When to Cool a Roast

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Nunas
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#1: Post by Nunas »

For years, I've adhered to the advice to cool a roast immediately after dropping to avoid having the roast coast to a darker level. Lately, I've been messing with an alternative :idea: . I roast to a bit shy of the finish temperature for a given roast level, then let the beans sit for a short time in the cooler before turning on the fan. My idea is that the exterior of the beans at drop must be significantly hotter than the interior. By letting the beans intentionally coast for a few minutes, the roast level throughout the bean will be more even. I've only done a few batches this way and I think my roasts are a bit more aromatic and the espresso a bit smoother, with more flavour of the particular bean. Of course, this could be all in my imagination :wink: So, the question is, am I onto something or am I the last roaster on the planet to try this <VBG>.

Pressino

#2: Post by Pressino »

Nunas wrote: ...My idea is that the exterior of the beans at drop must be significantly hotter than the interior. By letting the beans intentionally coast for a few minutes, the roast level throughout the bean will be more even... <VBG>.
I'm trying to understand this in terms of the roasting process and keep coming to the conclusion that at the end of a roast, given the amount of time the beans are in the roast, each bean should be at a stable uniform thermal equilibrium (i.e. the surface and innards of each bean should be more orless the same). Am I missing something? :?

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baldheadracing
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#3: Post by baldheadracing »

My guess - guess - is this would give a result similar to a mélange roast, as the beans in the middle of the mass would be roasted for longer than the beans at the top/bottom.
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

Nunas (original poster)
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#4: Post by Nunas (original poster) »

Pressino wrote:I'm trying to understand this in terms of the roasting process and keep coming to the conclusion that at the end of a roast, given the amount of time the beans are in the roast, each bean should be at a stable uniform thermal equilibrium (i.e. the surface and innards of each bean should be more orless the same). Am I missing something? :?
No, you're not missing anything. If the ROR is held to neither rise nor fall for several minutes at the end of the roast, then this would be true. But, I nearly always have some rise in the ROR, even at drop, which is exactly why I started this thread.

Nunas (original poster)
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#5: Post by Nunas (original poster) »

baldheadracing wrote:My guess - guess - is this would give a result similar to a mélange roast, as the beans in the middle of the mass would be roasted for longer than the beans at the top/bottom.
Yes, I thought of that, but not the same way. I was thinking that since the beans have airspace between them and since they're really hot, heat rises and cooler air might be slowly pulled in at the bottom, making the bottom most beans cool more quickly than the others, which should be at more or less the same temperature. If the bean collector bin, which has holes in the bottom, were placed on a flat surface, then perhaps this effect would be minimized.

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baldheadracing
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#6: Post by baldheadracing »

Yes, the cooling depends on how tray is designed/configured/installed. My main point was that differences in cooling - if they exist - would lead to differences in roast degree across beans, leading to the mélange roast effect.

On both my Hottop and drum roasters, the previous owner said that slowing down the drop out of the roasting chamber to 30 seconds total was sufficient for a good mélange roast effect for his 'traditional' espresso blend. As he did literally hundreds of carefully documented test roasts, I believe him.
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

bicktrav

#7: Post by bicktrav »

Typically, by the time a roaster drops, he/she has reduced heat precipitously (and, in some cases, increased airflow). That heat reduction guards against temp disparities between the inner/outer portions of the bean, so theoretically, proper roast procedures negate the need for the alternative cooling method you've described. Coasting is also an imprecise way to arrive at a final bean temp. It's hard to imagine any roaster, irrespective of experience, being able to achieve consistency by allowing the roast to coast to its final temperature. Finally, there's the concern about baking. Some roasters think rapid cooling is necessary to prevent baked tones. For the above reasons, I'd stick with the traditional "cool em as fast as you can" method. Then again, if you're enjoying the results, that's all that matters.

Nunas (original poster)
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#8: Post by Nunas (original poster) replying to bicktrav »

Yes, I think you're correct. As I noted earlier in response to another poster, if one were to hold the ROR to neither rising nor falling for even a minute or two at the end of the roast, logically, the BT should equalize throughout the beans. As you point out, this would be a more precise way of accomplishing it. While I generally let the ROR fall as the roast progresses, I usually end on a rising ROR; I'll try it for a while on a flat ROR and see how things come out.