Minerals in Brewing Water
Minerals (i.e., inorganic ions) are of importance for the flavor of beer. They mainly come from the water since water composes more than 90 percent of the beer, although some also originate from raw materials. Brewers use a wide range of water compositions for their beer production. The principal ions present in brewing water are calcium, sodium, magnesium, potassium, sulfate, chloride, carbonate, and nitrate. Minor concentrations of iron, copper, and zinc are also found.
Historically, different regions have become famous for their classic beer styles as defined by the waters available for brewing. For example, the famous brewing waters from the deep wells at Burton-upon-Trent are known for their excellent qualities in brewing full-flavored pale ales. Burton water is high in permanent hardness because of the high calcium and sulfate content, but it also has a lot of temporary hardness from a high level of bicarbonate. Munich water is poor in sulfates and chloride but contains carbonates, which are not very desirable for pale beers but ideal for producing darker, mellower lagers. The carbonates raise the mash pH, producing wort with a higher dextrin to maltose ratio.
The calcium (Ca2+) ions are by far the most influential mineral in the brewing process. Calcium is instrumental to many yeast, enzyme, and protein reactions, both in the mash and in the boil. Yeast flocculation is improved by calcium; most yeast strains require at least 50 mg/L Ca2+ ions for good flocculation (Taylor, 2006). Calcium reacts with phosphates, forming precipitates that involve the release of hydrogen ions, in turn lowering the pH of the mash.
The presence of carbonate (CO32-) ions and their effect in raising pH can result in less fermentable worts (a higher dextrin/maltose ratio), unacceptable wort color values, difficulties in wort filtration, and less efficient separation of protein and protein-tannin elements during the hot and cold breaks. High carbonate waters can affect hop flavor too—hop bitterness becomes increasingly harsher. It is essential, therefore, that temporary hardness is removed from brewing water.
Magnesium (Mg2+) ions react similarly to calcium ions and malt phytins, but since magnesium salts are much more soluble, the effect on wort pH is not as great. Magnesium is most important for its benefit to yeast metabolism during fermentation.
Nitrates and Nitrites
Nitrate (NO3¯), in and of itself, is not a problem; it has no effect on beer flavor or brewing reactions. However, high nitrite levels may reduce the fermentation rate, dampen the rate of pH reduction, and give rise to higher levels of vicinal diketones (Taylor, 1988).
Phosphate compounds are prevalent in malt and wort. Phosphates (HPO32-) are important pH buffers in brewing and useful for reducing the pH in mashing and during the hop-boil (Briggs et al., 2004).
Like sodium, potassium (K+) can create a “salty” flavor effect. It is required for yeast growth and inhibits certain mash enzymes at concentrations above 10 mg/L (Sanchez, 1999).
Sodium (Na⁺) has no chemical effect; it contributes to the perceived flavor of beer by enhancing its sweetness. Levels from 75 to 150 mg/L give a round smoothness and accentuate sweetness, which is most pleasant when paired with chloride ions than when associated with sulfate ions. In the presence of sulfate, sodium creates an unpleasant harshness, so the rule of thumb is that the more sulfate in the water, the less sodium there should be (and vice versa).
Calcium and magnesium chlorides give body, palate fullness, and soft-sweet flavor to beer. The certain roundness on the palate given by sodium chloride (NaCl) (common table salt) makes this salt eminently suited for all types of sweet beers—for both dark beers and stouts.
Sulfates (SO42-), positively affects protein and starch degradation, which favors mash filtration and trub sedimentation. However, its use may result in poor hop utilization (bitterness will not easily be extracted) if the levels are too high. It can lend a dry, crisp palate to the finished beer; but if used in excess, the finished beer will have a harsh, salty, and laxative character.
Iron (Fe2+) in large amounts can contribute to negative flavor characters to beer, such as metallic and astringent.
Chloride (Cl¯) is common in most water supplies. Chloride ions contribute to the mellow, palate-full character of beer.
Copper (Cu2+), in concentrations as low as 0.1 mg/L can act as catalysts of oxidants thus leading to irreversible beer haze.
Zinc (Zn2+) plays an important role in fermentation and has a positive action on protein synthesis and yeast growth. It also impacts flocculation and stabilizes foam (promotes lacing) (Bamforth, 2006a).
Manganese (Mn2+) is important for proper enzyme action and has a positive action on protein solubilization and yeast.
Click on the following topics for more information on brewing water.