What is preinfusion and does it really matter?

Postby jamiedolan on Tue Jun 03, 2008 12:34 am

I recently read the Weiss Distribution Technique http://www.home-barista.com/weiss-distribution-technique.html article while learning about my new Mazzer grinder. In this article they mention "espresso machines with the preinfusing E61 group" as being "especially forgiving brewing equipment"
I knew I had herd preinfusion mentioned last month when I was at the SCAA show, but was not able to catch any details on the subject.

I performed several searches, and found very mixed comments on the subject. Can anyone tell me more about what preinfusion actually is and what difference it will make in my shots? I am also wondering what machines may preinfuse or allow you to preinfuse. I have a cheap espresso machine now, but am looking at a number of possible upgrade options including the Dalla Corte.

Thank You

Jamie
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Postby mhoy on Tue Jun 03, 2008 1:36 am

The coffee is pre-wetted before the shot. It's suppose to be better, but heck since I can't disable it in my Anita and my previous machine doesn't really remotely compare I can't really say.

A nice coffee glossary at:
http://coffeegeek.com/opinions/markprince/07-20-2004

Mark
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Postby HB on Tue Jun 03, 2008 1:51 am

Minor quibbles on terminology and completeness aside, I agree with Mark's definition below. However, as I wrote about in Pressure profiles, preinfusion and the forgiveness factor, some espresso machines nicely demonstrate that preinfusion is not a prerequisite to exceptional espresso. Jim suggested in the Elektra Semiautomatica review that uniform water diffusion plays an unappreciated and yet significant role. I think he's right.

In terms of buying criteria, it would be a mistake to vet your choices based on the presence of some preinfusion mechanism. For example, the Elektra A3 has no preinfusion, the Vibiemme Domobar Super has the classic E61 preinfusion chamber, and the Ponte Vecchio Lusso is a spring lever where you control the preinfusion (I prefer about 3 seconds for the Lusso). Three completely different espresso machines in terms of preinfusion and all very easy to use.

An Espresso Glossary wrote:
Preinfusion: the act of pre-wetting the bed of ground coffee inside an espresso machine before actually commencing the brew. Some espresso machines do this by using the pump; water is pumped to the coffee for a second or two, then halted for another second or two. After this pause, the pump activates again, and continues brewing the shot. Super automatics and some automatic machines use this pre-infusion.

Another type of preinfusion is called "natural" or progressive preinfusion, and occurs in machines equipped with an E61 grouphead. When the pump is activated, a secondary chamber must fill prior to full pressure being applied to the bed of coffee. This gives a 3 to 7 second saturation time for the grounds before the pressure builds up. This type of preinfusion is preferable to pump and pause active preinfusion.

There is a school of thought that progressive preinfusion improves overall extraction from the coffee.
Dan Kehn
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