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Fresh Wort on a used yeast cake.

Discussion in 'General Brewing Techniques' started by RobinW, 13/9/18.

 

  1. RobinW

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    Posted 13/9/18
    I kegged a couple of brews this arvo and dropped a new cube of wort onto the yeast cake from one of the brews I just kegged. I've done this a couple of times before without issue.

    Question is, how many times can I repeat this before the yeast mutates and produces rubbish?
     
  2. Nullnvoid

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    Posted 13/9/18
    I can't comment on how many times you can do it as I don't know but you probably don't need the whole yeast cake. Unless it's a massive beer like a RIS you probably only need a couple hundred mls of yeast.

    From what little I understand that will have a greater impact than reusing again and again.
     
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  3. Schikitar

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    Posted 14/9/18
    I think you can push it between 6-10 times safely (but that really depends on your setup/cleanliness/strain), you do need to be careful what style you are dropping on what previous style etc., if looking to reduce potential off flavours. With similar OG's you really only need a cup of slurry, if you have a secondary clean fermenter, just scoop out a cup from the other one and drop on top of that..
     
  4. MrSheen

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    Posted 14/9/18
    I would be less concerned with yeast drift when placing wort directly onto a used yeast cake, and more concerned with the buildup of non yeast sediment, especially if you do significant dry hopping straight into the fermentor.
    Also when I do this, I try to keep oxygenation to a minimum as IMO there should already be an adequate amount of yeast from the previous fermentation, so it shouldn't need to undergo another aerobic growth phase. Though i'm keen to hear what others do.
     
  5. Naboo

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    Posted 14/9/18
    I would only re-use the yeast cake once if pitching straight in on top. Mostly for sanitation issues. I'm not sure how long you could guarantee the fermenter and krausen scum would stay sweet. Personally I'd rather gather some slurry, clean the fermenter and repitch the slurry if reusing the yeast. It may work better dumping it in on top if you've got a big beer going in second though.

    Purely hypothetical though as I've never pitched directly into the yeast cake. So take that with a grain of salt I guess.
     
  6. RobinW

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    Posted 15/9/18
    Cheers for the input.
    I always use starters, even for dried yeast, but I've only ever put a new wort cube on top of the 1st iteration.
    I'll try for 2nd iteration in about 10 days and see what happens. 6 to 10 iterations is way more than I thought.
    Better start drinking to make room :)
     
  7. Schikitar

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    Posted 15/9/18
    To be fair, that's more the case if you harvest and wash the yeast..
     
  8. RobinW

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    Posted 15/9/18
    I'm way to lazy for that caper. :)

    Spending 5 hours brewing is already a bit of a push.
     
  9. Danscraftbeer

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    Posted 16/9/18
    There are quite a lot of reasons not to pitch onto an uncleaned fermenter with the entire yeast cake. Its grimey with lots of crud and dead yeast too that can cause off flavors plus correct pitch rates have reason. Its about yeast growth and reproduction that goes with viability as well. An entire yeast cake can be up around 6 - 8 times as much yeast that is optimal. The yeast doesnt need to grow or reproduce that takes out a character in flavors too.
    Fresh yeast cake you may only need as little as ~60 - 100ml. All depends on your OG.
    and clean your fermenter! :)
     
  10. Black Devil Dog

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    Posted 16/9/18
    I regularly dump fresh wort on to the yeast cake, but I only do it once. It's not best practice, but it's practical for me and I'm satisfied with the results. I wouldn't do it any more than once though.
     
  11. Kingy

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    Posted 16/9/18
    The few times ive dumped onto a yeast cake I’ve come home to a Krausen explosion that’s blown the glad wrap off the fermenter.
    I used to collect a schooner of slurry to repitch but these days I just add a new packet of yeast. It only adds a few bucks to the total cost of a brew .
     
  12. Yobbo

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    Posted 16/9/18
    Ive seen a commercial Brewery in Ireland re-pitch over 128 times (Constantly fermenting and same beer)

    On a homebrew level, you can easily go over 10 if you are doing similar styles, there are many ways to do it, a cup of slurry is the easiest but not eh best.

    Taking 2 cups and rinsing the yeast is also a very good way to go as you are only pitching healthy viable yeast

    If you already do starters, freezing samples of yeast in test tubes and freezing them in Glycerine can lead to a large stock of pure strains (and generations of) is by far the best way.
     
  13. Yuz

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    Posted 17/9/18
    My W-34/70 is actually W-34/76 :cool: I just take away the collect bottle with all the crud, leaving some yeast on the bottom of the 'Saurus. There's minimal risk of infection as everything is under CO2 blanket and enclosed. And, since the yeast is "active" the fermentation starts within two hours - no lag whatsoever.
    Six batches is as far as I'd go however, I just like my fermenter clean.
     

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