If you’re keen on espresso or making specialty coffees like lattes then you’re probably interested in every possible technique you can use to get the most out of every brew. If you’ve done some research into this area of coffee making then you’ve likely come across the term ‘pre-infusion’.
To help you get to grips with pre-infusion and how it can transform your coffee brewing I’ve simplified the definition and have outlined everything you need to know about it. I’ve given it a go with my own espresso machine so I can truly verify whether or not it’s a worthwhile pursuit.
Let’s start with the basics and look at what pre-infusion actually is.
What Is Pre-Infusion
Pre-infusion, when talking about espresso, is the process of infusing water through the ground coffee as it sits in the portafilter before the extraction process has begun. Only a small amount of water is used, just enough to evenly wet the coffee puck and this is ideally done at a lower pressure and slightly higher temperature than those used for the extraction stage. It’s basically a method of pre-soaking the coffee, similar to the coffee ‘bloom’ process that’s recommended for pour-over.
Why Is Pre-Infusion Necessary
The pre-infusion stage means that the coffee is able to absorb water evenly during the brewing process so avoids channeling. The issue with channeling is that if the water chooses to flow through a small area of the puck rather than spreading out then you get an over-extracted coffee with more bitter flavors. When you pre-infuse the espresso shot, this gives a more even flow rate and so, a more consistent extraction.
How Is Espresso Usually Prepared
The standard process of brewing espresso depends on the kind of espresso machine you are using. A super-automatic machine does everything for you with just the press of a button whereas a manual lever machine has a lot more steps to the brewing process.
Whether or not the machine or the barista carries these steps out, here’s the typical process.
Coffee beans are added to the grinder and ground to a very fine powder. This is then added to a metal filter basket, held in a device (called the portafilter) that clips it onto the water outlet (known as the group head). A tamp is used to press the coffee into a puck.
The machine heats up water to around 195F and it creates around 9 bars of pressure. It’s a good idea to flush some water through the device before you attach the portafilter to pre-heat the group head.
The portafilter is then attached to the group head and the hot water is forced through the coffee puck at full pressure. This water trickles down into the espresso glass below and the brew time is usually 25-30 seconds.
How Do You Include Pre-Infusion
Pre-infusion is done after the portafilter has been fixed into place and just before the extraction stage. Unfortunately, not many espresso machines can easily achieve pre-infusion.
Plummed-in models that can achieve pipe pressure can work if you open the lever part way. This allows water to seep through to the puck and soak it at low pressure before coffee brewing starts. Some coffee machines with a water reservoir have the capacity for pre-infusion built into them.
You can, in theory, achieve something similar to pre-infusion when you use an automatic or semi-automatic espresso machine as you can switch on the water for a few seconds and turn it off again. Of course, this method doesn’t use the lower pressure that’s required and may start extracting your coffee sooner than you would like.
How Long Does Pre-Infusion Take
It really depends on the type of espresso machine you are using and can vary with dosing single vs double shots as well. It takes a bit of getting to know your machine and how long it takes for the coffee to start seeping out the spout. Typically, between 2 and 8 seconds is the ideal pre-infusion time before you start the higher extraction pressure.
What Is Pressure Profiling
If you’ve been keenly looking into pre-infusion then it’s very likely that you’ve come across the term pressure-profiling. The idea is that you pre-infuse the coffee puck and then gradually increase the pressure to a peak level about halfway through the extraction stage. Then you gradually close the lever to round off the pressure as you finish pulling the espresso shot.
The theory goes that exposing the coffee to a sudden slap of pressurized hot water is likely to create imbalances in the flow rate through the puck. Pressure profiling or flow profiling is this process of gradually increasing the pressure to ensure a balanced extraction.
Does Pre-Infusion Work
Before I give my opinion on this process I have to first make it clear that I have a semi-automatic espresso machine. It is not set up for achieving true low-pressure pre infusion so I can only comment on the slightly less-than-accurate method that I used.
I usually experience a bit of variability when it comes to making espresso. I love to try different coffees all the time and this does mean I struggle to get a perfect pour every time.
Despite this, I decided to give pre-infusion a go, so I grabbed my go-to, medium roast coffee and added it to the grinder. This is my favorite all-rounder when it comes to coffee making but when brewing espresso I do sometimes struggle to get a good crema with it.
I pre-heated the machine and group head and dried everything off. The coffee went in the filter as per and I took care tamping it to a smooth finish.
Unsure exactly how long I should pre-infuse using my machine I decided to opt for the quicker, 2 seconds as I knew I couldn’t reduce the pressure in my machine and I didn’t want to start the extraction too early.
I switched it on, 1… 2… and switched it off again!
I gave it another couple of seconds and then switched it on again.
A beautiful, thick, dark liquid started oozing out in a lovely smooth stream. Impressed, I gave it the standard 30 seconds and switched the machine off.
The espresso had a lovely thick crema that I usually only achieve using darker roasts. It was full-bodied, yet sweet and rich and everything you want your espresso to be.
I can’t say whether or not it was the pre-infusion that produced this delicious cup of joe or if it was simply my technique but one thing’s for sure. At best pre-infusion may produce the most delicious espresso you’ve ever tasted and at worse, it sure doesn’t harm the coffee. With nothing to lose, why not give it a go next time you make an espresso?