If you have mash steps before sacc rest, when do you measure pH?

[Horseflesh]

Recently I did a hefeweizen and took advantage of my electric single-vessel system to do a complicated mash schedule. I got a pH result I don't understand, though. It was much higher than I expected.

- 15 min at 113F (acid rest)
- 10 min at 126F (protein rest)
- 45 min at 146F (hochkurz beta)
- 45 min at 158F (hochkurz alpha)
- 10 min at 168F (mashout)

I took a pH sample at 15 minutes into the 146F step, though of course the mash had been warm for 40 minutes at that point. After cooling the sample it read 5.69 when I expected something near 5.36.

I'll put my grain bill and minerals below but I have made similar brews many times and had my Bru'n Water numbers work out... just not with this mash schedule.

So, assuming that I didn't screw anything up, it seems that I waited too long to take the sample. In a mash schedule like that, when is the right time to do a pH sample?

The beer tastes fine, BTW!

7 lbs 7.0 oz Wheat, Red (Briess) [MH] (2.6 SRM) Grain 7 66.5 %
3 lbs 4.0 oz 2-Row, Pilsen (Bestmalz) [MH] (2.0 SRM) Grain 8 29.1 %
WATER: 9.52 gallons total (my water is very low-mineral, 4 PPM Ca, 24 PPM bicarb)
MASH MINERALS: Gypsum: 0.476 g / CaCl2 13.8%: 4.76 g / Epsom Salt: 0 g / NaCl: 0 g
ACID: Lactic 88% 7.33 mL
BREWTAN B Mash: 0.952 g
pH prediction: 5.36

 

[Silver_Is_Money]

It appears that perhaps the only mistake you are making is to presume that the contrived output of any flavor of mash pH software must be held as superior to and thereby more correct than carefully undertaken actual pH measurement. You are clearly not alone in this perception.

Without the 7.33 mL of 88% lactic acid addition you would highly likely have mashed at a pH approaching or perhaps even exceeding 6.0, and instead you mashed at a pH of 5.69, so the software got you out of the danger zone and into the safe zone. I'd say it did its job.

 

[ajdelange]

When do you measure pH? As often as you can. Definitely at strike then at 10 minute intervals. Thereafter at the beginning and end of each step, at the start of the boil, at the end of the boil, 24 hours after pitching and when fermentation completes. The object is to get a pH roadmap for the particular beer you are brewing so that you will know what to expect when it is brewed subsequently. This should certainly be done the first couple of times you brew a particular beer but after you have your process for this beer pretty well established it is not necessary to check so often but rather at only a few points along the road to see if you are in the right place.

Wheat beers tend to run higher mash pH's than all barley grists (because wheat malts tend to run higher DI mash pH) and so some extra acid is required if you want more normal mash pH. Because of this 5.36 is not a reasonable pH estimate for the grist and acid you list. Depending on the actual parameters of the wheat and barley malt you use you should expect (with the specified acid addition) a mash pH between 5.59 and 5.66. Your observed pH was only 0.03 outside this range and is thus, consistent with reasonable predictions.

That level of pH is OK for wheat beers though I might want to try at about 5.55 or even 5.5. Wheat yeast strains are very good at lowering pH in the fermenter and that is, perhaps, why such high mash pH can be tolerated.