High wort pHs should be avoided because of extraction of excessive amounts of undesirable substances such as tannins, silicates, polyphenols etc.
The mineral composition of brewing liquor has a demonstrable effect on wort pH.
Range of Values
The acceptable range for the pH of boiled worts for cask conditioned beers is 5·0 – 5·3 units. However, a large variance is possible between the pH of strong (approximately 4·9) and weak worts (5·4 – 5·6).
When wort is boiled the pH falls usually by in the order of 0·05 – 0·15 units.
At least monthly, and when starting a new season’s malt or changing supplier, the pH should be measured of first and last runnings, of copper wort at make-up, and in fermentation at collection and on reaching the attenuation target.
pH measurement to ± 0·1 units requires daily calibration of the pH meter and either a fixed temperature for measurement or automatic temperature compensation.