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Thread: Reusing yeast from underpitched batch

  1. #1
    Join Date
    Nov 2016
    Location
    Sweden
    Posts
    8

    Question Reusing yeast from underpitched batch

    Hi all!

    We by mistake underpitched a 20hl batch of 1.047 (11.7P) wort that stalled at 1.026 (11.9P)
    (Forced ferment test down to 1.007 (1.8P)), lesson learned, but do you think that it is possible
    to harvest the yeast and use in a new batch with good results?
    (I have the means to do cell counts and viability).

    Cheers!

  2. #2
    Join Date
    Oct 2013
    Location
    Dallas, Bangalore and soon Goa
    Posts
    154
    Quote Originally Posted by ridgeback View Post
    Hi all!

    We by mistake underpitched a 20hl batch of 1.047 (11.7P) wort that stalled at 1.026 (11.9P)
    (Forced ferment test down to 1.007 (1.8P)), lesson learned, but do you think that it is possible
    to harvest the yeast and use in a new batch with good results?
    (I have the means to do cell counts and viability).

    Cheers!
    You probably should have done the cell count and viability before asking, lol.

    Seriously though, the numbers probably won't look good. You can try propping the yeast up and get it going again, but a lot of dead cell mass isn't good for any beer. You would probably need a few steps to get this back to a "good" pitch. Lots of cell counting, and some time and ingredients. All on a chance.

    A lot would depend on why you stalled.

    Lack of oxygen? I have been able to get good results with 1/2 pitches (or "regular" for lagers) for most beers with a good aeration. If this was a cause, then you likely spent the energy from the yeast and made few new cells. Not likely to get going again.

    Glycol kicked on and made the yeast go dormant? Then you may still have good viability (although glycogen reserves are probably low). This is probably your best hope. Make some wort, re-pitch, and viability/count check. If you look better, then give it a shot.

    Wort too hot at pitch? Yeast is dead. No hope.

    1.026 is ~ 6.7*P, by the way.

  3. #3
    Join Date
    Nov 2016
    Location
    Sweden
    Posts
    8
    Thanks! Will do a count just to check, but a new pitch is ordered

  4. #4
    Join Date
    May 2012
    Location
    Livermore, CA
    Posts
    473
    If the yeast doesn't perform as expected in a beer, why would you think to propagate that problem? It won't get better. If it doesn't work out, especially on an OG under 1.050, it is clear that yeast are not healthy, dump it and start over. Unhealthy stressed yeast produce different flavors, different flocculation character, and they mutate like crazy.

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