We have all heard about pre infusion and pre brew, words thrown around alot when it comes to espresso. Talked about in brew recipes and let's face it nearly every machine manufacturer has thrown their own version of this in. With so many methods and different times, do we know the difference this is having on our final cup? Well today's post will go into depth on what it is, how it works and how to use it, to achieve your desired flavour profile in the cup.
Pre Infusion vs Pre Brew
These two terms are often confused and referred to as the same thing. It needs to be noted that while very similar and both effecting the end result of your espresso, there is a difference in the method.
Usually when people are talking about pre infusion, they are referring to constant uninterrupted water being introduced to the coffee bed at a low flow and/or pressure to infuse the coffee and the water before fully engaging pump flow and pressure. The simplest example of this is a plumbed machine using line pressure (usually around 3 bar) to slowly saturate the coffee bed for somewhere between 2-8 seconds before engaging the pump and extracting at around 9bar for the rest of the shot.
On the other hand Pre Brew can be referred to as quickly wetting the top of the coffee bed with water then stopping for a set amount of time before re-engaging the pump to start the full extraction. This can be achieved with nearly any machine were you can manually start and stop the pump. A simple example would be engaging the pump for around 1 second, stopping it for around 2 seconds then restarting it to continue the extraction to your desired parameters.
Both these methods set out to achieve the same goal. Gently introducing water to the coffee bed to ensure even wetting, reducing channeling, increasing eveness and overall extraction. The perameters used for the pre infusion / pre brew can be changed to suit the coffee and the desired flavour you are chasing, it is also very handy with less soluble coffees, be that because of process, density or roast profile.
Should we always use some form of pre-infusion or pre-brew?
This is a question I'm often asked when training people. The answer is not as straight forward as the question and different people will have varied opinions on this. While methods like this are very handy and I often encourage using them for consistency and to aid in extraction, there is often times I stay away from it and aim to use other methods of extraction.
For an all around blend, especially when pairing with milk, it is a great technique. Pre Infusion or pre brew will help reduce channeling, increase body and often bring more sweetness to the cup. These are all goals to chase for a traditional espresso.
On the other side of that, well developed single origins and black blends, where a more modern espresso approach, aimed at drinking black is the goal, pre infusion / brew can be counter productive. Usually in this approach acidity and calriry is prized, something that can be dulled or reduced when using pre infusion / brew methods. That being said small amounts can still help depending on the solubility of the coffee.
How long should I pre infuse/brew?
Like with coffee recipes, there is no set answer to this and it will depend on the coffee and the recipe. The best method is to taste and take note of different methods to find what works best for you. Some simple starting parameters, just like with recipes is a good place to start and adjust from there.
Pre Brew: Usually starts with a pulse of water somewhere between 0.5-2 seconds with a pause of 2-6 seconds before re-engaging the pump to begin the full extraction.
Pre Infusion: Usually somewhere between 2-10 seconds before continuing with full pump pressure.
Some simple things to remember is the longer the water is in contact with the coffee, the more extraction will occur. Lengthening the pre infusion or pre brew will increase extraction, increase body and can increase sweetness to a point but with the trade-off of reducing clarity and often acidity in the final cup. If you have a coffee that seems to still be thin, acidic and sour with normal parameters, increasing your pre Infusion may assist you in finding a balanced extraction. I always consider my extraction to begin, the moment any water is introduced to the coffee bed, and either changing total brew time or pre infusion time will alter the final extraction, you can shorten or lengthen either to compensate for this.
Why & how it works.
Whichever method you choose to use the theory behind how it works is essentially very similar. Using low pressure/flow to gently saturate the coffee bed, ensures a more even and consistent wetting. As pressure and flow is increased water will fight to find the path of least resistance, creating channels that are over extracted and areas of the bed that are under extracted or sometimes not extracted at all. This is very much the way that turbo shots work, using a very course grind, high ratio with less resistance means water is flowing more freely and evenly.
Conclusion
Which ever method you choose to use can result in a brilliant cup. Like with most things in coffee, there is no one perfect recipe for this, it will depend on the coffee, roast profiles and exactly what you are trying to achieve. I generally use it with more traditional espresso and think it can produce a brilliant espresso for milk based beverages, I tend to avoid it when I am using coffees, where I am trying to highlight more acidity and clarity in my brew, unless I find the coffee very hard to extract and I need to bring more sweetness to the cup, then it is introduced as a final measure to push the extraction further.
My answer is the same as it is with many things. Test it, play with it and take note of the differences it has on your final cup. Taste should always be your only true indicator of what works for you.
Any questions on this topic, or any others feel free to contact me via Instagram or the comment thread below.
Stay caffeinated and enjoy those cups ✌️
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