Whale wrote:They may have stretched it a bit into roaster design...

Is the (electric heated) M3 roaster really pertinent in this thread?

I think we can stipulate that the beans in a typical wood-fired roaster are exposed to combustion products. It seems to me as though this thread has been refocused on the details of design for different roasters, to the complete exclusion of any conversation about the taste of the coffee.

If it stays on this track then there is no further interest in this particular thread for me at this time. Of course if everyone else is more interested in a conversation about roaster design and operation principals then by all means please continue (but it may become appropriate to change the thread title)

On the other hand, if again becomes a thread about wood fire roasted coffee beans then I look forward to some discussion about the effects on flavor and profiles that may come from wood-fired roasting.

Ooops! and darn.

I posted something at the same time someone split this thread... so my post is (apparently) gone in limbo...

Any way the gist of it was that the discussion was about air flow and not electric heating.

And as Jim has already mentioned, there are Quest M3 owners making mods to the air flow of their machine so possibly one could artificially introduce "wood burning combustion gas products" into the air inlet of a M3 and thus simulate the effect of wood burning into an electric roaster. This could be a valid test that would only introduce one variable. This would probably mess up the gleaming M3 a bit so I would understand nobody wanting to try. Who knows, maybe it would become the beginning of a new trend.

I do not own an M3 and will not buy one just for that. I do not know yet if my soon-to-be-delivered roaster would accommodate such an experiment.

Marty sent me some more info that may be of interest to those still reading this thread. I don't understand the roaster blowing up part, but here's what he said:

Marty Curtis wrote:The following direct-fired roasters do in fact have their products of combustion go thru the beans: Probat, Got Hot, Ambex, Barth, Primo, Diedrich, Toper, Joper, Semcia and a few others.

Also there is no damper in the back to be closed. What happens is you change a damper on the top which will change the air flow from either:
1. thru the drum, or
2. a percentage thru and the rest on the outside, or
3. no air flow thru drum but all on the outside.

But when you do #3 the burner shuts off so you don't blow up the roaster.

Now that is on a Probat. For the Gothot and Barth it is very similar but it is on the front of the roaster top. The others roasters I mention don't have the aroma roast valve. But again you can not roast this way it is only closed for a few seconds.

Kevin Sinnot, Coffee & Tea Journal, March 1996 wrote:Rather than offer much programmability, Probat shop roasters offer the user a sense of manual control. The Probats are known for being able to seal off the air, not only incoming but outgoing as well. This is called an aroma roast, and imparts a smoky pungency to the coffee. Most Probat roastmasters I know like to use this feature sparingly; like a zoom lens in the hands of a professional videographer. I should also mention that Probat is not the only roaster that allows this. Some older Jabez Burns models do it as well, but it is certainly part of the appeal of a Probat.

I never realized the "sparing use" part was about not blowing up the roaster, rather than not smoking the beans too much.

Since my search with the term 'afterburner' revealed no germane thread, I have questions that does fit the split-off title of this thread.

What gases are present in the roast process that requires an afterburner in large roasters? Does the afterburner simply prevent sensitive neighbors from complaining about the smell or what is the purpose?

Smoke and vapors are major factors in coffee roasting; they come from the coffee, not the roasting fuel.

Roasting even a half pound of coffee at home creates enough smoke to set off the smoke alarms and enough vapor to fill the room with strong aromas that are clearly coffee-like, but not quite like brewed coffee. An afterburner eliminates both smoke and vapor. One home roasting device, the Z & D has a catalytic converter that does close to the same thing. The Behmor has a lower temperature one that eliminates smoke, but not all odors. I have a recirculating hood exhaust with carbon filters in my coop. When I roast under it, the smoke is also eliminated, but the aromas are just about as penetrating as cooking a lamb curry (too late for me, but any budding apartment kitchen designers should realize carbon filters eliminate smoke, but not smell).

Bottom line, coffee is strong stuff, and commercial roasters, at least those in cities, have to make sure these aromas are eliminated, or they'd get shut down by the EPA.