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Carbonation Theory: Aroma Scrubbing Specific Theory

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  • Carbonation Theory: Aroma Scrubbing Specific Theory

    Hi All!

    Got a question that I really need some help answering I feel like I'm really missing 'that' link that'll help me understand this infinitely better!

    The Issue


    How does aroma 'scrubbing' and beer foam specifically work and why is it not an issue when carbonating a beer through a carb stone with no head pressure in tank?

    My Current Understanding of 'Aroma Scrubbing' and Beer Foam

    Beer foam is primarily caused by LTPs (lipid transfer proteins) leaving the solution(beer). LTPs are hydrophobic so when CO2 rises through beer they attach themselves to the bubble and bring themselves to the surface and therefore out of solution of the beer (beer foam). My current understanding is (and I can't find any paper that suggests otherwise) that once the LTPs have found their way out of solution they can no longer be reintroduced into the beer.

    Similarly, hop aroma compounds from dry hopping etc are in solution too and they too are hydrophobic meaning they will attach themselves to a CO2 bubble and break out of solution. Once again once these compounds are out of solution they cannot be reintroduced back into solution!?

    The Issue - Specifically

    So when carbonating through a carb stone into a tank with no head pressure with my current understanding it would mean you are in fact 'scrubbing' aroma and beer foam from your beer as most of the CO2 you are bubbling the beer with exits the solution and occupies the head space (hence the equilibrium head pressure) in this head space is there valuable aroma and beer foam compounds out of solution that cannot be forced back in?


    The current understanding seems to be if you carbonate 'too quickly' through the carb stone this will cause beer foam and aroma 'scrubbing' but I cannot see how the vigour of the bubbles specifically causes this and how slowing the volume of CO2 would not cause these hydrophobic compounds to leave solution - especially if the head pressure rises from 0 to X PSI meaning the CO2 that has gone through the beer is in the head space.

    To my current understanding just because the beer doesn't foam quickly (causing visible foam) it doesn't mean the compounds that cause foam are not out of solution. I am proposing that the same quantity could be out of solution but because they are taken out of solution slowly they do not appear to cause foam in tank.

    Thanks for anyone who made it through!

    Any links to good quality papers ALWAYS welcome as they are rarer than a clear beer in London!

    Chris

  • #2
    I never bleed my BBTs down to no head pressure when force carbing beers via a stone. I would increase the pressure to the tanks rated psi (15 psi). Then bleed them very slowly down to 5 psi then back up again if needed. Bleeding down to nothing or just leaving the tank with no head pressure while adding IMO is scrubbing.
    Joel Halbleib
    Partner / Zymurgist
    Hive and Barrel Meadery
    6302 Old La Grange Rd
    Crestwood, KY
    www.hiveandbarrel.com

    Comment


    • #3
      It comes down do a concentration gradient. When you are carbonating and venting, there is always fresh co2 coming through the beer and leaving, taking aromas with it. Though you start at 0psi and climb to saturation pressure gradually, the concentration of aromas in the head space reaches an equilibrium where the balance of the oils in the beer and oils in head-space gasses stays constant. You are correct that just because the beer isn't foaming aggressively doesn't mean that aromas aren't moving into the head-space. In-fact, as long as there is a fluid that the oils can dissolve into, they will naturally, albeit more slowly, move into the head-space by diffusion. Venting the head pressure just allows this to keep happening, not venting or even starting with pressure will yield the same aroma losses due to diffusion.

      Another thing you referenced is the foam losses. These are not due to the act of foaming itself, but rather that as the head builds in the tank, it will leave all of those hydrophobic compounds in a layer on the inside of the brite tank. If you don't foam up really high, they stay in the beer.

      Here is an article on how essential oils are measured in the lab, they sample headspace gasses. http://pubs.acs.org/doi/abs/10.1021/...nalCode=jafcau

      Its all physics, chemistry is just applied physics(some physicist told me this), diffusion from high concentration to low concentration, polar vs non-polar solvents and chemicals, and just plain losses from stuff sticking to the tank.

      Comment


      • #4
        Here is some essential reading on the topic From Charlie Bamforth:

        Comment


        • #5
          Originally posted by jebzter View Post
          It comes down do a concentration gradient. When you are carbonating and venting, there is always fresh co2 coming through the beer and leaving, taking aromas with it. Though you start at 0psi and climb to saturation pressure gradually, the concentration of aromas in the head space reaches an equilibrium where the balance of the oils in the beer and oils in head-space gasses stays constant. You are correct that just because the beer isn't foaming aggressively doesn't mean that aromas aren't moving into the head-space. In-fact, as long as there is a fluid that the oils can dissolve into, they will naturally, albeit more slowly, move into the head-space by diffusion. Venting the head pressure just allows this to keep happening, not venting or even starting with pressure will yield the same aroma losses due to diffusion.

          Another thing you referenced is the foam losses. These are not due to the act of foaming itself, but rather that as the head builds in the tank, it will leave all of those hydrophobic compounds in a layer on the inside of the brite tank. If you don't foam up really high, they stay in the beer.

          Here is an article on how essential oils are measured in the lab, they sample headspace gasses. http://pubs.acs.org/doi/abs/10.1021/...nalCode=jafcau

          Its all physics, chemistry is just applied physics(some physicist told me this), diffusion from high concentration to low concentration, polar vs non-polar solvents and chemicals, and just plain losses from stuff sticking to the tank.

          Great information thanks a lot! In your experience how have you managed to carbonate a beer in BBT losing the least amount of aroma and LTP's?

          This week I have been experimenting adapting the classic carbonation forumla from the carbonation charts (using temperature and head pressure). If they are successful I will share but in short by adding a certain amount of top pressure through the side arm of the BBT then carbonating through the stone at only a slightly higher pressure in an attempt to stem the quantity of co2 existing the beer into the head space and instead being forced back in the beer. I'll add that this method should not require spunding out any CO2. But Ill keep you posted if anything interesting comes up!

          Thanks again

          Chris
          Beavertown Brewery

          Comment


          • #6
            Originally posted by TiminOz View Post
            Here is some essential reading on the topic From Charlie Bamforth:
            http://www.mbaa.com/store/Pages/19002.aspx


            Great paper man thank you for sharing!

            Comment


            • #7
              Flowmeters. We carbonate at a very consistent rate, 4 scf/h max. This gives us a gentle carbonation over 12 hours. As far as aroma goes, just maximize how full the brite is and then keg it out as fast as you can. You will always lose some to the headspace it's inevitable, but the more you can minimize how long the beer is exposed to lower concentrations of aromas in the headspace gas the better.


              Originally posted by CLew92 View Post
              Great information thanks a lot! In your experience how have you managed to carbonate a beer in BBT losing the least amount of aroma and LTP's?

              This week I have been experimenting adapting the classic carbonation forumla from the carbonation charts (using temperature and head pressure). If they are successful I will share but in short by adding a certain amount of top pressure through the side arm of the BBT then carbonating through the stone at only a slightly higher pressure in an attempt to stem the quantity of co2 existing the beer into the head space and instead being forced back in the beer. I'll add that this method should not require spunding out any CO2. But Ill keep you posted if anything interesting comes up!

              Thanks again

              Chris
              Beavertown Brewery

              Comment


              • #8
                Chris--check out this post; I found it very helpful. Gitchegumee is the go to guy on carbonation here. http://discussions.probrewer.com/sho...l-to-2-volumes


                Sent from my iPad using Tapatalk

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