Posted Sat Oct 14, 2006, 6:16am Subject: Re: Crema by James Hoffmann
It crossed my mind this morning that with an article like this I should probably post a few references for my information.
"Isolationa and Characterization of a foaming fraction from hot water extracts of roasted coffee" by Marino Petracco, Luciano Navarini, Anna Abatangelo,Valentina Gombac, Elisa D'agnolo, and Flavio Zanetti
I also had conversation with various food scientists both at Illycaffe's research centre and at institutions in the UK. These are the bigger and more relevent works, though other materials were used. Any specific questions I will be happy to try my best to answer. The goal of this article is as much to generate discussion as it is to try and spread some information.
KevinCash Senior Member Joined: 21 Jul 2005 Posts: 152 Location: Columbus, OH Expertise: Pro Barista
Espresso: PID'd La Marzocco Linea 3 EE Grinder: Mazzer Major, Ditting 804 Drip: Fetco Extractor Roaster: Jeff Davis @ Cafe Brioso
Posted Sat Oct 14, 2006, 6:38am Subject: Re: Crema by James Hoffmann
As a former chemistry major and current cafe owner, I have to say that this article is a MUST read for all interested in espresso prep. I have read and re-read this article to fully visualize every aspect....and I have finally pieced together the mystery of crema production in my mind. Thanks for the science aspect of the piece.
jim_schulman Senior Member Joined: 19 Dec 2001 Posts: 3,772 Location: Chicago Expertise: I live coffee
Posted Sat Oct 14, 2006, 9:06am Subject: Re: Crema by James Hoffmann
Thanks for the article. I've often wondered why fast extractions have lighter crema than slow extractions. It's odd and wonderful that a seemingly opaque layer of crema can show the level of coffee extraction while the naked eye cannot.
macchiattomatthew Senior Member Joined: 6 Jan 2005 Posts: 17 Location: Vancouver Expertise: I live coffee
Grinder: Baratza Virtuoso Drip: Eva Solo, Bodum French Press Roaster: Popcorn popper
Posted Sat Oct 14, 2006, 8:40pm Subject: Re: Crema by James Hoffmann
In the article, you mentioned that flecking is just fine particles of coffee on crema. Are these particles even smaller than the fines that move during the extraction? If so, is the ideal grinder perhaps one that produces dust - but just a small and controlled amount of it?
Posted Sun Oct 15, 2006, 9:47am Subject: Re: Crema by James Hoffmann
To try and answer a few questions:
JulesG - What kind of coffee are you using? Is it a very dark roast? Any idea how hot your machine is running?
macchiattomatthew - I assume the flecks are the fines that are moved during extraction, but they are something I'd like to know a lot more about. There is no doubt that an ideal grinder needs to produce a complete cross section of particle sizes. As for how small they go - seems like an article in itself!
Jasonian - Nothing to do with the study group, this was researched and written solely for coffeegeek.
Everman - It would be a nightmare to do, because trying to standardise as many things as possible would drive you nuts. Without any standardisation it would be very difficult to pinpoint the results - was it the pump, the dose, the grinder, the basket, the pre-infusion, the water flow rate, the water temp etc... etc...
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