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Yeast propagation technique question

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  • Yeast propagation technique question

    For the sake of discussion, let’s say I’m propagating yeast using a 10 fold step up:
    1ml – 10ml – 1L – 10L – 100L
    But, my largest propagation tank is 10L and I still need more yeast. My plan is to pour off the wort from the 10L and replace it with fresh wort, repeating this process until I’ve built up the required cell count.
    Are there any problems with this method? Should I cold crash the starter before pouring off so I don’t send the suspended yeast down the drain? Or am I better off keeping the yeast active and losing some?
    Thanks for any input
    Dave

  • #2
    Thanks for the input. I only intend to replace the media 1 or 2 times for my purposes. Do you think a cold crash between each addition is a good idea?
    Dave

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    • #3
      With successive 10L propagations, I think you'll hit a wall in terms of final cell count that won't come anywhere near a 100L propagation. I'm also starting to believe, although I don't have data to back it up, that the conventional wisdom of "make each step 10x the volume of the previous step" is based on propagations with continuous aeration (where the yeast population that a given propagation can support is limited primarily by available sugar instead of both available sugar and available oxygen). If the final cell count at the end of a normal brewery fermentation is about 3x the cell count at the start of fermentation, why would a once-aerated "propagation" - which only differs from a normal brewery fermentation in size - result in a higher growth rate?

      My advice that if you can't build up enough cells on your own, spend the money to buy enough yeast from a lab. No amount of up-front savings will make up for the cost of lousy fermentations.

      Joe

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