Originally, brewing started up in areas where the water supply was suitable for the production of beer, but with the wide geographical spread of modern breweries and modern supply systems, the water available to the brewer can be at best variable and at worst quite unsuitable. The natural water in areas such as Burton-upon-Trent proved excellent for production of bitter ale beers and many brewers will now treat their incoming supply to adjust pH and salts content to emulate Burton water. Where dissolved salt levels are low, it is usually sufficient to make up the concentrations to the desired levels. The most important ions are calcium (Ca++), sulphate (SO4–), bicarbonate (HCO3-), and to a lesser extent magnesium (Mg++), and chloride (Cl-).
Calcium is a very important constituent and performs a number of functions:-
- Decreases the pH during mashing and wort boiling, favouring enzyme activity
- Promotes the precipitation of unwanted proteins in the kettle, hop back or whirlpool
- Promotes yeast flocculation at the end of fermentation
- Promotes head retention on beer
- Reacts with oxalate to form an insoluble salt, preventing gushing in beer
Sulphate is added to give beer a drier and more bitter effect
Bicarbonate has the opposite effect to calcium in that it causes an increase in pH, so reducing the desirable effects of calcium
Magnesium levels are typically rather lower than calcium and in addition its salts are more soluble,
so it has less effect on pH and flavour than calcium
High chloride concentrations are not usually found in water; its addition can impart palate fullness
Both temporary and permanent hardness can be treated using acidic products
The presence of calcium or magnesium ions in water gives rise to hardness, the familiar effect of which is to diminish or prevent the formation of soap lather. Calcium (or magnesium) bicarbonate in water is termed temporary hardness, so called because it can be removed simply by boiling the water and precipitating insoluble carbonate together with the evolution of carbon dioxide. Calcium or magnesium salts other than bicarbonates, typically sulphates or chlorides, are termed permanent hardness because they cannot be removed by boiling. Instead, other treatments such as sequestering, ion exchange are used.
This is now the most widely used method, for a number of reasons:-
- It is relatively inexpensive
- It is easy to use and does not produce sludge in the hot liquor tank
- Products such as AMS will add desirable anions, sulphate and chloride
- It can be achieved by using products such as Phosphoric Acid or Lactic Acid if no anions arewanted – for example in lager beers
It is essential to rouse the liquor when acid treating in order to encourage the removal of the carbon dioxide. This can have corrosive effects on the materials of construction of hot liquor tanks if left in solution.