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When we talk about extraction, what exactly is being extracted? : Coffee
If you look at the coffee compass the results of varying extraction are perceptual terms like astringent, creamy, etc. If you poke around some coffee websites like Barista Hustle you'll see more quantative terms like Total Dissolved Solids used to measure the results of extraction. I'm interested in digging into what is happening on a deeper, chemical level. What are the compounds that result in the various tastes and how do variables like heat, ratio, grind size, and brew time affect them? In beer brewing we talk about things like tannins and esthers. If you have any links to resources on the science of coffee brewing I'd greatly appreciate it! Thank you!

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[–]VoteLobsterV60 23 points 7 days ago* . . . This website has some nice tidbits.

It’s a lot of organic compounds, many of which are created during the roasting process from the breakdown of others. To my knowledge, there’s no comprehensive list of compounds because there are just too many.

Acids (citric, quinic, and malic, to name a few) are what contribute to brewed coffee’s pH and certain coffees’ citrusy traits. Certain acids break down under heat into their constituent parts

Lipids are nonpolar (water-insoluble) compounds that manifest in the cup as oils.

Lots of carbohydrates break down in the roasting process into simpler sugars. When we talk about sugars being caramelized, this really means thermal decomposition into water and carbon.

Coffee shares compounds with other organisms (like acids - citric acid cycle happens in all aerobic organisms, starches in plants) - that’s where you get common flavors, smells, etc.

Edit - link

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[–]aboogaboogabooga[S] 6 points 7 days ago
Thank you for putting together this response! Your summary seems like a great overview and starting point for diving deeper. I'll check out the website as soon as I'm free.

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[–]mastley3 7 points 7 days ago
I say this a lot because it changed my life. Coffee compounds extract by size of molecule in this order: Fruit and acid Maillard (roast) Sugars Tannins (bitterness)

The more energy that goes into your breqing, the farther you go into that list. Things that increase energy: finer grind, more heat, stirring, pressure, more time

The goal is to have similar sized particles and extract to the sweetness and not any further. In practice, there will always be some fines that are over extracted, and the sweetness and acidity needs to be balanced.

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[–]heybaybayBadlands Coffee 2 points 7 days ago
you've got a good comment and a good understanding but I think you're wrong on the part about not extracting past the sweet molecules.

if you don't extract into the bitter compounds then you end up with a sour or overly strong and sweet and acidic cup that lacks balance. you have to extract bitter compounds to make it pleasant

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[–]mastley3 1 point 7 days ago
That's possible. In practice, some of the grounds are going to be over extracted in every cup, even if the majority of the grounds are stopped right when they are about to become bitter, because there are always going to be some smaller grounds in there too. Its certainly a matter of taste about how much bitterness one prefers. I don't know

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[–]Indemnity4ǝʇıɥʍ ʇɐlɟ 2 points 6 days ago
You got the chemical order correct but it has little to do with the molecules size.

For instance, chlorogenic acid is a medium-large size molecule but it is one of the most readily soluble compounds in a coffee bean. Most of the oils are quite small molecules and they come out towards the end.

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[–]mastley3 1 point 7 days ago
Tannins, you are familiar with if you squeeze every last drop out of your grain. Similar process. No esters, as those are a yeast product, especially in a hot fermentation.

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[–]derps-a-lotChemex 6 points 7 days ago
Lipids, plant oils, phenols, terpenes, and some mind-altering chemicals. Shit, I forgot which subreddit I was on, but it this should mostly hold up.

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[–]BlackHorseMamba 1 point 6 days ago
What you are asking is alot of information, which are the particulars that most people wouldn't care to know, I believe. Here is one angle from an excerpt from a book: The Professional Barista's Handbook, p2.









brew colloids

body, taste, aroma
You probably need to read a fews books to feel satisfied about this stuff.
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