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Old 01-17-2014, 05:04 AM   #1
brewmeister13
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Default What Affects Final Beer pH

I was just reading through some posts and saw that AJ mentioned that mash pH does not correspond to or determine final beer pH (not his exact words, but my summation of what he was saying). He mentions that yeast dictate this. My beers seem to be finishing high (one as high as 5 when degassed and measured at room temp). As I understand it pitching rate influences final beer pH, but I thought I was pitching a sufficient quantity. What else can we control that affects the final beer's pH?

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Old 01-17-2014, 05:33 AM   #2
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Yeast try to regulate pH to a value that favors them. Obviously they can better do this if you make it easier for them than if you make it harder. Thus nominally correct wort pH out of the kettle which follows from nominally correct mash pH is a factor. Clearly, there must be enough yeast in good shape to overcome the proton deficit of the wort. This means pitching a suitable amount of healthy yeast into a wort with sufficient FAN and oxygen. Clearly the strain of yeast used has a major effect with ale yeasts striving for lower pH than lager yeasts as a general rule. There are doubtless dozens of other factors to consider such as presence of co-enzymes etc.

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Old 01-17-2014, 02:36 PM   #3
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Not to hijack, but is there a table of desired finished beer pH's per syle(or yeast strain)? Or anything like that?

thanks

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Old 01-17-2014, 03:22 PM   #4
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Im no expert on beer PH but im pretty sure co2 has something to do with beers final ph..its carbonic acid so it drops the ph into the 4's..im sure there is a laundry list of other factors

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Old 01-17-2014, 05:30 PM   #5
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CO2 does have something to do with it. I think I calculated that 2 vols would, based on some nominal assumption about the buffering capacity of beer, lower the pH by about 0.1.

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Old 01-17-2014, 09:21 PM   #6
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Quote:
Originally Posted by rabeb25 View Post
Not to hijack, but is there a table of desired finished beer pH's per syle(or yeast strain)? Or anything like that?

thanks
From what I've found at various sources 4.0-4.5 is a good range for ales. I've seen not above 4.0, but every source I've found talks about exceeding whatever limit they consider "ideal" resulting in dull flavors. Lagers are a bit higher and sours lower.

What got me interested in this was an IPA that I brewed (my best beer yet). It scored a 43 at a competition and took 2nd in BOS, but I got a chance to talk to a few judges (it was a smaller competition). They really enjoyed the beer, but each one said there was just something about it that was not quite right. One said that he felt the beer was too delicate for a highly hopped IPA (it was an estimated 82 IBUs). I was trying to find what to do to improve this brew and came across finished beer pH and how it can cause a beer to come across as dull. I didn't see a far jump from delicate to dull and decided to measure my beer. It came back at 5.0 pH, so I think I found my culprit. Problem is I'm not quite sure how to fix it.

My mash pH was 5.45, a bit higher than I was shooting for, but still within a good range, I feel. This was before I started measuring my pH at the end of boil, so I am unsure of that. I grew a starter for this and pitched 0.75M cells / mL / °P, estimated. I brew all grain and used almost 94% domestic 2-row, the rest was crystal and a touch of aciduated malt. I feel that due to this my FAN should be sufficient. I believe I used enough oxygen, even may have over done it. I aerated with pure O2 at 1L/min for 3 minutes through a .5 micron stone (I've since come to find that this may be too much and will be doing an experiment with aeration for my next batch). I believe I pitched the yeast after aeration, but may have pitched it prior (my notes are unclear). My understanding now is that if I pitched first there is a chance that levels reach a toxic level for yeast during the aeration period. I find this as potential problem area #1, but believe I pitched after aeration, which keeps me on the search. I used WLP001 and fermented at 64 F. As I've recently found, the colder the fermentation, generally, the higher the finished beer will be. I'm thinking this may have contributed to my high finishing pH, but am not sure that a few degrees could result in such a high shift.

If anyone has any other ideas or insight I would be greatly appreciative.
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Old 01-18-2014, 02:45 AM   #7
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There are doubtless dozens of other factors to consider such as presence of co-enzymes etc.
I'm not familiar with how to tell if there are enough co-enzymes or what affects this aspect. Could you help me out with this?
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Old 01-18-2014, 01:47 PM   #8
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Originally Posted by brewmeister13 View Post
From what I've found at various sources 4.0-4.5 is a good range for ales. I've seen not above 4.0, but every source I've found talks about exceeding whatever limit they consider "ideal" resulting in dull flavors. Lagers are a bit higher and sours lower.
4 is definitely at the low end but some ales and definitely sour beers (Berliner Weiße) drop under it. I had one wheat beer come in at 3.99 but given meter error that could have actually been a bit over 4 (or lower in the 3's).

I don't think high pH is the cause of dull flavors. I think it is a symptom that something or things went wrong in the fermentation and that an incomplete or improper fermentation is the cause of the uninteresting flavors. High mash pH leads to dull flavors even if the fermentation goes well and the beer pH winds up as what we call acceptable. You might prove me wrong by adding a little acid (dilute lactic or phosphoric) to your beer and seeing if that improves the flavor. Gordon Strong mentions doing that in his book and lectures. Check with a pH meter, of course, and do the additions in small increments tasting as you go.

Quote:
Originally Posted by brewmeister13 View Post
What got me interested in this was an IPA that I brewed (my best beer yet). It scored a 43...each one said there was just something about it that was not quite right. ... measure my beer. It came back at 5.0 pH, so I think I found my culprit.

My mash pH was 5.45, a bit higher than I was shooting for, but still within a good range, I feel.
5.45 is an excellent target. My gut tells me 5.4 is probably ideal but it doubtless varies some with the type of beer.


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Originally Posted by brewmeister13 View Post
This was before I started measuring my pH at the end of boil, so I am unsure of that.
Unless you sparged with highly alkaline water (and you say later that you didn't) kettle pH should have dropped down to 5.1 - 5.25 or something like that. Again, this is, AFAIK, just about ideal.


Quote:
Originally Posted by brewmeister13 View Post
I grew a starter for this and pitched 0.75M cells / mL / °P, estimated. I brew all grain and used almost 94% domestic 2-row, the rest was crystal and a touch of acidulated malt. I feel that due to this my FAN should be sufficient.
Sounds like enough yeast and all grain brewing usually results in sufficient FAN.


Quote:
Originally Posted by brewmeister13 View Post
I believe I used enough oxygen, even may have over done it. I aerated with pure O2 at 1L/min for 3 minutes through a .5 micron stone (I've since come to find that this may be too much and will be doing an experiment with aeration for my next batch). I believe I pitched the yeast after aeration, but may have pitched it prior (my notes are unclear). My understanding now is that if I pitched first there is a chance that levels reach a toxic level for yeast during the aeration period.
That would be hard to achieve though it is probably possible to do. Not all the oxygen you inject dissolves and of that which does quite a bit comes right back out as the solution tries to stay in equilibrium with the air over it.


Quote:
Originally Posted by brewmeister13 View Post
I find this as potential problem area #1, but believe I pitched after aeration, which keeps me on the search. I used WLP001 and fermented at 64 F. As I've recently found, the colder the fermentation, generally, the higher the finished beer will be. I'm thinking this may have contributed to my high finishing pH, but am not sure that a few degrees could result in such a high shift.
The problem is that you had wort at pH a little over 5 and the yeast didn't drop the pH below 5. The question is why? The answer is unhealthy yeast or unhealthy conditions for them but it sounds as if you did everything right. Sometimes you get bad yeast i.e. yeast that doesn't perform the way it is supposed to. I have had bad packs/vials from both the major manufacturers. The usual result is disappointing degree of fermentation. How was the ADF (apparent degree of fermentation) on this beer? The yeast may or may not have been the problem but the failure of the yeast to drop pH is a signal that something is wrong. As I don't know what that might be I don't have a fix to offer except to check that you are using good practices throughout i.e. protein rest for FAN (that comment will bring down a cascade of protests that protein rests are not necessary with modern highly modified malts), being sure that sufficient oxygen is supplied, controlling fermentation temperature, being sure that nothing toxic to yeast gets into the wort (iodine from table salt, for example), providing them with trace elements through the use of a yeast nutrient etc. pH at this point (the fermenter) is an indicator rather than a control point. If the yeast don't drop the pH of the wort dramatically in the first few hours of fermentation I don't think you can fix things by adding acid to lower it for them.
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Old 01-18-2014, 01:48 PM   #9
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I'm not familiar with how to tell if there are enough co-enzymes or what affects this aspect. Could you help me out with this?
Not really. I suppose you could ensure there are enough by using a yeast nutrient.
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Old 01-18-2014, 09:20 PM   #10
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You might prove me wrong by adding a little acid (dilute lactic or phosphoric) to your beer and seeing if that improves the flavor. Gordon Strong mentions doing that in his book and lectures. Check with a pH meter, of course, and do the additions in small increments tasting as you go.
Unfortunately this was from an IPA I brewed back in September. I have one bottle left, but the flavors are so far from when it was fresh I don't think it would help much.

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Originally Posted by ajdelange View Post
Unless you sparged with highly alkaline water (and you say later that you didn't) kettle pH should have dropped down to 5.1 - 5.25 or something like that. Again, this is, AFAIK, just about ideal.
Yeah, my final runnings pH was 5.6.


Quote:
Originally Posted by ajdelange View Post
The problem is that you had wort at pH a little over 5 and the yeast didn't drop the pH below 5. The question is why? The answer is unhealthy yeast or unhealthy conditions for them but it sounds as if you did everything right. Sometimes you get bad yeast i.e. yeast that doesn't perform the way it is supposed to. I have had bad packs/vials from both the major manufacturers.
I do reuse yeast (by growing an extra 100 billion cells every time I make a starter and keeping it in an as sanitized as possible mason jar until my next usage-usually within 2 weeks or so). This was the yeast's 4th generation, so perhaps that has something to do with it.

Quote:
Originally Posted by ajdelange View Post
The usual result is disappointing degree of fermentation. How was the ADF (apparent degree of fermentation) on this beer?
For this one the OG was 1.066 and the final gravity dropped to 1.009. By my calculations that gives an ADF of about 86.4. I did a single infusion at 148 for 75 minutes and the temp was at 146 at the end.


Quote:
Originally Posted by ajdelange View Post
The yeast may or may not have been the problem but the failure of the yeast to drop pH is a signal that something is wrong. As I don't know what that might be I don't have a fix to offer except to check that you are using good practices throughout i.e. protein rest for FAN (that comment will bring down a cascade of protests that protein rests are not necessary with modern highly modified malts), being sure that sufficient oxygen is supplied, controlling fermentation temperature, being sure that nothing toxic to yeast gets into the wort (iodine from table salt, for example), providing them with trace elements through the use of a yeast nutrient etc. pH at this point (the fermenter) is an indicator rather than a control point. If the yeast don't drop the pH of the wort dramatically in the first few hours of fermentation I don't think you can fix things by adding acid to lower it for them.
The only things that I did not do on this was a protein rest and adding a yeast nutrient. I always forget about the yeast nutrient, even when making starters (perhaps why a yeast on its 4th generation did not perform optimally?). The protein rest thing is new to me though. I've always heard it as you pointed out that the comments would come, it's not necessary. I've even heard that it can be detrimental. I do, however, recognize your expertise in the field and trust your advice, so if you could provide me with a little more information about this I would be grateful. First off, why? Even if it is the best practice, if I don't at least loosely grasp the reason it will drive me nuts. Secondly, what would you recommend for temperature (the standard 113-131 still considered good enough?) and duration (20-30 minutes is what I've heard).

From everything you've pointed out, to me it appears that the yeast may have been hampered by poor nutrition (both the generation that made this beer and the propagation of under nourished previous generations). Does this sound like it may be the right track to you? I'm really looking forward to brewing the beer again next month and really appreciate all of your help.
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