Thermodynamics of First Crack... Continued

#1: Post by **archipelago** » January 7th, 2019, 1:37 pm

Roast just came out with this piece by a chemical engineer that measures moisture loss during roasting - https://www.roastmagazine.com/articlepr ... akedBeans/.

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.

#2: Post by **jammin** » January 7th, 2019, 3:44 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!

#3: Post by **crunchybean** » January 7th, 2019, 10:33 pm

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

#4: Post by **EddyQ** » January 7th, 2019, 10:41 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)

#5: Post by **jammin** » January 7th, 2019, 10:59 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

#6: Post by **MaKoMo** » January 8th, 2019, 12:34 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

#7: Post by **yakster** » January 8th, 2019, 3:10 am

They used an electric roaster.

January 8th, 2019, 3:30 am

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

January 8th, 2019, 12:13 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

#10: Post by **jammin** » January 8th, 2019, 2:49 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