The importance for beer quality of maintaining the correct pH value throughout the brewing process is discussed. The logarithmic nature of the scale, on which a pH value of X actually denotes a hydrogen ion concentration of (10 to the power of minus X) g/litre, means that a slight change in the pH value indicates a relatively large proportionate change in hydrogen ion concentration. Pilot scale brewing experiments were used to investigate the effects of varying conditions during wort production, fermentation and conditioning. It was found that the calcium ion content of brewing liquor has a major effect on wort pH, which falls as the calcium level rises. Both mashing and sparging liquor should ideally have calcium contents between 100 and 200 ppm. Lowering the mash pH increases the recoverable extract, total soluble nitrogen and free alpha amino nitrogen in the wort and improves the permeability of the filter cake during lautering. Wort composition in turn influences beer pH, mainly through the FAN content, which on the one hand contributes to yeast growth during fermentation and on the other includes compounds which play a role in the buffering systems occurring in fermenting wort. Changes in pH towards the end of the production process (e.g. during dilution after high gravity brewing) can adversely affect colloidal stability or foam quality. The author recommends careful control of the calcium content of both mashing and sparging liquor as the easiest means of ensuring correct pH at subsequent production stages.
Keywords : beer brewing liquor calcium mashing pH process control quality sparging wort