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General Category => General Homebrew Discussion => Topic started by: James Lorden on December 04, 2010, 07:26:37 pm

Title: pH and finished beer
Post by: James Lorden on December 04, 2010, 07:26:37 pm
Recently I rushed a Helles to get into a comp. Although I employed a 2 day d'rest after a rushed ferment all judges came back with diacatyl.  Around that time I came across an article that was not about beer that noted the threshold for perceiving diacatyl lowered with decreases in pH.  To test this assertion I re-entered this brew but this time dosed with acid to lower the pH from 4.6 to 4.2 and the results were clear, diacatyl was only noted by 1 of 3 judges and that judge hinted that it was slight.  What did happen however is that all judges now noted acetaldehyde which had not been noted by any judge in the first comp. I attribute this to the lactic acid I used since I was out of phosphoric (lactic does have a "flavor" that I am thinking was judged as acetaldehyde).

I used this same procedure to dose a medal winning Oktoberfest. The results here were that the judges seemed to note that the malt was more pronounced but the beer was dinged for being  thin.  Personally I agreed that the pH drop made the flavor pop.

This was an interesting experiment.  I think based on these results that adjusting final pH in beer might be a valid addition to my process for making better beer (and adding control).  Unfortunately at this time I am unsure what the proper level is and how it changes by style.  More tests to come.
Title: Re: pH and finished beer
Post by: euge on December 04, 2010, 11:50:12 pm
Thanks for the experiment! I can say I learned something new today. Sounds like a legitimate tool. I wonder if this approach has been used by professional brewers to fix a batch.
Title: Re: pH and finished beer
Post by: mabrungard on December 05, 2010, 09:30:10 am
Interesting result.  High alkalinity in relation to the beer color is known to to produce problems and pH is one of them.  Thanks for adding to that list.

It certainly is worth additional investigation and quantification.
Title: Re: pH and finished beer
Post by: tom on December 05, 2010, 10:45:23 am
Thanks for your info. Can you add a link to the article?

 I know that the pH decreases during fermentation, but I don't know why. Anyone know?
Title: Re: pH and finished beer
Post by: James Lorden on December 05, 2010, 11:40:53 am
I'm sure that there is more to it then this, but one way first steps in fermentation is that glucose is broken down into pyruvic acid.  I also no that I have read that the pH drop in a lager is not as great as it is in an ale.  The explanation above doesn't explain why that would be so I can look into this further.

As for the article - it was written for the dairy industry

http://books.google.com/books?id=owr0BEo4aloC&pg=PA65&lpg=PA65&dq=diacetyl+cream+pH+perception+threshold&source=bl&ots=UzksbODbxC&sig=knGVlP6mLJ4yuZINd54uMi-rqT8&hl=en&ei=KNz7TOigJYGKlwfDrcyYBQ&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCoQ6AEwAg#v=onepage&q=diacetyl%20cream%20pH%20perception%20threshold&f=false

As you can see for skim milk, as the pH dropped the threshold for percieving diacetyl raised
Title: Re: pH and finished beer
Post by: Kaiser on December 05, 2010, 03:21:24 pm
I know that the pH decreases during fermentation, but I don't know why. Anyone know?

here is some info on that: http://braukaiser.com/wiki/index.php/How_pH_affects_brewing#Nutrient_uptake_by_yeast

I'm going to
play around with post fermentation pH adjustment as well. While not part of German brewing practice it can give good insight in determining how beer pH changes affec flavor.

Kai
Title: Re: pH and finished beer
Post by: mabrungard on December 05, 2010, 05:08:46 pm
I look forward to your findings regarding the pH experiment.  The buffering of a finished beer will be low, so it probably won't take much acid to affect a sigificant pH change.  But, I suppose there could be a flavor impact with lactic acid.  Will you be using phosphoric to avoid the flavor impact?
Title: Re: pH and finished beer
Post by: Thirsty_Monk on December 05, 2010, 06:02:02 pm
If you read this document:
http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:C:2009:073:0045:0049:EN:PDF

They talk about pH in between 4.2 to 4.9 for Czech Pilsner beers.
In another document they refer to "pH of 4,41-4,74"

Lower then 4.1 you start tasting sour notes.
Title: Re: pH and finished beer
Post by: tschmidlin on December 05, 2010, 11:50:13 pm
Thanks for this info James.  Next time, if possible, it would be great if you entered both the dosed and undosed beers for judging, to mitigate having a different set of judges as a source of the perceived difference.
Title: Re: pH and finished beer
Post by: Kaiser on December 06, 2010, 07:53:38 am
The buffering of a finished beer will be low, so it probably won't take much acid to affect a sigificant pH change.

I actually found the opposite in a recent titration experiment[/quote].

When I lowered the pH of a beer from 4.6 to 4.2 with lactic acid after James mentioned this to me, i did not detect a lactic acid taste at all. I think that fermentation also produces some lactic acid but sine it's concentration is still low the flavor is not perceived as sour.

Kai (http://braukaiser.com/lifetype2/index.php?op=ViewArticle&articleId=138&blogId=1)
Title: Re: pH and finished beer
Post by: James Lorden on December 06, 2010, 07:59:52 am
As a side experiment I think I am going to dose some distilled water with lactic and phosphoric acid to the same pH levels and then try to detect the flavor in a triangle test.  I have always heard that lactic has flavor and phosphoric does not... I want to test this theory with the amounts of acid that I would plan on using in my beer.
Title: Re: pH and finished beer
Post by: wingnut on December 06, 2010, 08:26:38 am
I also was pondering a similar experiment with my Octoberfest/Vienna Lagers, and I have been looking for any data on what the fnishing PH of beers tend to be.  I have not found any data on what the PH of finished beer tends to be, or if it varies by style, or over time as the beer ages.  I percieve a change in malt character as it ages, and I percieve I have noticed this even in the comercial examples I keep on hand.  The PH papers I have on hand that go down to the 3 range, show a change in PH as well, however, since they do not have the significant color variation of the ColorPHast strips I use for the higher PH range, it is hard to get very exact... other than to say the PH dropped a bit as the beers aged. 

Some thougths I had for the experiment was to add a base as well as acid to provide a wider range of data values. I also have been trying to decide on the best acid to use... citric, lactic, phosphoric...other... each can have a flavor contribution if the levels get high enough, and that may cloud the results a bit.

What got me started down this line was my fist batch of cider I brewed a year ago... It was OK, but kind of "flat" tasting.  One day, while brewing, I had a bottle of cider in hand during the mash, and I decded to add some acid to it... just a drop of citric acid I had on hand... and it was a completely different set of flavors that I tasted.  As I read more, I found the PH in food is often sited as key factor in flavor perceptions.  However, I could not find any data on finishing PH and beer.   

Title: Re: pH and finished beer
Post by: James Lorden on December 06, 2010, 09:30:43 am
From Braukaiser:

A low beer pH results in a crisper more lively beer while a high beer pH is generally associated with a dull flavor perception. But there are limits to how low pH can be before the beer's taste starts to take on sour notes. For all malt beers a pH range of 4.25 - 4.6 [Narziss, 2005] is generally accepted as optimal while adjunct beers can be as low as 4.0 [Kunze, 2007] and sour beers will be even lower.

I am finding that lower pH makes the malt flavor more distinctive but seems to make the body thinner.
Title: Re: pH and finished beer
Post by: gordonstrong on December 06, 2010, 09:44:19 am
I did some research and experimentation with this last summer while working on my book.  I think the desired target range is 4.1 to 4.5, with the tradeoff being between flavor and stability.  The higher the pH, the better the flavor.  The lower the pH, the better the (microbial) stability.  Above 4.5, you start to get into food safety issues (i.e., stuff can grow in it).  Lowering the pH does make the beer seem thinner, and eventually starts getting tart.  I only used phosphoric acid (it's an ingredient in soft drinks as a flavor enhancer).

When the pH of beer is above 4.6 or so, it does have a bland taste, sort of like underseasoned (undersalted) food. Adding phosphoric acid did improve the flavor, to a point.  Like salting food, there is an optimal point and it's somewhat subjective.  Going too far means you start tasting the flavor enhancer and not the enhanced flavor.  The flavor impact was different based on the serving temperature as well.  Measuring at room temperature and then tasting at the colder serving temperature can result in over-adjusted beer.  The desired final pH is also affected by the flavor profile (beer style) of the subject beer; there isn't one magic pH where all beers taste best.

I did find that finished beer did buffer pH change quite a bit.  Certainly more so than RO water.  Another way of illustrating that adding acids to adjust pH is not something with an easy linear formula.  You have to add and test carefully, at least until you've neutralized the buffer and start moving the pH.
Title: Re: pH and finished beer
Post by: bluesman on December 06, 2010, 10:40:13 am
This is somewhat related to the discussion.

I stumbled upon this and thought I'd pass it own.  Enoy!

http://www.weyermann.de/downloads/pdf/Weyermann_TKW_Mash-pH_2010.pdf
Title: Re: pH and finished beer
Post by: James Lorden 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.
Title: Re: pH and finished beer
Post by: Kaiser 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
Title: Re: pH and finished beer
Post by: James Lorden 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).
Title: Re: pH and finished beer
Post by: Kaiser 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
Title: Re: pH and finished beer
Post by: James Lorden 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?
Title: Re: pH and finished beer
Post by: Kaiser 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
Title: Re: pH and finished beer
Post by: James Lorden 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.
Title: Re: pH and finished beer
Post by: Kaiser 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

Title: Re: pH and finished beer
Post by: James Lorden 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. 
Title: Re: pH and finished beer
Post by: James Lorden 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?
Title: Re: pH and finished beer
Post by: James Lorden 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.
Title: Re: pH and finished beer
Post by: Kaiser 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