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hmmmm .... a simple explanation/driving analogy I think would amount to taking your foot off the accelerator and letting time and distance decrease speed naturally, neither braking nor accelerating aka coasting. No cruise control option ... lol
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This explanation for "coasting" doesn't really make sense. Heat and temperature are not the same thing.Originally posted by triton91 View Post"coasting" is when the beans losing heat.
This is why
"First crack is an exothermic reaction; the beans are giving off heat. But then the beans quickly become endothermic, meaning that a roaster that is not adding enough heat to the process will stall the roast at this point ...not a good thing. Once caramelization begins (340-400 f degrees internal bean temperature) a roast that looses heat will taste "baked", perhaps due to the disruption on long-chain polymerization. The melting point of sucrose is 370 f and corresponds to this window of temperatures when caramelization begins."
The beans can only lose heat if they are at a higher temperature than their surroundings - regardless of whether or not the *reactions* are endo or exothermic.
If a *reaction* is endothermic, it means the reaction products have higher chemical energy than the reagents.
In an isolated system (where no heat can transfer in/out), this will result in a decrease in the temperature until such time that the reaction stops because it is no longer kinetically favourable. The system is not losing energy (i.e. heat), it's merely being converted to chemical bonds!
In an open system, if the surroundings are at a greater temperature than the reacting system, then there will be a net transfer of heat (i.e. energy) from the surroundings TO the system, lowering the temperature of the surroundings until such time as they reach temperature equilibrium with the system.
In a roaster, you can maintain the temperature of the surroundings (i.e. the air and the roaster) provided your heat input (to the air/roaster) matches the rate of heat transfer from the air/roaster to the beans.
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"coasting" is when the beans losing heat.Originally posted by Wynton87 View PostWhy is coasting your roast bad?
This is why
"First crack is an exothermic reaction; the beans are giving off heat. But then the beans quickly become endothermic, meaning that a roaster that is not adding enough heat to the process will stall the roast at this point ...not a good thing. Once caramelization begins (340-400 f degrees internal bean temperature) a roast that looses heat will taste "baked", perhaps due to the disruption on long-chain polymerization. The melting point of sucrose is 370 f and corresponds to this window of temperatures when caramelization begins."
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Thanks designingbycoffee. Ok so as long as I can predict final result it shouldn't be a problem, I can continue to just blow a fan into the behmor.
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Faster. But not the final word by any means
If you leave the beans in a hot roaster to cool even with the power off, they will keep cooking. But this is no biggie really, because as you tweak your technique for taste in something like a Behmor, you will counter the effect this has by powering off earlier. Then a longer in-roaster cool will help to gently finish off the roast in effect. But if you power hard right to 2C or past - you'll want to drop and cool as quickly as possible…Last edited by DesigningByCoffee; 22 February 2017, 12:17 PM.
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Sorry to clarify what I mean is when you let the beans cool slowly for example using the behmor or gene inbuilt cooling system instead of rapid cooling outside the machine. Assuming you can predict same end result in terms of colour. Then what difference will slow vs rapid cool make to end result? Ta.
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I have had the roaster for several years now ruburu, I noticed subtle differences when I started doing roasts in Torre compared to the Corretto, instead of going from first crack to 2nd crack in around 4-5 minutes like in Corretto I found that 2-2.5minutes was sufficient development time in the drum with air flow control from around 150C to end of roast. It has a combination of conductive, radiant and convective heat and produces a great result for batches from 300g up to 1800g. An 1800g roast will reach first crack at 12m30sec and I usually hit the cooler at 14.30-15.00min. mark just shy of the first snaps of second crack.Originally posted by roburu View PostApologies for the off topic but how do you compare your new drum roaster to your old Corretto in terms of the characteristics it imparts to the coffee? Is it easier to get, say, a sweeter, more balanced roast or since it's a perforated drum it it's fairly similar to an air roaster?
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Apologies for the off topic but how do you compare your new drum roaster to your old Corretto in terms of the characteristics it imparts to the coffee? Is it easier to get, say, a sweeter, more balanced roast or since it's a perforated drum it it's fairly similar to an air roaster?Originally posted by greenman View PostRoaster Torrefattore 2kg perforated drum electric.
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I often kill the heat on a roast when there is sufficient momentum after the start of first crack to continue the roast to the required level without going to a stall and baking the beans. When I first started doing this I used to get very nervous not wanting to waste a batch but getting to know your roaster and it's capabilities gives one confidence to do this. Roaster Torrefattore 2kg perforated drum electric.Originally posted by roburu View PostI think the OP means turning the roaster's heating off after the FC ends or thereabouts and letting the beans "coast" on the accumulated drum heat, at very low ROR. I didn't know it was a bad thing, links would be appreciated.
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I think the OP means turning the roaster's heating off after the FC ends or thereabouts and letting the beans "coast" on the accumulated drum heat, at very low ROR. I didn't know it was a bad thing, links would be appreciated.
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I suspect that 'coasting' refers to the period of resting/de-gassing beans after roasting, but you know....who knows.
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I assume by coasting you mean maintaining a temp, neither rising nor falling, kind of simmering, or are you referring to stalling?
Why not roast a batch, let it "coast" describe the process and let us know how it turns out.
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