the drying time and total time to light brown with improved cup?

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
Ringo
High grown beans are much harder to get take heat and need higher temps to get the same drying time. Low grown soft beans just suck up the heat fast and will burn. The moisture of beans also change the heat needed for drying. Old beans loose moisture as they age and need less drying.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
Gregman
Absolutely Allen,

My drying time was 3 min at 300 but it was not sufficient.
Now my drying depends on the bean but goes something like.....
350f to drop in for 1-2 min. Then I turn the heat down to 300 an wait.
After 5-8 min when a good portion of beans have displayed yellowing I crank the heat to 400. The total time from green to browning is something around 10 min.

And the cup you ask, is it improved? Night and Day!
I don't even recognize some of the coffees I've roasted!
New flavors, nuances, sweetness, peak times its amazing really.

Also after a few days I open the air tight lid an poof a coffee fart.
The other thing I noticed was the smell of the whole beans is better.
It even seems as if the bean size has puffed out more?

I greatly dismissed the benefits of a proper drying phase.
But I'm a believer now.
Well now........ that's not suppose to happen!
jedovaty

Quote

Ringo wrote:

High grown beans are much harder to get take heat and need higher temps to get the same drying time. Low grown soft beans just suck up the heat fast and will burn. The moisture of beans also change the heat needed for drying. Old beans loose moisture as they age and need less drying.


What you wrote sounds counter intuitive, but dissecting it further makes sense to me? BT will rise more quickly with a bean that doesn't take heat, whereas those that absorbe the heat will take longer to dry. That would explain why some get through drying in 3-4 minutes, versus others that take 5-6 in my setup using the same heat power. Aha??

Then take it a step further for me please. In my drum setup, I can not only control airflow, but also block the escape of water vapor to some degree (i.e. seal the drum somewhat). I believe water has a high specific heat. I'm having trouble putting the resulting concepts together now - if I block water vapor during drying, would that slow down or speed up BT? It seems it should slow down, because the moisture cannot escape and so more heat is forced to be absorbed?
Ringo
This is what I think, and only think. I am still working on this myself. I believe the more air speed gives gives you more convection heating and less radiant heating. I believe this gives you more heat transfer to the bean with the same temp. I think early on radiant heat is good, with more moisture in the bean the heat soaks deep into the bean. I have cupped coffee dried with higher air in drying and med air and low air, the lower seems better. I preheat my drum to around 260 deg, to store radiant heat them drop in the beans with the air low for the first min. After 1 min I increase the air a little to get the moisture out of the drum. Then I never touch the air setting, controlling the heat is all I can handle. Trying to hit my target times 5 min drying, 5 more min till 1st crack, 2.5 to 3 min after first crack.

If I increase air speed during a roast the Rate of Rise will go up but the quality of the roast goes down. When I built my drum I read a lot of commercial drums are now designed with much higher convection to radiant heat than the older ones, gives a brighter coffee. I read somewhere that the goal was 85 % convection. So I put in big stirring veins to throw the beans in the air and also a lot of air going through the drum. I started roasting on the drum and the coffee from my behmor was better. I started closing the air way down after a min and my coffee was much better, bigger flavor, more complex and better acidity. Its now better then the behmor. This still make no logic to me, but I know it works. So long explanation too say do two roast of the same bean and only change 1 thing, cup the coffee and look for differences. Have friends try it and tell you which is better. My son has a much better plate than me when he comes home we have cuppings, he tells me the better one. Sometimes do three cup, two are the same one is different, can you pick out different one. If you ask me next month how I am drying I may give you a different answer, i keep trying new things cupping the coffee and changing how I roast. One reason I love this hobby it keeps my guessing.

One more thing and I will shut up, the difference between high grown and low grown beans is the density of the bean itself. A kona or a brazilian is like a sponge, less meat for the heat to get through so it heats fast and can burn. A Costa Rican is like a little rock, it loves lots of heat early and needs it to dry.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
Ringo
I have to say also more often than not life is just too busy to play with roast profiles. I just need to get coffee roasted and have no time to cup the results. This is ok because its just a hobby. So have fun, learn when you have time. The last post sounded like I cupped every time and changed profiles every time I do not.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
allenb

Quote

Gregman wrote:

Absolutely Allen,

My drying time was 3 min at 300 but it was not sufficient.
Now my drying depends on the bean but goes something like.....
350f to drop in for 1-2 min. Then I turn the heat down to 300 an wait.
After 5-8 min when a good portion of beans have displayed yellowing I crank the heat to 400. The total time from green to browning is something around 10 min.

And the cup you ask, is it improved? Night and Day!
I don't even recognize some of the coffees I've roasted!
New flavors, nuances, sweetness, peak times its amazing really.

Also after a few days I open the air tight lid an poof a coffee fart.
The other thing I noticed was the smell of the whole beans is better.
It even seems as if the bean size has puffed out more?

I greatly dismissed the benefits of a proper drying phase.
But I'm a believer now.


Wow, sounds like you've hit pay dirt! Now I'll bet you'll be itching to get your hands on some other coffee's to give them a whirl.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
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