is a property of liquids. Technically it is the ability of a solution to resist (or buffer) a change in its pH value when acids are added. See ph. The three key ions that contribute to alkalinity are the hydroxide ion (OH–), the carbonate ion (CO32–), and the bicarbonate ion (HCO3-). In water, they react with acidic substances to form salts. Alkalinity ions are thus acid reducers; they increase water’s pH value. Depending on the suitability of a given brewing water for a particular beer style, a brewer may use water additives to change the water’s pH in the direction of more acidity or more alkalinity.

Alkalinity is often reported as either milligrams of bicarbonate (HCO3–) ions per liter or as the equivalent amount of calcium carbonate (CaCO3) in milligrams per liter; the concentration relationship is CaCO3 = 0.82 × HCO3–. For brewing waters it is recommended that the alkalinity should not exceed 100 mg bicarbonate/l, with a value of 50 mg/l being much better.

The use, in specified amounts, of food-grade phosphoric acid, sulfuric acid, or lactic acid or acidic salts such as calcium and magnesium chlorides or sulfates (Wallerstein Lab’s Burtonization process, for example) helps to adjust the pH of alkaline brewing waters (by first breaking the buffer capacity). The recommended range for the pH of brewing water is between 6.0 and 7.5. The salts added aid in reduction of alkalinity while providing important ions to further benefit the processes of brewing. For the German Reinheitgebot purity law, neutralization by means of lactic acid fermentation or acidulated malt may also be employed. See acidification.

During brewing, pH is reduced further upon addition of malts and adjuncts, and ultimately a low wort pH results in a number of benefits to the brewer (increased extract yield, increased fermentability, and a decrease in the extraction of harsh tannins and hop bittering compounds). For optimal enzyme activity in mashing, a pH of 5.2–5.4 is desirable.See also mashing.