At what pH level is the kettle souring process considered complete?

The kettle souring process is a method used to quickly produce a sour beer by adding Lactobacillus bacteria to the wort and allowing it to sour in the kettle before boiling. The goal is to reach a specific target pH that indicates the desired level of acidity and sourness in the final beer.

A pH of 3.5 is generally considered the point at which kettle souring is complete because it produces a balanced acidity that enhances the flavor profile of the beer without overwhelming it. At this pH level, the beer has a noticeable tartness that is characteristic of sour beers while maintaining a drinkable quality.

Going lower than this pH, such as 3.0 or 2.5, can produce intensely sour flavors that might not be desirable for all styles, making 3.5 the ideal target for many brewers looking to maintain a balance between tartness and drinkability. Therefore, achieving a pH of 3.5 indicates that the kettle souring process has effectively soured the wort to a satisfactory level before it is boiled and fermented.