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Thread: Using a Unitank to Pre-Build Yeast

  1. #1
    Join Date
    May 2019
    Location
    Springfield, MA
    Posts
    2

    Using a Unitank to Pre-Build Yeast

    Hello,
    I'm curious if anyone has done this or knows of someone who has? When we move up to the next size system we will have several 1bbl unitanks available. My thought was to use the carb stone of the unitank and send oxygen through it to mimic the action of a stir bar. The goal being to amp up the yeast production vs a non agitated fermentation.

    Would this work? Would I need to do anything to the oxygen to avoid possible contamination? Would the growth rate match that of a stir bar?

    Right now I pre-build our yeast weekly with 2 stir plates and two 6 gallon carboys. From the pre-build I pull off what I need to start all over the next week. So our yeast never see hops until it hits actual production batch. We never harvest anything from our production batches.

    Thanks,
    Todd

  2. #2
    Join Date
    Oct 2013
    Location
    Cincinnati, OH
    Posts
    438
    Pure oxygen is toxic to yeast (and other living tissues). It is therefore, in effect, sterile. A virus may be able to survive in a pure O2 environment, but it would not support the host, so the virus would cease to exist or “die”. I think at about 35-40ppm O2 you are starting to do some real damage. Some haters will knock on it, but a heavy duty aquarium pump and sterile filter disc would allow you to run constant air without over saturation of O2 (theoretically). Some will say you can’t get above 8ppm saturation with “regular air” however I have seen studies with a Venturi system that was able to achieve a consistent 13-14ppm.

    Rate of growth will not be linear compared to your stir plates. You will need to homogenize, pull samples, and count/stain to build a database. It will be affected by wort gravity, pitching cell density/viability, temperature, DO, and agitation.

    TBH, I’d suggest you just go to harvesting and re-pitching from your commercial batches as you can probably crop great healthy yeast a lot faster and less labor intensive than propagating it. For the same amount of labor you could plate/test the harvested yeast prior to re-pitch. A lot of vectors for contamination when propagating, and the risk reward factor should be considered. Fresh pitching dry yeast to each batch is another alternative that can still weigh into that decision as well.

    Yeast from hoppy beers is a way over rated concern. There will be minimal transference of bitterness and it will be imperceptible unless you are pitching a heavily dry hopped harvested yeast into a light lager, and even that would be suspect. It’s can actually be beneficial for the yeast to be acclimated to its environment and often generations 2-5 have the healthiest cell viability and density in my experience.

    Either way, if you go on with the propagation, I would suggest you skip the oxygen addition and instead feed aerated wort incrementally. You can measure the cell density and match the wort addition to reach an optimal cell density to promote continued growth. Basically too much sugar induces fermentation and too little starves the cells.

  3. #3
    Join Date
    Jun 2012
    Location
    BEMIDJI, MN
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    130
    +1 on everything UnFermentable said.

    We used to do a mix of yeast propagation plus harvesting when we were at the 3bbl scale. As we grew, we adopted cell staining and counting and our beers are better because of it. Put your time and money into a basic cell counting setup and a couple yeast brinks and take good notes - you'll be better off than trying to prop all your yeast in vessels that weren't designed for it.

    I also agree on the comment regarding harvesting from hoppy beers. We have harvested from our IPA many times and have had great ferments as a result. We put much more stock in the age of the yeast, how long it has sat under the beer and temp that it's at rather than IBU or hop oil load.

  4. #4
    Join Date
    May 2019
    Location
    Springfield, MA
    Posts
    2
    Thanks for all the awesome information guys.

    I am in to process right now of setting up all the stuff we need for counting and verification of true viable cells. I totally agree that doing that is a huge and important step.

    I guess since the pre-build model has been working really well for us I was looking for practical ways to keep that going. I haven't needed to buy any new yeast since we opened in November and each round of yeast smells as fresh and ferments just as good as the last. However, at this point I have no real idea of how many true viable cells I'm working with. Just good estimated based on experience and repeating the same process as exactly as I can.

    Plus I was looking at some information on yeast propagation systems for larger breweries, such as the Esau and Hueber Micro Prop, and got idea's about doing something like that on a budget. However, I'm guessing my understanding/knowledge about how that really works is a little lacking.

    So to clarify, when you pull yeast from a hoppy IPA batch you don't do any "cleaning" of the yeast? Just check the viability and re-pitch?

  5. #5
    Join Date
    Jun 2012
    Location
    BEMIDJI, MN
    Posts
    130
    Our preference is to harvest our house yeast, 1056/Chico/A-56, from our Blonde...low IBU, low ABV, nice clean yeast that is pretty much always available and healthy. BUT, when the production schedule is in a pinch we don't hesitate to harvest from our IPA, 15P & 55IBU, and see great ferments coming out of that beer as well.

    Our standard procedure for this beer is to drop it to 60F after attenuated and passed VDK and drop the yeast the next day prior to dry hopping. We will do our yeast harvest at this time as well, if needed. During all harvests we dump any remaining trub until we see nice creamy yeast flowing in the sight glass and then switch over to collecting in the brink. No cleaning/washing/etc.

    The only consideration when harvesting at this temparature is that the yeast will most likely have a fair amount of CO2 in it so it will foam a bit. We harvest by mass on a floor scale into 50L brinks and our standard harvest is 45KG. For anything that is foamy we usually cut it at 35 - 40KG so we don't blow yeast out the top of the brink. Also, having a bit of head space in the brink allows us to roll it on the floor a bit to homogenize the slurry prior to counting + allows us to vent the brink without yeast shooting out.

    We haven't experienced any flavor carry-over from the IPA harvests or even more flavor-intense beers either. We've even harvested 1318 from a smoked brown ale to pitch into a NEIPA and saw zero flavor carry-over from the pitch...although that one kept me up at night.

    Cheers,
    Tom

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