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  • Oxygenating wort in the tank

    Hello All,

    I'm having trouble locating a calculation to properly oxygenate my wort. I can't do it inline, I have a stone but our heat exchanger underserves our system, our knock out is so slow that if I try to oxygenate the wort it just foams up and flies out the blow off arm. In the interest of saving volume, I want to oxygenate in the tank immediately after knock out. I have a flow meter for my 02 tank. Generally knock out temp in the tank is 82F, and comes down to 66F within 30 minutes. They are 7 bbl fermenters, we're probably getting 7.5 bbls in there. I have a stone to hook up to the tank, I just need to know what rate to oxygenate at for how long. I'm using pure 02. I've seen numbers like 1L/minute, but never with temp taken into account. If anyone can point me in the right direction it would be greatly appreciated!

  • #2
    Just go for it

    I know there are people out there that are going to argue with me about this. However, over oxygenation is not really a concern. Just hook it up at 1-2 L/m for about 25 mins and go to town. The yeast consume all the O2 they need within the first 9 hours after the pitch and any excess with come out of solution anyway. Under oxygenating is a much larger concern in my books.

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    • #3
      Ya, So using too much O2 is actually a pretty big deal in a lot of beers. It causes over reproduction in many cases which causes higher vicinal diketone rates (diacetyl). This can change the profile of a lot of beers, especially lagers, and if you are using a yeast that creates a lot of diac, such as a British yeast strain, they will not eat it all out during aging most of the time. If I was you, I would find a way to time O2 rate per flow, and just add it after knockout through where you already have your stone. I'm sure you can shut a valve, if you don't have a check valve, so that the O2 doesn't go back towards your brewhouse. We have dialled in most of our beers, so we get a consistent O2 reading after knockout, but if you don't have an O2 meter, I would use the rule of thumb: 3L/min(1 min per bbl). Then I would adjust as necessary. Obviously you need more for higher gravity beers, and will need to adjust depending on yeast, but its better to have some sort of a starting point.

      Hope this helps.

      Randy Jensen
      Head of Brewing OPs
      Molo Brew Ă…lesund Norway

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      • #4
        We only recently (last 6 months) started adding pure O2 as well, with no O2 meter. We add via a stone on the cold side of the counter-flow chiller en-route to the FV. You can see some 02 in the top part (Say top 20%) of the sight glass as it enters the FV. We run 2.5 L/Minute for 30 Minutes for our single and double 10-13 BBL Batches. I can't say in confidence I taste a difference in the two. Note we only use new dry yeast, so Aeration is not really that crucial, but I taste no detectable change in diacetyl from when we didn't use aeration. We are seeing slightly shorter lag times, and slightly quicker fermentation times and an ever so slight increase in attenuation. Seems like a quicker starting, more consistent fermentation and taste since adding the 02.

        The reason we aerate dry yeast is that I do plan to re pitch eventually, even if only for our 2 BBL Pilot system.

        Without the tools needed I guess I experiment, note the details, taste and compare. I know enough about yeast not to starve them of oxygen and will continue to give them hopefully adequate 02 based on my gut instinct and whatever else I have to work with that day.
        Leigh Davison
        Head Brewer, Partner & Beer Alchemist @ Schoolhouse Brewery
        Windsor, Nova Scotia
        "The Beer with Class"

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        • #5
          If you are using fresh dried yeast every time, then the suppliers reckon there is no need for wort oxygenation except perhaps for some very high gravity beers.

          The problem with any aeration / oxygenation system is that unless you can guarantee you have fully dissolved it, then you really have no idea how much oxygen has been dissolved. I worked with one global brewing company, and they haven't actually any idea how much oxygen they dissolve, but they have a very standard process, and know that works well for them and their yeasts. When we tried to use pure oxygen when we started brewing their beers, the yeast didn't respond well at all, but as soon as we used their methods - all was well. Using an oxygen meter to check was a waste of time as the wort was supersaturated immediately after wort transfer, and once the undissolved gas had risen to the top of the wort, the yeast had already mopped up variable amounts of oxygen - the results were different every time. But the beer was (is) incredibly consistent.

          What I am really trying to say is that you will not find a calculation that will allow you to determine how much oxygen will dissolve when bubbling air or oxygen into an FV. Any calculations assume total solution of the gas, which can only be effectively achieved at very high turbulence levels / small gas bubbles and normally high pressure. So once you find that bubbling air at X litres / minute into Y litres wort at Z gravity produces the flavour you want, and the yeast performance you want, then stick to that method religiously.

          Many, perhaps most re-pitched yeasts fermenting to produce 5% ABV beers will perform happily with air saturated wort, and don't need pure oxygen. If producing higher than that, then a consistent second aeration after say 12 hours will usually work well.
          dick

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