prof_stack wrote:One way a popper can be improved to better retain heat is to gently wedge a soup can (free of labels, natch) on top and increase the roasting chamber.

Yep, some of the Aussie homeroasters use chrome exhaust tips.

I think that I might get rid of my heat gun for a popper, just for sport.

Cheers,

Luca

Thanks Jim, reduction and lowering the temp is such a great simple piece of advice. I had forgotten the correlation between impeding airflow/ temp/ roast time...

I use a Turbo-Oven unmodified to roast. Some mod this with a stir crazy popper, but I've found by simply lifting the bowl by the handles and agitating, I can get good uniformity. However, with fewer beans (less mass) I get more uneven roasts. I started with 150g and have doubled that. I've found that 300g provides a nice even roast just starting the 2nd crack after about 30 minutes. I suspect that is because with fewer beans in the turbo-oven and so much empty space, the beans give off their heat to the surrounding spinning air, and with more mass, they give off their heat to each other. Does this make sense?
mbach

mbach wrote:I use a Turbo-Oven unmodified to roast. Some mod this with a stir crazy popper, but I've found by simply lifting the bowl by the handles and agitating, I can get good uniformity. However, with fewer beans (less mass) I get more uneven roasts. I started with 150g and have doubled that. I've found that 300g provides a nice even roast just starting the 2nd crack after about 30 minutes. I suspect that is because with fewer beans in the turbo-oven and so much empty space, the beans give off their heat to the surrounding spinning air, and with more mass, they give off their heat to each other. Does this make sense?
mbach

Not really. A 30 minute roast, and letting the beans cool by lifitng the lid, in a roaster that uses convection heating, sounds like a prescription for a completely flat tasting roast. However, I don't know enough about the Turbo Oven to be very positive on this.

I'm not lifting the lid to cool the roast. I must not have been very clear. The turbo-oven is pre-heated, then the beans are put inside. It remains on and I agitate the beans by swirling the whole machine. I do not know if my roasts taste flat. I don't believe they do, but I was addressing uniformity of the roast as opposed to taste. I think since the turbo-oven is, essentially, an air roaster but with much more space that it is able to cope with more beans. I was just thinking that the roasts with more beans might be more uniform because of conduction heat x-fer between beans en masse. Isn't that a reasonable assumption?
mbach

mbach wrote:I was just thinking that the roasts with more beans might be more uniform because of conduction heat x-fer between beans en masse. Isn't that a reasonable assumption?
mbach

Roast evenness is best determined at the first crack. The beans should be fairly even going into it and coming out of it; they will go piebald during the first, no matter how good the roast. Evenness at the end of the roast is no sign of a good roast, although if they are uneven at that point, it's a sure sign something went awry (this doesn't apply to Yemens or DP Ethiopians, which usually go uneven after the first crack.

In a convection oven, the airflow and therefore the temperature does not depend on the bean weight. So, like a drum, small amounts should roast faster than large, since the more airflow around any bean, the faster the heat transfer. If your 300 gram roasts are 30 minutes, you might consider dropping the weight to get down 15 minutes tops. If the roast is uneven at this speed, get the stir crazy, optionally disconnecting the heater, since this indicates a problem of exposing all the beans equally to the heat.

There is a caveat to this. If the oven is thermostatically controlled, so the air temperature goes up and down by a large amount as it turns off and on (unlike the SCR control in electric range ovens); you may want to stay with the slow roast and the large bean mass. When beans drop in temperature during the roast, the flavor compounds polymerize and the flavor is gone. Beans are mostly cellulose which is a great insulator, so a large mass of beans retains heat very well, and may resist the air temp fluctuations.

However, if the Hobson's choice is between a flat tasting 30 minute roast or a flat tasting fluctuating bean temperature roast; it's time to consider fixing the heater controls on the Turbooven.

another_jim wrote:Knock a few holes into the tin, and at the end of the roast place it over the popper or airroaster. This will slow down the airflow enough to maintain the temperature.

End of the roast? I would have thought you were aiming to hold the temp at the end of first crack. Am I misunderstanding?

At the end of my roast I cut heater power and up the variac to 140V on my poppery 1 to cool as fast as possible. Is it bad to cool with such a large amount of air? Perhaps better to let it cool by itself? I have not read up on cooling techniques.

Keith

MOSFET wrote:End of the roast? I would have thought you were aiming to hold the temp at the end of first crack. Am I misunderstanding? :

You have it right, I was using "end" poetically. The beans lighten during the first crack, and in a popper with no heat control, you need to slow down the air at that point.

Jim...you are correct that bean volume at the start can make a difference in speed...even for the CO/UFO (or Stir Crazy) combo
I've found the optimum...for my choice of profile/taste, etc to be 14oz by VOLUME....Thus, there is usually no difference whether I'm roasting a peaberry or a normal size bean...obviously, those large Nicaraguan beans expand greatly, so i use a touch less green in that case....
Any less than 14oz and I find I'm getting to first in less than 10 minutes...too fast for me....
Of course, as you know, different varietals will roast faster/slower....I keep a journal...and update if the lot is different, or from a different farm, etc....
The combo, due to it's somewhat slower temperature increases, give us a better opportunity to temp profile our roasts...I can easily stretch between cracks 5 minutes or more...without a Variac...
But back on topic, I agree with that sometimes "less is more"...

Anybody know where to find a variac? It appears that both sweetmarias and coffeebeancorral no longer carry them.

Ray