Author Topic: Correlation between pre-fermentation pH finished beer pH  (Read 1266 times)

Offline joshua.engdahl

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Correlation between pre-fermentation pH finished beer pH
« on: April 30, 2016, 02:00:32 PM »
Long time reader on here but first time posting. For the past 6 batches I've been monitoring pH during all phases of the brewing process rather than just the mash.  I use Bru'n water to make water additions and it always gets me pretty close to my target mash pH.  I typically mash at a pH of about 5.3.  I add all sparge water additions to the kettle rather than the sparge water and my pre-boil pH is usually within the target range of 5.2-5.4. If pre-boil pH ends up a little high I add some lactic acid to bring it down.  Since I've been monitoring pH, every batch of beer has had a high post boil pH.  They have all been between 5.5-5.8.  My understanding is the pH pre-fermentation should be about 5.0-5.2.  Is this correct?   Subsequently, my finished beer pH have all finished high.  The lowest was a saison at 4.28, but they've mostly been in the neighborhood of 4.5 with the highest being a pale ale that finished out at 4.7 using London ale III yeast. I added lactic acid to the 2 batches I brewed this week to bring the pre-fermentation pH down, but I'm wondering if that was the right thing to do.  Is there something wrong with my process that causing the pH to rise during the boil?

Offline blair.streit

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Re: Correlation between pre-fermentation pH finished beer pH
« Reply #1 on: April 30, 2016, 03:05:46 PM »
Long time reader on here but first time posting. For the past 6 batches I've been monitoring pH during all phases of the brewing process rather than just the mash.  I use Bru'n water to make water additions and it always gets me pretty close to my target mash pH.  I typically mash at a pH of about 5.3.  I add all sparge water additions to the kettle rather than the sparge water and my pre-boil pH is usually within the target range of 5.2-5.4. If pre-boil pH ends up a little high I add some lactic acid to bring it down.  Since I've been monitoring pH, every batch of beer has had a high post boil pH.  They have all been between 5.5-5.8.  My understanding is the pH pre-fermentation should be about 5.0-5.2.  Is this correct?   Subsequently, my finished beer pH have all finished high.  The lowest was a saison at 4.28, but they've mostly been in the neighborhood of 4.5 with the highest being a pale ale that finished out at 4.7 using London ale III yeast. I added lactic acid to the 2 batches I brewed this week to bring the pre-fermentation pH down, but I'm wondering if that was the right thing to do.  Is there something wrong with my process that causing the pH to rise during the boil?
Something sounds off to me. All things being equal if you're not adding anything alkaline (like baking soda) then your post boil pH should be lower than your mash pH.

Can you describe in more detail how you're measuring your mash pH (cooling, measurement device, etc)?

Offline mabrungard

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Re: Correlation between pre-fermentation pH finished beer pH
« Reply #2 on: April 30, 2016, 05:12:33 PM »
There is something wrong. Wort pH does not rise during the boil. Either your measurements are off or your wort has something like chalk in it.
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Offline joshua.engdahl

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Re: Correlation between pre-fermentation pH finished beer pH
« Reply #3 on: April 30, 2016, 05:40:21 PM »
I'm measuring pH with a Hach pocket pro+ tester. I calibrate it on brew day and regularly check the calibration against buffer solution while I'm brewing.  I cool the samples down to around 70 deg before taking a reading.   I'm pretty confident the readings have been accurate because after getting a high reading I check the meter against the buffer solution and it comes pretty close. The water additions I've been making are gypsum, CaCl, lactic acid, and whirfloc. I also put a 1/4 campden tablet in my strike and sparge water.  I haven't added any chalk or any other type of bicarbonate to the kettle, but I did use 6 drops of fermcap-s the past few brews. I've gotten high pH reading with and without using fermcap. I have an aluminum brew pot, but that shouldn't effect anything right? The beer still tastes good but the pH being off is just bothering me.

Offline blair.streit

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Correlation between pre-fermentation pH finished beer pH
« Reply #4 on: April 30, 2016, 07:13:11 PM »
When are you pulling the sample? If the sample is pulled from the mash prior to sparging then maybe your sparge is raising the pH?
« Last Edit: April 30, 2016, 07:20:27 PM by blair.streit »

Offline blair.streit

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Re: Correlation between pre-fermentation pH finished beer pH
« Reply #5 on: April 30, 2016, 07:22:51 PM »
Sorry, re-reading the original it seems you are taking mash, pre and post boil readings. Unless there's an issue with the readings or something odd happening in the boil (i.e. beer stone dissolving into your wort) I'm stumped....

Offline joshua.engdahl

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Re: Correlation between pre-fermentation pH finished beer pH
« Reply #6 on: May 02, 2016, 02:18:26 PM »
There is some discoloration on the bottom of the kettle, so I guess it could be beerstone build-up.  I've only been giving it a light scrub with a blue scouring pad and dish detergent because I've heard your not supposed to clean an aluminum kettle super clean.  I guess I'll clean it better and see what happens next time I brew.  Thanks.

Offline blair.streit

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Re: Correlation between pre-fermentation pH finished beer pH
« Reply #7 on: May 02, 2016, 07:26:30 PM »
It can't hurt to clean it, but I'll admit that I kinda pulled that beerstone comment out of thin air when racking my brain for an example of something unintended that might be dissolving into your wort during the boil.

Since beerstone tends to build up rather than dissolve into wort, on further reflection I'm skeptical that is actually the cause. Perhaps Martin or someone with a better chemistry background could weigh in on whether beerstone (or any other kind of buildup in your kettle) could possibly contribute to an increase in pH during the boil?

Looking back to why the boil pH is expected to drop, this is from Braukaiser:

Quote
During boiling the pH drops by about 0.1 – 0.2 pH units from 5.3 – 5.5 pH to about 5.2 – 5.3 pH. This may be due to the addition of bitter acids from the hops, formation of acidic Maillard products, precipitation of alkaline phosphates or the reaction of polypeptides with calcium, liberating protons [Briggs, 2004].

More here:

http://braukaiser.com/wiki/index.php?title=How_pH_affects_brewing

Note that there are several things going on here. I haven't ever seen this discussed, but based on the underlying mechanisms is seems possible that depending on when you're taking your post-boil pH measurement (and what has or has not precipitated out of solution), you could end up with different results.

I'm still perplexed as to how something like that could increase from a 5.3 pH reading pre-boil to a 5.6pH reading post-boil. It still seems to me that there's a simpler explanation, but I'm out of ideas.

Offline joshua.engdahl

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Re: Correlation between pre-fermentation pH finished beer pH
« Reply #8 on: October 15, 2016, 04:42:57 PM »
Just to follow up on this post, I cleaned the kettle pretty good and it didn't seem to help.  The pH still rose after the boil on my next brew.  After that, I took apart the threaded fittings in my mash tun and found some mold in there.  I got rid of the mold, and since then I've brewed 3 times and haven't had an issue with pH rising during the boil.  Rather it has been behaving like normal and dropping slightly.  Now I disassemble the mash tuin after each brew and reassemble on brew day. 

Offline mabrungard

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Re: Correlation between pre-fermentation pH finished beer pH
« Reply #9 on: October 15, 2016, 07:12:14 PM »
Hmm? I'm wondering how this could have affected it. Somehow that mold was producing alkalinity...curious!
Martin B
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