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Thread: PH increase during and after fermentation.

  1. #1
    Join Date
    Apr 2018
    Location
    Ireland
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    PH increase during and after fermentation.

    Iím just wondering if anyone has experienced issues with PH rising directly after fermentation and in some cases before fermentation is even finished. More of an issue with higher gravity beers. We drop trub daily or every 2-3 days
    Just to give a brief overview I joined a new brewery a few months ago and we are experiencing some things during fermentation that Iíve not experienced in any other brewery Iíve worked at. Typical water profile CaCI2 75ppm(mash), CaSo4 30ppm(Kettle), Zinc 0.2/0.3ppm(Kettle/whirlpool), CaCI2 50ppm coldside to fermenter. We do forced ferments on all beers so we have a fair idea what the terminal gravity should be. We use Stevenson reed hydrometers and calibrate PH meter daily so are confident in our readings.

    1. For all high gravity beers we aerate with pure O2 to between 15-20ppm while casting out, we pitch at 1.5 million cells per mL per degree plato. Viability over 90% and oxygen levels checked on Hamilton Beverly. We then aerate again within 24 hours of pitching. High gravity beers ferment really well for the first 2-3 days and taste great then on day number 3-4 the yeast seems to die in suspension and the PH stops dropping we get a PH spike well before we hit terminal. For example 5.1 initial PH then 4.6 day 2 then day three 4.62 gravity sill dropping a few points, day 4 4.8 and then we start to get what seems very much like autolysis as we get that super burnt rubber aroma. We drop trub daily and as soon as PH spikes, dump whatever yeast we can immediately however thereís often very little yeast to dump as itís all still in suspension. We assume that itís a nutrient deficiency and are trialing both Wyeast and Murphy and Sons yeast nutrient. While we think itís made a difference with most we still have issues with some.
    2. Normal fermentations much less dramatic but still occurs, beer will ferment to terminal we will crop or drop yeast and then we still see a slight increase before we dry hop. If we are not dry hopping and transfer to a brite tank we sometimes still see a slight increase here and in some cases we will see gravity drop by a point.
    3. We do HLP on all of our beers and have had one positive result in the last 6 months.
    4. We have sent our wort to be analyzed and found that calcium was low despite our large addition in the mash so now we do a coldside addition as well.
    5. Our Brite tanks are actually conical tanks that act as unitanks.


    If anyone has any ideas what may be causing the PH spike any theories would be greatly appreciated.

  2. #2
    Join Date
    Sep 2015
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    Guadalajara
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    Hi Conor.
    Yeast Autolysis does cause a spike in PH, and there is a lot of documentation on that issue.
    My best bet, and this is just a theory, is that you are aerating too much, 20 ppm of oxygen is high, and your day after aereation is to my opinion causing an excessive population of yeast. Oxigen is needed during the propagation phase of yeast, too much oxigen will lead to a higher population making it more prone to autolysis.
    The problem arises when your alcohol levels rise and the yeast start to suffer, I think that is why your high gravity beers suffer the most.
    There are a number of approaches to try as a solution, but I would reduce the oxigen to say 10 ppm and no aereation, it might take longer to ferment, but on the upside maybe the autolysis will be limited.
    Our highest gravity beer is 7.5%ABV and we add oxigen to 8.5 - 9 ppm. And have never had an issue.
    I hope this helps.
    Cheers


    Sent from my iPhone using Tapatalk

  3. #3
    Join Date
    Oct 2002
    Location
    Chesterfield, UK
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    1,866
    The oxygen requirement is very yeast strain and OG specific. You have not given an indication of the starting gravity, or the gravities associated with the pH figures, which makes sensible comments nigh on impossible as we don't have the complete fermentation profile details. You also don't mention temperature.

    So, a couple of thoughts -

    I am surprised at the low reduction in pH - an ale will typically be between 3.8 and 4.25, depending on your spec - 4.6 sound very high, with poor (slow) yeast growth being the main reason - but there are a multitude of reasons why it could be slow, not just lack of oxygen.

    If you are using dried yeast, then you don't normally need any additional oxygen - the exception normally being once you get over about 1060 OG

    If you are using recovered wet yeast, then 15 - 20 ppm oxygen is normally OK for most ale yeasts up to about 1060, but I do know one UK national ale brand that required 27 ppm DO2. Based on your comments about only a few days fermentation, I guess you are brewing ales.

    If you are brewing very high gravity, I used to brew one where the same yeast required 8 ppm for say 5 % ABV beers, but for 10 % + beers, required additional intermittent aeration for a few days until the gravity had dropped to about 1040

    Are you sure all the oxygen is dissolving fully? Residual gas bubbles when you test the wort will often lead to falsely high DO readings.

    Drop me a PM with more details and I will attempt a better answer.

    Cheers
    dick

  4. #4
    Join Date
    Apr 2018
    Location
    Ireland
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    Quote Originally Posted by forrestmz3005 View Post
    Hi Conor.
    Yeast Autolysis does cause a spike in PH, and there is a lot of documentation on that issue.
    My best bet, and this is just a theory, is that you are aerating too much, 20 ppm of oxygen is high, and your day after aereation is to my opinion causing an excessive population of yeast. Oxigen is needed during the propagation phase of yeast, too much oxigen will lead to a higher population making it more prone to autolysis.
    The problem arises when your alcohol levels rise and the yeast start to suffer, I think that is why your high gravity beers suffer the most.
    There are a number of approaches to try as a solution, but I would reduce the oxigen to say 10 ppm and no aereation, it might take longer to ferment, but on the upside maybe the autolysis will be limited.
    Our highest gravity beer is 7.5%ABV and we add oxigen to 8.5 - 9 ppm. And have never had an issue.
    I hope this helps.
    Cheers


    Sent from my iPhone using Tapatalk
    Thanks for your input....I'm of the opinion and I may be wrong, but I feel like anything up to 15-20ppm for a 25 Plato beer should be ok. If the problem only arose with high gravity beers that we aerate a lot I might agree however this happens across a multitude of yeast strains and with lots of different plato beers, some with aeration as low at 10-12ppm. We have used US05 dry second and third generation, 2nd generation Chico from BSI, London III from BSI and all exhibit slight rises in ph....some more than others. The latest example is a wheat beer I just fermented with Wyeast 1056 with a pitchable qty, 12ppm aeration, fermented fine for three days slowed down and ph went from 4.3 to 4.6 on day 4 when 2 points from terminal, this actually smells ok and tastes ok but obviously theres an issue somewhere, again meter calibrated and all other beers showing normal results so I don't think thats the issue. Dropped trub daily, just about to do a yeast count to see how healthy it is.

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