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Pressure Profiling Using the Synesso Hydra

Five Senses CoffeeNathan Borg 19 June 2014

This is a practical approach to finding your preferred flavour profile using the individually adjustable pump pressures on a Synesso Hydra.

I’ve written this article with the intention of giving baristas a guide to experimenting and finding their own results using the world of pressure profiling. I have added some basic outlines about how these different pressures function and included some suggestions about how to adjust them to achieve the results you are looking for. Included in this article is a printable PDF to assist in charting your way to brewing great espresso.

When using the following approach, you should be able to make your own adjustments to reach your preferred flavour or texture for espresso. This method is important because (as you may know), comparing espressos when more than one variable has changed can be quite difficult.

You may find yourself, ‘Lost in a sea of variables from which I never really found my way out,’ as James Hoffman said about profiling on the LM Strada.

So what is pressure profiling? Pressure profiling is basically modulating predetermined pump pressures during espresso brewing. Prior to this, espresso brewing was almost always done at a standard pump pressure of 9bar throughout the entire extraction.

It’s important to remember that there is no official “perfect” recipe for espresso. But having the ability to pressure profile opens up new avenues for variables and new extraction possibilities. If you can find a genuine improvement in the texture and/or flavour of your espresso by setting some new pressure parameters, then controlled experimentation is key and to be encouraged!

Profiling on the Synesso Hydra is made up of four stages:

Stage One- ‘Pre-infusion’
Pre-infusion occurs when hot water is dispensed through the group head and into the coffee puck at a low pressure of around 3-4 bar, before the pump then progresses to its next brewing pressure. One benefit of pre-infusion is that it gently saturates the coffee with hot water and allows the dry coffee to swell before the full 9 bar of pressure is applied. This prevents pressurised water from pushing through any weak spots in the dry coffee puck (which can potentially cause channeling). Pre-infusion can also bring an extra textural element to your brew in the form of a greater volume of crema. It can also lead to a more syrupy mouthfeel overall.

Stage Two
This stage uses 6 bar of pressure and is the gateway from pre-infusion to full brewing pressure.

Stage Three
Stage Three takes up the majority of the shot and is the standard brewing pressure for most espresso machines. We do not give this stage a value, rather it is made up of the remaining brew time.

Stage Four
This is a gentle ramp down of pressure back to 6 bar near the end of the extraction. This value is expressed as a percentage of the entire shot length.

These ‘stages’ can all be programmed using the control pendant attached to your Synesso. For each group head, you will have three Stages to set; Stages One, Two and Four. The actual pump pressures for each stage are set at install. The values we adjust come in the form of time (e.g. how many seconds it will be in that stage before switching to the next), with the exception of Stage Four which is a percentage of the shot volume programmed into a volumetric key pad.

Note: if you pull a shot using the manual override switch, it will skip Stage Four.

Example: If we set Stage One at 3 seconds and Stage Two at 0 seconds, then when the group is activated, hot water at 3 bar pressure will flow for 3 seconds then automatically go to 9 bar, as it will bypass the Stage Two and go straight to full brewing pressure.

On the control pendant attached to your Hydra, use the top button to scroll through the pages. You will notice two pages per group. The group number is at the top of each page as you scroll through. To adjust a value, press the corresponding button for each text line. The value will then flash. Use the up and down arrows to adjust the value. Save the value by pushing the corresponding button for each line again. After setting values for Stage One and Two, scroll to the next screen and you will find the adjustment for your Stage Four percentage. You can disable this stage on the line above the value.

Important information before starting

  • Be sure that your brewing parameters are the same with regard to dose, grind, brew temperature and espresso weight. Weigh each dose with scales, so that with each experiment you only taste the effect of changes in the brewing pressure and not that of dose changes or other variables.
  • Brew all three espressos in each set as close together as possible so that temperature is not a variable when tasting.
  • Give yourself a generous amount of time to go through this evaluation. I would not recommend attempting an experiment like this during service. Doing them together as a small group works well and may give you a broader set of notes to compare.

Note: Your extraction time may change a small amount when comparing shots with different pressure values. In my experience, the length of Stages Two and Four will change the extraction time by a few seconds, although varying the length of Stage One didn’t have a huge effect on overall time.

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Let’s start charting some brews!

Variables in Stage Four seem to be the most subtle to me, so this is where I start before other tastes and textures enter the equation. Click here for a PDF template of this chart.

Set up your control pendant with three different Stage 4 values and make sure there are no other variables in the equation. Make an espresso on each group head and use the table as I have here:

Stage 1 Stage 2 Stage 4 Ext Time Weight Notes Score
Group 1 0 sec 0 sec 99% 28 sec 36g Clean / Soft acid 7/10
Group 2 0 sec 0 sec 90% 28 sec 37g Silky texture / Sweet / Long finish 9/10
Group 3 0 sec 0 sec 80% 28 sec 36g Sharp / Sour / Dry finish 6/10

You can then carry over the most liked of the three and programme it into all the groups on the control pendant as shown here. Then add three levels of Stage One pre-infusion to judge and score.

Stage 1 Stage 2 Stage 4 Ext Time Weight Notes Score
Group 1 0 sec 0 sec 90% 30 sec 36.5g Tart / Sharp / Unbalanced 7/10
Group 2 3 sec 0 sec 90% 31 sec 37.5g Fruity / Great acidity / Longer Finish 8.5/10
Group 3 6 sec 0 sec 90% 30 sec 36g Silky texture / Balanced 9/10

Once a favorite pre-infusion time has been scored, set all groups with the same Stage One time. Then add three levels of Stage Two times.

Stage 1 Stage 2 Stage 4 Ext Time Weight Notes Score
Group 1 6 sec 0 sec 90% 30 sec 38g Clean / Fruity / Balanced / Soft finish 9/10
Group 2 6 sec 3 sec 90% 28 sec 37.7g Great acidity / Toffee like / Sweet 9.5/10
Group 3 6 sec 6 sec 90% 29 sec 36.6g Sweet / Long finish 8/10

This is now your opportunity to taste this new profile and compare it with an espresso which has everything disabled. If you were currently running a profile before this experiment, add this in too.

Stage 1 Stage 2 Stage 4 Ext Time Weight Notes Score
Group 1 0 sec 0 sec off 28 sec 36.6g Clean & sharp / Citrus /10
Group 2 3 sec 6 sec 90% 29 sec 36.9g Sweet / Textural /10
Group 3  sec  sec % sec g /10

Ask the group some questions:

  • Have we improved our espresso? If so, what are we enjoying about it?
  • Were there some attributes in one espresso that you wish were present in another, and vice versa?
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Using this system, you can then fine tune your espresso. Test parameters with one second differences between them. Maybe some scores were tied? You may like to evaluate pre-infusion times of 3 seconds, 4 seconds and 5 seconds. The differences when using one second gaps may taste negligible to some, but you could also quite clearly find a preferred value through this type of fine tuning. Some baristas may choose a target Extraction Percentage using a refractometer and VST Extract Mojo software. You could use a similar table to do this.

Try different coffees with alternate profiles.

You may find one that highlights specific qualities you want to bring out. Maybe you prefer less viscosity and higher clarity and acid or a sweeter and more subtle espresso might be your vibe.

Whatever your preference, go forth and experiment.

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