What does grind quality mean?

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jbb
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What does grind quality mean?

Post by jbb » Wed Apr 20, 2011 12:32 am

perhaps this is way pedantic, but this term does get used a lot throughout the coffee web-o-sphere. What does it really mean? Is it quantifiable in some sort of way (like as a metric for objectively comparing grinders)?

for full disclosure, i did post a somewhat related question on CG about a year ago. And it went down...like a big...lead...balloon. :-( And maybe deservedly so. but i've been really interested in all these higher quality small footprint grinder coming on the scene, and it still strikes me as a useful thing to know more about.

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Endo
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Re: What does grind quality mean?

Post by Endo » Wed Apr 20, 2011 2:39 pm

It's a good question. Especially when you're dishing out $2K for a titan grinder that reportedly has better "grind quality".

I would work backward from the cup. Assuming you could first repeat this "godshot" indefinitely (meaning all variables besides grind quality are kept constant) and then rewind and see what the properties of the grounds are that produced that shot. This I would consider the highest "grind quality".

These properties would be obvious things like particle size and shape, but also some less obvious things like proportion of fines and even things as subtle as flavour alterations due to heat build-up during the grinding process.

Of course these things are almost impossible to isolate on their own, so we tend to skip a few steps and just go with how it tastes in the cup. Hence some grinders produce better "grind quality" (aka better taste).

I'm afraid if you were to actually investigate this further, you'd proabably find a great deal of what we consider to be attributed to a "grind quality" is simply reduction in scatter. That...and probably a heavy dose of $2K grinder "placebo" effect. In other words, your more willing to remember the "God Shots" overlook the "GAWD Shots" :roll:
Endo

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jbb
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Re: What does grind quality mean?

Post by jbb » Wed Apr 20, 2011 6:09 pm

The working backward approach you suggest puts me in mind of the titan grinder project/can it bear the robur shoot out. If I recall, these tests were done blind although sample size was small. while there were some surprises (like the Rocky win at low doses) the trend seemed to be that the Robur led the field, although in many cases it was very close.

and maybe that's all it is, titan class grinders exhibit less play in the burr carrier assembly, more effective transfer of power, better adjustment mechanisms. stuff like that.

so maybe one view is that grind quality simply refers to a more uniform, consistent grind, accompanied by a ratio of fines to particles that packs within the puck in a way that creates an even cross-sectional flow. that is grind quality is expressed through puck hydrodynamics.

perhaps a second view would be the these larger grinders exhibit fracture mechanics that better preserve the intrinsic porosity of roasted coffee. such that extraction surface area per unit mass would be increased.

i wonder what the outcome would be if one dialed in a range of titan and non-titan grinders such that, at a given dose, they yield a fairly equivalent shot volume in the same extraction time. one placed at those settings, acquire grind samples and compare the saturation volume of a given mass of coffee. Or, with the grinders dialed in to produce equivalent flow rates, would there be reproducible differences in shot density/extraction efficiency? then, if any meaningful differences are observed, what does you palate say.

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