Author Topic: pH and finished beer  (Read 6960 times)

Offline James Lorden

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Re: pH and finished beer
« Reply #15 on: December 06, 2010, 11:46:46 AM »
Gordon:

I agree, I think that every beer style could have an "optimal pH".  My tests were done on a helles and an oktoberfest.  The helles seemed to benefit more from lower pH, although that perception is flawed because I also feel the acidification was masking a diacityl issue that would also make the beer more pleasing.

To perform the test I used 3 ounce samples, an eye dropper, and a pH meter adding 1 drop at a time trying to find the optimums.  Then I made adjustments directly to the bottles before filling for the comp.

Ron:

Great resource, really enjoyed reading it.  I exchanged emails with Kai a few weeks ago before joining this forum to discuss how mash pH translated to final pH at packaging.  After that discussion and a little research it was best to just use acid at bottling.  I have never used acid malt before but I think I will start experimenting with it in the future.
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Offline Kaiser

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Re: pH and finished beer
« Reply #16 on: December 06, 2010, 01:56:29 PM »
After that discussion and a little research it was best to just use acid at bottling.  I have never used acid malt before but I think I will start experimenting with it in the future.

And you should use acid malt. A correct mash pH does more than its benefit to the beer pH. It optimizes many of the reactions in the mash, boil and fermentation that are needed for good beer.

In addition to that, the pH of the beer and the pH in the mash have only a loose correlation. There are many factors that affect beer pH and only one of them is the pH of the cast out wort which is more closely related to mash pH.

Kai

Offline James Lorden

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Re: pH and finished beer
« Reply #17 on: December 06, 2010, 02:08:45 PM »
My problem with acid malt is that I don't know how to quantify it's effect on the mash pH.  With my water report, some brewing salts, and a good spreadsheet I can hit my number with ease... I haven't seen a spreadsheet that incorporates acid malt (only malt variable I have seen is SRM).
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Offline Kaiser

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Re: pH and finished beer
« Reply #18 on: December 06, 2010, 02:17:55 PM »
My problem with acid malt is that I don't know how to quantify it's effect on the mash pH.  With my water report, some brewing salts, and a good spreadsheet I can hit my number with ease... I haven't seen a spreadsheet that incorporates acid malt (only malt variable I have seen is SRM).

My spreadsheet incorporates acid malt: http://braukaiser.com/documents/Kaiser_water_calculator.xls

It's just a matter of doing the conversion between 88% lactic acid and acid malt which has about 3% w/w lactic acid content. But you may also use other acids like phosphoric acid for example.

It has been my experience, backed up by experiments, that even water with very low alkalinity will not give you an optimal mash pH when your grist contains only pilsner malt.

Kai

Offline James Lorden

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Re: pH and finished beer
« Reply #19 on: December 06, 2010, 05:22:52 PM »

It has been my experience, backed up by experiments, that even water with very low alkalinity will not give you an optimal mash pH when your grist contains only pilsner malt.

Kai

Even with calcium additions?
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Offline Kaiser

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Re: pH and finished beer
« Reply #20 on: December 06, 2010, 07:21:48 PM »
Even with calcium additions?

I guess it depends on the beer.

To drop the pH by ~0.3 units from 5.75 (pilsner malt in distilled water) to 5.45 you need about 350 ppm Ca in a 4 l/kg mash. So even if you put all (mash and sparge) calcium in the mash you have an equivalent water profile that has about 150 ppm Ca. This is a bit much for many lagers (IMO).

Another interesting aspect with calcium is that it precipitates phosphates which are a major pH buffer in wort and beer. It is very much possible that a beer brewed with calcium rich water can end up with a lower pH compared to the same beer brewed with water low in calcium even if they both had the same mash pH.

Kai

Offline James Lorden

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Re: pH and finished beer
« Reply #21 on: December 07, 2010, 09:05:11 AM »
Even with calcium additions?


Another interesting aspect with calcium is that it precipitates phosphates which are a major pH buffer in wort and beer. It is very much possible that a beer brewed with calcium rich water can end up with a lower pH compared to the same beer brewed with water low in calcium even if they both had the same mash pH.

Kai

If the phosphate is a buffer and pH drops during fermentation then wouldn't that mean that the pH of the the finished beer would drop less then the beer with less phosphate buffer... hence calcium rich water in mash could lead to higher pH in finished beer since there will more phosphate buffer to counteract the yeast pumping out those H+ during fermentation?....  I am not correcting you just asking for clarification - still working through the finer points of water chemistry.
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Offline Kaiser

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Re: pH and finished beer
« Reply #22 on: December 07, 2010, 10:03:06 AM »

If the phosphate is a buffer and pH drops during fermentation then wouldn't that mean that the pH of the the finished beer would drop less then the beer with less phosphate buffer... hence calcium rich water in mash could lead to higher pH in finished beer since there will more phosphate buffer to counteract the yeast pumping out those H+ during fermentation?....  I am not correcting you just asking for clarification - still working through the finer points of water chemistry.

The more calcium there is in the mash the more phosphates are precipitated. This reduces the amount of phosphate that buffers the pH during fermentation and as a result there is a larger pH drop during fermentation. 

A similar aspect of this topic is the effect of low temperature rests and lightly kilned malts where there is noticeable phosphates activity.  Acid rests are a prime example. It has been shown that the resulting increase of phosphate also increased the worts pH buffer capacity. This again results in a lower pH drop during fermentation.

Phosphatase activity is also affected by the mash pH. Low mash pH causes more activity than high mash pH which is why a mash mashed with a high pH (5.7 for example) but with acid additions during the boil (wort acidification) can end up with a lower beer pH than the same beer brewed with a low mash pH (5.3 for example) and not additional wort acidification.

Narziss/Back show some interesting data on the comparison between mash, wort and combined mash/wort acidification:

No acidification: mash pH = 5.75, cast out wort pH = 5.65, beer pH  = 4.61
mash acidification: mash pH = 5.52, cast out wort pH = 5.47, beer pH  = 4.55
wort acidification: mash pH = 5.74, cast out wort pH = 5.20, beer pH  = 4.36
combined mash/wort acidification: mash pH = 5.52, cast out wort pH = 5.20, beer pH  = 4.43

You notice that of the beers with the same cast-out wort pH the one with the higher mash pH results in the one with the lowest beer pH.

However, this is pretty far beyond the basic water chemistry for brewers and the idea of lower mash pH -> lower beer pH holds true enough that making this simplification is better than getting into the details of phosphatase activity in the mash.

Kai


Offline James Lorden

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Re: pH and finished beer
« Reply #23 on: December 07, 2010, 11:07:36 AM »
duh!, I just read it wrong... for some reason I thought you were saying that the calcium would lower mash pH but create additional buffers which would prevent the final beers pH from dropping (obviously this doesn't make much sense).  Great explanation by the way -thanks. 
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Offline James Lorden

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Re: pH and finished beer
« Reply #24 on: December 08, 2010, 11:04:33 AM »
Is there anyway to estimate how many phosphates the malt contributed to the mash?  In other words is there a point when the phosphates are used up so adding additional calcium and magnesium will have no effect on pH because there is no more HPO4 to react with?

Also, does this mean a bigger beer will have more buffers because there is more malt in the mash releasing phosphates?
« Last Edit: December 08, 2010, 11:08:24 AM by James Lorden »
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Offline James Lorden

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Re: pH and finished beer
« Reply #25 on: December 09, 2010, 07:27:49 AM »
Now, you may recall that Guinness does purposely acidify their stout with sour beer.  But you should also recognize that they add this soured beer AFTER fermentation.  This avoids the thinning action that would happen if they tried to acheive their preferred finished beer pH by adjusting their mash and wort pH lower.


From a different thread, this does show a large comercial brewery adjusting their finishing pH post ferment.
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Offline Kaiser

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Re: pH and finished beer
« Reply #26 on: December 09, 2010, 07:42:48 AM »
Is there anyway to estimate how many phosphates the malt contributed to the mash?  In other words is there a point when the phosphates are used up so adding additional calcium and magnesium will have no effect on pH because there is no more HPO4 to react with?

A.J. deLange has some data on that. In addition one mat also be able to estimate the phosphate content by matching the titration curve of phosphate to a titration cure of a mash sample. But I suspect and assume that there is sufficient phosphate in the mash to make sure that calcium is the limiting substance.

Quote
Also, does this mean a bigger beer will have more buffers because there is more malt in the mash releasing phosphates?

I would think so. But bigger beers also mean more yeast and more yeast growth which means that there will be more force that drives down the pH.

Kai