Coarse and cold: how and why?

Coffee preparation techniques besides espresso like pourover.
wearashirt
Posts: 228
Joined: 9 years ago

#1: Post by wearashirt »

Does anyone have some technical insight as to why coarsely ground coffee, mixed with cold water, yields a delicious cold brew?

I'm baffled as to why it works, when brewing with super low energy supposedly doesn't mobilize as much of the solubles. Apparently, there's more to it than that.

I used to do a super find grind, but I found that it stales on the 3rd day. WIth the coarse grind, the drink is good up to the 3rd day. (I also vacuum the mason jars where they brew.)

So: what's the deal with coarse and cold?

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FastGlass
Posts: 67
Joined: 8 years ago

#2: Post by FastGlass »

Just wrote you out a nice response but somehow back buttoned it and it's gone. The long and short of it has to do with larger surface area but also greater volume of grinds and a LONG extraction process (usually)...extraction efficiencies. As luck would have it, I'm making a dual batch of Yamas as we speak and can get you some hard numbers to play with tommorow if you'd like. I loaded each with 456 grams of a slightly more coarse than would be used in pourovers (7.2 on the EK43) blend of Kona and Guat I love. I'll measure volume and we can figure it all out.


bobdole2000
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#3: Post by bobdole2000 »

FastGlass wrote:Just wrote you out a nice response but somehow back buttoned it and it's gone. The long and short of it has to do with larger surface area but also greater volume of grinds and a LONG extraction process (usually)...extraction efficiencies.
Slight nit pick, but larger particles give you less surface area per volume.

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FastGlass
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#4: Post by FastGlass replying to bobdole2000 »

Too true! I was a bit asleep at the wheel there.
Anyhow, this batch was a poor one...somehow. Still scratching my head as it's the same beans, roast and grind I've been using for two years, but I had a ~2" x 3" section in EACH cylinder that were bone dry. As you can imagine, the resultant brew was a bit thin. Still ok, but not worth measuring TDS etc...
Next batch.

wearashirt (original poster)
Posts: 228
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#5: Post by wearashirt (original poster) »

Hi Cliff.

This post was largely went unnoticed, so I rolled my sleeves up, set aside a lot of beans to run some tests. It's in one of my posts after this one. Basically, I compared coarse and fine grinds for cold brew, and found similar transluscence of the solutions after filtering, as well as somewhat same strength, but the coarse grinds lasted better with longer exposure and had better volatile aromas. I now believe that solubility of coffee is dynamic with brew temp and exposure time, and is prone to off-tastes when over exposed, which is why coarse grinding is favored because it facilitates (1) solute/solvent circulation, (2) delays onset of dissolution of off-tastes, and I guess (3) facilitates filtering process.

Cheers! Cold brew is the best! I has so much potential for R&D.