Posted Tue Jun 5, 2012, 5:42pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
According to Illy the total solids in espresso are typically 90% soluble. So a target soluble extraction of 18-21% would imply a solids yield of about 20-23%. Does that mean further testing showed that the following line from that Home-Barista post turned out to be not quite true?
The proportion of soluble to insoluble solids in espresso may vary a lot. I would accept Illy's figure as an average of Italian espresso prepared using typical Italian baskets manufactured with indifferent quality control. (One of the design goals for VST filter baskets was keeping the insoluble solids around 4-5% or less of the total solids).
Plug for VST baskets aside, if I get espresso soluble extraction yields above ~20.5%, the shots often develop a bitter tinge. My best shots are usually around 18.5% - 19.5% solubles yield. Every once in a while a 17% shot will taste really good and intriguing -- don't ask me why!
Posted Thu Jun 7, 2012, 6:56pm Subject: Re: Coffee Extraction Discussion, Questions for the membership:
If I work a brew ratio around 18% with a pourover, and produce stuff that's 4.9% strength, I find that I tend to prefer this over same brew ratio at 5.30-5.35% - backcalculated extractions are ~19% for the former, ~>20% for the latter. When I start pushing strengths with this brew ratio approaching 5.5%, I get what you're finding - a bitter tinge and some increased astringency.
jpender Senior Member Joined: 11 Jul 2011 Posts: 755 Location: California Expertise: I like coffee
Grinder: OE LIDO Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Thu Jun 14, 2012, 10:07am Subject: Re: Coffee Extraction Discussion, Questions for the membership:
I was just thinking that if I did that and the strength didn't double, it would indicate interference or saturation due to the concentration of the already-brewed coffee TDS in the following extraction.
Well we know coffee can be a lot stronger than 3% so you're not reaching saturation. But a high enough soluble concentration could affect extraction. At some level it might be possible to drive solubles INTO the grounds. Didn't Schulman postulate that for the initial wetting of espresso pucks?
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