"This coffee is over-extracted" or "This coffee tastes under-extracted". This word can be used in a very pretentious kind of way, to almost make it sound like this topic would go right over your head or if you don't understand what it means then you will be made to feel like a fool.
I get it.
When I first got into coffee this phrase was constantly used and all I wanted was to make a good cup of coffee that I could enjoy. I didn't know the correct way to use it. I didn't know the effect it had on my brewing. It wasn't until I started to really dive into the differences (and tasting thousands of cups of coffee) that I was able to put 2 and 2 together. I now know that having a good cup of coffee and having it extracted correctly go hand in hand, I just think the coffee world has had a difficult time conveying that to the masses. When it comes down to it, once you know and learn what to look for, you can brew some of the best coffee you have ever had even in the comfort of your own home. Coffee was made to be enjoyed. It is supposed to be fun experience. It can easily be bogged down with words and phrases that can over-complicate the process. But hopefully this can help.
What is "Extraction"?
Extraction simply means "the action of taking out something". This idea becomes complicated with coffee because the use of the word becomes twofold. In a chemistry way, it means the actual soluble compounds that you "extract" from the coffee itself. That is a conversation for another time. When you hear baristas and you-tube videos talk about extraction, they are almost always talking about the THING that is extracted. This case, the coffee in the cup. Now these two concept are not mutually exclusive. EXTRACTING your coffee correctly does lead to the EXTRACTION of the correct solubles that make your coffee taste good. A bunch of compounds that make coffee taste the way it tastes. Again, this isn't meant to be confusing, its a pre-cursor to talking about the actual brewing of our coffee and how to make it taste the best it possibly can.
If you have ever had a cup of coffee that makes you pucker your cheeks, a coffee that leaves a dry/ashy feeling at the back of your throat, or a perfect coffee that leaves a sweetness on your taste buds and has a clean finish as it goes down, you've tasted the results of extraction. Granted how a coffee is roasted does come into play (i.e. a lighter roast versus a darker roast), but all coffee has to be extracted to give you the end product of coffee in your cup.
How I learned to correctly identify extraction
Yep... that is what you think it is... a sifter. I like to think of it as a giant espresso portafilter. You know... one of these:
I know its strange, but let me explain. Take the image of the sifter. Take that sifter, fill it up with marbles, hold it over a bucket, and pour water right over the top. What is that water going to do? It's going to flow straight through and come out the bottom of the sifter super fast. The water to marble contact time is going to be almost non-existent. This is the idea of under-extraction.
Now take that same sifter, do the exact same steps, but instead of filling it with marbles, fill it with sand. Pour your water over it and what will it do? The sand will take in all that water and eventually if you pour enough water through it, it will finally come out the bottom very slowly through the now muddy sand that is in the sifter. This is over-extraction. The water to sand contact time is exponentially longer then the water contact time with the marbles.
When we pull double shots of espresso, our "golden time'" of when we like it to finish is around 28 seconds. Now when the coffee grind size is too coarse (think of the marbles), the water will come out of the portafilter at a much quicker rate. Say the shot of espresso finishes at 18 seconds. Without even having to try it, I can tell you it is under-extracted because it finished way faster then what we planned it to be. Now if you have an espresso machine at home, I would challenge you to taste that shot that pulled really fast so you can taste what under-extraction taste like.
One more example, your morning pour over. You have a manual pour over brewing method, you get a new coffee from your favorite roaster, you brew it up that next morning, and it seems to be brewing much slower then usual. If you time your pour overs, you may be aiming for just under 3 minutes but for some reason this coffee is finishing closer to 4 min. I can almost guarantee that coffee will taste over-extracted (sifter filled with sand).
Great! ... Now how do I know what that tastes like?
Timing is the first noticeable element of extraction. But the next step of learning the importance of extraction is taste. This one is a little harder to explain without you actually being able to sit here and taste coffee with me (which I would love to do with all you at some point!) but I'll try to make it as discernable as possible.
All of coffee come down to one simple idea: balance. Balance of sweetness and acidity, balance of aroma and flavor, etc. Having too much of one can lead to coffee that is lacking or that is too intense. For lighter roasts, during the roast process you want to balance sweetness and acidity so that you don't have a coffee that only makes you pucker every time you drink it. For darker roasts, you want to balance mouthfeel and taste and not roast the beans too dark to where all the flavor is gone.
We deal with lighter to medium roasts specifically at our shop, so this balance is crucial to give you all a coffee that isn't roasted too light or too dark. Now in brewing specifically, when things are not in balance, we get over and under extracted coffee. An under-extracted coffee will typically hit you in the front your palate (not in a great way), and an over-extracted coffee will hit you in the back of your throat (leaves you wanting more, dry feeling). Now get a coffee that is perfectly balanced and extracted, it will hit you so nicely in the front of your palate (sweetness, juicy acidity) and pass your tongue to your throat all the way down in such a clean way that it's like you just hydrated with coffee. (weird right? Its the only way I can explain it lol). Our goal is to get to this point.
Under extraction is described as being sour and lacking sweetness. It will make you want to almost "pucker". This is accentuated in espresso (if you have ever had a shot that made you "pucker" I would bet it pulled very fast). In a cup of coffee, its harder to tell but you can definitely taste some sourness and you can feel it in the front of your palate. This is where taking the timeframe into consideration really helps with identifying under extracted coffee.
Over extraction is less "hit you in the face" and more leaves a wanting taste in the back of your throat. This is where bitterness comes into play. Bitterness is sharp and pungent (leading to an astringent taste) as opposed to sour which is more acidic. It leaves you feeling "dry" as if you just drank sand. (ok... maybe not that drastic.... but you get what I mean). Its very hollow and leaves you wanting so much more. Again, take these astringent flavors with the time the coffee finished brewing into consideration.
ok... now how do I fix these to make my coffee taste great!
I hope that all that info helped to make identifying incorrect extraction a little easier. But the crappy part is you have to drink a coffee that is potentially very unpleasant. The great part is your next cup can be so much better. Hers is the simple solution:
If your coffee is under-extracted (think marbles, think sour, think fast finish time), then you need to fine up your grind size. That simple. Fining up your grind size would look like taking your coffee from coarse table salt size to maybe a finer powder. This will make the contact time between the water and coffee last longer and allow more extraction because their is more of a hinderance of letting the coffee out of the brewer (or espresso portafilter).
If your coffee is over extracted (think sand in the sifter, think dry and bitter, think long finish time), then you will need to coarsen your grind. A visual aide would be to take your coffee grind size from table salt size to red pepper flakes size. This will allow the water to more freely pass the coffee and EXTRACT (soluble compounds) in a way that makes the coffee taste much more sweet and clean.
These grind size changes don't have to be drastic. They can be minimal. Unless your coffee is finishing minutes later, you may have to adjust your grinder a few notches finer or coarser. Brew the next batch, and see the difference. It may surprise you how much different the coffee tastes after these adjustments!
Notes about Extraction and taste
There are a few asterisks worth noting with extraction and how to adjust coffee that may not be tasting right.
Hope this helps!
I know its a lot, but it has been years of research and learning that has brought me to this point. (With much more learning still to be had on my part!) If you have any more questions or need help with brewing, reach out and let us know! We'd love to help. Thanks again for reading!