Air Roasting versus Drum Roasting

[jason_casale]

As some of you know I now make my living as a coffee roaster and a barista and trainer.
We roast on a samiac 12 kilo at the shop with agtron 2 controls.
I was loaned a heat gun that was a sample roaster at one point. The popular mt 500
I bought the right size galvinized pipe to finally get it roasting fairly well.
I am very impressed that you can roast a very small sample of coffee thru this thing.
We are talking about 2 to 2.5 ounces is all but still cool.

I roasted a batch of Colombian in the air gun.
And had some Colombian from the shop roaster for cupping purposes.
I set them up in the cupping bowls.

The air roaster was a bit brighter than the drum roasted.
However some of the flavors that I got from the air roasted where just missing all together or muted and replaced with much more body on the drum roasted sample.

Anyone else have this experience.
I almost want to say I gave the nod to the air roasted.
But I liked the additional body the drum roast had.
Tormented I guess by positive attributes of both.

Here are some pictures

[Randy G.]

My first question would be to find out how close the roasting curve from the heat gun was to the larger roaster.

It would be interesting to hear how other coffees did in this situation. In my limited roasting experience, Colombian, when roasted for drip or perc (or cupping), benefits from a fast roast profile, stopped somewhere just at the end of first, or shortly thereafter.

[jason_casale]

Roaster picture

[jason_casale]

Very good questions I could not answer Randy.
An agtron controller provides an automated roaster curve based upon air density batch weight calculations and density of each bean you roast.
You plug in the transition temperature into the roast controller and the roaster roast the coffee for you when you get to 430 bean temp you eject the coffee. The roast actually shuts the burner on and off thru the roasting process at various lengths to get it to profile correctly.
The roaster is full flame on or full flame off several times thru out the roasting process for various lengths of time the controller controls this process.

hopefully that answers that question.

The air gun who knows what it does.
It heats the coffee up I roasted it just into second crack by keeping track of the time and the cracks.
I would like to add a probe eventually but that is not going to happen anytime soon.

I find it fascinating how you can roast with a simple heat gun fairly effectively not perfect.
I am thinking about upgrading to the new variable temp heat guns to be able to profile the roast better.

Here is the one I am thinking of buying.
http://www.masterappliance.com/master2.html

Thanks Jason

[jason_casale]

The first batch I did in the heat gun was stopped shortly after first but exhibited sour grassy hay flavors which indicate the roast was underdeveloped.

So I roasted to second crack that is what is in the picture the color looks very even and nice some divots or blow holes in them. But other than that not bad.

My theory about air roasting has always been if you can profile an air roast to match a drum roast profile you would have similar or same results.

I have not been able to scientifically prove this but it is my gut instinct.
Since I have access to kind of play around with this maybe I will figure it out for myself.

The flavors where chocolate may a hint of raisin or fig.
The drum roasted batch had lots of body with some barley as well reminded me sort of like a Guinness stout oddly enough.

[Randy G.]

I would question the value of a heat gun roaster for use in a commercial environment such as yours. Without some sort of fairly detailed control systems it will be quite difficult to get a meaningful roast from the heat gun set up. For a home enthusiast it is a lot of fun to put together such a roaster, but the samples from it for your assumed purposes will be of little value because, as you have found, the roast is so different from what your commercial roaster produces... all IMO, of course.

The other problem is whether or not the heat gun's life will be affected. They are not designed to have their output restricted in that way. They usually are equipped with an overheat thermostat so if they get too hot they shut off the heating element...

[another_jim]

The bright versus body difference between air roasters and drum roasters is well known. Most experienced home roasters end up speeding up their drums or slowing down their air roasters in search of the happy medium.

[popeye]

I roasted for a while with air roasters, (mostly the iroast2) and then picked up a behmor when it came out. While not exactly a drum roaster (it's significantly IR), it's close enough to approximate. I sure miss a lot of the high notes, particularly from my kenyas. However, on an air roaster, espresso was 10 misses for every hit. And i could never dream of doing a SO costa rica, or anything else that was moderately bright on a drum. I've posted before, and i continue to believe that describing air-roast profiles to temperature and time oversimplifies the problem. All roasting, but especially air roasting, is about heat transfer. With the quick nature of air roasts, the interior of the bean can significantly lag the exterior, throwing off agtron and eyeball measurements. I had to recalibrate my eyeball moving to the behmor.