# What exactly are under & over-extracted espressos?



## MikeHag (Mar 13, 2011)

Espresso only. We may have had this discussion before, memory fails. Anyway, please help me get my head around this! Often people use the phrase 'over-extracted' to refer to running the shot too long. But as the shot runs longer, the liquor concentration (TDS) eventually decreases. In turn, extraction yield, which is calculated base on TDS, eventually decreases too. So running a shot long gives a low extraction yield, which is commonly referred to as UNDER-extracted, not OVER.

A silly head-twisting thing that I shouldnt be confused by, but I am!!


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## forzajuve (Feb 2, 2011)

I was thinking about this the other day and I think technically you are right and is perhaps the better use of the expression but I think it is merely the use of wording. I think most people use the term over-extracted in terms of the length of extraction (in time) going beyond the optimum. I suppose this is used as the terminology as most people can easily time a shot rather than have access to measuring of TDS. Although probably extraction terms by yield rather than time are a more accurate approach.


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## garydyke1 (Mar 9, 2011)

You can look at this from a taste perspective or by the numbers and %'s

I think it only adds value to refer to TDS if you have means to measure it, most of us don't (but would love to!)

Most folk on here will use the tongue to decide if espresso is under or over extracted, the more OCD amongst us will use scales to weigh input versus output... so yield might be more useful.

I personally use yield (input v output) as a method to dial-in...THEN I go by taste and adjust the recipe from there, tweeking as my palate dictates.

Overly sour = under extracted (not enough time or not enough water)

Overly bitter = over extracted (too much time or too much water)

Some coffees taste better slight under extracted and some over extracted (from a yield point of view)

My head hurts


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## MWJB (Feb 28, 2012)

MikeHag wrote: "Often people use the phrase 'over-extracted' to refer to running the shot too long. But as the shot runs longer, the liquor concentration (TDS) eventually decreases. In turn, extraction yield, which is calculated base on TDS, eventually decreases too. So running a shot long gives a low extraction yield, which is commonly referred to as UNDER-extracted, not OVER."

I think the head twisting element comes from the fact that TDS (strength, solids as % of beverage in the cup) and extraction yield (% of grinds that leave the PF) are not directly related, only inter-related. So water content of the final beverage is a little moot...theoretically anyway.

E.g. you could have an underextracted lungo (let's say 120g beverage from 15g dose @ 17% Yield/2.13% TDS/2.55g dissolved solids) and an overextracted ristretto (let's say 20g out from the same dose, 23% yield/17% TDS/3.45g dissolved solids). But the overiding thing is a good extraction yield (18-22% of grinds as dissolved solids that leave the PF) can happen at pretty well any TDS (solids as % of beverage in the cup). Grind being a big factor in the result.

I guess some might call a cup too strong/pungeunt for their taste as "overextracted"...which wouldn't be technically correct, it may just be too strong. For the above 15g dose, a "good extraction" of say 19%/2.85g solids can happen at any strength/TDS.

I only reiterate points above in brackets, not because I assume you, or anyone else are "hard of thinking", more because it helps me arrange it in my own mind...because it is a bit of a brain-bruising concept!


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## garydyke1 (Mar 9, 2011)

Good points. Where does this leave us when someone asks ''My espresso tastes too strong , help me fix it'' .

Today was a good example of this (as per the whats in my cup this morning thread)

- 45 seconds, 20g from 18g - didnt taste too bad

- 23 seconds 33g from 18g - didnt taste too bad

- 28 seconds 28g from 18g - worst shot of the lot!?

There are so many variables at play, it a wonder the growers trust us to ever get an accurate representation of their coffees in the cup!


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## MWJB (Feb 28, 2012)

Gary wrote: Good points. Where does this leave us when someone asks ''My espresso tastes too strong , help me fix it'' .

Americano/long black, cortado, capp, flat white...? If you have narrow parameters where the beans to hand only extract properly (Ext Yeild 18-22%) at lower beverage weights, then it may be simpler for some to dilute with more water or milk. If you generally prefer longer shots then beans/roasts that better suit those beverage volumes may be in order. When you dilute a shot, with either water or milk, you change the TDS/strength (dissolved solids become a smaller percentage of total beverage weight), but not the extraction yeild (your 18-22% of the dose that dissolved & made it into the cup stays the same).


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## Outlaw333 (Dec 13, 2011)

You ask an intriguing question Mike,

I define over extraction as the point at which you tip the scales and extract the undesirable compounds in the coffee beyond an acceptable level, this can be done either by running the shot too long or by channelling causing small areas of the puck to over extract while the rest underextracts.

Under extraction I would define as the opposite.

This is where to me it gets a bit more complicated..

When you have gone too fine and made a choker and thus in what you would deem an acceptable time frame you still haven't completed the extraction of all the desirables, you could of course increase overall extraction time to counter it and achive the desired TDS/extraction yield but some would define that as over extraction..

It seems to me that espresso is just a case of juggling grind, temp, extraction time and TDS/extraction yield etc so that what makes up those disolved solids (of which the chemical menu is larger and more complex than i care to write right now!) are are all at the desired ratios.

I would say under and over extraction is far more complex than just TDS and Extraction yield alone and in fact does such a thing as general under or over extraction even exist atall? Is it all just a case of desirable compounds vs undesirable ones?


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## garydyke1 (Mar 9, 2011)

This morning through groggy eyes and a misty brain, the only way i can think about this topic :

Underextraction = pre sweet spot....a sour start

Within correct range = sweet spot....happy middle ground

Over extraction = post sweet spot...to the bitter end

Ah thats better : )


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## lookseehear (Jul 16, 2010)

I think the key is that under and over extraction has to be about how much you have extracted from the beans rather than the volume of the shot. From my limited knowledge extracting 19% of the dissolvable solids of the bean is meant to be 'ideal' meaning you have removed most of the 'good' tasting compounds and not yet any of the 'bad' tasting compounds. So that would mean that removing more than this ideal amount is overextracting and less is underextracting, regardless of how much water it takes to remove it.

Using this logic it makes sense to me that if you run any shot long enough it will overextract, but it begs the question if you have a 5oz shot at 25% extraction that takes a minute to extract and you also have a 1oz ristretto at 25% extraction that took 25 seconds to extract would they taste the same if you dilute the 1oz shot with another 4oz of water?

What makes sense to me is that the percentage of solids extracted will influence the flavour of the shot and the volume of water used to extract those solids will affect the strength. Maybe this is total nonsense but it makes sense in my head!


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## MWJB (Feb 28, 2012)

@Outlaw333 - Well, it could be argued that the primary cause of undesirable flavours is under (sour) or over (bitter) extraction. Time, like grind, temp & beverage volume are all factors in whether a shot (or brewed) overextracts, but none of them on their own dictate overextraction, only how they play out in the whole scheme of things?

Extraction yield is the parameter that decides under/over extraction (backed up with tasting). TDS has nothing (directly) to do with under/over extraction...it's a byproduct of extraction yield vs final beverage weight.

Undesirable flavours may just exist in a coffee that you don't like, or at a strength that you don't like, or at a different profile within the accepted "correct" extraction yields? You may well prefer some coffees on the border/grey areas of under/over...whether they technically are under/over within the context of 18-22% (especially as this is something nigh on impossible to check without a refractometer) is less important than whether they are under/over according to your palate ...but I kind of guess that the vast majority of good tasting shots, determined by sensory perception, would fall within those yields?


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## Spazbarista (Dec 6, 2011)

Outlaw333 said:


> You ask an intriguing question Mike,
> 
> I define over extraction as the point at which you tip the scales and extract the undesirable compounds in the coffee beyond an acceptable level, this can be done either by running the shot too long or by channelling causing small areas of the puck to over extract while the rest underextracts.
> 
> Under extraction I would define as the opposite.


I thought the common accepted use of the terms is the exact opposite, is it not.

Over extracted is when you an overly fine grind resulting in a slow pour that tastes shit even if you let it run on. Under-extraction is when the shot runs too fast for it to pull out enough of the goodness (solids) from the grinds.

I'm sure Mike will take any opportunity to handle his probe, so he might like to pull an over and an under extracted shot and give us a TDS reading.


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## MikeHag (Mar 13, 2011)

I can pull shots with all kinds of parameters, and provide tds & extraction yield, and say whether they taste sour, bitter, weak or strong. But at present that still doesn't tell me if they are under extracted or over extracted, because (as I think this thread illustrates) I still don't think there's a clear meaning that is commonly agreed upon. I therefore don't think they are helpful expressions that we should be using. Just my opinion.


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## Spazbarista (Dec 6, 2011)

I agree that these terms are used in a confused way, because 'over' implies too much, and some think this refers to water, rather than solids. However, I still think they are useful for espresso because they are shorthand for 'you've ground too fine and maybe stopped the shot too short' and 'you've ground too coarse/ let the shot run on too long'.

With the terms weak/strong, you have the confusion over TDS and taste. Weak coffee can have a 'strong' taste, as you will know because you will certainly have tasted an under-extracted espresso at some time. Continental roast coffee has a 'strong' taste however weak you make it.

Of course these terms are not a universal given, and only relate to the beans you are using at a given time, if you know what I mean, and therefore you may pull a series of perfect shots but using different beans and find that when you stick your probe in them you have a different reading for each one.


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## denishicks8 (Jul 18, 2012)

I explain it like this under-extraction being too little flavor extracted, and over-extraction being too much flavor being extracted from the coffee.To be more exact especially in the espresso brewing process, both of these things can be happening at the same time. This is especially true when you have distribution problems, and/or un-level tamping.


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## MWJB (Feb 28, 2012)

Here is a little table I use for determining target shot weight...it might help show the relationship between Ext Yield, TDS, beverage volume etc?

MikeHag wrote: "I can pull shots with all kinds of parameters, and provide tds & extraction yield, and say whether they taste sour, bitter, weak or strong. But at present that still doesn't tell me if they are under extracted or over extracted, because (as I think this thread illustrates) I still don't think there's a clear meaning that is commonly agreed upon. I therefore don't think they are helpful expressions that we should be using. Just my opinion." - Well sour may well equate to under, bitter to over...but weak/strong are something else.

Expo wrote: "I agree that these terms are used in a confused way, because 'over' implies too much, and some think this refers to water, rather than solids. However, I still think they are useful for espresso because they are shorthand for 'you've ground too fine and maybe stopped the shot too short' and 'you've ground too coarse/ let the shot run on too long'."

I agree, I think that there is confusion because of the frequency and manner that the terms are often used with...the terms themselves are quite specific. It's a bit like wine, a lot of folks will taste a wine, not like it, referring to it as "corked". Corked wine is fairly rare really...often it's used as a catch-all phrase for something people don't like.

GaryDyke summed up the over/under breakdown pretty succinctly this morning.

Water volume & time alone do not dictate under/over extraction...only when considered in the context of grind & result in the cup.

Denishicks8 - You could just as easily be discussing "strength"? If you overextracted a small amount of strong coffee, then diluted it down, you would have a larger quantity of weaker, but still overextracted coffee.


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## MikeHag (Mar 13, 2011)

So the words are fine, it's just how people use them that's wrong?


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## MWJB (Feb 28, 2012)

I think that's a large part of it...;-)


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## Spazbarista (Dec 6, 2011)

https://www.sweetmarias.com/library/content/espresso-almighty-crema

Not a bad guide and sort of relevant


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## Milesy (Mar 8, 2012)

As far as I am concerned with my own espresso.

With the same volume by weight:

Over Extracted. Bland, too thick, bitter, burnt

Under Extracted. Sour, watery, bitter as well.

I don't really consider the extraction time in the calculation as I have had a shot at my preferred volume run much longer but yield a well extracted (to me) shot. I think I can only go on my desired shot volume by taste.

Some coffees might bring out a really nice flavour (to me) at a certain extraction point that others might find horrible and regard as over extracted?


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## Outlaw333 (Dec 13, 2011)

The thing is, when you start looking at shot analysis,(Cosimo's is very interesting) you discover that even in the best shot you have ever tasted, there are still very significant levels of what would on their own or when out of balance be described as undesirable flavour compounds, when there are so many ways round to achieve ones target extraction yield and TDS it seems to me that extraction is far more than just a simple over extracted vs under extracted. You could for instance pull a shot at one grind setting and hit your target extraction yield in 27seconds but then you could grind finer and have to pull the shot for 40seconds in order to hit the same yield, the resultant shots would have very different flavour profiles but have the same yield, which to me highlights what i was saying, is there such thing as simple under or over extraction?


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## MWJB (Feb 28, 2012)

Yes, because you can change/balance the flavour profile (as you outline) within the ideal extraction range...e.g. 19% yield won't taste just one, single way. There is such a thing as simple & obvious over/under extraction...however, dialling in to suit your palate, within the ideal range...maybe even sightly below it, is more complex.

Say I had 3 apples, one weighed 8oz, one weighed 10oz, the other 12oz - which one is the sweetest? Which one is the most sour? Which one is red? Which is the ripest? My point being that the weight is just one parameter (as is yield), all 10oz apples won't taste the same. Even if all 3 apples had the same relative level of acidity, or sourness the balance of other flavours will make them taste different.


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