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  • Post brite tank issue's... Diacetyl?

    Been having some issue's with our beer and am trying to pin down exactly what it is. Essentially after we have transfered our beer to our brite/serving tanks it will start to darken in appearance over the course of a week and start to take on some more malty/slight diacetyl qualities. The color of the beer changing is really baffling me.

    At first I thought this was just happening in our beers using ale yeast, but just noticed it in one of our saisons. The beer tastes fine after fermentation and good for the first few days in the bright/serving tank, but then starts to change.

    Here is an outline of our process (including any chemicals)

    At the end of our brew day we transfer the beer to our fermenter, add fermcap because we have unsealed fermenters.

    When the beer hits terminal (average about 12-14 days) we allow it to rest for 3 days at terminal gravity

    We then blow off our trub and cold crash.

    After two days of cold crashing we harvest the yeast and transfer the beer to our serving tanks (sometimes we wait another day to transfer depending on brew schedule)

    In the bright tank we will sometimes add bioclear fine if the beer needs it (we don't filter). However I'm detecting the problem in beers that we don't use it (at least the color change)

    After about 3 days we will tap the beer. The first 20ish pints (which are discarded) are full of any yeast that might have settled after sitting in the bright tank/biofine addition.

    After that the beers taste and appearance is great for about 3-4 days then it starts to take on a darker appearance and change flavor. At first I figured it might be just maturing more, takes on more of a carmel malt flavor in our IPA and the hops die down a bit. I feel as though im detecting some slight diacetyl, but it could be in my head?


    Any thoughts on this would be helpful, thanks in advance.

  • #2
    Oxygen

    Darkening beer and increasing levels of diacetyl, with no sour or odd fruit notes, points to oxygen exposure.

    2,3 pentanedione oxidizes to diacetyl, and color compounds in the malt will darken with exposure to O2.

    Hotspots might be prepurging your BBTs, pump heads, or I don't know.

    Good luck,
    Bill

    Comment


    • #3
      Sounds like some precursors are getting by you before you crash it. Take a sample in a closed container and heat it to 180+ for 15 min. to convert the alpha-acetolactate into diacetyl, and then chill it back down and taste it. I've had trouble getting the beer warm enough for a quick D-rest so I began using enzymes for our lager called SEBmature L from http://www.specialtyenzymes.com. It has to be added pre-fermentation.

      Comment


      • #4
        Ok. Two parts. And Just my opinion here. A beer with anything in suspension will appear lighter in color than one without. The suspended bits reflect the light and will definitely make a beer look lighter. Since you said that after a few days you dump 20 pints due to more settling, then maybe the beer is simply continuing to clear (and thereby darken) over the next period of days. Maybe the beer really isn't darkening, it is simply clearing.

        AND...maybe you are looking for a taste difference due to what you see as a darkening. Since you feel you may be imagining it. As it continues to settle there will obviously be a slight taste change.

        Bottom line. How does the beer hold up?

        Sometimes the simplest answer is just that.

        I could be wrong, but I try to keep it simple first.

        Good luck

        Comment


        • #5
          Why not send a sample out for analysis of Diacetyl from the Fermenter right after cold crash and then another 2 weeks after transfer to the brites? Then you'll know if it's in your head.
          Eric O'Connor

          Co-founder/Brewmaster
          Thorn Street Brewery
          North Park, San Diego, CA

          Comment


          • #6
            Originally posted by rbrewhead View Post
            Sounds like some precursors are getting by you before you crash it. Take a sample in a closed container and heat it to 180+ for 15 min. to convert the alpha-acetolactate into diacetyl, and then chill it back down and taste it. I've had trouble getting the beer warm enough for a quick D-rest so I began using enzymes for our lager called SEBmature L from http://www.specialtyenzymes.com. It has to be added pre-fermentation.
            Really. Not trying to be disrespectful.

            Do you happen to know where this enzyme comes from (plant/bacteria/fungi). Do you pasteurize your beer? Is it inactivated by this heat?

            Would never allow the use of exogenous enzymes in my brewery, no matter how tempting it may seem sometimes. Others, I'm sure, will disagree.

            One of my many lines in the sand, I guess.

            In the hollow 'Age of craft' beer, I think we all need them. Otherwise, we essentially become them. Whoever they are.

            Pax.

            Liam
            Liam McKenna
            www.yellowbellybrewery.com

            Comment


            • #7
              One more "addition"

              Not to pile on here, but using Fermcap S or any other silicone anti-foam requires a filtration to remove it. Agree that darkening points to oxidation, although I'd think it would be of the trans-2 form and not taste like diacetyl. Good luck!
              Phillip Kelm--Palau Brewing Company Manager--

              Comment


              • #8
                Just to clarify...

                2,3 pentanedione does not oxidize to form diacetyl (which is 2,3 butanedione). They are separate compounds, both VDKs. 2,3 pentanedione is more subtle than diacetyl, but still undesirable. It does sounds like an oxygen uptake issue, however, as any residual D precursors could be oxidized to diacetyl (a-acetolactate). As mentioned above, a qualitative test is a "forced-D" (also can be done quick and dirty with a microwave), but having the beer actually tested is a better way to determine whether it is really diacetyl present (or not).

                You may also want to bottle some of the beer off of the brite tank...say 6 bottles...keep them stored at room temperature, then taste them on a weekly basis. As a control experiment, bottle another 6 bottles and keep them refrigerated. See how the beer "ages" at room temperature vs. cold stored.

                Just out of curiosity, which yeast are you using?

                Jim Matt
                Head Brewer, Rhinegeist

                Comment


                • #9
                  Seems like a really long time for a beer to ferment and condition in an unsealed fermenter.
                  Especially with the cold crashing; i could see the change in temperature causing a change in pressure, sucking in atmospheric air, leading to the oxidation/diacetyl issues mentioned above.
                  -Gerard
                  Gerard
                  Forest and Main Brewing Company

                  Comment


                  • #10
                    Thank you all so much for the input.

                    Revisiting all our procedures, we dialed our problem down to oxidation. I never got a "wet cardboard" taste from the beer, which is what i would normally associate with oxidation, so I looked past it.

                    We were not properly purging our brite tanks with co2. We would do a burst of co2 up to 5 psi and release it and call it good. After looking up some other posts, its seems that doing a 5psi purge and release 3 times in a row is much more effective. We also have been releasing the final purge through our 30' transfer hose that goes to the beer before we connect it to rid of any oxygen in it as well.

                    Our last two batches of beer have been substantially better. They have not gotten noticably darkened or changed taste over time like some of our last ones.
                    Last edited by TPBC; 03-15-2013, 11:55 PM.

                    Comment


                    • #11
                      Originally posted by Terroir View Post
                      Seems like a really long time for a beer to ferment and condition in an unsealed fermenter.
                      Especially with the cold crashing; i could see the change in temperature causing a change in pressure, sucking in atmospheric air, leading to the oxidation/diacetyl issues mentioned above.
                      -Gerard
                      Always assumed the "blanket" of co2 from fermentation would prevent this. Although unsealed, they are covered, I believe they were called unpressurized uni-tanks we we purchased them? They have lids that don't form a seal, but aren't what I would call "Open" fermenting vessels.

                      Comment


                      • #12
                        Originally posted by gitchegumee View Post
                        Not to pile on here, but using Fermcap S or any other silicone anti-foam requires a filtration to remove it. Agree that darkening points to oxidation, although I'd think it would be of the trans-2 form and not taste like diacetyl. Good luck!
                        It was my understanding the it was removed by the yeast and also stuck to the tank after fermentation....? We are using about a teaspoon for 3~3.5BBL batches... seems like a very small quantity to need filtration?

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