Flow Profiling recipes

 Flow profiling in espresso involves controlling the rate at which water flows through the coffee puck during brewing to influence extraction and flavor. Recipes often involve a pre-infusion phase with a low flow rate, followed by a gradual increase and then a decrease in flow to optimize the extraction and compensate for changes in the coffee puck's resistance.

 

In understanding Flow Profiling we need to understand Flow Rate:

This is the speed at which water passes through the coffee bed, measured in milliliters per second (ml/s) or grams per second (g/s). 

Water debit is a term used frequently.

This is the speed that water exits the shower screen (when nothing is inhibiting it).

That is there is no puck, portafilter, etc.

This typically falls within the range of 200-250ml per 30 seconds. (6.66g/s - 8.33g/s)

My ECM Classika is fitted with a Flow Control knob.

Stock, these E-61 machines have a flow of about 7g/s.

To get  similar flow (with the flow control) turn 1.25 revolutions from the fully closed position.

0.25 revolutions = 2g/s

0.50 revolutions =  4g/s

0.75 revolutions = 5.5g/s

1.00 revolutions = 6.25g/s

1.25 revolutions  = 7.0g/s

1.5  revolutions   = 7.7g/s

1.75  revolutions = 8.3g/s

2      revolutions  = 10g/s 

These measurements are specific to my machine. It will of course change if I tweak the OPV.

This range is often cited as a "sweet spot" or a range that is most forgiving for achieving a good espresso extraction. 

To measure this place a glass under the shower screen and measure the amount being collected every second. (its easier if you measure the amount of H20 after 30 secs & divide by 30).

Most machines have a water debit between 4g/s  to 10g/s.

It's commonly 5g/s for vibratory pump machines & 8g/s for those with rotary pumps.

It's important to distinguish between water debit (flow rate without a portafilter) and flow rate during espresso extraction (which is influenced by the portafilter and coffee puck). 

The pic on the left is from my Gagguino. 

Adaptive mode.

The flow starts at zero, quickly rises to 8.5

then drops to zero. Then rises to 4 and drops 

to 1- 0.5

In Flow Profiling we adjust the flow rate throughout the shot to influence extraction and compensate for changes in the coffee bed. 

Flow & pressure are linked.

Pressure = Flow x Resistance

Modern espresso machines, particularly those with flow control and pressure profiling, allow for adjustments to water debit, enabling finer control over the extraction process. 

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Common Flow Profiling Techniques:

Ramping Pre-Infusion:

Starting with a low flow rate to saturate the grounds evenly, then gradually increase the flow rate to build pressure. 

Tapering Flow at the End:

Reducing the flow rate towards the end of the shot to maintain a consistent output and prevent over-extraction. 

Compensating for Grind Changes:

Adjusting the flow rate on-the-fly to compensate for changes in grind size or freshness of the coffee.

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General Recipe:

Start with a flow rate that allows for full saturation (e.g., 7-8 ml/s), then reduce the flow to soak the puck (e.g., close the valve to return to 2 bar), and then adjust the flow rate to reach the desired pressure and extraction. 

Benefits of Flow Profiling:

Improved Extraction: Helps to extract more evenly and consistently from the coffee puck. 

Reduced Channeling: Ramping pre-infusion helps mitigate or eliminate channeling, leading to more even extraction. 

Flavor Control: Allows for greater control over the final flavor profile of the espresso by influencing the extraction of different compounds. 

Compensating for Grind Size: Adjusting flow can compensate for minor grind size variations. 

Tips for Using Flow Profiling:

Start with small adjustments:

Begin by making small changes to the flow rate and observe the impact on the shot. 

Use visual cues:

Pay attention to the appearance of the espresso stream and the pressure gauge to guide your adjustments. 

Experiment with different profiles:

Try different flow rates and timings to find what works best for your coffee and your taste preferences. 

Consider your machine:

Different machines have different capabilities and characteristics, so adapt your approach accordingly.