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The Value of Flow-control & Pre-Infusion

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  • #16
    Originally posted by Budgiesmuggler View Post
    As a decent user I’d try this -

    start with the paddle 3/4 open for about 5 seconds then shut shut the flow off until you see drips coming from the bottom
    of the puck - this indicates it’s evenly wet, and the high start flow rate gets it even quickly. Then pull at whatever bar you want.
    So you start the pre infusion at around 6bar and then reduce it to 0bar once the coffee starts dripping out the puck before taking it up to 9bar or so?

    Comment


    • #17
      If you have a bluetooth scale, there is an awesome app named SE Profiler. What it allows you to do is track the flow of water through your puck into the cup when you pull a shot.

      It can get pretty complex, but a good rule of thumb is after pre-infusion, during the brewing phase, 1.5-2.5ml/s is a good flow (happy to be corrected on this).

      Comment


      • #18
        1.5 - 2.5 is good ballpark. You don't really want to go below 0.8 or above 3.5.

        Comment


        • #19
          This is a pretty complicated topic and I'm not going to give exhaustive responses.

          Most internet discussion on this is pretty useless; you don't know what sort of coffee people are using or what their definition of "good" is; you just get some vague assertion that what the person posting is good. And you seldom get a grownup discussion that things may be good in some respects and bad in others, so it may be a matter of taste. You also seldom get carefully conducted apples and apples comparisons; much is a matter of impression. You get tonnes of assertions about the "channeling" boogeyman, which are about appearance. So for all we know, a lot of the discussion about this may be about making shots look prettier and spurt less, rather than actually about making them taste better.

          So on the front side of the shot, you can use pressure and flow profiling for preinfusion. There may be conflicting things at play here. Some slow pressure buildup may allow the shots to look more orderly and to be more repeatable, so baristas tend to prefer, for example, 0.6mm restrictors in LMs to having a bigger kick of water without them. E61 groups have gicleurs and preinfusion chambers to do a similar thing. Whatever you do, you can adjust this side of the shot to create something more chocolatey and viscous, drippy and ristretto like. Blooming is different, and you constantly read people talking about doing "blooming" on paddle group machines. If the pump is creating pressure, it's not "blooming". The way Rao et all use "Blooming", it is to designate a pause with no pump pressure. Many machines cannot do this because if the pump is off, the valve opens and dumps excess pressure and water into the drip tray. What blooming can do is to increase your extraction yield and allow you to get more aroma into less volume. This is different from crushing the aroma and overriding it by imposing a generic ristretto taste. There may be another factor to consider here of how much water can you get into the puck quickly. Some machines can put out a tremendous flow rate; others less so.

          On the back side of the shot, there's a question that I don't think has really been answered. So, effectively you're only ever really going to use profiling to slow down the shot, which may be because you'd underdosed, ground too coarse, or the nature of the coffee was such that the extraction sped up. But basically what you're going to do is probably to adjust the flow rate so that the shot looks pretty. So the question is, if the grind is too coarse, do you get a better cup if the shot flows at your intended rate and at a lower pressure, or if it flows much faster and at your intended pressure?

          Personally, I like shots with a blooming start, into a pressure profile, which will probably result in the shot speeding up towards the end and flowing quickly. I think that these maximise aroma from the aromatic light roasts that I like. I suspect they probably reduce body, they may result in higher acidity, and they don't generate much generic ristretto chocolate flavour. I haven't done as many head to heads as I might like. There is probably more than one way to skin a cat here, and, of course, the contribution that flow and pressure control makes is a drop in the ocean compared with the contribution of the roast and green.

          If you like your extractions to be really viscous, chocolatey, lower in acidity and you don't mind them being less aromatic and extracted, then you might like different extraction conditions to me. This might also be a benefit if what lies to be extracted in the coffee that you have isn't very nice, but, like I said, you don't get grownup discussions where people acknowledge that the coffee that they like has shortcomings, so you probably won't see a frank assessment of this or be able to relate to whether that applies to your coffee. Because, of course, defects are things that happen in other peoples' coffees, not the coffee of anyone that writes anything about coffee on the internet.

          Finally, there's the issue of manual repeatability to consider, and that's probably a pretty obvious one.

          Comment


          • TheBoneRanger
            TheBoneRanger commented
            Editing a comment
            Great post!

            To your point about the channeling boogeyman, I’ve been watching a lot of videos from Decent lately about dialing in flow etc. I’m often struck when the presenter decides that a shot is much better based on the data and look alone, and never seems to taste it! Perhaps it’s years of experience that teaches that this will be so, but still…

          • CleanFinish
            CleanFinish commented
            Editing a comment
            "Personally, I like shots with a blooming start, into a pressure profile, which will probably result in the shot speeding up towards the end and flowing quickly. I think that these maximise aroma from the aromatic light roasts that I like. I suspect they probably reduce body, they may result in higher acidity, and they don't generate much generic ristretto chocolate flavour. I haven't done as many head to heads as I might like. There is probably more than one way to skin a cat here, and, of course, the contribution that flow and pressure control makes is a drop in the ocean compared with the contribution of the roast and green."

            +1....I do essentially same and prefer similar.

        • #20
          Hi Luca,
          Very interesting point about slowing down the end of your shot to make the flow look pretty.
          I have to admit to being guilty of this as a way of correcting the shot if it was not properly dosed or ground too coarsely or I was in a rush or the various other factors that can contribute.
          On my Bosco, there is a reducing pressure profile, and controlling the lever as it declines is possible. A pretty pour does not always guarantee a tasty brew and vice versa.
          I am wondering if with a really fine grind, long pre-infusion soak, and then allowing the lever to follow its own course with an ugly pour, would improve the flavour of light roasted espresso. I have only dabbled briefly with light roasted coffees for espresso, but am interested in the outcome.
          My most recent light roast of a Colombian pink bourbon natural had a smidge too much development for my taste in V60 brews, but might be suitable to experiment with for the type of brew you describe.
          Choice of green coffee is exemplary, roast quality is not on a par with SR or TW, yet.....

          Comment


          • Bosco_Lever
            Bosco_Lever commented
            Editing a comment
            By definition, if the pressure at the end of the shot is less than the pressure at the start, the pressure is reduced therefore "reducing pressure profile".
            This is a rabbit hole with so many variables including equipment accuracy that I have no interest in following.
            Different techniques and approaches are interesting if it results in a tasty brew.
            However, baked coffee is still baked regardless of equipment etc.
            Quality of greens and the roast have more influence on the outcome.

            2 handed espresso shots???

          • Caffeinator
            Caffeinator commented
            Editing a comment
            Agreed. The thing is with most spring levas is it's not. People just think it is.

            2-handed: one on an e-61 leva and the other on the flow control at the top of the group.

          • Bosco_Lever
            Bosco_Lever commented
            Editing a comment
            But levers make tasty coffee, regardless of the group.
            They are also simplistic in design and easy to maintain.
            As to how much the pressure changes, and whether it is 100% accurate or indicative (I am well aware of the shortcomings of such equipment as a close friend is a consultant in the field and has discussed this with me) is a guide only, but extremely useful..
            The important matter is which lever delivers the tastiest shot, only the privileged or lucky ones can assess for themselves.

        • #21
          Luca just very succinctly and eloquently explained what I was getting at (I’d expect nothing less from him of course). When I said ‘it depends’ I wasn’t being flippant I was simply pointing to the fact that ‘better’ can never account for the two biggest variables - personal preferences and the coffee being used.

          Comment


          • #22
            Originally posted by Bosco_Lever View Post
            I am wondering if with a really fine grind, long pre-infusion soak, and then allowing the lever to follow its own course with an ugly pour, would improve the flavour of light roasted espresso. I have only dabbled briefly with light roasted coffees for espresso, but am interested in the outcome.
            My most recent light roast of a Colombian pink bourbon natural had a smidge too much development for my taste in V60 brews, but might be suitable to experiment with for the type of brew you describe.
            Choice of green coffee is exemplary, roast quality is not on a par with SR or TW, yet.....
            Oh was that that Manos Juntas natural pink bourbon that was going around? That was great. So clean, good pink bourbon bubblegum type flavour. I found it tasted really roasty with just the slightest amount of development, but you could drop it seemingly with almost no cracks and at a seemingly ludicrous colour and it seemed fine; didn't taste vegetal or underdeveloped. That coffee was a great advertisement for home roasting; at $27/kg or whatever it's kind of expensive for a coffee roastery, but pretty high quality for a home roaster and you can be braver with it than a commercial roaster could, since, you know, you don't have customers to worry about. Unfortunately, I think if you go coarser, higher flow rate and let it gush, you emphasise the roast flavour as much as you emphasise the fruit and florals, so I don't know that pressure profiling really fixes it applied that way. Maybe it's more of a candidate for pressure profiling to dumb it down with more of a gooey generic chocolate, slower flow rate style shot.

            To your point about the channeling boogeyman, I’ve been watching a lot of videos from Decent lately about dialing in flow etc. I’m often struck when the presenter decides that a shot is much better based on the data and look alone, and never seems to taste it! Perhaps it’s years of experience that teaches that this will be so, but still…
            It might be more that they have made shots with that coffee before and recognise from the graph that it came out as expected. If you can make the shot with the same parameters and have the graph look the same, it's a good bet that it tastes like your last shot did. So that might be it. Or it might just be unjustified assumption, which a lot of coffee conjecture on the internet is. Or it might be things that you start to recognise; for example, the flow rate in the last stages of the shot probably gives you a good idea of how rich the shot is going to taste vs how watery it's going to be, and the max pressure in conjunction with the flow rate can give you some idea if you're making a chocolatey shot or an aromatic one. So I think there's probably some stuff that you can tell pretty easily from the graphs. Like if you had a dark roast and the flow rate really opened up, I think most people would probably think that would taste pretty bad. So, yes, there are probably a lot of things that you learn to predict from the graphs based on experience.

            Comment


            • #23
              Thanks Luca for the feedback. Will try it and see. I have another lever arriving soon, it has a PID, so it will be interesting to see what differences the temp will make to this bean, or if it has to be relegated to the slow flow rate style of shot.

              I really enjoy my Colombian pink bourbons as filter, and have learnt to roast them by colour, and also to drop them no later than 30 seconds after the first audible crack, otherwise the roasty notes are there. Underdone is better than overdone, like you said. The MJ was a great coffee, anything similar is now closer to $40/kg, You are right, these types of coffees when offered as roasted tend to be very expensive, hence I agree with you about home roasting.

              I applied the same technique to my geishas as well. It works well. Ethiopians are a different matter and need more development.
              Next experiment will be Colombian decaf.

              Comment


              • #24
                I think with all of these debates and different strategies, there is value in fractioning the shot- perhaps into 5 or more components. If you don't like the taste, why is it in there?

                I like my shots better than those which most cafes want to serve me. If that makes me a luddite, so be it. I have zero interest in cupping roast espresso.


                Comment


                • #25
                  Originally posted by Caffeinator View Post
                  I think with all of these debates and different strategies, there is value in fractioning the shot- perhaps into 5 or more components. If you don't like the taste, why is it in there?

                  I like my shots better than those which most cafes want to serve me. If that makes me a luddite, so be it. I have zero interest in cupping roast espresso.
                  All good thoughts. Absolutely agree that different people have different preferences, and I think we all want everyone to get the coffee they like best. Interesting question as to if you use different pressure and flow for different intended results. From memory, you have a total baller vintage lever machine that you're making sort of amazing high concentration gooey shots from, don't you?


                  The MJ was a great coffee, anything similar is now closer to $40/kg, You are right, these types of coffees when offered as roasted tend to be very expensive, hence I agree with you about home roasting.

                  I applied the same technique to my geishas as well. It works well. Ethiopians are a different matter and need more development.
                  Oh wow, don't get me started about buying Ethiopian coffee. I've basically avoided buying it from Australians over the last few years; quality has been down, historically, I think. It's hugely complicated, but TLDR my impression is that Australian green importers seem to pretty much feel that they can't go over about $15/kg for Ethiopian coffees as an importer to roaster price, unless they have a gimmick. We've historically enjoyed ludicrously underpriced Ethiopian coffees that have, really, been not far off from decent Panama geisha in quality and style, but those golden days seem to be at an end. And, to be fair, I absolutely think that Ethiopian producers should be rewarded with high quality premiums. So it feels like the Ethiopian coffee that we've seen over the past few years has, by and large, been down in quality; usually more washed out, muddy and astringent. I wondered if this was across the board, agricultural, to do with their civil war, etc. But I've had Ethiopian coffees from overseas roasters that have been quite good, and I think that there are some overseas importers into other countries that are simply willing to pay more, and, consequently, their stuff is more expensive. If you look at the specialty coffee transaction guide, there actually does seem to be a bit of a price premium at the top end. The great ethiopian coffees that we used to be able to buy without really a retail consumer price premium were probably 88+, and the SCTG has the price of entry for that score at ~$16.5AUD/kg ... but that's of course FOB, so by the time it lands here you've got to figure a few bucks a kilo more before the importer's margin is even added to it. So it's not really very surprising that the really great Ethiopian coffees are now pretty thin on the ground here.

                  I'm still very much bumbling around figuring out roasting, but my impression is that the processing method probably makes a bit of a difference for ending the roast. I like naturals at lighter colours and less development time than washed coffees. Naturals seem to taste burnt at very little DT and lighter colours, compared with washed.

                  Comment


                  • Caffeinator
                    Caffeinator commented
                    Editing a comment
                    Originally posted by luca View Post

                    All good thoughts. Absolutely agree that different people have different preferences, and I think we all want everyone to get the coffee they like best. Interesting question as to if you use different pressure and flow for different intended results. From memory, you have a total baller vintage lever machine that you're making sort of amazing high concentration gooey shots from, don't you?
                    Yes. 100% with you of that. If you're drinking it, you choose.

                    Yes on the vintage leva and plenty of other options to play bloom, preinfusion and pressure. Light roasts also do it for me, but I'll go manual with them.

                    Cupping roasts- excellent for cupping- and initial QC for bean choice.

                • #26
                  Originally posted by luca View Post
                  Oh wow, don't get me started about buying Ethiopian coffee. I've basically avoided buying it from Australians over the last few years; quality has been down, historically, I think. It's hugely complicated, but TLDR my impression is that Australian green importers seem to pretty much feel that they can't go over about $15/kg for Ethiopian coffees as an importer to roaster price, unless they have a gimmick. We've historically enjoyed ludicrously underpriced Ethiopian coffees that have, really, been not far off from decent Panama geisha in quality and style, but those golden days seem to be at an end. And, to be fair, I absolutely think that Ethiopian producers should be rewarded with high quality premiums. So it feels like the Ethiopian coffee that we've seen over the past few years has, by and large, been down in quality; usually more washed out, muddy and astringent. I wondered if this was across the board, agricultural, to do with their civil war, etc. But I've had Ethiopian coffees from overseas roasters that have been quite good, and I think that there are some overseas importers into other countries that are simply willing to pay more, and, consequently, their stuff is more expensive. If you look at the specialty coffee transaction guide, there actually does seem to be a bit of a price premium at the top end. The great ethiopian coffees that we used to be able to buy without really a retail consumer price premium were probably 88+, and the SCTG has the price of entry for that score at ~$16.5AUD/kg ... but that's of course FOB, so by the time it lands here you've got to figure a few bucks a kilo more before the importer's margin is even added to it. So it's not really very surprising that the really great Ethiopian coffees are now pretty thin on the ground here.

                  I'm still very much bumbling around figuring out roasting, but my impression is that the processing method probably makes a bit of a difference for ending the roast. I like naturals at lighter colours and less development time than washed coffees. Naturals seem to taste burnt at very little DT and lighter colours, compared with washed.
                  This explains my frustration with most Ethiopian coffee of late. I only got into lighter than medium 2-3 years ago and must have caught the tail end of the good stuff. I'm usually a huge fan of good Ethiopian naturals, but they've been mostly disappointing for a year or more. Just got some good stuff from Passport though. Meseret Tegenu from the Yirg. region, big aromatic notes of blueberry and strawberry.

                  Comment


                  • Caffeinator
                    Caffeinator commented
                    Editing a comment
                    I'm prepared to cut them some slack. With the happenings there and in Yemen, I'm thankful that we're still getting greens from them. #firstworldproblems

                • #27
                  Just in case it hasn't already been mentioned: Don't underestimate the importance of good puck prep. That entails three main parts 1) good beans, well roasted 2) good grind 3) good tamp. Your final results in the cup will be limited by any of these, regardless of whatever jiggery poker is going on with variable flow rates, etc. A well prepped puck at a boring flat 8-9 bars for 30 sec will beat a poorly prepared puck regardless of what transpires after -- every time. Quality beans, quality grinder, good tamping -- that will probably get you to 90% of the optimal result.

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