Rising pH during BIAB mash. Normal?

[briantompo]

Hi,
I just brewed my third batch since buying a pH meter and for the second time, watched the pH creep up to the predicted value during the mash. Is this normal for full-volume BIAB and should I account for it when planning acid addition?

Latest batch started at pH 5.0 and climbed to 5.2 during the 70 minute mash. I use Brewer's Friend and meter is a Thermoworks 8689 that I calibrate at 4.0 and 7.0 every brewday. I add minerals and lactic acid to the full volume (typically 7-8 gals) of strike water before dough-in and take pH samples 2-3 times when I stir the mash. This latest batch measured 5.02 after 5mins, 5.19 after 45 mins and 5.23 after 70 mins. I'd added 3ml of lactic acid just before dough-in to hit Brewer's Friend predicted 5.27pH.

Is this a fluke or do BIAB'rs account for this increase when planning recipes?
Thanks, Brian

 

[Silver_Is_Money]

Mostly it depends upon whether or not your grist is overall basic with respect to your intended mash target, or overall acidic with respect to your intended mash target. It takes time for the strike water to fully penetrate the grains and thereby release their aggregate/inherent base or acid nature. So the trend you observed could just as easily go the opposite way as well.

 

[dmtaylor]

My pH sometimes starts high around 5.5 or whatever then migrates down to 5.2-5.3 by itself. Something key to keep in mind: malt wants to be beer. Humans have cultivated barley malt for thousands of years, such that the chemistry in the malt is ideal to get it where we want it to be, even without interference from the brewer and regardless of the water source. If we didn't know any better about water chemistry, odds are we could make excellent beer regardless because the malt just wants to be turned into beer. Pretty cool stuff when you think about it.

 

[mabrungard]

I've witnessed this sort of pH creep too. However, I've got the feeling that part of the issue is how much the wort and grist is mixed. In the case of BIAB, there is no mixing of the grist, but maybe you recirculate your wort?? If there is no recirculation, then its no surprise to me that you witness this pH creep as the entire mass of the grist is extracted and converted.

With respect to this natural pH creep, I've found that mash pH tends to converge on a pH of about 5.4. If the pH starts out higher than that, it drops. If it starts lower than that, it rises. I've studied the buffering systems in wort and have come to the conclusion that this phenomena is likely a product of the carboxylic acids and amino acids. I've found a few papers on buffering systems in wort, but they didn't shed any light on this pH phenomena that I mention.

 

[SoCal-Doug]

I see pH creep sometimes also, but it has not effected the brews (that I could detect). I still hit my numbers and efficiency targets. I did a 10 gallon batch of Wit last weekend so I could split it and compare a couple different yeasts. I run a 3 kettle recirculating HERMS system. Looking back at my notes...

10 minutes into the first rest (112F) pH=5.37
10 minutes into the second rest (122F) pH=5.44
10 minutes into the third rest (152F) pH=5.51
Final sparge runnings (169F) pH=5.92, SG=1.010

No acid was added. Mashed with RO water adjusted to Ca 58 Mg 10 Na 4 SO4 74 Cl 74. Sparged with straight RO water.

I found the creep odd, but not concerning. The final runnings makes total sense, the creep during mashing didn't. I chalked it up to some magical chemistry thing

 

[ajdelange]

I've studied the buffering systems in wort and have come to the conclusion that this phenomena is likely a product of the carboxylic acids and amino acids. I've found a few papers on buffering systems in wort, but they didn't shed any light on this pH phenomena that I mention.

That's because the phenomenon is not real. I have explained here before that 'buffer' is a poor word to use when describing a mix of acid, base and salt that is intended to hold pH at a particular value such as those that we use to calibrate our pH meters because all mixtures of polyprotic acid cations and their parent acid exhibit buffering which is the property of absorbing the 'shock' of addition of acid or base and thus resist pH change. If the mixture is from a single acid system (such as phosphoric) and the pH is near one of the pKs of that acid then the buffering strength (resistance to change in pH shift from an acid or base shock) is much greater than it is at other pH values.

Mash does not 'buffer' to 5.4 or any other pH in the sense that pH calibration solutions buffer to the values printed on their labels. If they did so the preferred pH would be seen in the mash titration curve. It isn't there as you can see in the graph which also explains why it isn't there.

The blue curve shows the amount of base one has to add to 1 mmol of phosphoric acid in order to reach the values of pH on the horizontal axis. The phosphoric acid system makes fine buffers (the pH 7 buffers we use to calibrate our pH meters are phosphate buffers). Strong buffering occurs where quite a bit of acid must be added to effect even a modest change in pH. These are the places on the curves where the slopes are steepest i.e. at 2.15 and 7.2 which are the first two pK's of phosphoric acid.

The red curve is similar but is for a mix of 1/4 mmol each of tartaric, citric, mallic and oxalic acids. I am not asserting that malts contain these acids though they very well may but not in this equimolar mixture and there are doubtless other carboxilic acids as well. The goal here is to show what happens when multiple acid systems of acids are present. As the curve shows the curve smooths - the region of strong buffering is broader because each of the several acids buffers near its pK.

It is usual to consider buffering good within ±1.0 pH of a single acid's pK (at least that's the rule of thumb for buffer design). Comparing the blue curve at 2.15 ± 1.0 and 7.2 ± 1.0 to the red curve we might conclude that the red curve exhibits strong buffering over a band of 3 to perhaps as much as 4 pH units.

The final curve represents the titration of a mash of 10% 20L malt and 90% pilsner malt. Were Martin's thesis valid it would be steeper at 5.4 than at other pH values and clearly it isn't. In fact it is a little steeper at pH 4.5 than it is at pH 5.4 from which we would conclude that it is a better buffer at that pH than at mash pH. But it is only slightly steeper. Thus the buffering at mash pH is about as good as it is at the lower pH. There is no appreciable tendency, thus, to head to any particular pH in the range 4 - 6 for such a mash.

Every time Martin brings this up I explain that the mechanism behind migration of pH is that the meter originally responds to the acids or bases that are in the mash water and eventually to the mix of those with malt acids/bases. If you put bicarbonate in the mash water pH will originally read high and decrease as malt acids neutralize the bicarbonate. If one puts acid in the mash water the pH meter will read low (sometimes alarmingly slow) until the bases (remember a base is something with a higher intrinsic pH than the solution pH) in the malts neutralize it. The pH will go to the pH at which all the protons emitted by acids are equal to all the protons absorbed by the bases. Ideally this would be the design pH of the mash and I find that it is that pH that things settle out near. If Martin sees pHs migrate to pH 5.4 more than other values that simply means that the balance pH for the mashes he is designing (intentionally or not) are near 5.4.

 

[ajdelange]

Something key to keep in mind: malt wants to be beer.

Humans have cultivated barley malt for thousands of years, such that the chemistry in the malt is ideal to get it where we want it to be, even without interference from the brewer and regardless of the water source.

I'd advise getting those notions out of your mind ASAP as malt has no tendency whatsoever to go to the pH that makes the best beer (or any other particular pH, as I went to some pains to explain in my previous post) especially if the water is alkaline. A mash will go to the pH at which protons absorbed by the malts and bicarbonate are just equal to the protons given off by the acidic malts or added acid. Yes, mix malt with arbitrary water and you will get beer but decarbonate the water first and add acid to overcome the natural alkalinity of malt and you will make beer so much better than if you do nothing that you will probably regard beer made without action in this regard undrinkable. Why do you suppose that the Germans fiddle about with sauergut and sauermalz and the British with sulfuric and hydrochloric acids?

If we didn't know any better about water chemistry, odds are we could make excellent beer regardless because the malt just wants to be turned into beer. Pretty cool stuff when you think about it.

If you think about it I'm sure you will realize that excellent beers cannot be made without regard for mash pH. With the proper combination of malts and naturally soft water it is, of course, possible to attain excellent beer but in most cases a combination of decarbonation and acidification are necessary. Modern brewing practice (professional and home) confirms this.

I am curious as to where you got this idea.

 

[SoCal-Doug]

My head hurts now. Here's the solution, so we can make pretty good beers until we all become bio-chemists and actually pick the fly crap out of the pepper...

Purchase some brewing software (or spreadsheets, or use a web site, or whatever). Start with R/O water (about $1.25 for 5 gallons). Plug in your recipe. Add a few cents worth of chemicals (local shop, amazon, pick your poison), based on the suggestions of whateverthehell software you are using.

Brew. Drink. Share. Enjoy

 

[dmtaylor]

Water isn't as important as some people think. It becomes important when you have really bad water. But if you really don't have really bad water, it's really not so important.

 

[ajdelange]

It is clearly more important than you realize. You don't need 'really bad water' at all to spoil a beer. Perfectly nominal water as is supplied to millions of households throughout the world will make drinkable if uninspiring beer without treatment but if treated (or if its properties are considered in grist formulation) will produce beer that will elicit that 'Ahh' from the drinker. Commercial breweries know this and accordingly treat their water. Home brewers are now aware of it and so treat theirs. You need to become aware of this too. Once you appreciate this simple fact your beers will become much better. The fact that commercial operations practices in this regard directly contradict your hypothesis should trouble you.

 

[BeardedBrews]

Water isn't as important as some people think. It becomes important when you have really bad water. But if you really don't have really bad water, it's really not so important.

My water is essentially flat, and without adjusting for pH and elevating chlorides and sulfates at least to 30ppm I get poor efficiency, and generally mediocre finished product. I make a fermented beverage, but it is hardly good.

It is clearly more important than you realize. You don't need 'really bad water' at all to spoil a beer. Perfectly nominal water as is supplied to millions of households throughout the world will make drinkable if uninspiring beer without treatment but if treated (or if its properties are considered in grist formulation) will produce beer that will elicit that 'Ahh' from the drinker. Commercial breweries know this and accordingly treat their water. Home brewers are now aware of it and so treat theirs. You need to become aware of this too. Once you appreciate this simple fact your beers will become much better. The fact that commercial operations practices in this regard directly contradict your hypothesis should trouble you.

This.

You don’t have to do much, but in most cases your product improves if you at least do something.

 

[mabrungard]

Dave, I'm not sure if you're pulling our legs, or not. While its true that virtually ANY water will make beer, that doesn't mean that the beer is going to be good. Its even less likely to be great. As thousands of brewers and all the experimental brewing blogs have decisively found, water chemistry makes the most profound difference in the beer quality and perception.

You apparently don't understand the brewer's art in how they managed ingredients and processes in creating great beer. While you may not recognize their actions as 'messing with water', it still is part of the water equation in the brewing process. Brewers throughout history learned how to work with what they had to make better beer. Clearly, it wasn't as overt as calculating an acid addition, but in many cases their actions were a method of altering the chemistry of the mash.

 

[Nordic Brewer]

Ph Change (drift) during mashing

Preconditions:
1. NO SPARGE, total water volume 30.2 litre
2. Temperature step infusion mashing with Speidel Braumeister equipment.
3. Source Water profile:
- Ca++ 6.25 mg/l
- Mg++ 1.50 mg/
- Na+ 0 mg/l
- Cl- 2.46 mg/l
- SO4-- 4.34 mg/l
- Alkalinity as CaCO3 12.5 ppm
- Ph 7.18
- Ione balance 0.07 mEq/l

Water profile adjustment:
- + 3.4g CaCl2*2H20
- + 9.05g Lactic Acid 80%

Grist (Grist Crush 1.3mm):
- 4.6kg Pilsner malt
- 0.3kg Wheat malt
- 0.3kg Cara Pils

Using Brewer's friend water calculator gives an estimated mash PH = 5,20

4. Using Testo Ph meter with temp adjustment with accuracy and precision +/- 0.01 Ph.
- Automatic reading when measurement is stabel.
- Measurement is done when sample is cooled down to 25C.
- Ph meter calibrated in 2 step buffer before mashing
- Ph meter truned on for each measurment to avoid drifting.
- Ph meter is controlled against calibration buffer after mashing is completed.


Step-Mashing and Ph readings:

Dough-in at 37C.

- 20 min at 40C => Ph= 5.22
- 10 min at 55C => No Ph reading
- 0 min at 66C => Ph= 5.46
- 60 min at 66C => Ph= 5.51
- 20 min at 72C => Ph= 5.51


The interesting part is the correlation between actual Mash ph = 5.22 after 20 min rest and estimated Ph.
Estimated Ph in Brewer's friend calculator is 5.20.
In other word estimated and empirical Ph reading is within accepted range.
What I see is that the Ph continue to drift upward during the mashing and stabilize at 5.51.

I read from the discussion above that this can be explained as:
- Ph meter is drifting or instability
- It takes time to reach chemical equilibrium in the mash.
- Or there maybe some interaction with proteins in the mash


I have been searching for scientific papers where Ph drift in the mash has been observed and I found this one:
Recipitation of Protein During Mashing: Evaluation of the Role of Calcium, Phosphate, and Mash pH1
by M. J. Lewis and N. Nelson Wahnon, Department of Food Science and Technology, University of California, Davis 95616

http://www.agraria.com.br/extranet/...precipitacao_de_proteina_na_mostura_-_ing.pdf


The interesting thing about this article is that it seems to correlate with my observed Ph-shift measurements over time and temp.

The experiment in the article was doing step mashing (also sigle step) and what they found out was:
- Ph was creeping upward with time and maxing out at 70C before creeping down again
- When they mixed CaCl at different concentrations into the mash the Ph-creep function shifted down as expected (lower Ph)
- They also observed a sharp increase in the consentration of dissolved proteins from 40C and into the beginning of the saccrification temp interval and then decreasing sharply after.
- Ca++ concentration had a decrease over time.
- They also did a so called "Grain out mash" where all the grains and particles was filtered out of the mash and then did the mashing.
What they found in "Grain out mash" are both Ca++ and Ph did not drift over time but dissolved protein pattern remaind the same (Grain in Mash.
What can this indicate ? That dissolved protein concentration does not have impact on observed Ph drift.

The article does not conclude over the cause of the Ph drift over time.

So what could the cause of Ph drift over time be if is not caused by:
- Ph meter is drifting or instability
- It takes time to reach chemical equilibrium in the mash.
- Or there maybe some interaction with proteins in the mash.

We know that there is a lot of particles and husk material in the mash and it could be that they may influence the Ph
It could mean that free Ca++ and/or free protons H+/(H3O+) are absorbed by this material over time and temp and hence lower the Ph in the mash.

What is the practical impact of this?
- Measure Ph after 20min mashing before comparing with your estimated/calculated values and eventually do adjustments.
- Depending on mash schedule and dough-in: The timing of acid addition is important.