[denny]

As I mash in my modified Janet's Brown, I started to wonder if mash hops can lower mash pH. No pH meter to test, just a thought.

If you mean due to alpha acids, everything I've read says that there is so little acid it has no effect on pH.

[klickitat jim]

I'm going to say no, or not enough to make any difference.  I measure pH like a lot lately. The pH shift between preboil and post boil doesn't seem to be corollary to hops. On one occasion I get a .2 pH drop during the boil, usually little to no drop. I think that first noticed .2 pH drop may have been operator error. Anyway, results seem to be fairly the same regardless of hopping rates or AAUs. So if 4 extra ounces of simcoe/mosaic dont change the boil pH, I doubt that a couple ounces of hops changes the mash pH.

Think about it this way. Supposedly, .15ml of 88% Lactic per pound of grain bill will drop .1 pH. So in a 10 pound grain bill thats 1.5 ml to drop .1 pH. Lactic is a weak acid, i assume that hop acids are too. But 88% is quit a strong concentration compared to 4-15%, not to mention utilization... even at a boil, hop acids are not being utilized anywhere near how the 88% lactic is being utilized. I dont have a clue how readily hop acids give up hydrogen ions, but I have a feeling its not on the same level as lactic. It seems too that a lot of us who add hops at whirlpool in ~170F for 30 minutes aren't detecting any additional bitterness from the acids. At a <160F mash there probably is near zero utilization.