Announcement

Collapse
No announcement yet.

Underextraction vs Overextraction!

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Underextraction vs Overextraction!

    Hey guys, just moved this topic to a thread of its own. I've researched around a bit and found differing descriptions.. So moreso a varied semantics thing (which term for what type of extraction), and also varied end result (flavours/acids/bitters etc). Included Barry's response (hope that was ok!).

    And yeah I may have moreso described 'signs of', and mixing it with 'causes of', but hopefully it's understood what I'm getting at.


    [quote name="simonsk8r" post=612545]Speaking of vocab, was actually going to start a thread regarding underextraction vs overextraction, but fitting to put it in here! (Thanks Otago, but sorry for hijacking :S..)

    Cannot for the life of me find a definitive answer anywhere...
    I keep seeing these terms being interchanged. I know what each is (if I stick with one understanding relatively speaking!).
    It's moreso the terms themselves I've seen:

    Underextraction= too fast a flow/extraction, not extracting the coffee properly as the water-coffee contact time is too short. Contradictory flavour indicators too: will result in too flat, sour, bitter (I've also seen a faster flow being described as flat in some places, sour on others, and bitter in others.....which I'd love if someone clarified? Experience-wise I've found all three to occur... an Ethiopian bean I've had alot of sourness from a fast flow/larger yield, alot of bitterness from Indian, and flatness from others...)

    Overextraction= far too slow a flow/extraction, too high contact time, have seen descriptions of harsh, sour, acrid/astringent, also seen bitter described for these shots...

    To me this makes sense (the flow rate moreso, not flavour descriptions..), but I've seen the opposite said. That underextraction is that the flow is too slow hence coffee being 'underextracted', and overextraction having too much water flow through the coffee hence overdoing it, which also sort of makes sense..

    Just trying to get clarification on the terms, but also the end result (which I'm feeling may be more dependent on the bean characteristics than generic flavour outcomes for all coffee...). Even after all these these of coffee-ing I'm still confused haha..

    Thanks so much guys!

    Simon[/QUOTE]

    Originally posted by Barry O'Speedwagon View Post
    Probably better starting a separate thread. You seem to be confusing factors that may cause under/over extraction, with what under/over extraction is. As I understand it, under/over extraction refers to the extent to which the solubles in the ground coffee are extracted in the brewing process and land in your cup. Under-extracted coffee is more acidic as the those flavours are extracted more easily. Yes, that may result from too quick a pour (or too coarse a grind or......). The best indicator of whether coffee is over or under extracted is the taste.

  • #2
    As I have understood it, both over-and underextraction are characterized by an unbalanced taste profile. When a shot is underextracted, the intense flavors from a bean (which may be fruity/acid and/or bitter/nutty) are insufficiently balanced by sweetness obtained by the extraction of caramels. Depending on the variety/origin/roast the overall impression of such a shot can be either sour or bitter. Too coarse a grind setting may be the root cause, but also channeling or too cool a grouphead.
    At overextraction, the dry distillates (the least-wanted from the bean) become more prominent and overextracted shots I had on occasion I would describe as dull-bitter or ashy. The darker the roast, the more ashy an overextracted shot tastes. My impression is that with machines that allow you to control / extend the amount of low pressure pre-infusion, you can run slower shots overall before they become overextracted. With fixed speed pump machines that do not offer such controlled LP preinfusion other than an inherent pressure ramp-up, the sweet spot lies with somewhat faster flowing shots.

    Comment


    • #3
      Over/under extraction is subjective, one persons over/under may well be a god shot to others.

      30 ml in 25/30 seconds is a guide only, it should get you well and truly into the ball park, from there its all about experimentation, use some beans and vary extraction times using your standard dose, the flavours you enjoy/dislike will quickly become evident.

      We can discuss the terms ad infinitum on the forum, these terms will still remain a mystery to many, taste and experience are by far the best teachers.

      Comment


      • #4
        Underextraction vs Overextraction!

        Yes extraction is actually a measurable outcome (with the correct equipment) as it's the amount of dissolvable coffee solids that end up in the cup. It's a result of the level of contact the coffee has had with water while brewing which is determined by time and/or the volume of water used.
        Obviously we're not going to check every coffee we make with a refractometer so whether a drink is under or over extracted is usually decided by taste. I get what Yelta is saying that this is somewhat subjective, although I'd add that this is within an acceptable range (which I'm sure is what Yelta meant). Seriously under or over extracted coffee isn't going to be enjoyable to anyone, no matter what your preferences. The biggest mistake people make is that they confuse sourness and bitterness. This is common and isn't only related to tasting coffee. So to be clear under extracted coffee can be sour, but never bitter and over extracted coffee can be bitter but never sour. Work out the difference between these two flavour traits and you'll be able to detect under or over extracted coffee much more easily.

        Comment


        • #5
          As Leroy said, it is determined by how much coffee solids are extracted. Coffee has ~30% soluble solids by mass. We want to extract 18-22% of those into our cup. Above 18-22% =over extraction, and under 18-22% =underextraction.

          In espresso, flow rate and total extracted volume go hand in hand. So you can't just look at how fast or how slow the flow is, independent from how much total water is through. The trend is : high flow rate = lower extraction rate = less extracted solids per ml water, and vice versa. Water is the solvent, so the more water is through the puck, the more you extracted.

          Under-extraction : Not enough solids was extracted. Scenarios : (i) flow rate is slow/ok but not enough water through. ie. only 10ml water flow through puck in 30s, or 10ml in 10s. (ii) flow rate too high (very low extraction rate per ml water). ie. 80ml water flow through coffee in 10s (iii) puck channelling : flow rate is ok, 30ml in 30s. But some portion of the puck is dry/not extracted, thus not extracted properly.

          Note that if you grind too fine, the flow rate can get too slow (supposedly higher solids extracted per ml) but channelling starts happening (you see more dead/dry spot with a bottomless portafilter) so you end up with underextraction.

          Over extraction : Too much solids was extracted. Scenario : (i) flow rate was ok/slow, but too much water was drawn. 30ml water flow through coffee in 60s, or 80ml water through coffee in 40s.

          Note that the numbers are approximate/chosen randomly just to deliver the point.


          Typically it is much harder to over extract and underextraction is more common place.

          To identify extraction via bitter/sour can be a bit more murky. Typically sour=underextracted,bitter=overextracted. But with coffee roasted so light nowadays, the coffee may taste extremely sour to some even if it is overextracted. Some improperly roasted coffee (too light or too dark) can also taste bitter if under extracted.

          Comment


          • #6
            @degaulle: Ah that makes sense, that's what made sense to me, underextracted will show up AS water flowing too fast through (from either too coarse, channeling, low temp etc), and flavour will be too sour OR bitter depending on bean.

            I'd say sourness would be more prominent, would you say too much bitterness comes through only when a shot is left pouring for far too long (that is, it may be a normal good flow, but cut off too late as opposed to a gusher/underextracted shot)? Pieces coming together now haha...

            And overextracted being far too slow and somewhat too harsh and the bitter component being emphasised.

            This is what I've trying to understand (and I've been at this for an odd 8 years now...), just the proper definition and the outcome. I've seen the definitions reversed (underextr resulting from too slow etc), and also the flavour outcomes reversed (too fast equals bitterness or sourness, too slow equals bitterness or sourness...).
            But I'm thinking people may be referring to when shots are cut off also and using some terms a bit willynilly...

            @Yelta: Good points, and definitely appreciate your thoughts. But I guess I'm not aiming at defining what people like as such subjectively, but the definite outcomes of under/overextraction, and the definitions that are used. Like baking a cake for faaaar too long will definitely have certain flavour results, even if people may like that or not.
            But true in that the end result is what matter and what one prefers, I've enjoyed shots that have lasted a minute, and also ones that lasted 15 seconds haha. Just flavour outcomes and proper definitions as to exactly what under/overextraction means not only the signs of it, but the flavour result.

            @LeroyC: Yeah great points there.. Definitely sour and bitter get mixed up, and has to do with not only sensation and flavour, but positioning on the tongue huh. Time to pull some 4 minute long 20ml shots, and some 15s 200ml shots and get tasting 😄

            @samuellaw178: Thanks for that, great point about not only flow rate being important, but total water volume put through (for sure cutting a fastflowing shot at 15s as opposed to cutting it at 40s is going to be to fairly different drinks...)

            Yeah that's made me think...
            So we can ballpark it as such:

            Both under and over extraction is dependent not only on flow rate, but also volume of water put through.

            So

            -fast flowing shot or stopping shot too short (even if it's a slowflowing shot) are both underextracted (BECAUSE in both cases we've achieved less than 18% solubles dissolved)
            =generally too sour, flat

            -slowflowing shot or stopping a shot far too late is overextracted (BECAUSE in both cases we've achieved more than 22% solubles dissolved)
            =generally too harsh, bitter

            Would that be fair to say? Wow, am blown away thanks so much for your answers guys, in a way I knew this but it didn't really click fully until it was explained in that way... (not to mention many years of seeing different terms thrown around and different things described, and my lack of wrapping my head around it moreso haha)

            Comment


            • #7
              Underextraction vs Overextraction!

              Originally posted by simonsk8r View Post
              @degaulle: Ah that makes sense, that's what made sense to me, underextracted will show up AS water flowing too fast through (from either too coarse, channeling, low temp etc), and flavour will be too sour OR bitter depending on bean.

              I'd say sourness would be more prominent, would you say too much bitterness comes through only when a shot is left pouring for far too long (that is, it may be a normal good flow, but cut off too late as opposed to a gusher/underextracted shot)? Pieces coming together now haha...

              And overextracted being far too slow and somewhat too harsh and the bitter component being emphasised.

              This is what I've trying to understand (and I've been at this for an odd 8 years now...), just the proper definition and the outcome. I've seen the definitions reversed (underextr resulting from too slow etc), and also the flavour outcomes reversed (too fast equals bitterness or sourness, too slow equals bitterness or sourness...).
              But I'm thinking people may be referring to when shots are cut off also and using some terms a bit willynilly...

              @Yelta: Good points, and definitely appreciate your thoughts. But I guess I'm not aiming at defining what people like as such subjectively, but the definite outcomes of under/overextraction, and the definitions that are used. Like baking a cake for faaaar too long will definitely have certain flavour results, even if people may like that or not.
              But true in that the end result is what matter and what one prefers, I've enjoyed shots that have lasted a minute, and also ones that lasted 15 seconds haha. Just flavour outcomes and proper definitions as to exactly what under/overextraction means not only the signs of it, but the flavour result.

              @LeroyC: Yeah great points there.. Definitely sour and bitter get mixed up, and has to do with not only sensation and flavour, but positioning on the tongue huh. Time to pull some 4 minute long 20ml shots, and some 15s 200ml shots and get tasting [emoji1]

              @samuellaw178: Thanks for that, great point about not only flow rate being important, but total water volume put through (for sure cutting a fastflowing shot at 15s as opposed to cutting it at 40s is going to be to fairly different drinks...)

              Yeah that's made me think...
              So we can ballpark it as such:

              Both under and over extraction is dependent not only on flow rate, but also volume of water put through.

              So

              -fast flowing shot or stopping shot too short (even if it's a slowflowing shot) are both underextracted (BECAUSE in both cases we've achieved less than 18% solubles dissolved)
              =generally too sour, flat

              -slowflowing shot or stopping a shot far too late is overextracted (BECAUSE in both cases we've achieved more than 22% solubles dissolved)
              =generally too harsh, bitter

              Would that be fair to say? Wow, am blown away thanks so much for your answers guys, in a way I knew this but it didn't really click fully until it was explained in that way... (not to mention many years of seeing different terms thrown around and different things described, and my lack of wrapping my head around it moreso haha)
              Simon I have a really good book that you're welcome to borrow if you like that explains all this stuff really well (photo of cover shown below). In the past I'd read plenty of stuff online by the likes of Hoffmann, Perger etc and had a basic understanding but had never quite wrapped my head around how something could be under extracted and strong or over extracted and weak.
              The way it's explained in this book is much the same, but for some reason it's done in a way that worked for me so it might do for you too. Like you I've been doing this coffee thing for 8-10 years and I'm still learning. I read this whole book front to back and while a lot of it was stuff I already knew it was an easy and enjoyable read.
              The author is a true coffee snob and pulls no punches in this area. He is always very clear about when things he's expressing are his personal opinion though, so he doesn't come off as being 'holier than though'. It's a nice book that's well presented, the only thing that lets it down is a few too many typos which is a shame. Anyway if you're interested send me a PM with your address and I'll send it your way.

              Last edited by LeroyC; 23 July 2017, 08:51 PM.

              Comment


              • #8
                Originally posted by LeroyC View Post
                The way it's explained in this book is much the same, but for some reason it's done in a way that worked for me so it might do for you too. Like you I've been doing this coffee thing for 8-10 years and I'm still learning. I read this whole book front to back and while a lot of it was stuff I already knew it was an easy and enjoyable read.
                The author is a true coffee snob and pulls no punches in this area. He is always very clear about when things he's expressing are his personal opinion though, so he doesn't come off as being 'holier than though'. It's a nice book that's well presented, the only thing that lets it down is a few too many typos which is a shame. Anyway if you're interested send me a PM with your address and I'll send it your way.
                Ha might need to become a bit of a chain mail thing, sounds like a good read!

                Some good questions Simon, and great input on something I too have been but trying to fully appreciate yet also I fear mistaking sour/bitterness as one and the same. Every 'bad' shot I've tasted this far i would describe as 'sour' vs bitter - but sure I've encountered a few of the latter

                Heck I've even been offered a shot from experienced coffee snobs Only to exclaim 'ugh, it's sour' yet they've been shocked when having a shot from the same pour and thinking its spot on. It's left me thinking my taste buds are pretty mixed up if I don't know a 'good' shot when I'm tasting one

                Comment


                • #9
                  Ah thanks so much Leroy that's very kind of you I'll let you know if am keen, what was the title of the book? May just end up buying it as a good reference to have if it's stuff with a good knowledge base!

                  Ahh Crema_Lad I know what you mean hey, and the thing is, no one will EVER know what another person is subjectively tasting, I think I brought that up as a topic when I was studying philosophy at uni, that we could be tasting (even seeing etc) completely different things but be arbitrarily describing something based on our reference point only. We use the same term, and could be experiencing something completely different, but we're using our perceptive reference point, and still be in agreeance. (Of course some loopholes could be explored haha).

                  I might work more on palette refinement, cupping was never a strong point for me. I might research and buy one of each: the most bitter food possible, sour, sweet etc etc, just to REALLY drill it in haha

                  And I actually don't think sourness is an unpleasant as such, it's when it's overbalanced and overdone in that direction when it's overkill I reckon. The delightful sourness of lemon water as opposed to straight biting into a lemon haha

                  Comment


                  • #10
                    The punch of straight espresso is easy to mistake for sourness if you aren't regularly drinking straight espresso

                    Comment


                    • #11
                      Thanks, that's making sense level3ninja!! I am normally a milk based drinker, but getting to know my new machine I've been tasting the shots and I think that initial 'always sour' impression is dissipating somewhat as I'm getting a little more accustomed to the taste of a straight shot. Just today I tried one which was a little sour-ish but I could taste other notes beyond that. I've also had some shots where sour doesn't come into the descriptive, even had one where I could taste distinct marzipan notes and another berries.

                      Exciting progress, sadly not consistently replicating the experience which is what I continue to work on!

                      @Simon, yes I agree it's s good idea to fine tune the tastebuds of sour vs bitterness to apply back to our espresso quest! I actually quite like sour and could easily suck away on a raw lemon, but not so keen on my coffee tasting that way!
                      Last edited by Crema_Lad; 23 July 2017, 10:13 PM.

                      Comment


                      • #12
                        Originally posted by simonsk8r View Post
                        Ah thanks so much Leroy that's very kind of you I'll let you know if am keen, what was the title of the book? May just end up buying it as a good reference to have if it's stuff with a good knowledge base!
                        Sorry, I forgot to insert the cover shot in my post. I've added it now - it's called 'The Curious Barista's Guide to Coffee'.

                        Comment


                        • #13
                          Ah thanks for that mate I'll look into it

                          Comment


                          • #14
                            Originally posted by LeroyC View Post
                            Sorry, I forgot to insert the cover shot in my post. I've added it now - it's called 'The Curious Barista's Guide to Coffee'.
                            Originally posted by simonsk8r View Post
                            Ah thanks for that mate I'll look into it
                            If you search for it on Amazon.com, it has a 'look inside' feature that lets you preview some sections, maybe enough to give you a feel for its overall content.

                            Comment


                            • #15
                              Cheers yeah it looks like it'd be quite a read. Never read any official coffee books, only online stuff, might be an idea

                              Comment

                              Working...
                              X