I’m reading up on preinfusion this morning. Since I use a 9Barista, there’s no control over preinfusion, so I’m trying to figure out how this might impact things. I’m sure something resembling preinfusion is happening, as I can hear the valve open, and then there’s about a 5 second lag before espresso starts coming out.

  1. Besides wetting the puck so that channelling is reduced/eliminated, what does preinfusion do, if anything?
  2. Given that preinfusion seems to take place at a relatively lower pressure in a conventional espresso machine, does any significant extraction take place during the preinfusion phase?

Thanks!

[edit — clarified question #2]

You need a coarser grind without pre-infusion.

  1. If you pull the entire shot to expected weight in the cup, at pre-infusion pressure and achieve a normal extraction, then yes, significant extraction has taken place. If you stop the shot at any time, including during pre-infusion, and no liquid has been produced in the cup, then there is no extraction.

Pressure is less relevant to extraction than the production of actual beverage.

Even if you have ‘no pre-infusion’ there will still be some time whilst the PF & puck fill at a lower pressure than the rest of the shot.

    MWJB Thanks for the answer. I realized that I worded my second question badly, so I edited it. Apologies for the confusion.

      Found out that the 9Barista does do preinfusion. Here’s a graph from the 9Barista Instagram feed that shows what happens during an extraction. They mention in the caption that heat was kept on, which is why the pressure curve goes up during the extraction, and that modulating the heat could change the pressure curve. I don’t do this myself, as there’s really no feedback as to what’s happening. Also, the times I tried things like cutting the heat when the extraction started seemed to have very little effect on how the espresso came out.

      Would still love to know if preinfusion does anything else besides reducing channelling.

        wilburpan My view is that it also prepares the coffee in 2 ways.

        1. The soaking of the coffee makes it swell and become more eager to extract the goodies.
        2. The water in the puck reduces hydraulic compression allowing a slightly finer grind (which ma be a good thing for certain coffees)

        I have found that not all coffees react well to preinfusion.

        Contact me

            DavecUK Thanks, that helps a lot.

            In terms of the taste of espresso, and assuming that the coffee in question does benefit from preinfusion, does altering preinfusion parameters have as much impact on the taste as grind or dose? My sense is that the answer is no in general, and that adjusting preinfusion parameters has a relatively modest impact on the taste of the espresso, but wanted to check.

                I agree that some sort of preinfusion is happening but to paraphrase Spok “It’s pre-infusion Jim, but not as we know it”.

                My understanding (relative novice = feel free to correct me) of pre-infusion is that a relatively lower pressure (say 2 - 4 bar) is held constant for a period of time (typically 5 seonds although Rao will do up to 39 seconds for his “blooming” light roast pours) to soak the puck before ramping up to say 9 bars for the bulk of the extraction.

                By the look of the above graph, the ramp up of pressure is starting lower and moving to 9 bars so it is going to have a similar effect.

                You clearly like the result of the 9barista so I guess your quest to know more about pre-infusion is motivated by the same thing that keeps many of exploring further down the rabbit hole: I wonder if this could be even better?

                  tompoland I guess your quest to know more about pre-infusion is motivated by the same thing that keeps many of exploring further down the rabbit hole: I wonder if this could be even better?

                  It’s like you’re saying that folks who get into espresso making are predictable! 😆