it's raining here in san antonio. something rare during the summer months here. and it got me onto some rainy morning ponderations and note-taking experimentations. i decided to think toward and play a bit with two parallel tracks: pour techniques for a manual brewer such as my chemex; and how taste perception changes as temperatures cool.
typically, when i use my chemex (which is about every morning) i set up the 6-8 tablespoons of grounds using a sort of aztec-maya inverted step pyramid array. meaning, i poke my finger into the middle and carve out a niche point in the bottom center, followed by a wider layer above it with a terrace, and finally capped with a rim about an eighth of an inch in diameter around the outer top. when my water reaches temp i pour from the melitta kettle (love that surgically precise spout tip!) into the bottom cave and up onto the next layer, leaving the outer rim of grounds dry. the center blooms--as chemex recommends--for about 30 seconds, at which time i encircle the wet grounds with another string of water...carefully, carefully so as not to overflow the center grounds. eventually, the water level has risen to the point that all the grounds are wet, but water has not been poured and agitated over either the very center or the very outer rim. this is built upon the assumption that you don't want 100% complete saturation of 100% of the grounds, which helps ensure that you don't over-solublize the final brew. pretty soon all the grounds are wet, as you would expect. eventually, as the water levels dip i pour water closer to the center and let it all drain down--the whole thing generally taking around 4:30 and producing in my 30 oz brewer about 20-22 oz.
i've blogged all that before, i think. suffice it to say i was looking to try something different this morning. so i thought i'd migrate my melitta pour over technique onto the chemex and see how it goes. the grounds and water quantities are the same, though the setup is basically the exact opposite: set up a little mountain in the middle of the filter; pour your hot water around the outer most rim of coffee and work your way inward. in this method, water actually never gets poured over the center peak (about a nickle's circumference) because the surrounding water eventually overtakes the peak and sinks it into the center inverted-cone the chemex brewer shape forces the filter to make. same principle as above--you don't want all the coffee grounds saturated the same way and to the same level.
i digress. aside from the fact that i was very pleased at the liquid results of my migratory brewing adaptation betwixt apparati, the main show for me this morning was how coffee cools, or rather, how we perceive the change in flavors as coffee cools.
i decided to use the last of my samples of a very nice coffee, one kenya gethumbwini (peaberry) (which brown has chosen to add to its lineup, btw), since it possesses such an unmistakable flavor signature. roast level and profile were typical of my production roasts and where the drop happens in the no man's land period toward the very end of first, awaiting the imminent invasion of second crack.
i set up my mountain in the filter cone and carefully poured water at 200F even over 3:45, yielding me ~19 oz and was, as per my usual ritual, careful to give a "decanting swirl" before pouring.
brew temp was a constant 178F throughout, falling to 165F by the time I poured into my mug. my first sips were at 154F. at that point all the fuss and glory was in the top end acid. no surprises there. as we worked lower, though--into the 140's--the depth began to show and at about 133F i would say i found the "center mark" of the roast i applied to this coffee. at that temp i found the acid and body were in their best balance. or rather, in their best dynamic tension, as complex coffees such as this, in my opinion are always pulling thither and yon, showing you something different, giving you a different angle.
anyways, toward the high 120's the deepness this coffee has latent in it really begins to come out to play: the black currant, the ruby red grapefruit, the overripe thompson grapes/raisins. acid almost completely disappeared from my perception, or i should perhaps rather say that though it was surely present, the fireworks were now well deeper in my tastebuds and i was mostly perceiving these lower tones.
i kept sipping this coffee with similar taste results, thermometer probe faithfully submerged into the mug, until about 102F, almost body temp. i had walked away from the table for a bit to put on a c.d. of one of the kids' favorite bands and when i picked up the mug for my last sip of the "experiment" i was surprisingly jolted back to the acid, something i thought had long dissipated in the taste mix. my only explanation for that is that as i kept tasting this coffee, the perception of acidity had become dulled and accounted for in my brain in much the same way as the midnight trains' traffic horns aren't even heard anymore from my downtown apartment's sleep. but upon return the great acid this coffee possesses was suddenly recalled in glorious splendor from a gloriously splendorous coffee.
my on-the-fly analysis? yes, complex coffees will present different stuff at different temps. no surprises there. maybe this is the appearance of different sugars that dance most at their respective temperature ranges between the tongue signals and the brain synapses. but the disappearance and re-emergance of acidity after i had walked away and revisited the cup was what i found most interesting, and that is what spurred this whole wander-through-the-forest-post.
would this phenomenon of resurgent acidity perception hold true with the same coffee roasted differently? or with other acid-forward coffees? what would be the result if i used a very low acid coffee? how much did/does brew technique affect that? brew apparatus?
just some swimming thoughts as i prepare to swim back out into the deluge of rain we're enjoying and run some errands. constructive comments welcomed.