I finally got around to titrating wort and beer. Something I wanted to do for a while since it would give me insight into how both these substances’ pH would be affected by acid and base additions.
Here is the writeup: Wort and Beer Titration
Here is the chart I ended up with:
While this is not necessarily an All Grain topic I put it in here in lieu of a Science section.
For the geeks of you enjoy 
Kai
Very nice Kai!
So when are you going to write your first book?
Thanks. We’ll see about the book. First I need to gather much more brewing science information and answer at least some of the questions I run into.
Kai
Wow Kai…I’m impressed once again.
You definitely could put a book together just from the experiments and brewing info on your braukaiser website.
That’s the thing I miss the most since Dr. fix passed away, the experimental side of homebrewing. Anyone can buy and quote Narziss, but it’s something different entirely to challenge dogma and demonstrate conclusively how things work for homebrewers. That’s what’s missing in the last 10 years and deserves more attention in the literature. I applaud people like Kai and A.J. deLange for filling in the gaps but I’d still like to see more Fix-like work. There certainly is a book or two worth of material to address.
I guess it bothers me most when people assert that there’s only one right way of brewing. Just because someone does something and it works doesn’t imply that other ways don’t work or are inferior. I prefer to see the source material and make my own conclusions. That’s why I like to see these topics addressed. So I can decide on my system and with my processes whether it’s worth my time to do something differently.
Well said.
I have quoted Narziss/Back a lot over the years but one thing that pushed me towards experiments was the inquisitive nature of the on-line community which always wants to know: “And how exactly does this matter for my brewing ?”. And then there is the quest for the perfect German beer
[quote]I prefer to see the source material and make my own conclusions. That’s why I like to see these topics addressed.
[/quote]
Sometimes even the reputed (home)brewing literature perpetuates facts that are not necessarily true. One of those is the temperature dependent shift of the mash pH. Everybody lists a 0.35 pH difference between room temp and mash temp (65 C, I believe) and I’d love to see the original research for this. Both A.J. and I have run experiments that showed a difference of only ~0.22 pH units. While this matters little to practical brewing it shows that there are many facts that are not even questioned by brewing authors.
But the reason why I’m back in this thread is that I got a chance to titrate mash samples tonight : Mash Titration
Kai
I’ve always assumed that the 0.35 pH difference was an assumption based on the water ionization constant’s relation to temperature, as opposed to an observation, since it seems that it would be different in a buffered solution, like wort.
kai,
very interesting
reading your article you comment on the difference in buffering capacity going one way with the acid and the other with the base. most noticable in the wort and not the beer. i can understand a little error in the beer as measurement, technique etc. any ideas on what i would call this apparent “hysterisis” to take a term from old physics/electronics curves?
not that it matters for my beer.
Don
The 0.35 offset in pH readings due to temperature is established fact. But as pointed out by Malzig, that is for straight water, not wort. I appreciate that Kai pointed out that this offset may be smaller in brewing practice. This is good to know.
I had been going on the assumption of the former offset when recommending the room temperature pH reading range we should be striving for.
The next question needs to be >>> if wort is affecting the offset, how are the pH readings affected? Is the room temperature pH reading somewhat lower in wort than it would be in water or is the mash temperature pH reading somewhat higher in wort than it would be in water??? Or is it a combination?
Kai, this is another experiment for you!
Good pH meters have ATC. What curve do they use to adjust their readings? Do different manufacturers use different curves? I’d be interested in knowing how good a job ATC does in wort as well.
When I did some measurements, it seemed like a difference of 0.3 at mash temps and 0.4 at sparge temps. If it turns out the real difference is 0.22, I can deal with that. I’m not worried about +/- 0.1.
What to shoot for with respect to pH and how to measure it had been very confusing to me which is why I did spend quite some time in looking into this. This is what I found.
pH targets and optima are generally given at room temp. As a result it is good practice to only test the pH of a room temp sample which is also prolongs the life of pH meter probes.
The pH measurement with a pH meter is affected by both the pH shift in the sample and a change in the pH probe’s response to pH. The latter is what ATC meters correct for. This leaves the temperature pH shift in the sample which is genuine change in the H+ concentration and pH meters cannot correct for it since this pH shift depends on the chemical composition of the sample.
To answer Gordon’s question, all ATC meters use whatever curve is needed to report the correct pH regardless of temperature. In the end they probably use the same cure since they all use a glass electrode.
If all measurements are taken at room temp and if pH data in the literature is reported at room temp the pH shift in the sample does not matter which is why I don’t think it is at all important if the shift between room and mash temp is 0.35 or 0.22. This is why I also think why a brewer’s pH meter doesn’t need an ATC function.
I checked Brigg’s Malting and Brewing Science again and here is the page that talks about the temperature depended pH shift: Google Books
Looks like he references a source that did that experiment. I should run my experiment again and record what I did. It’s just that I don’t like subjecting my pH meter to high temperatures.
For those interested, here is some info about pH meters and what I found useful features: pH meter buying guide
Here is some info about mash pH and temperature: http://braukaiser.com/wiki/index.php/Starch_Conversion#pH_and_brewing_water. To be honest, I also quote the 0.35 correction there. Most likely b/c I got it from Briggs and the experiment that showed 0.22 was done after I wrote that article.
Kai
So if I test the pH of the wort at room temperature and it reads 5.5 then I’m good right (presuming I’m shooting for the “optimal” 5.2)? I would correct that pH down by some factor, maybe 0.22, maybe 0.35 and that would get me in the ballpark.
If you are testing the pH at room temp and you are at 5.5 you are good. I consider the optimal pH mash pH to be between 5.2 and 5.6. I shoot for 5.2-5.4 in lighter beers and for 5.4-5.6 in beers with lots of enzymatic weak dark malts. 5.2 (in room temp sample) is pretty low and I don’t generally shoot that low.
No need to worry about the pH shift. Just make sure your pH targets are at room temp, which they likely are.
Kai
Thanks Kai. That’s pretty much what I’ve been doing. Just wanted to confirm.
I usually use the EZ Water spreadsheet to plan my water profile but with the latest version I’m a little confused as to whether those predicted pH values are supposed to be at room temp or mash temp. From my experience they seem to perhaps be projecting pH at room temp but I’ve only used it for a couple of batches so far.
But here you are talking about an imagined mash temperature, pH, right?
Do you mean a measured pH of 5.4 - 5.8, at r.t.?
no, I’m talking about a mash pH target of 5.2-5.6 when measured in a room
temperature sample. I don’t really care what the actual pH at mash temperatures will be like.
Kai
5.2 just seemed low for an r.t. mash pH. I’ve never gone that low.
I agree with Malzig that a room temperature mash pH of 5.2 seems kind of low. When I’ve made water adjustment mistakes and ended up with mash pH in that range, the resulting beer is well attenuated and thinner.
I don’t think that I would go lower than about 5.4 for a room temperature mash pH.
the 5.2 number comes from Kunze. Narziss/Back suggest 5.4 as the lower limit. I too agree that 5.2 is a bit too low, but I have used it with sucess.
These days I oftentimes employ combined mash and wort acidification where I adjust the mash pH to 5.4-5.5 and adjust the kettle-full wort pH to 5.3-5.4.
Kai