Thermodynamics of First Crack... Continued

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
archipelago

Postby archipelago » Jan 07, 2019, 2:37 pm

Roast just came out with this piece by a chemical engineer that measures moisture loss during roasting — https://www.roastmagazine.com/articlepreviews/janfeb19/BakedBeans/.

Back on the question of 'what is baking?' as well as the cause of the 'crash' at first crack — this seems to support the notion that the phase change from liquid to gas is one of the mechanisms responsible for what Illy described as 'endothermic flash' at first crack. By staging our heat to manage that event we can control the environment and rate of phase change to prevent cooling/stalling/baking in the roasting environment.

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jammin

Postby jammin » Jan 07, 2019, 4:44 pm

That's pretty much exactly what I said in follow up to the key note thread. I agree, the energy required to change phase is a logical explanation.

And thank you for posting this!

crunchybean

Postby crunchybean » Jan 07, 2019, 11:33 pm

Now that's a lab write off I can get behind! :wink:

EddyQ

Postby EddyQ » Jan 07, 2019, 11:41 pm

I really like the work done here. Almost unbelievable accurate results with regards to computing how much water escaped and when through a roast.

I would like to have seen his BT RoR plotted with the drying curves. I think we all believe there is a "crash" where the drying rate peaks. But, we don't know. And if he was able to reduce a crash with greater release of moisture prior to FC by altering either heat, air or time. Of coarse, I am assuming a crash = baked as Scott Rao says. (I realize baked could be when a roast stalls)

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jammin

Postby jammin » Jan 07, 2019, 11:59 pm

^EddyQ I think you raise a valid question with your assumption: does crash = baked?

I will say no, at least not directly. I believe the baked aspect comes from the recovery induced by the crash. Momentum is lost & target finish is pushed out... at the worst time. Stretching out the development phase without any tangible power going to beans when they're all dried out is a bad fork in the road leading to baked or too roasty

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MaKoMo

Postby MaKoMo » Jan 08, 2019, 1:34 am

EddyQ wrote:I really like the work done here. Almost unbelievable accurate results with regards to computing how much water escaped and when through a roast.


Isn't propane releasing moisture on getting burned and thus messing up all this precise calculation?

home-roasting/combustion-of-propane-effect-on-total-water-content-t26695.html

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yakster

Postby yakster » Jan 08, 2019, 4:10 am

They used an electric roaster.
-Chris

LMWDP # 272

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MaKoMo

Postby MaKoMo » replying to yakster » Jan 08, 2019, 4:30 am

Oh yes. I just see this now. Sorry. So it might get difficult to transfer those results to a propane powered roaster.

archipelago

Postby archipelago » replying to MaKoMo » Jan 08, 2019, 1:13 pm

There's nothing to transfer here, I think — the principles at work will be operating in any roasting environment — but the deltas may be slightly different. Our conclusions remain the same about moisture loss and volatilization

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jammin

Postby jammin » Jan 08, 2019, 3:49 pm

archipelago wrote:There's nothing to transfer here, I think —


Not entirely. Water is one of largest bi-products of combustion so you'd need to know how much gas you burnt & subtract accordingly