I've been messing around with the influence of ph in the finished product. It appears that most commercial beers are at or below 4.5 ph. I've measured a few that ive brought home. The SNPA that I measured was 4.3 ph (20ml sample with lid, sat till room temp) I think that if my mash and sparge ph is right, then it drops a couple more tenths in the boil, then a good healthy fermentation seems to get me to 4.5 or so.
For kicks I tracked my ph all the way through the APA I have on tap now. When I kegged it thee ph was 4.5. I was shooting for 4.3 so I could been cool like SNPA. So I had no idea how much 10% phosphoric to add. I took a guess and added 5 ml. After it was carbed up, I took another reading. I was also unsure how much carbonic acid would effect the ph. It didn't effect it at all. The ph was still 4.5. So I added 20ml. Now its at 4.4 ph and I think I'll leave it there. The difference in the glass between 4.5 and 4.4 is remarkable. The flavors are much more lively and the beer doesn't have the slightly watery feel it had before. And im not detecting any off flavor from the acid, at least not in that moderately hoppy beer.
Anywho, ive heard and parroted the carbonic acid bite thing. Near as I can tell, 2-3 volumes of Co2 is not going to create enough carbonic acid to change beer ph. Apparently its a fairly week acid. It might drop low RA water several points, but it doesn't drop beer much at all. At least my meter can't detect it. I also have my doubts about carbonic acid flavor thresholds being such that its even detectable in beer ar 2-3 volumes CO2. My personal opinion is that what many are calling carbonic acid bite is actually just mouthfeel of CO2 coming out of solution.
At least I learned a ball park amount of 10% phosphoric to add in order to drop one tenth. Its a start.