When you hear a brewer comment that their sour beer is around 3.3 PH, are they speaking of final PH or mash PH? I hear a lot of (and measure) mash PH here on the forums…how does this equate to final PH?
Well, you’d have to ask them to be sure, but I’m pretty certain it’s final pH.
When sour bacteria are used there is no relationship between mash pH and final pH.
Mash pH is in the 5.2-5.6 range. In the kettle it will drop a bit, like 0.1. Yeast make acids to protect their food source, so the pH quickly drops when you pitch the yeast, and gets down to the 4.0 - 4.6 range for most beers. The acids from bacteria will take it down to the range for sours that you quote.
Read this page. 3.3 is so low the enzymes would be out of their optimum ranges.
http://howtobrew.com/book/section-3/how-the-mash-works/mashing-defined
I create Berliners and perform a regular mash at around 5.4 and then sour that wort with my naturally-cultured lacto to bring the wort to around 3.0 to 3.5. The soured wort is then boiled with a minimal amount of hops and then pitched with a neutral ale yeast. You should see the HUGE head that forms in the kettle as that soured wort is brought to a boil. It is impressive, but it falls once the boil starts.
The most sour beerI have achieved is 2.9 pH as final pH. It was pH 4.3 after boil then pitched with Omega Y-06, if I recall correctly - it got to 2.9 after about 20 hours, perhaps slightly less.