Friday, December 18, 2009

stovetop versus hot air roasting test 1

I'm finally getting around to doing some controlled tests between hot air coffee roasting and stovetop popper roasting. For this test I used Sweet Maria's Moka Kadir blend.

Stovetop roasting was outdoors at about 50 degrees, high humidity, no wind. Hot air using the Poppery II was indoors at about 68 degrees. Beans started at room temperature in both cases.

I roasted 10 ounces in the stovtop roaster, ending up with 8.43 ounces. Temperature was 550+ at bean drop. I ran it hotter than usual, staying above 350 for the duration and climbing to around 450 at the end. It came out at 4:20 with heavy smoke and some beans well into second crack. This was a fast and uneven roast.

I roasted 5 ounces in the hot air popper, ending up with 4.2 ounces. I preheated the popper for a few minutes and agitated the beans for the first few minutes as well. By three minute it was fluidizing unassisted, with a few already very dark and others barely colored. It came out at 8:00 with moderate smoke, when I judged the color to be comparable. It was even, as usual for hot air.

The closeness of the final (proportionate) weights may be a good indicator of the average darkness being nearly identical.

Toss-cooled both outdoors. There's a nonlinear relationship between mass and cooling time; the smaller batch takes perhaps one fourth as long. I don't have a way to measure the internal bean temperature so don't know whether that's also a factor.

Stovetop results:

Hot air results:

Tasted after resting for a day, pulling single shots. The grind was a little fine (30+ seconds). The hot air beans were a touch slower.

The stovetop-roasted coffee's initial moderate acidity mellows into sweetness, some fruit. Can detect both the very dark and bright tones, probably due to variability in bean doneness. It has both a slightly underdone and a slightly overdone quality, but it's quite good. I think it will be better in a day but it's totally drinkable.

The air-roasted coffee produced much more crema and the espresso had a much stronger coffee aroma. The acidity stays on the tongue considerably longer, with the sweetness blending into it. There is less complexity in the flavors and it's just not as lively. More body. Also good, but I think I slightly prefer the stovetop variant.

For the next test I should slow down the stovetop roast and try to reduce the variability in darkness. This can be done by starting at a lower initial temperature, running at a lower gas setting, or using more beans. Weather is a factor, too. While my opinion is that some variation is actually desirable, being responsible for the more interesting flavors, a better comparison can be made if it is limited.

Overall, a pretty successful test. I'll happily drink both of these roasts straight, with milk, and as Americano.

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