Importance of pH control during brewing

 David G. Taylor 

Abstract 

There is a tendency to accept pH in wort and beer as a consequence of the brewing and fermentation process, rather than to assume that mechanisms for controlling pH represent a major element of brewing process control.

pH control during wort production has a significant impact on brewhouse behaviour and wort composition. Data from small-scale experiments and production trials have been gathered to illustrate the impact of pH variations on extract recovery, wort protein and carbohydrate content and permeability of the mash bed.

The mechanisms determining pH control during fermentation have been investigated and the influence of wort composition in terms of small peptide amino acid on beer pH composition and potential for turbidity stability and foam formation have been explored at laboratory, pilot plant and production scales. The results obtained have allowed us to reach conclusions regarding the relative significance of the factors stimulating yeast growth and the buffering capacity of the wort on the pH of beer and consequently their influence on the flavour and stability of the beer.

pH Control During Wort Production 

The key point for control of pH throughout the brewing process is during mashing. This is due to the major influence that can be exerted at this stage on the content and format of the buffer systems that will operate subsequently in wort and beer.

The results show that residual alkalinity and calcium ion content in liquor can exert considerably influence on mash and wort pH

The reactions involved include contributions from the carbonate/bicarbonate buffer system

and from associations of calcium ions with other buffer systems

It is questionable, however, whether the phosphate buffer system actually has any great significance in wort/beer pH control, since it has poor buffering action in the pH range 4.0-6.0. 

Clearly, there is much merit in reducing liquor alkalinity as low as possible and adding calcium salts to achieve a level of 100-200 ppm during mashing and lautering. The benefit of maintaining a high level of calcium ion during sparging relates to consistent pH control during run-off; thus avoiding excessive extraction of polyphenols and silica, which will be favored as pH rises