Roast and Learn Together - May 2014 - Page 2

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
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Boldjava (original poster)
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#11: Post by Boldjava (original poster) »

Roasted this morning. Both seam and quick movement to 1C (9.00) suggest lower elevations than fifty three hundred feet as stated. Will cup 3 days with roasting data on the Gene.

22 lbs remain.
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fu11c17y

#12: Post by fu11c17y » replying to Boldjava »

How about weight loss? Just curious.

From my (in)experience, higher elevation, or fresher crop (higher moisture content?), gives me a faster time to 1C, given all else being equal. I think of these beans as catching momentum more easily once they get going.

Not sure if that's true, just wanna see what you guys think.

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Boldjava (original poster)
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#13: Post by Boldjava (original poster) »

fu11c17y wrote:How about weight loss? Just curious.
Will weigh them out. Invalsa said, "all the micros are current crop"
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TomC
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#14: Post by TomC »

fu11c17y wrote: From my (in)experience, higher elevation, or fresher crop (higher moisture content?), gives me a faster time to 1C, given all else being equal. I think of these beans as catching momentum more easily once they get going.

Generally speaking, it's the exact opposite. With exceptions for certain oddballs like Geishas that have a wide, open center cut that allow heat to penetrate easier and faster. The higher the altitude, the cooler the evenings, means the slower development of the cherry, which means a denser cherry, which means it takes more heat imput to get to 1C. Moisture content follows along that same algorithm.
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Boldjava (original poster)
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#15: Post by Boldjava (original poster) »

17 lbs remain.
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fu11c17y

#16: Post by fu11c17y »

TomC wrote:Generally speaking, it's the exact opposite. With exceptions for certain oddballs like Geishas that have a wide, open center cut that allow heat to penetrate easier and faster. The higher the altitude, the cooler the evenings, means the slower development of the cherry, which means a denser cherry, which means it takes more heat imput to get to 1C. Moisture content follows along that same algorithm.
Thanks Tom for your explanation. I also found similar info from here:
http://bootcoffee.com/wordpress/wp-cont ... _Mar04.pdf

I gotta review my roasting logs.

fu11c17y

#17: Post by fu11c17y » replying to fu11c17y »


I guess I"m still not comfortable with what I'm reading from Boot and what I'm seeing on my own logs. Let's say, given the same bean, but it's gone stale. I give it the same amount of heat as before. Why I should believe that the stale bean will get to first crack faster. I guess it depends on many factors.

Let's say the stale beans have 8% moisture, and the fresh ones have 13%. Same weighted batch gets charged in the roaster. That means the fresh batch would have 5% *less* bean mass to start with. To me, once the bean temp is sufficiently above boiling temp, say after drying stage, with sufficient amount of air flow, the batch with less bean mass will raise toward FC a bit faster... Right??

So Boot keeps saying the bean with higher moisture content will require more heat input, and he kept saying it's especially true during drying. Now while I agree that the fresher bean should be dried a bit longer, it doesnt necessary mean that it will get to a certain temperature target (say 300F) slower given the same amount of heat. If so, it would imply that the 5% (diminishing) moisture is a poorer heat conductor than the 5% bean mass. I cant seem to accept that's the right assumption.

Likewise, for denser, higher grown beans, I think of them as better heat conductor. Assume there is no bean mass difference from a lower-grown less-dense beans (spongier if you will?) when you start with the same weighted batches. The lower grown beans would not conduct heat as well because the cell structure is not as densely packed. I'm sure many of you have experienced the effect of applying high ET heat to a bean and yet the bean has a hard time ramping up (after drying, for example). At the same time, for example, when I roast an Indonesian bean, FC comes at a higher BT probe reading. This is because, I'm guessing, heat transfer takes a bit more to get to the bean center, so the temp difference is higher between the bean exterior (where the probe reads) and the bean interior (where FC gets started) for a lower grown bean. This is also the reason why Brazils and Indonesian beans are better roasted longer, because we dont want ET to be higher than necessary for the BT to follow your target RoR.

Why does all this matter? For me I want to know why from time to time, I cannot replicate a roast on the same bean but from a different lot or date. I also want to know how to tweak a roast when I dont like something about it. It helps me to think of how heat is transferred to the bean in the best way I want it to. Or maybe I just like to know how roasting works. I know I"m not amongst the most experienced roasters here, and everything I stated was just based on my assumption. But I hope to open up dialogue.

Feel free to chime in. I feel like I'm rambling again.

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PacMan

#18: Post by PacMan »

Did a quick, literally and figuratively, roast of this in my P1 (fan and heat separate w/ dimmer and router speed control, respectively). Been messing around with different configurations on the roaster and I think my BT probe was a little out of whack because I was hitting 1C a lot faster than I was expecting. I did a 125g batch and it went super fast. Dumped it ~1min into 1C at 8min. Will try it in a day or so and roast a few more batches this weekend. Hopefully I can get a handle on the roaster and bean in a few more roasts.


**Edit**

Forgot to add that from the 125g in I got 107g roasted out.

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TomC
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#19: Post by TomC »

No, sorry, you're wrong on many points
fu11c17y wrote:I guess I"m still not comfortable with what I'm reading from Boot and what I'm seeing on my own logs. Let's say, given the same bean, but it's gone stale. I give it the same amount of heat as before. Why I should believe that the stale bean will get to first crack faster. I guess it depends on many factors.

Let's say the stale beans have 8% moisture, and the fresh ones have 13%. Same weighted batch gets charged in the roaster. That means the fresh batch would have 5% *less* bean mass to start with. To me, once the bean temp is sufficiently above boiling temp, say after drying stage, with sufficient amount of air flow, the batch with less bean mass will raise toward FC a bit faster... Right??

Wrong, the mass is the same if you've charged the same weight (as you've stated), they just have less moisture and will race thru the first part, the drying phase quicker. So there's no consideration for the "batch with less bean mass" since the correct term is the batch "with less moisture" heading to FC faster

So Boot keeps saying the bean with higher moisture content will require more heat input, and he kept saying it's especially true during drying. Now while I agree that the fresher bean should be dried a bit longer, it doesnt necessary mean that it will get to a certain temperature target (say 300F) slower given the same amount of heat. If so, it would imply that the 5% (diminishing) moisture is a poorer heat conductor than the 5% bean mass. I cant seem to accept that's the right assumption.

Yes, it does. It requires either a hotter charge or a longer drying phase, one of the two, when compared to a similar bean with less moisture. You have to drive off a large majority of free water ( but not all of it) before you are creating steps beyond the dry hay aroma in the roast process.

Likewise, for denser, higher grown beans, I think of them as better heat conductor. Assume there is no bean mass difference from a lower-grown less-dense beans (spongier if you will?) when you start with the same weighted batches. The lower grown beans would not conduct heat as well because the cell structure is not as densely packed. I'm sure many of you have experienced the effect of applying high ET heat to a bean and yet the bean has a hard time ramping up (after drying, for example). At the same time, for example, when I roast an Indonesian bean, FC comes at a higher BT probe reading. This is because, I'm guessing, heat transfer takes a bit more to get to the bean center, so the temp difference is higher between the bean exterior (where the probe reads) and the bean interior (where FC gets started) for a lower grown bean. This is also the reason why Brazils and Indonesian beans are better roasted longer, because we dont want ET to be higher than necessary for the BT to follow your target RoR.

To your first point, put a large sponge and a large, completely dry lump of clay in an oven at 300°F put thermocouples in the center of each one. Tell me which one gets to 300°F in the center faster. There's your explanation.

Why does all this matter? For me I want to know why from time to time, I cannot replicate a roast on the same bean but from a different lot or date. I also want to know how to tweak a roast when I dont like something about it. It helps me to think of how heat is transferred to the bean in the best way I want it to. Or maybe I just like to know how roasting works. I know I"m not amongst the most experienced roasters here, and everything I stated was just based on my assumption. But I hope to open up dialogue.

Because green coffee is a living, organic complex compound that's constantly changing. The same bag of greens, if you split it up and roasted it in 20 batches, all with identical profiling software capabilities, even if you could control the exact same environment conditions in which it was roasted ( ambient air temp, barometric pressure, humidity etc), would still yield subtly different results because of the changing aspects of coffee. It's not a inert, stable material.

Feel free to chime in. I feel like I'm rambling again.
Red added by me to emphasis points.
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fu11c17y

#20: Post by fu11c17y »

Thanks for your time, Tom. :-)
At least I know I still got a lot to learn.