Intro:
It seems like it's generally accepted that a conical burr grinder tend to give a brighter taste profile than a flat burr grinder. I got a Pharos with 68mm conical burrs and 83mm Major flat burrs and I believe that I was tasting that and the difference was kinda apparent without serious testings. This got me I thinking for a while about how flat burrs differ from the conical burrs and why they act so and so.

It kinda curious me that the same coffee will taste slightly different with different burrs. There must be some reason for that.

Hypothesis
One hypothesis that I came up with was that given the same brew ratio and timing, the conical grind tends to extract at a lower rate as compared to the flat burr. So this results in slight under-extraction flavor (relative to flat burrs) which then gives the brighter taste profile.

Reasons:
From what I read, the conical burrs give more micro-fines and thus results in a fuller body as compared to a flat. Because of this, flat burr results in a more uniform but relatively smaller average size grinds; while the conical burr gives a bigger size but with more fines/micro-fines, both to achieve the same flow rate/brew ratio with the same timing. Well, as I said, this is just my hypothesis. One thing that I wasn't sure of, is brightness always associated with fruitiness? If this is true, what we're tasting is actually a slight underextraction from the conical?

Also, another thing about the flat vs conical is the separation of the taste by conical tends to be better, again, from what I read. It kinda makes sense that this might also be a result from the slight under-extraction of conical that give slightly less complexity. Thus, our palate is able to pick up better. The flat burr extracts everything(again,relatively to conical) and thus all the tastes were kinda like info-overload for our little tastebuds.

The separation queen - Elektra spring lever, also probably extract less because of its lower extraction pressure, which explains the separation. Again, this kinda fit into the puzzle. But as I said, all these are just my hypothesis.


Disclaimer:
I might make a fool of myself by sharing these thought experiments but it's bothering me that I couldn't figure this out on myself. Plus, these all pieces of info seem to fit each other, so what do I lose from sharing it? Please be gentle if I am wrong.

If it could be explained by 'slight underextraction' couldn't you just get the same results with a flat burr grinder by cutting the shot short?

I sure as heck don't know but is does taste different.

Bluecold wrote:If it could be explained by 'slight underextraction' couldn't you just get the same results with a flat burr grinder by cutting the shot short?

Theoretically you could do that to get a brighter cup but it's not the same as a conical normale(assuming we're talking about normale all along). And it probably lacks the microfines of the conical and it's more concentrated because you cut shorter. So it'll be brighter but not more separated with a different body. You could probably dilute it or something to get a better flavor separation but that's another story. So there's no easy way to get one(conical) taste from the other (flat) burrs. They sure have different characteristic. What I am proposing here it's that the brighter flavor is actually caused by the lower extraction rate from the (slightly) bigger average grind size.

The closest is probably to updose a little and to cut it short to get the same volume. Still it probably lacks the extra body by the fines. And updose by how much?I have no idea.

opother wrote:I sure as heck don't know but is does taste different.

Yeah, me too. But I just don't believe that a burr can emphasize a fruity taste or chocolate tone on the same bean, something must be going on there.

Also, another thing about the flat vs conical is the separation of the taste by conical tends to be better, again, from what I read. It kinda makes sense that this might also be a result from the slight under-extraction of conical that give slightly less complexity. Thus, our palate is able to pick up better. The flat burr extracts everything(again,relatively to conical) and thus all the tastes were kinda like info-overload for our little tastebuds.

Pardon the reduction. You're saying a conical shot tastes more complex because it's actually less complex. Could be. But the ordinary rules of logic tell us "probably not."

BDL

boar_d_laze wrote:You're saying a conical shot tastes more complex (separation of tastes = revelation of nuances = complexity) because it's actually less complex. Could be. But the ordinary rules of logic tell us "probably not."

Thanks for being kind for not rejecting it completely. Probably a better way to put this: In a room with a lot of noises, it's hard to pick up the nuances. But in a quiet room(less noise), the nuances become so much apparent. The nuances did not become louder, just easier to pick up comparatively.

About the grind size, I actually did some crude observation using a light microscope in my lab. It's not totally scientific so I did not intend to post it initially. I sampled the dialed in espresso grind for Pharos and Major, along with some different coarse grinds from Pharos. To my eye at about 40x, the espresso grind size of the Major seems more uniform with fines while the Pharos seems to vary a bit more(Just a bit) also with fines. The average size of Pharos is slightly larger (ignoring the fines). Unfortunately, my iphone is struggling to capture the image for better comparison. So it was really not scientific(nor accurate) and shouldn't be used for anything. Statistical error could heavily influence the result.

samuellaw178 wrote:It seems like it's generally accepted that a conical burr grinder tend to give a brighter taste profile than a flat burr grinder.

No, I don't think it's "generally accepted." There is a conventional wisdom in the industry that big conicals run their throughput faster and so build up less heat in a retail environment. Some think they clump less. (But Mahlkoenig and Mazzer flat burrs have their legions of fans, too, which is neither here nor there.)

I think you are taking the personal experiences of a few posters on H-B and expanding it to a rule that bears further testing.

P.S. You must be the only person in State College looking at a computer screen today, instead of a football game.

The Kony was brighter than the Jolly for many of the TGP tasters; the other flats and conicals did not show this level of difference.

The Kony had higher extractions than the Jolly in many instances, and never extracted less. One reason the conicals were more consistent is that they never underextracted in the normal grind and dose range, whereas many of the flat burr grinders did.

Underextraction does not make a coffee taste brighter, it makes it taste less sweet and less buffered.

The Pharos showed no particular bias in its balance of bright to bitter in the tests that Sherman and I did. It produced as comfortable a shot as any other 68mm conical. However, it was extraordinarily difficult to dial in so the same grind and dose produced the same flow as the comparision grinders. We only managed it on the third test session. This means we couldn't even do any valid taste tests the first few times we used it.

You may want to do more tasting, and even more importantly, get precise with the dose and grind setting, before characterizing the grinder's taste.

another_jim wrote:Underextraction does not make a coffee taste brighter, it makes it taste less sweet and less buffered.

I understand "less sweet" but I don't understand "less buffered". What does the latter term mean?

In my crude way of identifying flavors, I would characterize the taste of underextracted espresso as sour. Is that inaccurate or too simple?

An underextracted coffee has the fast dissolving compounds that, if the coffee is good, you want. This includes all the fruit acids and the short chain sugars. It will also have the medium speed compounds (unless you really screwed up) like the toasty, rooty, herbal, and nutty flavors. The mark of underextraction is that you are missing the caramels, along with the cola and cocoa flavors, and the long chain compounds that give the sensation of body and that reduce astringency (i.e. take the edge off the taste).

A fully extracted coffee is just as acidic as an underextracted one, it just has the sweetness and body to balance the sour tastes. When the coffee is very ripe and has a lot of sugar, a relatively underextracted cup will have more clarity and still be sweet; but that is rare. Older coffee looses its less stable, short chain compounds more quickly than the long chain ones; so coffee should be extracted less as it ages.

This is why you lengthen the usable shot making window by starting with fine grinds and low doses on fresh coffee, and grinding coarser and dosing higher as the coffee stales.