is the process of lowering the pH of a solution until it falls below pH 7.00. Brewers will sometimes acidify the mash and/or wort to effect certain changes, via pH, of the efficiency of brewing or to alter the flavor profile of the final beer. In general the process involves the use of acids, acidic salts, or microbial fermentations (generating acids biologically) to shift the pH of the mash, wort, and ultimately the resulting beer to the desired final levels. Brewers require a clear understanding of water chemistry, mash reactions and wort reactions, and chemistries to use acidification to the full effect. The general quality of water for brewing as well as the emulation of world-famous brewing waters can also be attained via adjustment by food-grade acids and acidic salts.

Various enzymes participate during beer production; for example, in the mashing process, starch- to-sugar conversion takes place and proteins are subject to breakdown to peptides and amino acids to provide nutrients for yeast. These enzymes all work at their own best or optimal pH values. The brewer ultimately has substantial leeway in adjusting conditions to best promote the enzymatic reactions taking place. Acidification provides one powerful way to selectively influence the process and final beer stability.

Average malts when mashed will result in a pH of about 5.65–5.75. This pH is usually above the optimum for many of the important enzymes involved in beer production. Acidification techniques can reduce the pH to 5.40 and promote the activity of most enzymes involved in the conversion of the components in malt to desirable wort constituents. Fermentation will then be more efficient and the final beer flavor improved. Better colloidal stability—reduced potential for hazes to appear in the beer—can also be attained and beer is often lighter in color, which some consumers prefer. Flavor will be rounder, fuller, and softer and hop bitterness more pleasant and not “lingering.”

Because of the German Reinheitsgebot purity laws of 1516, German brewers must resort to biological acidification of the mash because they cannot add exogenous acids or salts to the brewing water, mash, wort, or beer. See reinheitsgebot. Acidification involves steeping malt, which naturally harbors lactic acid bacteria (beer-acidifying lactobacilli, with the preferred strain being Lactobacillus delbruckii), under defined conditions (sometimes following inoculation of specific strains of lactobacilli) to result in lactic acid production. Through the use of the collected acid “wort” or use of the “acid or sour-malt” (2%–10% added to the mash), a resultant lowering of the pH in mash, wort, and beer can be attained. The propagation is not unlike a sourdough culturing.

Brewers may also inject a lactic acid strain into a portion of wort. Following fermentation, a portion of the acidified wort is pasteurized to kill off the bacteria and then returned to the brewing process. This biological acidification is stated to provide superior results to simply adding commercially available lactic acid. If they do not have to follow the German purity laws, brewers can also add hydrochloric acid or sulfuric acid to mash and/or wort in specified amounts to adjust the pH in a similar manner.

Although water chemistry is highly complex, some simple adjustments to the pH of the water can be attained. Sulfuric and phosphoric acids as well as lactic acid (see also above), acidic salts such as calcium chloride, calcium sulfate (gypsum), and magnesium sulfate (Epsom salts) can be used to lower the water pH to render its quality more suitable for brewing. Generally, here the brewer is lowering the alkalinity of the water by the acid adjustments, but the ions added such as calcium, magnesium, chloride, and sulfate also aid in promoting enzyme chemistry during mashing and final beer stability and in promoting flavor development in general and the quality of the hop flavor.

See also acidulated malt, ph.