Thursday, March 19, 2009

hot air popper roasting 4

I've been experimenting a bit more with the Popcorn Pumper hot air popper, exploring its heating behavior and maximum temperature and capacity. It can easily exceed 450 degrees (the most I can measure with a compatible thermometer), several minutes of pre-heating will get it there, and behavior changes dramatically based on bean quantity.

With the same beans (classic Italian espresso blend) I've now seen that the difference between roasting two and three ounces is dramatic. With more beans, second crack actually happens, smoke appears, and surface oil becomes evident, all with very little change in roasting time. With three ounces and a preheated popper, 8 minutes will deliver FC or greater.

At four ounces, the popper sounds like it's working a little harder but still moves the beans fine. There's much more vertical action, with beans bouncing nearly all the way up to the opening rather than just swirling. This is the most I've tried, but I think it can handle more as long as the beans aren't being prematurely ejected. Further, this can even reduce the time required to achieve a given roast level.

So my initial ideas were incorrect. Adding beans, not removing them, will increase the temperature and decrease the relative roasting times. It does make sense that the cumulative effect of the exothermic reactions in the individual beans will be greater with higher volume and density. Besides bean quantity and roasting time a significant variable is preheating time. That looks like it might provide a few minutes of control over the total time. Achieving much more control would probably require modification of the popper and/or control over input voltage. Regarding the latter, I do have some crude control given that the dining room and kitchen lights are on the same circuit that I've been using. The dining room will draw 500 watts and the kitchen 450. There's a clear effect on the popper's performance!

On 2009-03-16 I roasted four ounces of Yemen Mokha Sharasi. This is no longer available from Sweet Marias, as far as I can tell. It took only six minutes in the preheated popper to hit a raging second crack and blow off quite a bit of smoke. Roasted weight was 3.2 ounces, or 80% of original.

Not that these tasting notes matter much, since my remaining four ounces are probably all I'll ever have, but they do illustrate a few things.

Shots pulled immediately were horrible. I mean, the worst espresso I've ever had. Overpowering solvent-like flavors. There was improvement after 24 hours, with the raw gasoline flavor abating somewhat. I was unable to detect any of the theoretical fruit flavors, though. After 48 hours it had become quite good, with just a faint solvent edge and noticeable sweetness and fruitiness. It was pretty good straight and very good in a milk drink. Long, mellow aftertaste. After 72 hours, the recommended minimum rest period, it was really nice. No off flavors, some pleasant sharpness, and definite sweet and fruit notes. I would put this into my regular rotation.

So the lessons are that good results certainly are possible with this popper and I shouldn't rush to judge those results.

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