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Overextraction.... um... what is it?

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  • meg-e
    replied
    Re: Overextraction.... um... what is it?

    Originally posted by grendel link=1170933141/15#21 date=1171102158
    Meg-e as a presso user myself, grind size, good tamping and pre-heating the presso and group head have been the three biggies for me. I always pull the shot early too.
    thanks Grendel

    Does pulling the shot early mean not letting the puck get too wet before pushing the arms down? or does it mean cutting the shot short after it starts pouring?

    That is... I hold the arms up for 10 seconds after pouring the water in before I pump the arms. Do you do this for less time? and I wait until Ive squeezed the last drop of water out of the machine (Ive been doing a double pump as thats what I saw Cam do).

    Im playing around with grind size at the moment (variable numero uno). I would have thought it is best to start coarser and gradually go finer or is it the other way around?

    I practiced tamping on the bathroom scales much to the amusement of significant other. Cant seem to do 14kg (is that right?). So *Sigh*... now I just HAVE to get a Pullman Tamper!  ;D

    Thanks again everyone for the discussion

    Meg

    Leave a comment:


  • Dolcimelo
    replied
    Re: Overextraction.... um... what is it?

    JavaB, your explanation is great. I would just summarise by saying that, if your temperature and pressure are correct, then other factors can cause local overextraction at the surface of the coffee grain, but global underextraction of the puck. This is why I would say that even early blonding is usually over - not under - extraction, as you said. It is interesting, is it not, that coffee snobs can still have lots to discuss about even the most basic of (coffee) lifes questions?

    Originally posted by JavaB link=1170933141/15#15 date=1171000974
    Even correctly extracted coffee has different components during an ideal 30 ml shot..... Next time you make an espresso.... collect it into 3 shot glasses - 10 ml in each.

    Taste the first 10 ml...... rich smooth and sweet
    2nd 10 ml.... not as rich or as smooth and the sweetness will be a lot lower.
    3rd 10 ml... starting to get bitter and unpleasant... no smoothness left...

    Combined together they taste fine..... but continue extraction and the quality gets less and less causing the overall taste to rapidly deteriorate.....
    Yes, but that would assume that you only want a rich, smooth, sweet taste in your cup - a bit two dimensional, isnt it? You know, if you let the pour go for a few seconds into the blond, you can add a few high notes to the flavour which are not at all unpleasant. It is all about balance; too much of the smooth, and it is a little dull. Too much of the harsh, and it is undrinkable. A balance of different tastes produces a well-rounded cup, much like a balanced wine, with the right proportion of tannins, acids, sugars and fruits. At least, this is what I prefer. This is perhaps why true doubles are harder to pour, and harder to appreciate, but in the end are more complex and satisfying.

    I think you have made it much easier for Meg-e and others to understand this very important concept.

    Matt

    Leave a comment:


  • grendel
    replied
    Re: Overextraction.... um... what is it?

    Meg-e as a presso user myself, grind size, good tamping and pre-heating the presso and group head have been the three biggies for me. I always pull the shot early too.

    Leave a comment:


  • scoota_gal
    replied
    Re: Overextraction.... um... what is it?

    Originally posted by mean bean link=1170933141/15#19 date=1171065799
    Originally posted by meg-e link=1170933141/0#14 date=1170999548
    Im sure you had other things to do - I appreciate it!
    I dont know what gave u that strange idea. Other things to do?!!
    Are u kidding!! Were Coffee Snobs. What else is there in life besides talking coffee?!! ;D

    Exactly! Since a certain event in my life, it comes to pass that some of my local friends are finding out what I do with some of my spare time! Any way, some were having a chuckle at the fact that there is a whole forum dedicated to all things coffee! Like, their point being "Its only a cup of coffee!". I started to rattle off the different forums we have for discussing coffee and their mouths dropped open in amazement. When I got to the part about roasting at home that really floored them! LOL!

    Leave a comment:


  • rgow6208
    replied
    Re: Overextraction.... um... what is it?

    Originally posted by meg-e link=1170933141/0#14 date=1170999548
    Im sure you had other things to do - I appreciate it!  
    I dont know what gave u that strange idea. Other things to do?!!
    Are u kidding!! Were Coffee Snobs. What else is there in life besides talking coffee?!! ;D

    Leave a comment:


  • Dimal
    replied
    Re: Overextraction.... um... what is it?

    Hi All,

    And heres a link to an explanation about the finer points of coffee extraction, in a practical sense, from Home Barista. The relevant info is found towards the latter half of the page,

    Cheers,
    Mal.

    Leave a comment:


  • Thundergod
    replied
    Re: Overextraction.... um... what is it?

    Originally posted by JavaB link=1170933141/0#8 date=1170972253
    Kind of a glass half empty / glass half full discussion
    Everyone keeps forgetting the third option........the glass is the wrong size.

    Leave a comment:


  • llama
    replied
    Re: Overextraction.... um... what is it?

    Originally posted by Kaffee Schnüffler link=1170933141/0#11 date=1170983339
    ....
    My brain is also a tad scientific, and I have found a few articles over time that explain what actually gives coffee its taste:

    http://cosmicvariance.com/2006/08/07...ence-of-coffee
    ...
    The article by Illy linked from the above that Kaffe gave is a fantastic read. In there he goes into quite a bit of technical detail about what makes up the shot and the differences in under/over extraction.

    Great for people like me that like to understand such things at a deeper level 8-)

    Leave a comment:


  • JavaB
    replied
    Re: Overextraction.... um... what is it?

    Originally posted by mean bean link=1170933141/0#10 date=1170980815

    I stand by what i said about overextraction. But you are right also. Its all to do with how much of the oils are extracted by the flow of hot water. Too fine a grind or too heavy tamping will choke the flow and cause it to leech too much of the oils out of the grounds by the time it gets through the puck. Overextracted and bitter. So in this scenario, overextraction is in process even before the coffee starts to drip out of the PF.
    But I can now see what you were saying, JavaB, about the extra-long pour also leading to overextraction. I wonder, is it due to different oils (more bitter in taste) being extracted, or a difference in surface oil and oil deep within the grounds (if there can be deep within a coffee ground!) or a difference in what happens to the flavour of the oil if exposed to boiling hot water for too long (gets burned)?
    Likewise, in my scenario above, do you agree that it leeches too much of the oils or do you think it is that the oils get burned by the hot water not flowing and thereby spending more time (and presumably applying more heat) to the puck and its trapped oils?
    mean bean.....

    A sort of non technical explanation (which works for me)...

    Remember the sugar coated nasty tasting pills you give to children.....

    Well if you swallow them fairly quickly - before the sugar coating is dissolved- they leave a sweet taste in your mouth...... extract the flavour for too long - by sucking on the sweet coating and then yuck!!!

    Chew the tablet up so it is smaller..... and the nasty taste starts sooner....... and if the pill is too large to swallow.... you have to chew it first.....

    The more technical explanation goes into the volatility of the various oils, the temperature which these oils are extracted, their depth below the surface of the coffee grain etc......

    Even correctly extracted coffee has different components during an ideal 30 ml shot..... Next time you make an espresso.... collect it into 3 shot glasses - 10 ml in each.

    Taste the first 10 ml...... rich smooth and sweet
    2nd 10 ml.... not as rich or as smooth and the sweetness will be a lot lower.
    3rd 10 ml... starting to get bitter and unpleasant... no smoothness left...

    Combined together they taste fine..... but continue extraction and the quality gets less and less causing the overall taste to rapidly deteriorate.....

    The 30 ml volume is a good compromise..... you could just extract 10 ml which would be wonderful..... but you would require a lot more coffee (plus some people actually like a little of the bitter taste).

    Leave a comment:


  • meg-e
    replied
    Re: Overextraction.... um... what is it?

    Gawd!

    Thank you so much for spending so much time answering this! Im sure you had other things to do - I appreciate it!  

    And I guess Im glad I asked! :-/
    Ill need to read it all through a few times but Im sure Ill get there. Im using a presso and its all a bit manual and inconsistent at the moment so Im looking to narrow down the variables. I suspect grind size might be my issue but Id rather work through it systematically.

    Thanks again, I hope this has also helped anyone else who was wondering the same thing.

    Meg

    Leave a comment:


  • JavaB
    replied
    Re: Overextraction.... um... what is it?

    Originally posted by nunu link=1170933141/0#12 date=1170983624
    I like the non-scientific version better. Over-extracted = crap, under-extracted = crap.
    ;D ;D ;D ;D

    nunu...

    Ive got to agree with that statement..... if all the good bits are in the cup and the bad bits are in the puck - we have correct extraction...... the rest is down to semantics... but you have defined it very accurately as cf@p coffee!!!

    Now onto the meaning of life?- easy answer- to get the least cr@p during whatever time we have ;D ;D ;D

    Leave a comment:


  • nunu
    replied
    Re: Overextraction.... um... what is it?

    I like the non-scientific version better. Over-extracted = crap, under-extracted = crap.

    You can over-extract a shot and still have the required volume. Same with under-extraction. Brew temperature in this case is the culprit. Bitter shot vs. sour shot.

    Leave a comment:


  • niallpedlow
    replied
    Re: Overextraction.... um... what is it?

    This is the way I look at it, and I may be wrong, but this is the way my logical brain works:

    The over / under extraction refers to the coffee grounds left in the basket, after the shot has been poured.

    If the coffee grounds have "good bits" (Ill leave the pros to define the good bits) left in them, then they are underextracted.  If the coffee grounds have all the "good bits" extracted, plus some of the "not so good bits", then the coffee is over-extracted. Then theres the bit in the middle of the two extremes where the coffee is good.

    My brain is also a tad scientific, and I have found a few articles over time that explain what actually gives coffee its taste:

    http://cosmicvariance.com/2006/08/07...ence-of-coffee
    http://www.coffeeresearch.org/science/aromamain.htm
    http://www.coffeeresearch.org/science/bittermain.htm

    It may or may not help you to make a better coffee, but it sure is some interesting reading, and puts a bit of scientific explanation around extraction.

    Leave a comment:


  • rgow6208
    replied
    Re: Overextraction.... um... what is it?

    Ok, I got caught out.   Trying to dish out knowledge i didnt have  :. Stuffed up the ristretto thing  :P.

    Youre right, you adjust the grind or the tamping so the flow is restricted and you only get 15ml in 20-25 secs (not 15 secs, as i was thinking).

    I stand by what i said about overextraction. But you are right also. Its all to do with how much of the oils are extracted by the flow of hot water. Too fine a grind or too heavy tamping will choke the flow and cause it to leech too much of the oils out of the grounds by the time it gets through the puck. Overextracted and bitter. So in this scenario, overextraction is in process even before the coffee starts to drip out of the PF.
    But I can now see what you were saying, JavaB, about the extra-long pour also leading to overextraction. I wonder, is it due to different oils (more bitter in taste) being extracted, or a difference in surface oil and oil deep within the grounds (if there can be deep within a coffee ground!) or a difference in what happens to the flavour of the oil if exposed to boiling hot water for too long (gets burned)?
    Likewise, in my scenario above, do you agree that it leeches too much of the oils or do you think it is that the oils get burned by the hot water not flowing and thereby spending more time (and presumably applying more heat) to the puck and its trapped oils?

    Leave a comment:


  • marcstolk
    replied
    Re: Overextraction.... um... what is it?

    So true JavaB.. so true....

    Leave a comment:

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