[James Lorden]

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.

[euge]

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.

[mabrungard]

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.

[tom]

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?

[James Lorden]

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

[Kaiser]

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

[mabrungard]

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?

[Thirsty_Monk]

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.

[tschmidlin]

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.

[Kaiser]

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

[James Lorden]

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.

[wingnut]

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.   

[James Lorden]

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.

[gordonstrong]

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.

[bluesman]

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