When looking for optimal mash pH you need to keep in mind that we are not just trying to make the amylase enzymes happy but we are trying to set the stage for the pH of other brewing processes. In particular boil and cast-out wort pH. This is why the cited range is a bit lower than what’s actually optimal for just amylase activity.
Kai
I don’t know and I don’t think it matters much. If I were to take a guess, I would think that it is fairly linear in the pH range that interests us.
Kai
Denny gets at my question a few post back.
What is the room temp mash pH target range?
All the data and texts I’ve seen indicate that the better pH range is 5.3 to 5.5. I’m not sure there really is an optimum mash pH since a brewer can have differing goals for their brew. These are room temp measurements. Denny’s range is a more forgiving 5.2 to 5.6, but it still centers on about 5.4 as the median value.
Martin, thanks!
It’s roughly linear, but it isn’t a constant. This difference is for mash temperatures. It’s larger at sparge temperatures (maybe 0.1 more). The difference is 0 at room temp (68F, or whatever they were calibrated at). And this is using water. I’ve seen some (credible) sources say the variation is lower when using a mash rather than water (maybe 0.2).
Gordon,
I’m very interested in the original source of this number. If it’s based on the pH change in plain water, which is caused by the change in the water’s dissociation constant, then the 0.35 number is not going to be correct in wort. This is because the pH of wort is determines by the dissociation constants of all the various acids that are in there.
Briggs, et. al. mentions a 0.35 shift at 65C and a 0.45 shift at 75 C.
Note that the 0.35 number may reflect both a change in mash pH as well as a shift in the enzyme’s pH optimum. Testing cold and hot wort with a temperature correcting pH meter only shows you the actual mash pH change.
BTW, congrats on your book that’s coming out soon.
Kai
I ran tests when working on my book. I was doing a variety of tests to test pH adjustment and decided to capture the temperature curve while I was at it. I did it in a chemistry lab with professional equipment (I have all the various models written down somewhere) and RO/distilled water. Mostly I was trying to quantify the adjustment of sparge water.
The numbers you are quoting (0.35 @ 65C and 0.45 @ 75C) is what I was referring to when I said the variation at sparge temps were 0.1 higher than at mash temps. So we’re saying the same thing there. A graph would illustrate it easier, but I didn’t take the time to generate one.
I think it was private correspondence with A.J. deLange where he was telling me he thought 0.2 was more realistic in mash conditions than 0.35. I just noted it, but didn’t have a chance to test it. I’m going based on memory, so it may be faulty. I just found it interesting, and something I’d like to investigate myself some day.
Thanks about the book; I mention you (positively) in a few places.
Gordon,
I did a similar experiment like yours with wort and found a pH shift of ~0.2. A.J. also mentioned to me that he found a similar number when he did such an experiment. But we both agree that the actual shift matters little if we stick to the convention of only testing and reporting room temp sample pH values.
Kai
OK, so now I heard it from two credible sources…