pH Changes During Mash

[HopSong]

Haven't tried taking multiple pH readings. I'm doing McQuakers Oatmeal Stout from Brewing Classic Beers as a BIAB. My numbers as far as pre-boil gravity look good. It will only be a 2g batch into the keg. Did a 90 minute mash and kept it at 154*F. pH changes are:

75 min (15 min in) = 5.4
40 min (50 min in) = 5.5
10 min (80 min in) = 5.7

Is this to be expected? If I'm to be on top of things.. should I have added some lactic to bring it back down to 5.4?

I'm doing a 75 or 90 min boil.. haven't cast that in concrete yet.. but, likely 90 min.

Thanks

 

[ajdelange]

A small upward drift over an hour is normal but not so much as 0.3 unless sauermalz was used in which case you can expect to see that much but over the first 15 - 20 min. Have you done the meter stability check in the Stickies?

 

[HopSong]

Thanks AJ. No, I haven't done that test. The first two checks jives with my pH strips.. yah, I know . I didn't do a side by side on the third test. No sauermalz. Just chocolate and black roasted barley.. along with 2-row, Maris Otter, victory and oatmeal. I probably don't have the best pH meter.. it's one from Thermopen. I did check it against the standards each test. I'll look up the sticky