Understanding the Mash pH
Balancing the Malts and Minerals
When you mash 100% base malt grist with distilled water, you will usually get a mash pH between 5.7-5.8. (Remember, the target is 5.1-5.5 pH.) The natural acidity of roasted specialty malt additions (e.g. caramel, chocolate, black) to the mash can have a large effect on the pH. Using a dark crystal or roasted malt as 20% of the grainbill will often bring the pH down by half a unit (.5 pH). In distilled water, 100% caramel malt would typically yield a mash pH of 4.5-4.8, chocolate malt 4.3-4.5, and black malt 4.0-4.2. The chemistry of the water determines how much of an effect each malt addition has. The best way to explain this is to describe two of the world's most famous beers and their brewing waters. The Pilsen region of the Czech Republic was the birthplace of the Pilsener style of beer. A Pils is a crisp, golden clear lager with a very clean hoppy taste. The water of Pilsen is very soft, free of most minerals and very low in bicarbonates. The brewers used an acid rest with this water to bring the pH down to the target mash range of 5.1 - 5.5 using only the pale lager malts.
Table 14 - Influence of Brewing Water
The other beer to consider is Guiness, the famous stout from Ireland. The water of Ireland is high in bicarbonates (HCO3-1), and has a fair amount of calcium but not enough to balance the bicarbonate. This results in hard, alkaline water with a lot of buffering power. The high alkalinity of the water makes it difficult to produce light pale beers that are not harsh tasting. The water does not allow the pH of a 100% base malt mash to hit the target range of 5 - 5.8, it remains higher and this extracts harsh phenolic and tannin compounds from the grain husks. The lower pH of an optimum mash (5.2-5.5) normally prevents these compounds from appearing in the finished beer. But why is this region of the world renowned for producing outstanding dark beers?. The reason is the dark malt itself. The highly roasted black malts used to make Guiness add acidity to the mash. These malts match and counter the buffering capability of the carbonates in the water, lowering the mash pH into the target range.
The fact of the matter is that dark beer cannot be brewed in Pilsen, and light lagers can't be brewed in Dublin without adding the proper type and amount of buffering salts. Before you brew your first all-grain beer, you should get a water analysis from your local water utility and look at the mineral profile to establish which styles of beer can best be produced. The use of roasted malts such as Caramel, Chocolate, Black Patent, and the toasted malts such as Munich and Vienna, can be used successfully in areas where the water is alkaline (i.e., a pH greater than 7.5 and a carbonate level of more than 200 parts per million) to produce good mash conditions. If you live in an area where the water is very soft (like Pilsen), then you can add brewing salts to the mash and sparge water to help achieve the target pH. The next two sections of this chapter, Residual Alkalinity and Mash pH, and Using Salts for Brewing Water Adjustment, discuss how to do this.
The following table lists examples of classic beer styles and the mineral profile of the city that developed them. By looking at the city and its resulting style of beer, you will gain an appreciation for how malt chemistry and water chemistry interrelate. Descriptions of the region's beer styles are given below.
Table 15 - Water Profiles From Notable Brewing Cities
India Pale Ale
Burton: "The Practical Brewer", p. 10,
Dortmund Noonen, G., "New Brewing Lager Beer"
Dublin "The Practical Brewer", p. 10,
London "Fermentation Technology", p. 13, Westermann and Huige
Pilsen "American Handy Book", 2:790, Wahl-Henius, 1902
Pilsen - The very low hardness and alkalinity allow the proper mash pH to be reached with only base malts, achieving the soft rich flavor of fresh bread. The lack of sulfate provides for a mellow hop bitterness that does not overpower the soft maltiness; noble hop aroma is emphasized.
Dortmund - Another city famous for pale lagers, Dortmund Export has less hop character than a Pilsner, with a more assertive malt character due to the higher levels of all minerals. The balance of the minerals is very similar to Vienna, but the beer is bolder, drier, and lighter in color.
Vienna - The water of this city is similar to Dortmund, but lacks the level of calcium to balance the carbonates, and lacks as well the sodium and chloride for flavor. Attempts to imitate Dortmund Export failed miserably until a percentage of toasted malt was added to balance the mash, and Vienna's famous red-amber lagers were born.
Munich - Although moderate in most minerals, alkalinity from carbonates is high. The smooth flavors of the dunkels, bocks and oktoberfests of the region show the success of using dark malts to balance the carbonates and acidify the mash. The relatively low sulfate content provides for a mellow hop bitterness that lets the malt flavor dominate.
London - The higher carbonate level dictated the use of more dark malts to balance the mash, but the chloride and high sodium content also smoothed the flavors out, resulting in the well-known ruby-dark porters and copper-colored pale ales.
Edinburgh - Think of misty Scottish evenings and you think of strong Scottish ale - dark ruby highlights, a sweet malty beer with a mellow hop finish. The water is similar to London's but with a bit more bicarbonate and sulfate, making a beer that can embrace a heavier malt body while using less hops to achieve balance.
Burton-on-Trent - Compared to London, the calcium and sulfate are remarkably high, but the hardness and alkalinity are balanced to nearly the degree of Pilsen. The high level of sulfate and low level of sodium produce an assertive, clean hop bitterness. Compared to the ales of London, Burton ales are paler, but much more bitter, although the bitterness is balanced by the higher alcohol and body of these ales.
Dublin - Famous for its stout, Dublin has the highest bicarbonate concentration of the cities of the British Isles, and Ireland embraces it with the darkest, maltiest beer in the world. The low levels of sodium, chloride and sulfate create an unobtrusive hop bitterness to properly balance all of the malt.