@The Baron I can add some thoughts based on my own experience with pH:
- Ultimately I think ones subjective perception of the finished beer is what matters most, overriding anything objective that you can measure (e.g. SG, pH, temperature), i.e. if it tastes right it is right.
- I think we tend to focus a lot on mash pH but put much less emphasis on pH of the finished beer at serving. This seems odd to me. A while back I got into the habit of checking the pH of the finished beer (most of the time) - not really with the intention of changing anything but just out of curiosity. Even if perception has the casting vote it still seems good practice to me to take measurements where possible, including pH.
- (Being of a curious mind I'd be interested in a Tilt-like device that measures the pH of the fermenting beer instead of SG, to see how it changes over time)
- I don't think it's a bad idea at all to add some acid (lactic or otherwise) to the finished beer if that makes it more to your liking, just do a bit of experimenting in the glass first as below before you overdo it at ruin an entire batch.
- I have from time to time done a bit of kitchen science, playing around with dosing the finished beer with a drop or two of lactic acid or CRS and comparing with vs. without, or a little vs. a lot. From here you can scale up and dose a keg if you wish - go under rather than over as it's easy to add more but hard to take away!
- I used to add CRS and gypsum to my hoppy beers, but lactic acid and CaCl to my malty beers. I often found the former a bit flabby and after doing a bit of kitchen science as above found that I preferred the result with a slightly lower pH. I don't recall exact numbers but we're probably talking something like pH 4.2 vs. 4.4. Nowadays I simply use lactic acid and CaCl in all my beers and in general I'm happier with the results. I can't say if this is purely down to pH, flavour impact of CRS vs. lactic acid or of gypsum vs. CaCl. But I'm getting a bit more "zip" from my beers which I prefer.
- A more recent change I've adopted is dumping all the kettle trub into the FV. A result of this is that I'm seeing a touch more attenuation and a touch lower pH, again it's like pH 4.2 vs. 4.4. The beers seem crisper and drier which is sometimes good, sometimes less so, depends what you're after. I'm not sure if the attenuation causes the lower pH directly or if it's down to something else such as the presence of the trub.
- Something else to consider is the flavour impact of different acids. At the moment I'm fermenting an American wheat beer - I added lactic acid to the mash water as usual, but also added citric acid at the end of the boil, not to go full-on sour beer but just to add a lemoney-citrusey kick. Honestly I think I might have overdone the amount of citric acid but you could certainly taste it in the wort at pitching. If you're interested, the pH at pitcing was about 4.0 vs. 5.2 or so for a "normal" beer. However, whereas the pH of a "normal" beer might drop from 5.2 or so down to 4.2-4.4, the forced ferment I did only dropped to about pH 3.8 (though as part of that comparison we do also need to consider the meaning of pH with regard to the logarithmic scale and the number of H+ ions).
