Minerals in Brewing Water
The principal ions most likely to be found in brewing water are those of calcium, magnesium, sodium, potassium, sulfate, phosphate, chloride, carbonate, and nitrate/nitrite. The minor ions of iron, copper, zinc, and magnesium may be found in trace amounts.
The calcium ion is by far the most influential mineral in the brewing process. Calcium reacts with phosphates, forming precipitates that involve the release of hydrogen ions and in turn lowering the pH of the mash. This lowering of the pH is critical in that it provides an environment for alpha-amylase, beta-amylase, and proteolytic enzymes.
Magnesium ions react similarly to calcium ions, 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. Magnesium carbonate reportedly gives a more astringent bitterness than does calcium carbonate (23).
Sodium has no chemical effect; it contributes to the perceived flavor of beer by enhancing its sweetness. Levels from 75 to 150 ppm 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).
Like sodium, potassium can create a "salty" flavor effect. It is required for yeast growth and inhibits certain mash enzymes at concentrations above 10 mg/l (21).
Sulfates 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.
Phosphates are important pH buffers in brewing and useful for reducing the pH in mashing and during the hop-boil (3).
Calcium and magnesium chlorides give body, palate fullness, and soft-sweet flavor to beer. The certain roundness on the palate given by sodium chloride (common table salt) makes this salt eminently suited for all types of sweet beers – for both dark beers and stouts.
The presence of carbonate 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.
Nitrates and Nitrites
Nitrate, 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 (24).
Iron in large amounts can give a metallic taste to beer. Iron salts have a negative action at concentrations above 0.2 mg/l during wort production, preventing complete saccharification, resulting in hazy worts, and hampering yeast activity (14).
Copper, in concentrations as low as 0.1 mg/l can act as catalysts of oxidants thus leading to irreversible beer haze. At levels more than 10 mg/l, copper is toxic to yeast (14).
Zinc 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) (1).
Manganese is important for proper enzyme action and has a positive action on protein solubilization and yeast.
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