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Systematically Improving Espresso: Insights from Mathematical Modeling and Experiment

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  • #16
    Originally posted by Yelta View Post
    — suggests that the key to making consistently good espresso is using far less coffee at a coarser grind, with less water and a faster brew time than found in established methods.
    With the emphasis on coarser grind, just wondering if they have also played around with brew pressure in their experimentation?

    Assuming that 9 Bar was the setting used during these types of experiments? At 8 Bar for example wouldn't a coarser grind be required to achieve same volume for a given time? Wonder how that would have shaped up. It's on my list of things to play with. Currently pressure is set a little on the higher side so using a bit finer grind than I would for 9 Bar I guess to achieve same volume for the 25-30 sec. Seems to work well on my machine.

    Comment


    • #17
      Originally posted by simonsk8r View Post
      G=kcs(cs−cl)(csat−cl)

      There ya go! Clear as mud!

      Admittedly I skimmed through, fascinating... don't know if I can adjust pressure of group head on my machine, but that would be fun to play with..

      Always love a good research project in coffee!


      I don't fully understand what they can do but the Decent espresso machine is probably the tool of choice if one was to try and perfect this method.

      Ill stick to my old school ways and flagrantly waste 3gm of coffee, 10ml of water and 20seconds of my time in excess of what the mathematicians say is reqd.

      Cheers

      Comment


      • #18
        Cosmos magazine has a brief overview of the experiment in plain language...
        https://cosmosmagazine.com/mathemati...y-that-adds-up

        Mal.

        Comment


        • #19
          Yes you really need some control over flow and or pressure.

          For anyone with a BDB that wants to try it out this is what Ive been doing.

          18g VST
          Pre infusion set @ 75% for 25 sec.
          This gives a much lower flow rate and pressure peaks 5.5 to 6 bar then comes down to 5 bar.
          15g dose / 40g out / 15 - 17 sec.

          Coffee used to experiment was a sweet, clean Guat dropped just as first crack was finishing off at 1:25 DEV with total roast time about 9 min.

          The same grind setting dosed at 18g using flat 8.5 bar with no pre infusion produced 40g in 21 sec and was undrinkable astringency and sour.

          The 15g dose using the settings mentioned is quite sweet, bright and dilute but surprisingly no where near my expectations of watery. Once it cools to 45 - 50C its quite drinkable, soft, sweet, balanced acidity, zero bitterness or off unpleasant harsh flavours. Aftertaste is mild and sweet.

          With the trend to much smalller milk drinks i can see this working quite well for many cafes as long as they are using properly developed light / med roasts and their machine properly recalibrated to a lower pressure / water debit. I dare say this would be a drastic improvement on quality and consistency for many cafes still trying to push out 20 to 25g doses using much too fine a grind giving the aforementioned mix of bitterness / sourness, yes it can be great if the bullseye is hit but i reckon most of the time its like shooting with a blindfold.

          I will likely stick to this system for household milk drinks as its much easier for other people who dont know / care to get right. It produces a mild but very very sweet milk drink and im guessing for the daily consumer of milk drinks they might appreciate not needing any sugar.

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          • #20
            Originally posted by CafeLotta View Post
            With the emphasis on coarser grind, just wondering if they have also played around with brew pressure in their experimentation?

            Assuming that 9 Bar was the setting used during these types of experiments? At 8 Bar for example wouldn't a coarser grind be required to achieve same volume for a given time? Wonder how that would have shaped up. It's on my list of things to play with. Currently pressure is set a little on the higher side so using a bit finer grind than I would for 9 Bar I guess to achieve same volume for the 25-30 sec. Seems to work well on my machine.
            Linked articles and comments above talk about it being done at reduced pressure, e.g. 6bar

            Comment


            • #21
              I'm all for progress and evolution in the field of coffee, so I love some good experimentation.

              The article that robusto linked above is a really good (and easier to understand) summary.

              ------------------------------

              "“From a material science perspective, the expectation is that if you grind finer, you're going to produce more surface area, so you should increase the amount of coffee that you can extract per shot. So that was the expectation and for the most part, it definitely is true. As you start to grind finer, your extractions go up and up and up,” Hendon says.

              “The surprising result, actually, was that when Michael and I were working together, we identified our favourite tasting coffee of the bunch at a grind setting that was sufficiently fine that the espresso was behaving like most espressos do in Australia*– 20 grams [of ground coffee] in, 40 grams of espresso out, and in 30 seconds, 40 seconds*– but as we ground coarser from there, we noticed our extractions were going up. And that’s counterintuitive. It meant something was going wrong in terms of the way the water was contacting the coffee bed.”

              “It’s not just efficient, but also repeatable,” explains Cameron, who now works as communications manager at Melbourne speciality coffee pioneer St Ali. “So you may be able to get, using 20 grams of coffee, a really high-extraction shot of coffee, but then to pull that same shot again and again and again, what we found was that it's really variable, that you couldn't guarantee that you're going to get a consistent shot time after time.”

              -------------------------

              I wonder what Matt Perger would say about it, he is big on grinding as fine as you possibly can to maximise extraction, hence why he's a massive proponent of VST baskets.

              I wonder also what size baskets they used for the 15g doses, or whether they set up a very shallow 20g basket...

              What I don't understand is how you can get a higher extraction from this method... coarser grounds means longer to extract, quicker extraction time which is less contact time that the water has with the ground coffee... so they lowered brew pressure which must be the key, but the water is still passing through in a rather quick time.. meh dunno.

              I guess as it says in the quote above, when it's too fine, something maybe was going wrong with how the water contacts the coffee...

              What do you reckon @luca ?

              Comment


              • #22
                Originally posted by Dimal View Post
                Cosmos magazine has a brief overview of the experiment in plain language...
                https://cosmosmagazine.com/mathemati...y-that-adds-up

                Mal.
                Haha Cosmos getting in on it! It is quite a universe the microscopic level of coffee grounds [emoji14]

                Actually this bit from the article clears up a little regarding what I questioned about more finely ground coffee.... it can be hit and miss in terms of what is extracted, whether the water can actually reach what it needs to, due to it just being too dense and overcrowded so to speak. Still would have thought that saturation still occurs all throughout, but that 'clear portafilter' experiment I think showed that some bits of ground coffee were clearly still dry for a longer period of time, thus extracted at a different rate to te reso of the puck...

                "Grinding as finely as the industry standard suggests clogged the coffee bed, reducing extraction yield, wasting raw material, and introducing variation in taste by sampling some grounds and missing others entirely."

                Comment


                • #23
                  Originally posted by Steve82 View Post
                  Yes you really need some control over flow and or pressure.

                  For anyone with a BDB that wants to try it out this is what Ive been doing.

                  18g VST
                  Pre infusion set @ 75% for 25 sec.
                  This gives a much lower flow rate and pressure peaks 5.5 to 6 bar then comes down to 5 bar.
                  15g dose / 40g out / 15 - 17 sec.

                  Coffee used to experiment was a sweet, clean Guat dropped just as first crack was finishing off at 1:25 DEV with total roast time about 9 min.

                  The same grind setting dosed at 18g using flat 8.5 bar with no pre infusion produced 40g in 21 sec and was undrinkable astringency and sour.

                  The 15g dose using the settings mentioned is quite sweet, bright and dilute but surprisingly no where near my expectations of watery. Once it cools to 45 - 50C its quite drinkable, soft, sweet, balanced acidity, zero bitterness or off unpleasant harsh flavours. Aftertaste is mild and sweet.

                  With the trend to much smalller milk drinks i can see this working quite well for many cafes as long as they are using properly developed light / med roasts and their machine properly recalibrated to a lower pressure / water debit. I dare say this would be a drastic improvement on quality and consistency for many cafes still trying to push out 20 to 25g doses using much too fine a grind giving the aforementioned mix of bitterness / sourness, yes it can be great if the bullseye is hit but i reckon most of the time its like shooting with a blindfold.

                  I will likely stick to this system for household milk drinks as its much easier for other people who dont know / care to get right. It produces a mild but very very sweet milk drink and im guessing for the daily consumer of milk drinks they might appreciate not needing any sugar.

                  [ATTACH=CONFIG]24931[/ATTACH]
                  Awesome, that's really great input, thanks Steve

                  Comment


                  • #24
                    I think it is interesting article/data given 9 bar pressure has been the DeFacto for specialty coffee for a long time. Just because that is the defacto doesn't mean it is the best, a lot of time and effort in specialty and coffee nerds like us has gone into getting the best possible tasting extractions out of 20 gram doses at 9 bar.

                    We have seen ratios change from say for a double 60 grams out out in 30 seconds in the early days of specialty coffee with more like 14 gram doses of coffee change to now 1:2 ratios 20 grams in with a max of 40 grams out be trending toward 35 grams out for 20 grams in of coffee (if you read a lot of the good roasters recipes on roasted bags of beans).

                    I won't be changing my daily coffee routine now. But I would do some more experimenting if I had a pressure profiling machine and seeing how I liked 6 bar, 15 grams and 40 grams out with milk.

                    If we move forward 5-10 years and profiling machines are the norm, maybe 6 bar, coarser grounds with shorter extraction times will become the new norm. But it would take a big shift in the specialty market and coffee supply chain (e.g. tasting changing to low pressure fast extractions so the coffee is tuned for the applicable use). I was thinking that lever machines would support some of the evidence in the article due to lower pressure extractions but then recalled that long extraction times are common as with 30-40 seconds and often grind settings similar to HX and commercial machines.

                    Comment


                    • #25
                      Personally, I believe Flow Profiling is where it's at, then just allow the brew pressure to look after itself...
                      Trying to mange/control more than one interdependent variable simultaneously, just makes life more difficult than it needs to be, whatever preference you may have for what ends up in the cup.

                      Mal.

                      Comment


                      • #26
                        Originally posted by simonsk8r View Post
                        Haha Cosmos getting in on it! It is quite a universe the microscopic level of coffee grounds [emoji14]

                        Actually this bit from the article clears up a little regarding what I questioned about more finely ground coffee.... it can be hit and miss in terms of what is extracted, whether the water can actually reach what it needs to, due to it just being too dense and overcrowded so to speak. Still would have thought that saturation still occurs all throughout, but that 'clear portafilter' experiment I think showed that some bits of ground coffee were clearly still dry for a longer period of time, thus extracted at a different rate to te reso of the puck...

                        "Grinding as finely as the industry standard suggests clogged the coffee bed, reducing extraction yield, wasting raw material, and introducing variation in taste by sampling some grounds and missing others entirely."
                        ... and my first alternative take: use a crap grinder with an uneven particle spread and that is exactly what you get... Uneven extractions. What a surprise.

                        TampIt

                        Comment


                        • #27
                          Originally posted by TampIt View Post
                          ... and my first alternative take: use a crap grinder with an uneven particle spread and that is exactly what you get... Uneven extractions. What a surprise.

                          TampIt
                          Hahaha, yeah good call [emoji14]

                          Comment


                          • #28
                            Don’t forget that the primary driver here isn’t just improving flavour/quality. In fact that’s probably secondary. People like Matt Perger and Scott Rao among others have frequently spoken about the fact that they want to find a way to reliably increase espresso extraction so that coffee shops can use less coffee but still achieve at least an equal result. In many cases the result in the cup may actually be better - I’m sure we’ve all had some pretty awful, bitter coffee from cafes. The main benefit for the coffee shop is reduced cost, but there’s also a greater potential benefit of the coffee industry using less coffee. While there’s no shortage of commercial grade coffee globally we know that the specialty grades are starting to feel some pressure from changing weather and climate conditions. So it makes sense that as this market grows we look for ways to become more efficient in the use of high grade coffee, at least for the foreseeable future until someone works out how to grow high grade coffee at low altitudes (it will happen eventually). So I’d suggest that if you can and want to experiment with these parameters at home go for your life, but all other home baristas should just keep doing what they’re doing.

                            Comment


                            • #29
                              Originally posted by LeroyC View Post
                              Don’t forget that the primary driver here isn’t just improving flavour/quality. In fact that’s probably secondary. People like Matt Perger and Scott Rao among others have frequently spoken about the fact that they want to find a way to reliably increase espresso extraction so that coffee shops can use less coffee but still achieve at least an equal result. In many cases the result in the cup may actually be better - I’m sure we’ve all had some pretty awful, bitter coffee from cafes. The main benefit for the coffee shop is reduced cost, but there’s also a greater potential benefit of the coffee industry using less coffee. While there’s no shortage of commercial grade coffee globally we know that the specialty grades are starting to feel some pressure from changing weather and climate conditions. So it makes sense that as this market grows we look for ways to become more efficient in the use of high grade coffee, at least for the foreseeable future until someone works out how to grow high grade coffee at low altitudes (it will happen eventually). So I’d suggest that if you can and want to experiment with these parameters at home go for your life, but all other home baristas should just keep doing what they’re doing.
                              Yeah true, in the Highlights in the research paper two of the points were to minimize coffee waste and yield monetary savings. I can only hope that the quality of extraction and taste isn't affected. I'd love to taste the two methods side by side...

                              Can someone please explain this to me though, if less coffee is used, we would go through it much slower, and there is less demand for it. So won't this impact the farmers in a massively negative way? Or is it moreso that at the moment they're struggling to meet the demand and crops aren't growing/yielding as well nowadays, so this would help in that respect?

                              I can see how it would help cafes immensely, 25% less coffee used..

                              Oh and just got an email from St Ali this morning regarding the research and a link to it. Sounds like they are gonna for sure implement it...

                              It's such a massive change though, I wonder who will be on board!

                              Comment


                              • #30
                                Originally posted by simonsk8r View Post
                                Can someone please explain this to me though, if less coffee is used, we would go through it much slower, and there is less demand for it. So won't this impact the farmers in a massively negative way? Or is it moreso that at the moment they're struggling to meet the demand and crops aren't growing/yielding as well nowadays, so this would help in that respect?

                                I can see how it would help cafes immensely, 25% less coffee used..
                                I think it will slow the price increase from bean to cup. The bean price will still increase as good coffee gets harder to grow, but it will either slow the follow on effect of increased cost of a cup of coffee, or it will mean more profit for green bean distributors, rosters, and/or cafes. Given that past performance is the best indicator for future results I can't help but think it'll be the green bean distributors taking the bulk of it, roasters getting a little and cafes a tiny bit, with the farmers and end consumers seeing almost no benefit at all.

                                The only way I can see it changing for the consumer is if wage growth continues to fall behind inflation then fewer people will be able to afford fewer cups of coffee, leading to pressure on the cafes to reduce costs, which will send some pressure back up the supply chain, and who knows, it might do something if the overall profit is greater with a lower margin on more product.

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