Yes, pure RO water can damage your espresso machine. - Page 2

#11: Post by **Ciaran** » November 17th, 2020, 5:28 pm

Peppersass wrote:Interesting. I've read hundreds of posts here about proper mineral concentration for espresso, and of course I've read Jim Schulman's Insanely Long Water FAQ. This is the first time I've seen an assertion that mineral concentration has less effect on espresso than brewed coffee. Do you have any sources for this conclusion or is it your own?

I'm not saying it isn't true. Nate42 suggests that you simply compensate for low mineral content by changing dialing-in parameters. That makes sense, though I'd prefer to see some EY measurements comparing RO and water with recommended hardness. And my own experience is that removal of all hardness by my cation system hasn't made espresso extraction any different than my old Claris Everpure system adjusted to 70 ppm. I've always thought that either the salt ions or remaining alkalinity minerals, which are still high, took the place of hardness in extraction. But maybe it's just me dialing in higher extraction.

Anyway, if true, the notion that mineral content isn't important for espresso extraction would be news to most of HB's members.

I don't believe I said it isn't important, only that the mineral concentration has less of an effect on espresso extraction than it does for other brewing methods.

November 17th, 2020, 6:11 pm

Peppersass wrote:This is the first time I've seen an assertion that mineral concentration has less effect on espresso than brewed coffee.

In the special case of alkalinity, there is a very common-sense argument that espresso can tolerate much higher concentrations than filter coffee. Because an espresso drink has about 1/10th as much water, at a given alkalinity it would have 1/10th the acid buffering effect on coffee acids. So the effect that some tasters report that high alkalinity makes coffee dull, if due to neutralization of coffee acids, would be much less pronounced in an espresso. Here's an article about that by Marco Wellinger at ZHAW: https://scanews.coffee/25-magazine/issu ... e-issue-9/

As far as hardness minerals go, I don't think you can say much with any confidence. In that article Dr Wellinger says:

Observations from different sources cite a tendency for "overextracted flavor" at high levels of total hardness (> 250 ppm CaCO3) and conversely a trend for "underextracted flavor" at low levels of total hardness (< 40 ppm CaCO3). However, experimental measurements suggest that the impact of total hardness on the overall extraction efficiency is insignificant within reasonable variations in total hardness levels (20-250 CaCO3).

This is based on experiments trying to demonstrate an effect of brewing water minerals on extraction efficiencies based on refrctometer and TDS measurements . (Along the lines of Nate42's suggestions earlier in this thread.)