Airflow 'mistake' results in sweeter coffee?

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

We ran through several roasts this morning on our Ambex YM-2. Last roast was a high grown Guatemalan Huehuetenango. Usually a sweet chocolaty, brown sugary coffee with a malic acidity. Went through a fairly typical profile for us: Tan (320) at 5.5 minutes, 1st (385) at 9 minutes, and drop at 11:45 at 417 for a city plus roast. Toward the end of the roast I noticed I was having trouble maintaining a declining rate of rise and saw that I hadn't increased airflow as I usually do from tan to 1stC. We generally set airflow to a minimum until tan, slowly increasing it to approximately 80% by the start of 1st crack. When I saw the airflow hadn't moved, I quickly increased it to 80% and dropped the roast about 15 seconds later. I was sure there would be a smoke taint, but when we cupped it, it was the sweetest roast of this coffee we have ever had. The coffee was a city plus roast for us but also had more internal development and gave us a higher extraction at 21% than we usually get (19-20%). No smokiness at all. I'm wondering if we were always losing some sweetness by using higher airflow?

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TomC
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#2: Post by TomC »

On my Ambex clone, the only time the fan is on high is when I'm cooling the coffee in the tray.
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endlesscycles
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#3: Post by endlesscycles »

I've said in another thread that I don't see any reason to use any more than the very minimum airflow.
-Marshall Hance
Asheville, NC

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johnny4lsu
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#4: Post by johnny4lsu replying to endlesscycles »

I've been experimenting some with this. Results to follow. Would love to hear others thoughts on this as well.

saepl
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#5: Post by saepl »

general rule I have found is more air flow gives more acidity, less air flow gives more sweetness / caramel. In my opinion max airflow should be just what you need to get rid of the chaff and the smoke.

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endlesscycles
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#6: Post by endlesscycles »

If there's smoke, you're doing it wrong. Moisture and chaff... but mostly moisture, so keep it in there.
-Marshall Hance
Asheville, NC

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[creative nickname]
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#7: Post by [creative nickname] »

I've done a fair amount of airflow experimentation, some of which was documented in a Roast and Learn thread last year. In my experience too little airflow adds astringency, especially in the aftertaste, while too much airflow strips off aroma and subtler flavor notes. Unfortunately it is hard to say which settings might be best across different roasters because airflow controls are so variable from machine to machine. Some roasters may have max airflow that is still below the level where airflow effects start to become negative, while others may give airflow controls so coarse that there will be little useful variability that the user can control.

For this reason, I don't think there is a way to say what works best on any particular gear until you've done blinded comparisons of otherwise identical roasts of the same coffee with different settings (or gotten advice from someone who has done that sort of testing on the same gear that you have). This is a lot of work but the results are worthwhile. Such testing indicated that there was a sweet spot on my own roaster running between around 60% and 90% of max fan power, and that best results came from leaving air near the low-end of the range until the bean mass reaches 300F and then upping it towards the top from there onwards. But these same settings on a different machine, with different fan power settings, vent diameters, etc., might be far from optimal.

As for lowered air bringing sweetness, my blind tasting pretty much ruled that out, finding that it tended to be associated with more dryness. Of course, this is an "all things being equal" kind of proposition, and if your airflow change causes other aspects of the profile curve to shift in a useful direction, the benefits might outweigh the detriments. But you still wouldn't know if the lowered airflow was a necessary aspect of that shift, until you've separately tested what that profile tastes like at higher and lower airflow settings (with heat adjusted to produce the same temperature curve).
LMWDP #435

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roastimo
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#8: Post by roastimo »

I am beginning to think smoothing out in honour of Rao by using airflow reduces the good.
Count me +1 on minimal airflow, and I would go further to say "allow some of those bumps" on the ROR curve. :roll:

HoldTheOnions
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#9: Post by HoldTheOnions »

I concur with creative nickname, I believe it's primarily a function of the effect of the increased air flow on temperature at that point in the roast.

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NoStream
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#10: Post by NoStream »

[creative nickname] wrote:In my experience too little airflow adds astringency, especially in the aftertaste, while too much airflow strips off aroma and subtler flavor notes.
That's precisely what I noticed. There's a pretty clear division into three airflow regions - overly low, adequate, and too high. On my Quest, Rao's lighter trick got me close to minimum adequate airflow. Aroma-stripping airflow was quite a bit higher. I didn't notice any benefits from overly-high airflow when using constant airflow through the roast. (And, at least in the Quest, I'm not convinced that modulating airflow had any real, significant, positive impact.) I think people may be overthinking airflow - if it's high enough to get rid of smokiness and low enough to not push out pleasant aromas, you're probably OK. Where exactly this range is on the dial and how large it is depends on roaster design and fan strength. It's easy enough to find that range empirically.

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