Flavor profile and grinder burrs

Grinders are one of the keys to exceptional espresso. Discuss them here.
cai42
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#1: Post by cai42 »

Greetings,

Why does the flavor profile change with different burr sizes and shapes?

Cliff

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another_jim
Team HB

#2: Post by another_jim »

There's two issues: what does the best tasting espresso grind look like? And what sort of burr produces it?

The very incomplete actual answers we have so far to both these questions contain more surprises than enlightenment.

The expected answers were very simple and intelligible.
-- The best brewing grind should have particles of exactly the same size (i.e. surface area to volume ratio), so they all brew perfectly in exactly the same time. The best espresso grind should have coarse particles of all the same size for similar reasons, and it also needs some fine particles to glue the puck together and prevent channeling.
-- The best grinders are multi-roller grinders that gradually diminish the coffee particles in size step by step, and that, at each step, feed in particles of identical size. A large burr grinder with well defined bean crushing, coarse grinding and fine grinding sections would also do well. A grinder that reduced particle size chaotically, the whirly blade being the poster child for this process, would produce a poor grind.

The large number of grinders used in the titan grinder review roughly bore out the expected answer on burr size and grinder configuration. The more gradual grinders with larger, slower rotating burrs generally produced better espresso than the more abrupt grinders. We did not get a chance to test any titan flat burr grinders, but the buzz on the Mazzer Major, Caimano, and other titan flats does not contradict this assessment.

The huge surprise was in the look of the best espresso grind. John Weiss (Rapid Coffee) scored a great coup for HB by being able to put the Titan grinds through a laser sizer and scanning electron microscope. The huge surprise was this: the Robur, the unanimous choice winner of the Titan showdown, had a rather wider coarse particle distribution than the flat burr grinders, but with a more uniform particle shape.

Here's my personal explanation:

1. If you look at the odd shape of the grind particles, the entire concept of grind particles having the same extraction rate is ridiculous. The extreme shape variation makes this impossible. In terms of extraction rate, any two grinders that put all the particles in roughly the same order of size magnitude will do as well, regardless of which one is slightly more uniform or non-uniform.

2. The absolutely overwhelming factor of espresso grinder quality is how solid and uniform of an aggregate one can make out of the ground coffee. The minimum standard is a naked extraction with no apparent channeling. But it is abundantly clear from the much larger margin of error one has with the titan grinders that they are creating an aggregate in the puck that is a lot more robust and uniform than that created by the smaller grinders.

3. Then there is the lesson we all learnt from using extremely bad grinders such as whirly blades and knob "burr" grinders. They suck for both espresso and brewed coffee. My guess is that it is not so much the non-uniformity in grind that is the problem here, but extremely damaged cell structures. Ground coffee initially absorbs a lot of liquid and swells. One doesn't really want this absorption getting into the cup, since it tastes like instant coffee (just wet ground coffee, let it sit, and press it out, then do the same with already brewed ground coffee. In both cases you get the characteristic instant, over-extracted taste). So there may be a quality factor here that requires more exact definition

Sorry to go on so long. This is a topic I currently like.
Jim Schulman

cai42
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#3: Post by cai42 »

Hi Jim,

I learn from your posts whether they are long or short.

Thanks,

Cliff

cai42
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#4: Post by cai42 »

Hi Jim,

If you had to give a percentage on the influence burrs versus the parts that drive them have on the "cup", what would it be?

Thanks,

Cliff

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another_jim
Team HB

#5: Post by another_jim »

I actually had two honest to god real opportunities to find out:

-- the Compak WBC, the Doge Conico, and the Macap M7X all have the same 68mm conical burr, but the Compak has a 1 HP motor, the Doge a 2/3 HP, and the Macap a 1/2 HP. In terms of grind quality, they were indistinguishable. Their different scores in the various taste tests are within the shot to shot noise level; but more importantly, they always tasted the same and poured the same, just a hair more laid back than the Robur, but not as laid back as the Jolly. The difference the motor made here was in a smooth start. The Compak starts quietly, the Doge makes some noise, and the Macap shakes, rattles and rolls until it settles in. (I think one reason the Mazzers are so well liked is that they are never undertorqued).

-- But a slipping, jamming motor is another story. The Versalab M3 and the Cimbali Max have nearly the same burr set. The slower grind speed of the Versalab should have made it the better grinder. But the belt drive, drive shaft coupling, and grind setting, all being primitive friction mounts, always slip slightly, and sometime grossly, on anything except the darkest roast beans. So the performance is very inconsistent in terms of taste, although this is disguised by the fluffy grinds and nice pours. The Max was always a very clear tasting grinder, and nearly as consistent pouring as the big conicals.

I think experienced grinder manufacturers size their motors to get jerk free performance, so that power is not a factor. Silky startups, on the other hand, are an optional extra.
Jim Schulman