Source: Bunn Coffee Basics Brochure (.pdf).
Let’s use Mr. Coffee to validate the Bunn diagram.
What do those parts of the brew cycle look, smell, and taste like, coffee-wise?
Thanks to Mr. Coffee, I can find out, so you don’t have to.
Spoiler alert: There’s a reason you don’t see this done.
Just as a heads-up, those three fractions of the pot of coffee were each, individually and differently, lousy-to-undrinkable coffee. You have to mix the three (back together again) to have a pot of decent coffee.
Which means there is no practical point to doing this, ever, other than to verify the Bunn diagram. In so far as getting three different-looking, different-tasting, different-smelling cups of liquid validates it. Having done this once, you would never, ever, knowingly separate these liquids. There is less-than-no advantage to doing so.
But, interestingly, this means that fractioning of coffee by brew time is nothing at all akin to distilling liquor (fractioning alcohol/water mix by temperature.)
From an operator-goal perspective, that is. In liquor distillation, there’s a “good” fraction and it’s your job to find it (and discard the rest). With coffee, by contrast, there is no “good” fraction. Each fraction, by itself, is basically awful coffee. At least with my 5-cup Mr. Coffee, the mix of all three (as shown above) tasted better than any of the individual glasses. In some cases vastly better.
Channel your inner Heisenberg
The whole coffee-brewing process has a lot to it. Most of which is irrelevant here.
Here, I want to fraction a pot of coffee, by extraction by time.
That means exactly what it sounds like. I want to divide it into pieces. With the nuance being “chemically relevant” pieces, as opposed to pouring three mugs out of the finished pot.
Here, I want to try to match the Bunn diagram, separating out the stuff that leaches out first, middle, and last over the course of the brew cycle.
It’s an interesting process because it all takes place at the same temperature, and it’s all driven by the extraction rate. Roughly speaking, I’m guessing that the first things to come over is the stuff that’s most readily dissolved in hot water. But know, from Bunn, that the speed of the entire process is hugely dependent on grind size.
The only nicety here is that I’ve ground the coffee beans myself, and I grind them coarse to match the 8-minute Mr. Coffee brew time. Not quite as coarse as what my grinder marks for French Press.
Physics rears its ugly head once you scratch the surface of pot-capacity-and-brew-time. That, because you need to raise room temperature water to (near) boiling, and that requires a given wattage, to raise a given amount of water to boiling, over a given amount of time. This is why my dinky little 5-cup Mr. Coffee takes 8 minutes for the pot. He only draws 650 watts. If you want that same small pot, in just four minutes, it’s going to take a much higher-wattage appliance.
Oddly, Bunn offers an under-four-minute 10-cup pot, but they do that by keeping a reservoir of water hot. So a) they are always “on”, keeping that reservoir hot, and b) they only need to raise the water temperature from reservoir temperature to boiling, on the fly.
It’s easy enough to get a Mr. Coffee to produce those three “fractions” of a batch of coffee, thanks to what used to be called the Mr. Coffee “sneak-a-brew” feature. (Now, renamed “sneak-a-cup”, for reasons I cannot fathom. I don’t think I’m clever enough to have hallucinated “sneak-a-brew”, but I can now find no internet references to that phrase.)
Anyway, with care, I can remove, pour out, and replace the coffee pot every-so-often over the course of the complete coffee brew. Mr. Coffee doesn’t care. He just keeps brewing.
The resulting “fractions” of that pot of coffee are as different from one another as the pictures imply. (So different that now that I’ve done this, to a pot of coffee, I’d bet I could find ten examples of others doing that, on-line.)
For smell, the 3rd (last, lightest-colored) fraction was terrible. Noticeably god-awful. Not even remotely edible. But for taste, mostly, just kind of bland. I expected super-bitter, I got … not that.
Beyond that, and the obvious color difference, I should have take notes. The middlin’ fraction was, best I can recall, kind of middlin’. The first (darkest) fraction smelled good, but tasted bitter. Ish (“sour” might be the right technical term, but it came across as bitterness to me.)
Weirdly, the only practical advice that comes out of using the sneak-a-brew feature this way is never use the “sneak-a-brew” feature, or at least not on a device with a small coffee pot.
That’s because the three “distillates” were each, individually, awful. And, apparently, this is to be expected, by those in the know. Coffee needs a balance of all of that, to “taste like coffee”.
Coffee “deconstructed” in this fashion — at the cut-points of the Bunn brewing diagram, ideally — is terrible.
And yet, the three glasses, poured back together, made a typical pot of Mr. Coffee coffee.
Conclusion.
Source: I grind the beans coarsely, for my 8-minute Mr. Coffee brew cycle.
Nobody expects good coffee out of a Mr. Coffee.
They are often not disappointed.
That aside, what did I learn.
First, never use the “sneak-a-brew” feature. The “sneak-a-brew” feature probably only ever worked because that initial fraction, by itself, can pass for coffee. But what you end up with is two inferior half-pots of coffee, now, instead of one better pot six minutes from now.
That said, this means I misunderstood why the Aeropress was a good solution to the problem of finely-ground Christmas gift coffee. The problem is that finely-ground coffee, brewed in a Mr. Coffee, brews too long, over-extracts, and so becomes bitter.
I thought this had to be a consequences of getting too much from the final third of the extraction. From brewing too long.
But that explanation does not square at all with this little experiment. For the simple reason that the final third of the extraction didn’t taste bitter to me. The first third did.
And that’s the point at which I can no longer connect the dots.
For sure, the Aeropress worked. It’s not just my taste buds that say so, but my grinder manual as well. If I were to grind coffee fresh, for use in the Aeropress, I’d grind it fine.
Why it worked, I’m no longer quite so sure.
