Why am I getting the best espresso results at a lower TDS ? - Page 2

Water analysis, treatment, and mineral recipes for optimum taste and equipment health.
User avatar
Radio.YYZ
Posts: 551
Joined: 7 years ago

#11: Post by Radio.YYZ »

homeburrero wrote:This does seem to be a predominant theory and model lately. But I suspect it's far more complex than that. It has been observed for many years that brew water with high bicarbonate/alkalinity, as you would get after softening a very hard water, tends to cause a slower flow rate. One theory to explain why that happens that is that when the water first hits the coffee, the bicarbonate causes the grounds to saturate and expand differently which has effects on the subsequent flow.

It's also long been argued that high alkalinity tends to produce a flatter tasting coffee. This *might* be related to the acid buffering effect of that high alkalinity.

Computational chemistry (see Hendon) does predict that different cations bind differently to the coffee compounds we want to extract, with hardness minerals (magnesium and calcium) binding much better than potassium and sodium. This might argue in favor of using water with high hardness over softer waters, or over using zero hardness water like the rpavlis recipe. The trouble with that argument (one that rpavlis has made in the past) is that the liquid flowing through the ground coffee is nowhere near the same as the incoming water. It is loaded with chemicals and minerals from the coffee itself. The total magnesium concentration when the brew comes out is in the neighborhood of 800 ppm* (which equates to a magnesium hardness as CaCO3 of about 3300 ppm). And the potassium is higher. Given that, it's hard to understand why the relatively tiny amounts of these cations in the incoming water appears to have a pronounced effect on taste. The model is probably very complex. I've always liked the rpavlis view of the extraction process:

*You see some variation in the reported concentration of magnesium in espresso. The USDA numbers have it at 80 mg per 100ml: https://ndb.nal.usda.gov/ndb/foods/show/4278. Of course, that number is the total, which includes suspended solids and bound magnesium in addition to magnesium ion.
Agreed that its complex and until someone ran a specific coffee under battery of tests to get the composition of the beans and various elements present in it, it will just be a theory which may get loosely supported by anecdotal evidence.

Funny enough i wondered about this and am experimenting with different recipes of water... i started with 30/30ppm of mgso4 and nahco3, slowly moving up the scale... currently running 40/40ppm. I found lower ppm water was better, but i am only into 8ish drinks into the new water so i am not confident with my assertion yet.
Good Coffee: Technique/Knowledge > Grinder > Beans > Water > Machine

Post Reply