(by my son Christopher Palm, 3rd quarter Honors Chemistry essay)
In the Middle Ages, many European towns had their own brewery, each with its own particular style of beer. Over time certain locations became famous for their unique brew. For example, Dublin became distinguished for its dark Guinness stouts, Pilsen was noted for its pale lagers, and Burton-on-Trent was renowned for its pale ales. Brewers did not know then what we know now — that the mineral content of the water used in zymurgy greatly affects the outcome of the beer. Today, brewers take these chemicals into account when they brew beer.
Several ions, including calcium, magnesium, carbonate, sulfate, and chloride, typically found in water affect beer in important ways. Metal ions tend to aid enzyme activity, while anions directly influence the flavor. Water either naturally has a lot of these ions in it – this is considered hard water – or it has few minerals dissolved in it – this is considered soft water
Calcium ions (Ca2+) and magnesium ions (Mg2+) ions protect the enzyme amylase (also found in human saliva) that breaks down the starches into simple sugars. Without these, the yeasts would not be able to break down enough starches to eat and the flavor of the beer would be substantially different. This enzyme is all-important for this reason, as the malts used in beer are roasted specifically to obtain certain sugars in them. “High levels [of Mg2+] taste sour/bitter” (Palmer 38), however. Besides these useful metallic ions, there can also be dissolved iron in the water, which has no useful purpose. It must be removed, or it will give the beer a bad taste.
The carbonate ion (CO32-), which is frequently coupled with Ca2+ to form the basic compound calcium carbonate, is an important and common ion found in hard water all over the country. It is sparingly soluble in water, and generally is found there dissolved from the limestone with which ground water is in contact. Carbonate ions do not give beer a specific pleasant flavor, but they help neutralize the rather low pH of certain malts, especially dark beer malts. An excess of CO32-, however, can create an unpleasant bitter or harsh flavor. If the water used for a beer is too high in CO32-, rendering it highly basic, applying an acidic substance (such as a sulfate) or brewing a dark beer containing the more acidic dark malts will mitigate this.
Sulfate ions (SO42-), which are also often paired with Ca2+ in calcium sulfate, are a third important ion present in water in some locations. This compound, gypsum, is often added to hard water (water that has carbonates in it) to cancel some of the basicity of the water. It also enhances the hops' bitterness, so it is a perfect ion to include in hoppy, light beers. But, as Donald Gajewski, former assistant brewmaster at City Brewery in La Crosse, Wisconsin, warns, “Too low a pH gives a beer an astringent, harsh taste” (Gajewski 3/07/12). This happens if too many sulfate ions are added.
Another fairly common ion is the chloride (Cl-) ion. (This is not the chlorine added to water to disinfect it – that chlorine has a bad taste and must be removed if present.) It can be added as either NaCl or CaCl2. If calcium chloride is added, it boosts the calcium level (which is not necessarily needed if the calcium level is already adequate). If sodium chloride is added, the sodium does not have quite the same effect: it “acts like salt to accentuate the malt flavor at moderate levels” (Palmer 38) – or in too large a quantity, it imparts a salty flavor to the brew (not too surprisingly). The Cl- ion has similar effects, and it also helps give a beer a smoother taste. Some people actually use a salt shaker when they drink highly bitter beers!
The most prominent ingredient in any glass of beer is water, yet few people consider the great impact this ingredient has on the quality of the draft. Hard water is best for dark beers, soft water (with a few sulfate ions) is best for light beers, but too much of any of these chemicals can make any beer taste bad. It takes a chemist to understand why the chemical makeup of water – whether hard, soft, or nasty – makes all the difference in the taste of the beer.
Foster, Terry. Pale Ale. Brewers Publications. 1999. Print
Gajewski, Donald. Former Assistant Brewmaster at the City Brewing Company, La Crosse. Interview.
Palmer, John J. How to Brew. Brewers Publications. 2006. Print.
The Practical Brewer. Edited by Broderick, Harold M. Master Brewers Association of the Americas. Madison, Wisconsin. 1977. Print.