Need help understanding pH (and Beersmith) during the Mash?

[Javaslinger]

So I finally got a decent pH meter and began tracking pH during my last mash. I was brewing a pale ale so did not expect a lowering of the pH from the grain bill. Beersmith determined my pH without acid adjustment (but with mineral additions) to be 5.67 and suggested 5ml of Lactic Acid to get a pH of 5.4 during the mash.

I added 5.ml of lactic acid with the mineral prior to adding the grains as climbed toward the strike temp. I was shocked to find the pH at this point to be 3.96.

After adding the grain bill I checked the pH about 10 minutes into the mash and found it to be 4.17.

And near the end of the mash I took another pH measurement and found a finally reasonable pH of 5.2.

Is this a normal pH trajectory during the mash? Did I start too low?

Also, how does Beersmith calculate this pH? I noted that after adding my water additions the pH Beersmith was calculating did not change one iota. I would have expected the mineral additions to have some impact on pH or at least residual alkalinity.

Any thoughts, opinions or advice?

[Oginme]

First, that is not a normal trajectory for pH during a mash.  Generally, I have found it takes a drop with the addition of the grains and mixing thoroughly to within a few tenths of target, then it slowly equilibrates and will come down by 10 to 15 minutes into the mash to target.  It may drop another tenth or two by the end of the mash, but by then the enzymes have done their thing.

I have not used acid addition to control my mash pH, preferring to use water salts and acidulated malt to get in the range I want.  I will say that I have found that the BeerSmith recommendations for acid malt is about 5x to 10x higher than I usually add.  I am guessing that the model Brad uses would do the same for straight acid additions.

The other issue right now (being that this is a new feature, there are some gaps in performance), is that the model does not take into consideration acid malt in the grain bill nor water salts added to the ingredient list which are not linked to a set water profile.  To get the water salts to work properly, I have created a water profile for the different types of brews that I make [hop forward, malt forward, balanced, stout] and add the water to the recipe and say 'yes' to having the salts added by the program to the list of ingredients.  Honestly, I just started doing this just before my Spring/Summer hiatus from brewing, so I haven't fully vetted it out well.

I think the program is set up this way to prevent the addition of salts for flavor and not in the mashing from affecting the mash pH calculation.