Hi All

I have been playing around with my refractometer, testing the impacts of Brew Ratios on Total Dissolved Solids (TDS) results and thereby on the calculated Extraction Yield, all relative to my taste preferences.

What I found was no surprise. I ran 3 refractometer tests:

  • Test 1 - My preferred taste - shows an EY% of 18.6%. Goldstar blend of Kona Decaf and Espresso Decaf. My goto coffee. 17.0g in and 25.0g out (brew ratio of 1.47) in 35 seconds. No pre-infusion (by accident) and a temp of 95c. 0.2 on my grinder dial. TDS tested out at 12.63%. EY is thereby 25.0 × 12.63 / 17 = 18.6%.
  • Test 2 - My 3rd ranked (worst) taste - shows an EY% of 15.3%. Same coffee. 17.0g in and 26.3g out (brew ratio of 1.55) in 35 seconds, including pre-infusion. 11 sec bloom pre-infusion and a temp of 95c. So the shot ran somewhat fast, even though I had 0.2 on my grinder dial. TDS tested out at 9.9%. EY is thereby 26.3 × 9.90 / 17 = 15.3%. Tasted a tad sour and somewhat weak, due to faster flow and somewhat higher brew ratio.
  • Test 3 - My 2nd ranked taste - shows an EY% of 16.8%. Same coffee. 17.1g in and 25.6g out (brew ratio of 1.55) in 35 seconds, including pre-infusions. 11 sec bloom pre-infusion and a temp of 95c. So the shot ran somewhat fast, even though I had 0.0 on my grinder dial (a tad finer). TDS tested out at 11.21%. EY is thereby 25.6 × 11.21/ 17 = 16.8%. Taste is better than shot/test 2, but not as good as shot/test 1.

Conclusion from these tests: I still prefer the body and taste of espresso shots (alone and in cappicino) that are more ristretto, but would like to have more complexity and duration (long lastedness) in the taste.

So I need to get the EY up. But if I increase the brew ratio, the body reduces. Moreover, the increase in the brew ratio (towards a more normal shot) causes a proportionately greater decrease in the TDS%, such that the EY% decreases. I had hoped to have a higher EY% or at least break even.

I am guessing that if I can find a way to maintain the brew ratio but increase the TDS%, I could increase the EY%, with I hope a corresonding improvement in taste complexity and duration. Just don’t know how. Any suggestions?

PS

Sorry to wax technical on this. Just trying to see if using a refractometer to test TDS% and EY% will help me find a way to improve the taste of my shots (to my liking). I know I need to adjust until I reach a taste that I prefer, but would appreciate some suggestions on how to do so, and how this might impact the above technical parameters.

Thanks all.

I’d say the brew ratio difference between the shots is negligible. Any difference in TDS is likely repeatability issues (either shots or refractometer). Biggest difference between the first two on the list is probably preinfusion.

What refractometer do you have and how are you prepping and filtering samples? E.g stirring shots, letting them sit for the same time, skimming off crema etc?

    Rob1

    Thanks Rob1. It’s the Reichert R2 Mini. The original VST Coffee version. With regard to prep:

    • I let the RM sit until the glass reaches about 20c, as tested by a thermistor. I can/should use the RM’s built in glass temp checking function.
    • I add distilled water that is at a temp that is within 0.5c of the temp on the glass.
    • I check the temp of the distilled water bubble on the glass and note it.
    • I recalibrate
    • I clean the glass with distilled water and lense cleaning tissue
    • I pour the shot, noting the recipe, then taste a small amount of it, then weigh it again.
    • I prepare a small beaker of distilled water in a beaker that is 2x the weight of the shot (ie 2X the reweighed shot)
    • I add the shot and stir well
    • I note the weight of the diluted fluid in the beaker, and divide by the weight of the reweighed shot. It should be 3:1, but I use the weight ratio.
    • I let the shot sit (or warm/cool the beaker glass) until it is within 0.5c of the RF glass temp.
    • I withdraw a sample through a very very wide bore needle meant to take samples.
    • I attach a 45um filter and express a small amount on to the glass.
    • I let sit until and take a temp reading with my thermistor probe, to be sure that the temp is within 0.5C of the prior glass temp. I can/should use the RM to do that.
    • I take 10 readings and use the average.
    • I calc the EY% using the shot weight that I originally poured (ie the weight before my small sip).

    Tech questions:

    Are there any flaws in this process? For example, while the RM has automatic temperature correction to 20.0c, I am uncertain as to whether it’s temperature correction feature works for solutions that are not sucrose solutions. Do I need to use a temperature correction table or spreadsheet?

    Is there any way to shorten the process?

    Do I need a more current RM? Why? If so, which?
    .
    And how do I get that TDS up sufficiently to exceed the change in the BR and produce an equal or higher EY%. I’d like to see what a 20% EY tastes like!

    Thanks Rob1 and all!
    .

        JHCCoffee

        PS

        The TDS% is by math formula 3x the reading. Specifically, it’s the total diluted / redesigned undiluted shot weight X the TDS reading. I need to dilute, as my RM produces an error with a straight shot, as it can’t handle a TD above 10. I could dilute 1:1, but prefer 1:2 to be safe.

          1: The higher the EY, does not mean the better the taste is! It’s relevant if other trouble spots are ok and not, by itself, a measure of quality.

          2: You want to pull, say, at least 10 - 12 shots for your best cup to establish some consistency and repeatability. However, as some one who has done a lot of data science work in the past, even 10-12 shots is too small a sample.

          3: A sour cup means the extraction is probably in 15% - 17%; you may not be getting the 18%-22% or exceeding that; however, the 12-14% extractions are very low, but can be nice and sweet — not sour or bitter.

          4: A good refractometer is important. The VST is the best. I believe Atago is also fine for espresso. I don’t measure my EY, although it is very useful. I don’t have one; I need a VST as I also brew a lot. It’s not a necessity, as I have other considerations at the moment.

          5: I do not think there are any recommended ranges for TDS in espresso, which can taste good between 3% and 13%, as long as you can hit a range of extraction that tastes good.

          6: The TDS is a matter of personal preference IMO, based on brew ratio, mouth feel, strength.

          If you are adding exactly twice the original shot weight in dilution water, you will still get the same EY. If diluting to 1:3, multiply TDS by 3 for EY. However, you can’t be tasting much of the shot at the original strength?

          Why not drink more of the shot & sample less & measure with 0.01g scales?

          Essentially you are asking how to change the laws of physics. How to extract more at short ratios. I don’t think anyone knows how to do that with coffee roasted less than very dark.

          If you are getting 18.6%EY with one coffee, you may well be able to hit 20% with a very soluble coffee. See how things look after measuring shots with other beans.

          But if you want high TDS/mouthfeel and a pleasant taste, then lower extractions can deliver, but without the complexity.

          The only way I’ve heard you can get high-yield ristrettos is with something like an EK43, but also heard you don’t have the mouthfeel to the point some people say it should be called Ekspresso rather than espresso.

          DavecUK

          Thanks DavecUK!

          What pressure are Lelit Elizabeth’s factory set at? 9 bar is the traditional norm. I think I am getting 9 bar.

          What pressure would you suggest I try out? Should I consider 9.5 bar or even 10? Any equipment risks to 9.5 or 10 bar? Can the puck handle it if bloom pre-infused?

          I presume that I could adjust the pressure using the OPV valve. How many rotations of the screw are required to raise pressure by 1 bar? Clockwise or counterclockwise, when facing machine? Would you have a link to a pic or video on this?

          Happy to chat offline if you prefer.

          Thanks again.

              JHCCoffee - take the top of the machine off. Lock a blind filter onto the group. Hit the brew button (make sure there’s no pre-infusion set) and note the pressure. Do it again and note the pressure.

              With a spanner, rotate the adjusting nut on the OPV. Hit the brew button. Note the pressure. Repeat until you see the pressure you want on the gauge.

              A quick web search of “adjusting pressure lelit Elizabeth” will yield results of tutorials with videos on how to adjust the pressure.

              There’s no harm in a lower or higher pressure. Adjust to what you wish to.

              JHCCoffee Can the puck handle it if bloom pre-infused?

              Not sure what the above means. Bloom pre-infusion ideally is between 2 and 4 bar. You need to adjust the parameters (time and pump run) to achieve this, for the coffee and dose you use.

                  Thank-you MediumRoastSteam and everyone. You’ve all been most graciously helpful. What a great Forum!