Still slightly confused after all the reading I have done so just checking in to clarify here…
If Brunwater tells me that my latest IPA should have a predicted room temperature mash pH of 5.3 then wouldn’t my actual mash temperature pH be in the range of 5.0 (or so) given the approximate .3-.35 variance involving temperature difference?
If so, does that not seem a bit low for a mash pH for an IPA? I am not looking for any tartness in my finished product. Or, (as I have also read) should I not even be concerned with mash temperature pH and just only go by the pH at room temps and not worry about it?
Thanks for helping me out with this one. I do appreciate helping me wrap my head around this.
It’s room temp you need to be concerned with. For me, my IPA is target at about 5.4 at room temp.
Edit: here’s some helpful info from Kai…
This comes up once in a while and I just had an e-mail discussion with a fellow home brewer on the same subject.
Fact is that the pH of a solution changes with temperature. It is caused by a change of the dissociation constants of the various acids/bases that are in the solution. Even water is considered an acid since it can donate hydrogen ions although in most cases it is not dominating pH at all. The extent of the change depends on the substance. Even the pH optimum of enzymes may shift with temperature. I believe that the0.35 correction factor for mash temp (65 C) vs. room temp (25 C) pH contains both the aspect that the actual pH in the mash is lower at 65 C that it is at 25 C and that the pH optimum of the amylase enzymes shifts a bit from the value that can be observed by room temperature mashing.
But none of this matters since by convention pH values in brewing are reported as the pH of a room temperature sample. This arises from the laboratory practice of cooling pH samples before pH is tested. This also means that reported pH optima and pH ranges are for room temperature samples even though the actual reaction happens at higher temperatures. A.J. deLange mentioned to me the “by convention” aspect. Another thing we express “by convention” is SG. By convention we always correct SG for temperature since we all assume that the reported SG applies to a 68 F sample. The same is and should be done for pH measurements. To be exact you’ll have to cool hot samples and warm cold (e.g. beer) samples.
It’s also helpful to take into account how we arrived at these pH optima/ranges. They are determined by conducting a series of mashes (at correct mash temp for that enzyme) with differing pH. The pH is tested in a room temp sample. The amount of product produced during these reactions (sugar, for example) is then plotted over this room temperature pH.
The same is true with boil pH recommendations.
One problem is that hardly any author is explicit about this. I assume that most of them see it as a given that they talk about pH from room temperature samples. Briggs was the only one I found that made a distinction. This lack of explicitness, if this is a word, seems to cause a lot of confusion with home brewers.
So room temperature it is then. I will not even worry my simple brain about the mash temperature pH and only take readings on cooled samples for consistency. Thanks!
Another way to think of it is, pH is just a number and your beer came out tasting like ‘this’. If the beer was too harsh or tannic, you know you need to adjust your processes to produce a lower number. If the beer was too crisp or tart, you know you need to boost the number.
Its a reference standard that helps you ‘tune’ your beer.
