How important is the water you brew with?

We recently discovered an older U.K. study that changed the way we thought about the quality of water we used to brew our coffee. The study, "The Role of Dissolved Cations in Coffee Extraction," is fairly technical, and I'll admit that some of the chemistry went right over my head. However, I learned enough from the research to prompt me to do some more research into the subject of water quality.

Well, it turns our there are myriad studies surrounding the effect of mineral content of water on coffee taste. Overall, they conclude that the presence of certain minerals in your brewing water will do a better job extracting coffee flavor from your beans, and too many of those minerals will have a negative effect. These minerals are in an ion form, which bind to compounds in coffee like acids, caffeine, sugars, aromatics. This binding is what "extraction" is all about - removing the good stuff from the grounds and suspending them in the hot water in your cup.

So it follows that distilled water ("pure" water, just the H2O and no minerals) will do a poor job of extracting flavor from water. On the other end of the spectrum, some well or city water with a high concentration of minerals will introduce off flavors. In the middle might be bottled Spring Water. At my house, all our well water is passed through our water softener. To us, however, it still has a bit of an off taste, so we use a Reverse Osmosis system for drinking water. In additional to other impurities, these systems reduce the dissolved minerals to 10-50 parts per million (ppm) .

The Specialty Coffee Association recommends a hardness range of 50-150 ppm for optimal brewing. So perhaps we're on the low end, and need to boost our mineral content? We may experiment at some point with something like products from Apax Lab but we're currently pretty happy with our morning brews. And we use RO water exclusively in our coffee truck. 

So there's the tradeoff - you need some minerals, but not a lot. The conclusion I come to is this: if your drinking water tastes clean, good and refreshing to you, brew coffee with it! If not, you might want to try a different water to see if it makes a difference to you.

-steve