Grind size/quality - all hot air? How is it important at all?

[DubiousDrewski]

I need to understand this, maybe you all can help.

Smaller coffee grounds equals more surface area in contact with the water. Doesn't that simply mean more flavour is transferred? People keep telling me to grind my coffee course, but that makes no sense to me.

Also, I keep hearing that the quality of the particles plays a big role in flavour. Again, I don't understand how this would be. I use a simple little blade grinder, and people tell me it's the cause of my mediocre-tasting coffee. They say it's because of the uneven particle sizes it creates, but that doesn't tell me much.

Truth is, my coffee isn't really that great, and I don't know why. But this advice just confuses me. What's the science behind this?

 

[Surfer]

You just answered your own question, the blade grinders <----- just not suitable for any coffee even coarse drip vs a low end grinder (actual burr grinder not ones with burr sets made more for crushing). Grind quality is extremely important, you need even nice grinds across the board (espresso - drip) which is something a blade grinder cannot do. I.E. grinding with a blade, you'll end up with particles that are all various sizes from small to large, letting smaller ones over-extract and larger ones under-extract... hence coffee won't taste good. Something like the Baratza Encore would be good for coarser needs (drip, pour over, french etc), for espresso you'll need to step it up. Espresso grind quality is even more important but you didn't say what setup your using.

 

[DubiousDrewski]

Thanks for the info! I'm sorry I forgot to mention my setup: just a little grinder and a press pot.

grinding with a blade, you'll end up with particles that are all various sizes from small to large, letting smaller ones over-extract and larger ones under-extract... hence coffee won't taste good.

I do not understand at all. Scientifically and precisely speaking, why does having varying sizes of particles make the coffee taste bad? Is it the larger particles that taste bad, or is it the smaller ones? Or is it only when you have a mix of large and small particles? How does that make any sense anyway? It's all the same material from the same beans, just differing sizes.

This is how I understand it: If I take a butterscotch candy and eat it whole, it tastes like butterscotch candy. If I break it into smaller pieces, it will still taste exactly same. Why wouldn't it?

 

[expat]

Not hot air and very important!

A lot of it has to do with how long the water is in contact with the coffee.

Espresso grinds for instance are very fine because you are jetting high pressure water through the grounds. Maximum surface area is needed for this and it has a unique flavour because of the process. If you took the same coffee and coarse ground it and used it in a press or drip machine it would taste differently.

And if you took my coffee that we grind for a press (where we expect it will steep for 4-6 minutes) and put it through an espresso machine where you're getting water in contact with coffee for 30 seconds or less, you'd have very watery tasting coffee because you would not have been able to extract . . . how can I put this . . . all the coffee in the coffee (even though the coffee coming from the press would be bringing a big smile to your face). Does that make sense?

 

[Surfer]

Thanks for the info! I'm sorry I forgot to mention my setup: just a little grinder and a press pot.I do not understand at all. Scientifically and precisely speaking, why does having varying sizes of particles make the coffee taste bad? Is it the larger particles that taste bad, or is it the smaller ones? Or is it only when you have a mix of large and small particles? How does that make any sense anyway? It's all the same material from the same beans, just differing sizes.This is how I understand it: If I take a butterscotch candy and eat it whole, it tastes like butterscotch candy. If I break it into smaller pieces, it will still taste exactly same. Why wouldn't it?

The answer to this question is right in what you quoted from me lol. A blade grinder doesn't grind (big negative there), it just chops beans up unevenly. The candy analogy doesn't work here. Like I said you end up with some small pieces/fines that will 'overextract' and large pieces that will 'underextract'. Water stayed in contact too long for one and not long enough for the other. Coffee needs quality, even particles to extract correctly.

A good burr grinder will make your press pot taste massively better vs the blade. Hope your using fresh roasted beans as well (not Starbucks or anything store bought) b/c stale beans will taste stale no matter what.

 

[eldub]

Different grinds are better for different types of brewing set-ups.

A fine grind doesn't work well in a french press because the small particles get through the strainer. A course grind doesn't work well in espresso, as mentioned above but makes good coffee in a french press.

In general, it takes longer to extract the flavor from a course grind than a fine grind.

 

[VerS]

Thanks for the info! I'm sorry I forgot to mention my setup: just a little grinder and a press pot.<br>
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I do not understand at all. Scientifically and precisely speaking, why does having varying sizes of particles make the coffee taste bad? Is it the larger particles that taste bad, or is it the smaller ones? Or is it only when you have a mix of large and small particles? How does that make any sense anyway? It's all the same material from the same beans, just differing sizes.<br>
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This is how I understand it: If I take a butterscotch candy and eat it whole, it tastes like butterscotch candy. If I break it into smaller pieces, it will still taste exactly same. Why wouldn't it?

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The ground coffee bean does not scientifically react the same as butterscotch pieces. I believe if you put small butterscotch pieces in 95C water and agitated the mixture, the butterscotch would totally dissolve. Ground coffee does not totally dissolve. The coffee solids or fibre remain, usually with some of the bitterest flavors still trapped in them. Different flavors and components extract at different rates. Caffeine extracts quite quickly. The bitter flavors extract more evenly over a significantly longer period of time. That's why if you wait 30 minutes to press the plunger on your press pot, you will have very bitter coffee.
You already understand that fine ground coffee has a larger surface area. With this larger surface area in contact with the water, you can probably now understand how the later stages of extraction when the bitter flavors overpower the others is reached in a shorter time. The other scientific explanation that helped be understand this better was to think of the distance from the outside of the coffee particle to the center. With a coarse (larger) particle it takes the hot water longer to dissolve, extract or draw out the flavor since it has a greater distance of coffee solids or fibre to permeate through.
Regarding your question about which size particles make the coffee taste bad: in your press pot it would usually be the fine particles because they reach the stage of extraction where mostly bitter flavor is being extracted much faster. The coarser particles are just beginning to reach the most tasty stages and the fine particles are already spoiling the brew.
These concepts helped me understand what is happening. Hopefully they will do the same for you.
When selecting a conical burr grinder for press pot (usually my favorite as well) you do not want an expensive grinder optimized for espresso. Espresso relies on a range of particle sizes to properly compact. This range of sizes is precisely what you do not want for press pot coffee. I do not have the experience to prove this, but the physics makes sense to me.