Mash pH consistently out, could precipitated calcium be the cause

[Simonh82]

I use London tap water for brewing and have always had good success with this. I had a full water report done a while ago and regularly check the alkalinity and calcium hardness values before brewing. I use Bru'n'Water to adjust my water using 75% phosphoric acid and usually calcium sulphate to target a mash pH of 5.2-5.3. I check mash pH using a calibrated pH meter accurate to 0.01 pH.

I regularly find that my mash pH is 0.3-0.4 points above the expected value in Bru'n'Water. If I'm aiming for 5.2 or 5.3 I might end up at 5.6 or 5.7. I know this isn't going to ruin anything but I'd like to pin down the cause.

One thing that recently occurred to me is that it might be due to calcium phosphate precipitating out of solution (but I'm no chemist, so I've no idea if this could be it). I know calcium lowers pH, so if the combination of phosphoric acid and calcium sulphate causes calcium phosphate to precipitate out of solution, as it appears to do, could this raise the pH of the mash by 0.3-04?

My water report is:
Ca 100, Mg 3.9, NA 24, NO35.2,SO4 48.8, CL 48.7, HCO3 236.7

Below is the water adjustments summary for a pale ale I brewed recently. The target mash pH was 5.27 but it came in at 5.63 if I remember correctly.

Assuming the grain colour estimates are accurate and my phosphoric acid is really 75% strength, are there any other reasons that I might be consistently missing my target mash pH? I like using phosphoric acid but if this is the cause, would I be better switching to lactic acid?

Thanks, Simon

 

[Rodent]

I commonly see phosphoric acid available in a 10% solution. never seen it at 75%

https://www.northernbrewer.com/phos...MIj6iXguay2wIVAspkCh3yIAo1EAQYASABEgLUSvD_BwE

 

[Simonh82]

Different markets I guess. It's available in 75% strength in the UK http://www.thehomebrewcompany.co.uk/phosphoric-acid-75-250-ml-406-g-p-2852.html

 

[mabrungard]

Hmm? I’m not sure if the calcium level is high enough to incur the precipitation reaction with phosphoric, but a precipitation loss could lessen the amount of calcium available to participate in the malt phytin reaction and its pH reduction.

I would explore the strength of your acid. You never know if a supplier has diluted your stuff. If you have confidence in the alkalinity level of your tap water, you can do some acidification trials of the tap water to see if it responds the way that 75% acid should. The acidification sheet in Bru’n Water can be a useful tool in those trials.

Since I know that British brewers are used to alkalinity testing kits, double checking the tap water alkalinity is wise too.

 

[Simonh82]

Hmm? I’m not sure if the calcium level is high enough to incur the precipitation reaction with phosphoric, but a precipitation loss could lessen the amount of calcium available to participate in the malt phytin reaction and its pH reduction.

I would explore the strength of your acid. You never know if a supplier has diluted your stuff. If you have confidence in the alkalinity level of your tap water, you can do some acidification trials of the tap water to see if it responds the way that 75% acid should. The acidification sheet in Bru’n Water can be a useful tool in those trials.

Since I know that British brewers are used to alkalinity testing kits, double checking the tap water alkalinity is wise too.

Thanks Martin. I find the Bru'n'Water spreadsheet an invaluable tool and I'd like to nail this down. Can acids lose strength over time? The bottle of phosphoric acid is about 3 years old now. I thought they were probably quite stable but that was just an assumption.

I'll check out the acidification sheet and double check my alkalinity reading.

 

[cire]

It is potentially possible for diluted acids to strengthen over time should water be more likely to evaporate than the acid content. Testing alkalinity after treatment should confirm or otherwise the strength of your acid..

 

[ajdelange]

Can acids lose strength over time? The bottle of phosphoric acid is about 3 years old now. I thought they were probably quite stable but that was just an assumption.

Depends on whether the acid is more volatile than the water it it dissolved in. With phosphoric you should be on pretty solid ground. The acid itself is not volatile relative to water and as long as the water is prevented from evaporating the strength of the acid should remain the same for years.

With respect to calcium precipitation: that should be accounted for in the software based on its estimate of how much phosphate is being contributed by the malt which is much more than the amounts of phosphate you are adding as the acid. If you have very high calcium levels it is possible for phosphoric acid additions to remove some but the levels are extreme. There are some curves in the back of the Palmer book that deal with this. It's unlikely that this is your problem.

The most likely problem is simply that the program does not model the malts you are using very well. How could it? It is a miracle that these programs do as well as they do using only the loose correlations between malt color and type and malt acid base parameters. Most of the people that write the programs do not understand the acid/base chemistry of malt to the point where they can implement a robust algorithm hence most of the programs are more empirical than model based and it is not that rare that users see errors as large as you are but errors are usually lower than what you are seing. This does not, of course, mean that you can't make mistakes in using a programs and get a bad result when proper use would give a better one.

I note that you mention target pH's of 5.2 - 5.3. These are quite a bit lower than most find give the best beer which is 5.4 - 5.6 in general. Now those latter values are as measured at room temperature. 5.2 - 5.3 is more typical of what people think are appropriate mash pH's at elevated mash temperature. All the spreadsheets of which I am aware do pH estimation at room temperature. Is it possible that there is some confusion with respect to this?

 

[ScrewyBrewer]

Testing each malt's DIph value then entering those results will predict the most accurate mash pH values. Very few homebrewers I've spoken to over the years are willing to spend the time needed to do the testing though. As a homebrew club project myself and one out of 35 members tested several grains for their DIph values. Less than 10% of the members who opted out of the project were happy to toss a teaspoon of gypsum into the tap water while the other 90% thought adding campen tablets were enough.

 

[Simonh82]

I note that you mention target pH's of 5.2 - 5.3. These are quite a bit lower than most find give the best beer which is 5.4 - 5.6 in general. Now those latter values are as measured at room temperature. 5.2 - 5.3 is more typical of what people think are appropriate mash pH's at elevated mash temperature. All the spreadsheets of which I am aware do pH estimation at room temperature. Is it possible that there is some confusion with respect to this?

I am for 5.2-5.3 for pale ales and slightly higher for dark beers. I always take the reading at room temperature

 

[ajdelange]

As I said that's pretty low but if you are happy with the results....

 

[ajdelange]

Testing each malt's DIph value then entering those results will predict the most accurate mash pH values. Very few homebrewers I've spoken to over the years are willing to spend the time needed to do the testing though. As a homebrew club project myself and one out of 35 members tested several grains for their DIph values.

That's half the job but a step in the right direction. Only two other guys I know of (and apologies if there are others) is aware that you must make at least a second measurement in order to determine the slope of the malt's titration curve near pHDI. This is what I mean when I say that few understand the basic chemistry enough to prepare a robust spreadsheet.

 

[ScrewyBrewer]

That's half the job but a step in the right direction. Only two other guys I know of (and apologies if there are others) is aware that you must make at least a second measurement in order to determine the slope of the malt's titration curve near pHDI. This is what I mean when I say that few understand the basic chemistry enough to prepare a robust spreadsheet.

Admittedly if you remember after reading through your publication "Some Observations on Mash pH Prediction/Control" I struggled with the second part. Primarily due to a limited grasp of calculus solving for the a1 coefficient for different grains was and still is beyond me. Thank you as always for taking the time to explain the science.

 

[ajdelange]

You actually don't need any calculus but if you have it it certainly will help you understand what is going on. But if you aren't conversant with calculus how do you attract women?

 

[Silver_Is_Money]

Have you considered using any of the other currently available mash pH assistant software packages? Most (if not all) others appear to quite often yield mash pH projections which are a couple tenths (or more) higher than your chosen software. Using one of the other alternatives would likely yield results that are much more in line with your own carefully taken mash pH measurements. You are not alone in seeing this trend.

 

[ScrewyBrewer]

You actually don't need any calculus but if you have it it certainly will help you understand what is going on. But if you aren't conversant with calculus how do you attract women?

Haha that's a great question!

 

[couchsending]

As I said that's pretty low but if you are happy with the results....

So are you saying that all the positive benefits of Mash PH at 5.2 found in Kunze’s work are based on PH numbers taken at mash temp?

 

[ajdelange]

I can't say that because I don't know what temperature his pH measurements refer to and as I don't have his book here I can't check to see if he states what his pH temperature reference is and, as he is now brewing at that big brewery in the sky, we can't ask him. I don't recall him making a statement as to temperature. In fact I don't recall any of the older texts, with the exception of deClercks's (laboratory temperature) mentioning this. This has always been a problem because so few authors do state what temperature they are referring to. With the older texts we usually assume it is room temperature because in the days they were written samples had to be conveyed to the laboratory for measurement (pH meters did not slip into one's shirt pocket in those times) but one can never be sure.

My recall is that Kunze mentioned higher pH's than 5.2 but my memory isn't the greatest and as I said above my copy of his book is 600 miles south of here so I can't check. If he does indeed recommend 5.2 as the best range then it is quite possible that he is referring to mash temperature but then it is possible that, in his opinion, that 5.2 at room temperature (5.0 or so at mash temperature) is indeed the best.

The important thing here is that we use the pH range that gives us the beers we like best. For me that proved to be 5.4 - 5.6 at room temperature.

 

[mabrungard]

I also find that a mashing pH of around 5.4 tends to work best. There are also mentions in German texts of further reducing kettle pH at the end of boil with additional saurergut. That makes sense since SMM and DMS reactions are enhanced at higher pH and beer flavor tends to be crisper at lower pH. That end of boil pH reduction helps the wort on its way to becoming beer, although yeast is the primary arbiter on final beer pH.

 

[couchsending]

Yeah I'm not sure either. I can't find a temperature reference in Technology Brewing and Malting anywhere. I always assumed
it was at room temp, especially if you're quoting PH in the boil I would think they would have cooled samples to room for consistency.

I haven't skimmed all 1000 pages for mention of PH and the Index in the back is basically worthless but he mentions PH a few times before the chapter on Mash Acidification.

He states Alpha- Amylase PH optimum is 5.6-5.8, Beta Amylase optimum is 5.4-5.5.

in 3.2.1.3.3 Effect of PH on Starch Degradation

When discussing enzymes it was mentioned that their activity is very dependent on the pH. It has also been shown that Beta Amylases in the mash have a pH optimum of 5.4-5.5. By mashing within a pH range of 5.5-5.6 which can be regarded as the optima pH range for both amylases, the extract content can be increased in comparison to that obtained at a higher PH value. More fermentable sugar is produced and the attenuation limit is higher. The "normal" mash PH is, however, - depending on the composition of the brewing water and the malt - considerably higher, being 5.5-5.8. It is therefore advantageous to lower the pH value when mashing to 5.2. (This doesn't make a ton of sense but I'm pretty sure those are room temp PH measurements he's quoting)


Anyways in 3.2.1.8 Mash Acidification, this is what he says.

Through the interaction of the pH-efffective calcium and magnesium water salts particularly with phosphates and other components of the malt, the pH-value of the mash levels off at 5.6-5.8. We have already seen, however, that there is a series of processes and changes which proceed considerably faster and better at low pH-values. It is therefore of interest to considerably reduce the pH to 5.2

- talks about methods of acidification

An important measure is mash acidification at the beginning of the mashing process and/or acidification of the wort. The advantages are
- the range of enzymes is considerably improved because all the important enzymes, with the exception of beta amylase, are activated
- at low PH-values more growth promoting substances go into solution, e.g. the supply of zinc is increased
- the extract yield is increased
- the protein excretion improves (better break formation) - this seems like wort acidification not mash
- the redox potential improves, a reduced susceptibility to oxygen thereby develops
- lautering proceeds faster
- coloring during wort boiling is suppressed
- the activity of the phosphates is promoted and they strengthen the buffering capacity through the release of phosphates
- fermentation is faster due to better true excretion, a faster drop in pH and higher degree of attenuation in the cellar
+ again this seems more referring to wort acidification at the end of the boil
- the flavor is mellower fuller and softer
- the hop battering is more pleasant and does not linger
- the beer is fresh, and has a fresher, stronger, and more characteristic taste
- the form has finer bubbles and is more stable
- the color of the beer is lighter
- a better flavor stability is to be expected particularly as the lipoxygenase is sensitive to pH values below 5.2 and is then no longer
effective
- the chemical-physical stability is better, less tendency to protein haze
- digestion is aided, which is a positive effect of lactic avid
- reduction of the biological susceptibility of the beer because of the low ph beer spoiling organisms no longer from below a pH of 4.4
- the higher degree of attenuation leading to a lower amount of non-fermentable sugar and hence
- a greater pressure towards selectivity of the yeast which forces back the beer-spoiling competitors

By reducing the pH value of the mash to 5.2, fewer aging components are formed.

During wort production an optimal pH of 5.1-5.2 should be aimed for.

He then talks about adding lactic acid to the boil but only at the end as the half reaction time in the splitting of the DMS-P into DMS is shortened because of higher PH.

And then at the end in 3.2.1.10 Conclusions for carrying out mashing he states

mash PH below 5.4; optimal 5.2 produces softer, more rounded beer in a fresher condition, better flavor stability.