Roasting smoke influencing output - Page 2

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Alan Frew
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#11: Post by Alan Frew »

In short, as I'm sure Alan will agree, if you don't remove the smoke from the roasting chamber, the beans will taste of it.
No. In "real life roasting" the only way to do this would be to shut down airflow, which would increase the temperature really quickly ... can I say "third crack?" I'm sure the beans would taste smokier, or at least more charcoal-like, but that would be purely a function of the temperature increase.

Alan

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yakster
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#12: Post by yakster »

another_jim wrote:...repeated blind cuppings show no difference in roasting atmospheres (see Illy) The taste going from the smokiest Burns unventilated roasters to the most ventilated Sivetz air ones and all steps in between is the same, providing the bean and environmental temperature profiles are the same (see Schenker). You can even air roast in all CO2 or N2 to prevent oxidation, and it's still the same. The outgassing of the beans protects them from the roast chamber atmosphere.
This would explain why my open basket campfire roasts don't taste smokey, yet when I tried to roast almonds over the campfire they were way too smokey for my likes.
-Chris

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weebit_nutty (original poster)
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#13: Post by weebit_nutty (original poster) »

Alan Frew wrote:As an experiment, put a test tube of boiling water over a Bunsen burner in a confined but ventilated space and blow a constant supply of smoke into the space for a few minutes. Remove the test tube while still boiling, allow to cool, then check the water for smoke contamination. You won't get any. The pressure of the steam going out of the test tube is greater than the pressure of the smoke trying to get in.
thx. I get your point but this doesn't sound like an apt comparison. The physical properties of boiling water in a confined space such as a test tube and the gassing out of a bean surrounded by other beans doing the same is quite different. In the latter beans make physical contact with one another as carbon particles are formed and released from every bean. What you suggest sounds like there is so much pressure emitted from every bean that any residue from each bean is instantly blown off from the intense gasses from the bean. Perhaps that might be the case during a crack event but clearly cracks don't happen constantly or all at once so when each bean cracks it sheds oily smoke and carbon particles into already cracked beans. Your comparison suggests that the beans are all out gassing with the same constant violence and pressure of boiling water. Just doesn't sound right however I admit I am not scholarly in the least bit when it comes to physics so if I am wrong I gladly appreciate any education that comes my way. These are just questions from an inquiring mind, so forgive me if I seem unconvinced.

Nevertheless for now I will stick to Jim's assertions on this topic given his knowledge of the studies that I was unaware of. His answer is precisely the one I've been looking for. So we can probably lay this topic to rest since there already exists a definitive answer on question of whether any of this matters or not.
You're not always right, but when you're right, you're right, right?

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another_jim
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#14: Post by another_jim »

It's a good question, which is why it attracted a great deal of research. The speed and temperature of the airflow affects the speed at which the beans absorb heat, but the chemical composition of that airflow doesn't seem to matter.

The out gassing pressure of coffee peaks at around 30 bar at the fist crack, but is high throughout the roast. I don't know of any research where people have roasted in high pressure chambers to see what happens if the out gassing pressure is equalized or exceeded by the roast chamber pressure. Effervescent coffee soda with lots of aromatics from the roast, I guess.
Jim Schulman

bohemianroaster
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#15: Post by bohemianroaster »

Picture the 150Kg roaster at Mr Espresso in Oakland . . . there is a firebox below the roasting drum, the back plate of the drum is perforated, an average of 10 logs are burning all during the roast, and the smoke is going directly through the bean mass and out . . . a Probat-style airflow system . . . no smoke flavor in the beans at all.

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yakster
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#16: Post by yakster »

Or just picture this...



Uneven roast when agitation isn't maintained, but not smokey.
-Chris

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bohemianroaster
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#17: Post by bohemianroaster »

Yer killin' me! I used a popcorn popper rig just like that in my brick oven before I bought my actual roaster. That was some truly abominable brew! Your results are probably better just because it looks like you're getting enough heat to get through FC. Whoa. Cowboy coffee! :lol:

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Mile High Roaster
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#18: Post by Mile High Roaster »

another_jim wrote:It's a good question, which is why it attracted a great deal of research. The speed and temperature of the airflow affects the speed at which the beans absorb heat, but the chemical composition of that airflow doesn't seem to matter.
Does any research exist regarding mechanical contamination of the beans in an unventilated drum via pulverized solids; i.e., soot from burnt chaff, etc.?

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another_jim
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#19: Post by another_jim replying to Mile High Roaster »

I was talking about taste tests, which show no difference at all with regards to any kind of ventialtion, if the other parameters are cotrolled. In terms of health ...

Long time ago, and controversial. Sivetz, when pushing air roasting, hypothesized in the 1970s that poorly ventilated drum roasters coat the bean surfaces with soot and possible carcinogens. Most larger roasters (1 bag plus) in those days were using the Burns Thermalo design, which recirculates combustion air to save energy. Smaller roasters were either Probat single pass ventilated (with whihc he had no problem) or the older Burns unventilated sample roaster style.

In the mean time, recirculating roasters have scrubbers, and almost all commercial roasters have chaff cyclones and afterburners. There's a lot more regulation, and no lawyer has filed a class action suit. So I somewhat doubt it's a problem now, although it may have been in the past.

If there were a problem, it would have shown up first as a higher morbidity and mortality rates among people who roast coffee, whose exposure to the coffee smoke is orders of magnitude higher than everyone else. Since this is not the case; it may be that the combustion smoke from coffee is not all that unhealthy in the first place.
Jim Schulman

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boar_d_laze
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#20: Post by boar_d_laze »

Mile High Roaster wrote:Does any research exist regarding mechanical contamination of the beans in an unventilated drum via pulverized solids; i.e., soot from burnt chaff, etc.?
Intuitively, most of the mechanical action inside a roaster is bean against bean, rather than bean against drum; and (still intuitively) will have an abrasive, scrubbing effect as opposed to painting drum sludge on the beans.

But there are always limits. A really filthy drum is not your friend. Which reminds me, I need to change the oil in my car.

Since smoke flavor comes from particulates, I'll guess abrasion plays a much greater role in keeping (or at least limiting) smokey taste off beans than an impenetrable nimbus created by out-gassing.

Rich
Drop a nickel in the pot Joe. Takin' it slow. Waiter, waiter, percolator

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