Preinfusion of espresso

What is espresso preinfusion?

Simply put, preinfusion is the brief moistening of ground and aerated coffee in the portafilter strainer before extraction begins - the actual process of pushing hot water through the coffee. Onlya small amount of water is used for the preinfusion and at apressure many timeslower than for the extraction itself. The principle of espresso preinfusion is essentially very similar to preinfusion in the preparation of filter coffee.

Why is preinfusion important?

During preinfusion, the coffee saturates the water into itself, causing the entire coffee budto sit in the strainer. The coffee is thus freed from air, which remains in some quantity between the individual particles despite the perfect grinding and tamping of the coffee with a tamper. This reduces the risk of channeling or coffee bypassing during the extraction process.

Channeling is a phenomenon in which water under high pressure takes the path ofleastresistance in the coffee bud - finding a crack or creating a channel in a weak spot - and flows unevenly into the cup through the strainer. Thus, some of the coffee will be under-extracted and some over-extracted. If we want a balanced cup of espresso, we may not need channeling.

How long should preinfusion take?

This is a question that every experienced barista will have a unique answer to. This is because it depends on many aspects such as the type of coffee machine, the degree of roasting, whether we are preparing single or double espresso etc. But we can say that the preinfusion should take within units of seconds.

The important thing is that at the end of the preinfusion, immediately should come the extraction of the coffee. If this does not happen, the resulting espresso will be overextracted.

So there is no universal answer. But definitely don't be afraid towork with the preinfusion time, taste and compare.

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How to preinfuse espresso?

On most modern professional coffee machines, you can adjust pressureprofiling electronically over time. And this includes the water flow rate. After pressing the brew button, the coffee machine will then take care of the correct preinfusion and extraction.

This is similar to many homemachines. For example, on the LelitVictoria PL91T coffee maker, the user can set the length of the desired preinfusion in seconds and just watch the coffee maker work after starting the brew.

Manual preinfusion

With practically all coffee machines with head group E61 the so-called manual preinfusion can be achieved. This is because the E61 basically offers the possibility of running hot water at the pressure of the water line (if the coffee machine is connected to it) through the portafilter. This pressure varies from about2 to 5 bar in the Czech Republic.

Preinfusion and extraction with E61 | clivecoffee.com

Apart from the legendary Faema E61 itself, manual preinfusion applies to most coffee machines from the brands Rocket, Bezzera or Lelit.

The E61 group can be further supplemented with the Flow Control Kit for the real possibility to change the desired preinfusion pressure. As a point of interest: e.g. the LelitBianca coffee machine has this E61 enhancement already in the base.

In the video below you will see how to preinfuse the coffee machines with the E61 group.

Pressure Profiling

Pressure profiling is the term used to refer to theprogression of water pressure over time. That is, how during preinfusion and extraction the water pressure rises, falls or is kept at the same value. By profiling the pressure, we can thus influence how rapid the onset of extraction will be, to what value the preinfusion will rise, howconsistent the coffee stream will be etc.

If water at a pressure of 9bar hits the coffee bud at the same time and without pre-wetting, the coffee will simply "give way" to the water. The water finds the best way and the aforementioned channeling is born. It is the correct pressure profiling with possible preinfusion that will prevent this problem.

In the picture below, note the roughly 13 with preinfusion in the first graph. Next, the water flow (blue curve) and temperature (red curve) are checked.

Should preinfusion be counted in the total brew time?

There are 3 possible ways to time the entire espresso preparation with preinfusion:

Start the time the moment you press start (or lift the lever) on the machine. The preinfusion will then be counted in the total time.
Start the time as soon as the pump is started. Thus, the preinfusion will not be included in the total time and only the time when the coffee is exposed to water at approx. 9 bar will be counted.
Start the time when the first drop of coffee touches the bottom of the cup.

The most preferred and generally used is the first option. Thus, as in the case of filter coffee, you count the total time the coffee is in contactwith the water.