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Discussion about first crack
allenb
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Posted on 01/21/2023 6:22 PM
I'm sure many of you have heard comments from commercial roasters who say they finish first crack in the cooling tray. During my time at a commercial roastery, we often would end roasts when 1C was still well underway and the crackling sounds could be heard throughout the roasting and production floor. This would consistently occur whether it was a light roast or a light-medium roast.

When roasting in my 1 lb gas fired drum roaster, even with a fairly aggressive RoR at first crack during a very light roast and with a minimum air flow through the cooling tray, I may hear one or two pops at best immediately after dumping. So why the big difference between a larger batch size versus my 1lb batch in the amount of first crack activity besides the obvious larger number of beans? I'm always very careful to keep cooling tray airflow to a bare minimum to prevent excessively fast cooldowns. i also noticed this to be the case when visiting small roasteries using 12 kilo drums with lots of airflow across the cooling tray beanbed.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
renatoa
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Posted on 01/22/2023 1:17 AM

Quote

...with lots of airflow across the cooling tray beanbed.


Could this be a hint ? More oxygen, intensify burn, and a last breath... producing crack.
Maybe your cooling tray is the culprit...
 
allenb
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Posted on 01/22/2023 7:57 AM
That's an excellent theory and sounds plausible but I've had the same results whether I'm running lots of air across the bed or very low airflow.

The reason this is a concern of mine is this. One of the roasteries I used to frequently visit in the 1990's who produced stellar coffee on a consistent basis focused on ultra light roasts. They were doing what would be considered "third wave" very light roasted coffees with a perfect balance between body, acidity, sweetness and lots of bold origin notes well before anyone had thought of third wave as a concept.

When chatting with the roaster during many of his roasting sessions, I noticed that first crack was audible and very aggressive and easily heard from outside their Probat L12 drum roaster. This went on for at least 30 seconds before they dumped the coffee and development was slow enough for them to be pulling the trier many times while checking color and giving it a sniff. When the coffee hit the cooling tray, it was always a massive wave of popping that took another15 to 30 seconds to finally stop. Now these were ultra light roasted coffees that were a light cinnamon color.
If I were ever to try and replicate this kind of aggressive first crack for that amount of time in my 1 lb drum, it would be way beyond a light roast by the time I hit even 2 minutes of development.

My theory is this. Larger batches develop differently than small home roasting size batches during the development phase and in a positive way. I don't have a theory as to why this would be but I'm certain the difference exists.
Edited by allenb on 01/22/2023 8:11 AM
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
exer31337
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Posted on 01/22/2023 11:01 AM
Larger batches store more heat... If the heat stored is the temp past fc that heat can transfer to beans not hot enough for fc causing additional fc. Smaller batches won't have as much stored energy to transfer to other beans. They will also have more surface area to bean Mass allowing for faster cooling.
 
oldgrumpus
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Posted on 01/22/2023 12:27 PM
Regarding the first crack happening in the cooling tray of the commercial roaster... Is there an underlying assumption that there is a possibility that this is the key to their producing stellar coffee?

Just for fun, it would be interesting to try roasting 1 lb this way, which might work. But then again maybe not. Only one way to find out.

For a "third wave" coffee, CoffeeMind Academy suggests this as a starting point before any tweaking : First crack at 9 minutes and drop at 1:20 after first crack. There are details I'm leaving out for the sake of keeping this post concise... But might be enough to play with for now.

Their training is mostly geared to drum roasters, but they do have an Ikawa sample roaster and a Stronghold S7 vertical drum roaster, as well as several other roasters. They achieve the same results on all the roasters considering color of the roast as the primary determining factor.

Most of us are used to lingering in the development phase for a certain percentage and completely disregarding color.
Clever Coffee Dripper
Grinder: Macap M4
Roaster: Completed drum roaster project photos shown here:
Photos https://goo.gl/ph...Da6K4wfqw5
Videos https://www.youtu...Bd1NrdpSUH
 
allenb
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Posted on 01/22/2023 8:16 PM

Quote

Regarding the first crack happening in the cooling tray of the commercial roaster... Is there an underlying assumption that there is a possibility that this is the key to their producing stellar coffee?


No, that was not my assumption but I agree with you in that it would be nice to be able to replicate it in our smaller roasters to see if it improves a roast. My assumption is that there is something happening with larger batches that creates an environment where reactions are enhanced or maybe more active. I think the livelier party is already taking place in the roaster and just naturally makes itself known when hitting the cooling tray.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
oldgrumpus
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Posted on 01/22/2023 10:47 PM

Quote

allenb wrote:
My assumption is that there is something happening with larger batches that creates an environment where reactions are enhanced or maybe more active.


Could it be evidence that FC is an exothermic reaction? I've heard that it is. Maybe we see that on the bean-temp curve. If it really is a chemical reaction that would explain it but I'm not sure it's proof.
Clever Coffee Dripper
Grinder: Macap M4
Roaster: Completed drum roaster project photos shown here:
Photos https://goo.gl/ph...Da6K4wfqw5
Videos https://www.youtu...Bd1NrdpSUH
 
allenb
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Posted on 01/23/2023 1:23 PM
I think it definitely lends support to the claim that the steam induced cracking during 1C is from a chemical reaction. What intrigues me the most is what could be the cause of larger batch sizes having a majorly higher level reaction during this phase of the roast?

If you take it apart logically, the only real difference between a small and large batch of coffee that could possibly cause a different level of or enhanced reactions is the size of the cross section of coffee when nested when the coffee tumbles momentarily at the bottom of the drum, or, in the case of a spouting bed roaster, the cross sectional size of the coffee bed when nested in the roast chamber awaiting it's turn to make it's upward spouting trip.

If this allows an enhanced reaction during 1C while not increasing RoR, and possibly causing an improved cup, could it be that the other reactions during the Maillard phase of a roast might also be positively affected by the larger cross section?
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Yasu
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Posted on 01/23/2023 7:07 PM
My interpretation of the cooling time is.
For roasting times of around 10 minutes, the surface temperature of the beans and
I think there is a difference in the central temperature.
I believe that this temperature difference is an important factor in the depth of flavour and aroma.
(It is important to have a gradation of roast temperature difference from the surface to the centre, as if the beans were blended within a single bean).
I believe that slow and even roasting results in all parts having a similar temperature and a simple taste. (This is not good roasting)

For example, if the surface temperature of the beans immediately after the drop is 210°C and the centre temperature is 200°C, the surface temperature will be in the direction of falling from 210°C, but the stop temperature will continue to rise until the surface temperature falls to 200°C.
The abort temperature will continue to rise after the drop.

Rapid cooling ⇒ The temperature difference remains.
Slow cooling ⇒ Temperature difference becomes uniform.

Therefore, it is an important element of the roasting technique to change the cooling time according to where the surface and centre temperature difference at drop (determined by ROR) and the overall gradation (temperature difference between surface and centre) are brought to.

I have experimented with inserting thermocouples into the green beans and applying hot air, but I could not get quantitative data, but I would like someone to challenge me.
 
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