Water makes up some 95% of the content of beer so its impact on the quality of the beer that you brew cannot be understated. However, understanding the chemistry involved can be quite confusing and is enough to finish off even the most experienced brewer. So a few settling words before continuing. You can brew perfectly decent beer with whatever water comes out of your tap. But if you want to take control of your brewing and recreate some of the great beer styles from around the world then a basic understanding of the impact of your water is useful. A great place to start is with this home brewers guide to water.
How does the water that you use affect the quality of the beer that you brew.
If you look around the world at the established brewing regions you can draw some conclusions about the beers that they brew by looking at the water that they use. For example Burton-Upon-Trent in the UK, Dublin in Ireland and Pilsen in the Czech Republic. These three areas all produce very different beer styles which have become strongly associated with these areas. Full flavoured strong pale ales such as IPA are associated with Burton-Upon-Trent, dark porters and stouts from Dublin and soft pale lager style beers have made Pilsen famous. When you look at the chemical analysis of the water you can see why these significantly different beer styles are synonymous with these three areas.
Burton-Upon-Trent water is high in calcium sulphate, or as it is more commonly known gypsum, whereas Dublin water is rich in calcium bicarbonate or temporary hardness. Finally the water in Pilsen is quite soft with low concentrations of both calcium sulphate and bicarbonate.
The question is how do these small differences in the salt content of the water have such an impact on the type of beer produced?
The difference is due to the presence of calcium (Ca2+) and carbonate (HCO3-) and the impact that these two ions have on mashing pH.
First things first what is pH?
The pH of a solution is a measure of the solutions acidity or alkalinity. The pH scale runs from 0 to 14 with 0 being very acidic, 14 very alkaline and 7 neutral. The pH scale actually measures the concentration of hydrogen ions (H+) in solution. In brewing pH is an important measure as many of the reactions that occur, for example in mashing, are pH dependent. This is due to the fact that the enzymes that are critical for mashing, because they are proteins, are very sensitive to pH. That is to say that they operate in a very tight pH range. If the pH moves outside of that range the enzyme may still function but the activity of the enzyme is significantly reduced.
How do calcium (Ca2+) and carbonate (HCO3-) ions affect pH?
The presence of carbonate ions increases the pH by reacting with hydrogen ions in the mash to produce carbon dioxide (CO2) and water (H2O).
Whereas the presence of calcium ions encourages the release of hydrogen ions thus reducing the pH of the mash making it more acidic.
The impact of the change in the pH is that the amylases, in particular beta-amylase, work better at a lower pH giving a more fermentable wort.
Incidentally calcium ions also stabilise the structure of the amylases making them more resistant to being broken down at the temperatures used during mashing.
However, what can a home brewer do about the water they use? Gaining an understanding of the ionic or salt composition of your water is a good place to start. Many water companies are happy to provide a basic chemical analysis of your tap water and this gives you some excellent background information.
In terms of adapting your water if you are in an area of high temporary hardness, that is your water is rich in calcium carbonate and you want a more fermentable wort then you can boil your water to remove the temporary hardness. If there is a low level of calcium sulphate in your water you can do what is known as Burtonising your water by adding gypsum either directly to the water before mashing or to the mash itself.
Remember it is possible to produce decent beer from the water out of your tap. But if you enjoy experimenting and are keen to accurately recreate particular beer styles then having a better understanding of the quality of your water will certainly help.