pstam Senior Member Joined: 27 Jan 2004 Posts: 2,302 Location: Beijing Expertise: Professional
Espresso: ECM, SAN MARCO, EURO 2000 Grinder: MAZZER Vac Pot: YES Drip: YES Roaster: YES, HOME STYLE
Posted Sun Sep 17, 2006, 1:16am Subject: Pre-infusion, does it work and how?
When I talked to our trainees this afternoon, a new understanding came to my mind. It is about "pre-infusion".
Do you believe it? Or how do you understand it? Even if you do not believe it but heard about some kind of explanation of it, please let me know and I would compare it with mine.
I do not tell it before we collect all different udnerstandings, in order not to disturb your description and uderstanding.
I am looking forward to hearing as much as possible.
Peter in Beijing ------------------- http://www.kaffa.cn/ ------------------- I am looking for the way and the place to extend our trainning courses.
Posted Sun Sep 17, 2006, 11:45am Subject: Re: Pre-infusion, does it work and how?
Hello ..
I'm no expert but here are the two reasons I have read about.
First, coffee expands as it gets wet so pre infusion helps the puck surface seal up as it expands providing a tighter fit when the high pressure water starts to flow.
Second, the pre infusion helps loosen up coffee oils in the puck. Like a pre soak stage before the water really starts moving.
emradguy Senior Member Joined: 31 Mar 2011 Posts: 1,711 Location: Houston Expertise: I live coffee
Espresso: Izzo Alex Duetto II Grinder: MacapM4T, Macap M4, OE Lido,... Drip: Espro press; Aeropress Roaster: internet
Posted Fri Mar 2, 2012, 3:47pm Subject: Re: Pre-infusion, does it work and how?
I found this ancient thread about preinfusion, because I don't understand it - when to do it, why to do it, etc. When I took my barista training course with Heather Perry, she told me don't worry about it, and that was about all the explanation I ever got. I was using my Silvia at the time (at home, not in her course). Is the second post accurate? Can anyone elaborate, or should I just get a book and read?
Would anyone use a manual pre-infusion technique with a Duetto? Is it worth experimenting?
Posted Fri Mar 2, 2012, 4:29pm Subject: Re: Pre-infusion, does it work and how?
A machine with an E-61 group preinfuses every shot if the group is working correctly. For detailed information on how that works, download the Vibiemme Domobar double from http://www.espressocare.com The working of the group are diagrammed and described in detail. On plumbed manual E-61 groups, the preinfusion can be extended as long as you want by simply holding the lever up without turning the pump on. This opens the brew valve and allows line water pressure to infuse. Other machines may have to go about it differently, usually though the electronics.
Preinfusion gives the coffee throughout the puck to become saturated and helps give an even extraction across the entire puck. It also swells the coffee which lessens channeling and fracturing. As far as a low pressure water stream assisting directly in any extraction process, I would have to assume that whatever can be so easily extracted at around 1.5 to 2bar could be even more easily extracted at 9 BAR after the pressure increases when the pump kicks in.
emradguy Senior Member Joined: 31 Mar 2011 Posts: 1,711 Location: Houston Expertise: I live coffee
Espresso: Izzo Alex Duetto II Grinder: MacapM4T, Macap M4, OE Lido,... Drip: Espro press; Aeropress Roaster: internet
Posted Fri Mar 2, 2012, 5:31pm Subject: Re: Pre-infusion, does it work and how?
thanks, Randy!
That's a nice document. I wish the Duetto came with as much detailed explanation. I'm looking forward to reading it thoroughly. I skimmed it thus far and noticed in the E-61 section you explained the fully opened valve and fully closed "idle" position. Again, I plan to read through it thoroughly, but in case the answer is not there...what is the purpose of the intermediate lever position (I'm assuming that what I'm referring to on my Duetto is common to other E-61 group levers - where the lever can be raised about halfway towards open and seems to cick into an intermediate position, without apparently allowing extraction from the puck out of the portafilter)?
...what is the purpose of the intermediate lever position (I'm assuming that what I'm referring to on my Duetto is common to other E-61 group levers - where the lever can be raised about halfway towards open and seems to cick into an intermediate position, without apparently allowing extraction from the puck out of the portafilter)?
There really is no intermediate position. It feels that way for a couple of reasons: - it is when the lever's external cam hits the brew switch - there is a transition internally when the internal cam closes the infusion valve (and indirectly, the exhaust valve) and the lever effort momentarily is very light. Right after that, as the lever moves a bit further, the cam opens the brew valve. If the machine is plumbed, this will allow the water to flow into the coffee at the pressure supplied to the machine. The feedback on the lever causes you to think that this is doing something, or at least to say, that something more tactile, auditory, or functional should be apparent. That's the preinfusion point. Lifting it fully closes the contacts on the brew (pump) switch and holds the lever in the brew position.
pstam Senior Member Joined: 27 Jan 2004 Posts: 2,302 Location: Beijing Expertise: Professional
Espresso: ECM, SAN MARCO, EURO 2000 Grinder: MAZZER Vac Pot: YES Drip: YES Roaster: YES, HOME STYLE
Posted Mon Mar 5, 2012, 7:47pm Subject: Re: Pre-infusion, does it work and how?
preinfusion can really help to avoid uneven extraction, but only for single cup extraction. For double cups extraction, it is not useful at all. Excluding that preinfusion has nothing to do with coffee extraction.
Sometimes, I use manual preinfusion. It's not necessary, but sometimes helps.
This is a really old thread, and I totally forgot it, until someone dig it out these days. Thanks.
Peter in Beijing ------------------- http://www.kaffa.cn/ ------------------- I am looking for the way and the place to extend our trainning courses.
Why would it act any differently on a double than on a single?
You know those people that want to tell you how to raise your kids but have none of their own? That is how i feel when someone with a kitchen appliance tells me how the merits or dis-merits of my machine or how to use it.
It doesn't. it may appear that way to some observers because single are a bit more difficult to dose and distributes because of the shallower coffee bed, so it would appear make one conclude that it works better for singles, but really , it just points out that a poor preparation was being done and the preinfusion helped it. It does help the coffee expand and that helps to limit gushers, sprites, and other such problems because the coffee expands before the full pressure is applied.
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