Because coffee is 98% water, the quality of that water has a significant effect on the quality of your coffee. Water, while often assumed to be a simple chemical compound (two atoms of hydrogen, one of oxygen), is actually anything but, and may contain any or all of the following: calcium, magnesium, potassium, zinc, iron, sulfates, fluoride, sodium, and potentially a host of other trace elements. All these compounds affect water’s flavor, and thus the flavor of the coffee.
The Chemistry of Water
The best “coffee water” has a slightly below-average mineral content—coffee grounds need the metallic ions of calcium, magnesium and barium to bond with flavor molecules to produce great taste. Magnesium specializes in extracting sharper, fruitier flavors, while calcium extracts heavier, creamier flavor notes. The carbonate in the water, which soaks up acid, acts as a regulator in that regard—it has the ability to stabilize the acid when there is a surplus, or release more of it as needed.
The Specialty Coffee Association of America has set certain standards of water quality related to its use for coffee. Such measurements as sodium content, alkalinity, pH factor and calcium hardness are delineated and standardized, creating a “quality bar” of sorts that intends to preserve the integrity of specialty coffee.
Interestingly, the ideal water for coffee—which must have a temperature near boiling and include sufficient minerals if it is to extract the flavor from the beans effectively—is less ideal for the brewing of espresso. In fact, boiling water is slightly detrimental to the espresso, as it will begin to over-extract the grounds, giving the shot a bitter flavor. Hot water (195-200 degrees) is optimal, and since the water is in contact with the espresso for such a short time, mineral content is less relevant—a minimal amount is sufficient, and too much will quickly start to build up inside the espresso machine, necessitating more than regular cleaning.
Water of The Future
Coffee is well into its third wave, which attempts to know, embrace and perfect all aspects of coffee—from its origins to its brewing methods to its delivery system. In the spirit of this, a new interest has developed in achieving the ultimate quality of water, something superior to distilled, purified or filtered water, with just the right combination of minerals present. Enter Third Wave Water, a recent idea launched by the company of the same name.
The new startup hopes to optimize water for coffee by providing “the perfect amount[s] of calcium, magnesium, and sodium” in the form of a soluble tablet you can add to your distilled or reverse-osmosis brewing water. This “remineralizes” the water and makes it as coffee-friendly as it’s possible to be.
While we usually don’t think about it, like coffee, water has a flavor, which is impacted by soil, rainfall and solar intensity. The taste of water is primarily a result of different amounts of subterranean minerals like dolomite, halite and limestone.