For this post, I ran four roasts with altered airflow to investigate airflow’s effects on cup character. I’m using Sweet Maria’s Kenya Gakui PB, which they scored an insane 94 (!) and promptly sold out of. All profiles were aiming for 4-3-1:45 (20% development ratio), charge at 460 MET and drop at 403 BT. Here they are:

(1) Lowest plausible airflow - on my Quest, 3.2-4-6 for dry-ramp-development respectively. (By the way, 3.2 is the lowest fan that achieves negative pressure in my roaster, as measured with Rao’s cigarette lighter technique.)

This roast slowed a bit in 1C, sadly, so I can’t generalize perfectly. Also, ignore the fact that I had to swap the BT and MET probes’ measurements early on. I had been dealing with some interference issues and accidentally swapped the probes.

(2) Increased airflow in ramp - 3.2-6-6

Ignore the erroneous 1C start at 366 and you get the 20% development I was aiming for.

(3) Increased airflow in development - 3.2-4-8.4. (8.4 is the max airflow on my Quest.)

(4) Increased airflow in both ramp and development- 3.2-6-max. This was my previous standard profile and fits most guidelines.

Higher resolution imgur link: http://imgur.com/a/DpXX2

I cupped the roasts today, 3 days post roast. 1:18, 203 F, 7.5 grind on an EK, break at four minutes

Here were my findings:

In the dry fragrance, roast (1) exhibits more spice and vanilla flavors - roast aromas were not ventilated as thoroughly. Roasts three and four exhibit more fruit character, tartaric-grape noticeable for three and tangerine citrus for four.

In the wet aroma, (1) exhibits a brown sugar sweetness versus the more fruited sweetness of the others. (4) is definitely the sweetest smelling.

Upon break, the increased sweetness of (3) and (4) is evident.

And the most important thing… flavor -

Roast (1) is the most earthy and very possibly the most complex and intensely aromatic. It isn’t as sweet as (3) and (4) but the complexity helps compensate. It also has more bittersweet cacao character - either due to the slightly longer development or the reduced airflow.

Roast (2) may have slightly more sweetness than (1) but also has more savory character. It’s also a bit nuttier and stew-like than any other roast. Ultimately, this is my least favorite and does not offer any support for increased fan in the ramp phase.

Roast (3) has really impressive sweetness compared to (1) and (2). I also note the pronounced light florals in this roast.

Roast (4) seems best. It’s profoundly sweet and bright but may lack some complexity compared to the slightly darker roast (1). It’s quite delicate. Both (3) and (4) have great and comparable sweetness, but (4) is slightly brighter. Ultimately, this is my favorite roast and was my baseline and projected winner ahead of time. (This was entirely unblinded, by the way.)

Overall preference was 4 >> 3 > 1 >> 2.

So here are my main take-aways and points for further study:

1) As I feared, it seems aromatics may peak later in the roast than acidity and sweetness. I will investigate this further.

2) It’s not exactly clear what increased ramp airflow causes. I will also investigate this further. It seems that ideal ramp airflow is either the same as drying airflow or slightly higher.

3) Increased airflow in development has a noticeable effect on sweetness, increasing it. Perhaps this is due to eliminating roast aromas or flavors, or perhaps it actually spares the sugars from caramelization. It also seems development airflow may increase acidity, though this effect wasn’t as pronounced. In any case, I’ll stick with lots of airflow in development.

4) Increased airflow, especially in ramp, seems to decrease weight loss and allow a lighter overall roast.

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By the way, here are my notes from a V60 of batch 4. Safe to say I’d recommend it.

V60-01

1:18 (12:216) ratio, 203 F, 2:20 for 186 g beverage

1.35 TDS, ~21% extraction Aroma: profoundly sweet red grape, candied sugar, orange wedge candy, ginger, orange peel, fig / dried red fruit Taste: intensely palate-fillingly sweet - one of the sweetest coffees I’ve ever had; orange, sweet cherry, concord red grape juice, tangerine; juicy body Easily a 90+ point coffee. I feel sorry for you if you didn’t get any :)

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Possible future experiments:

Ramp airflow levels -

I don’t feel that this test fully captured what happens by adjusting ramp airflow, so I’d like to investigate more thoroughly. Say airflow of 3.2, 6, and max with dry and development airflow held constant at 3.2 and max respectively.

Roast depth and aroma -

I fear that aroma is maximized darker than I roast. (I’ve read that caramelized sugars are more aromatic.) If so, then I probably just end up sacrificing aroma, but I’d like to see if this really is the case. I’d probably do drop at 400 F (might wind up a hair underdeveloped), 403, and 408, and compare.