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Harvesting yeast from bottom of keg

Discussion in 'Homebrewing' started by Seany, Jan 23, 2013.

  1. Has anyone done this. I brewed a batch using yeast harvested from a commercial brew. I was not overly happy with the fermentation or the initial sample flavours...so I foolishly dumped the yeast. Well move forward a few weeks and this beer is awesome. I want to use this yeast again and the commercial beer is not easy for me to obtain. I was thinking of trying to harvest the yeast from the bottom of my keg. I figured this would be much like harvesting from a bottle. Any thoughts, ideas or experiences to share. Thanks.
  2. NiceFly

    NiceFly Savant (375) Tajikistan Dec 22, 2011

    Probably depends on how many PSI they were subjected to in the keg.
    Don't quote me but I think they start to die off over 20 PSI. Don't know where I heard that, probably on the internet.
  3. Now that you mention it, that sounds familiar. I'll have to look into that. Anyone else know about this?
  4. WickedSluggy

    WickedSluggy Savant (425) Texas Nov 21, 2008

    If the source beer is still available, I would just repeat the propagation from bottle. After all, you successfully propagated for the first batch.
  5. It couldn't hurt to try. You lose nothing by harvesting some of that yeast and making a starter to see if it's still viable. And 15 psi isn't that much pressure. If yeast can survive the pressure of fermenting in a 500BBL conical tank, I'd expect they can survive in a corny keg under a bit of pressure. Only thing I'd be worried about is the carbonation in the beer in the keg you're harvesting from. CO2 can be toxic to yeast in high enough concentrations.

    Still, you really lose nothing by trying.
    warchez likes this.
  6. pweis909

    pweis909 Advocate (715) Wisconsin Aug 13, 2005

    Some possible issues might be that the residual yeast are effectively a product of artificial selection. The could be the offspring of late floccers for example. You could find that the next batch has slightly different properties, maybe higher attenuation, for example. I wouldn't let that stop me from using it just as you suggest. It's only a possibility and not one that seemes too risky. If you are concerned about the pressure issue (I have no idea), make a starter to establish whether it is healthy before introducing to a wort,
  7. I did this once when a starter didn't turn out as planned. I recovered some Wy1945 from the dregs of an empty keg of brown ale and used it to make a starter for an old ale. The yeast was plenty viable.
  8. rocdoc1

    rocdoc1 Savant (405) New Mexico Jan 13, 2006

    A lot would depend on how old the keg is, I think anyway. Most of my kegs last 3-6 months and I'm not sure how viable that yeast would be. But a starter is cheap and easy so I would give it a try. In fact I might try this when my hefeweizen finally kicks.
  9. Am I not crazy to think that whatever PSI is required to get to X vols of CO2 in a keg is the same as in a beer bottle? Something about partial pressures or the like...
  10. skivtjerry

    skivtjerry Advocate (540) Vermont Mar 10, 2006

    I think you are not crazy. If you've ever grown a starter from a corked Belgian bottle, you know they can handle a lot of CO2. Not an issue.

    OP: as long as the keg wasn't left in a hot garage or something you should have viable yeast, without too much mutation or extreme selection, unless you've gone several generations prior to this beer. Step it up gently and it should get there. I have revived 4 year old slurry successfully, and the beer was fine (not that you should do this; it was just an experiment).
  11. VikeMan

    VikeMan Champion (750) Pennsylvania Jul 12, 2009

    Just guessing, but I think Nicefly may have been talking about fast force carbing at gimongous pressures. So the beer and the yeast would feel abnormally high pressures (not actually dissolved volumes of CO2) during that time. I have no idea where the danger zone would start though.
  12. NiceFly

    NiceFly Savant (375) Tajikistan Dec 22, 2011

    I just looked it up. Paragraph 5 states toxicity begins at 35 PSI. So not the 20 PSI I stated above.
  13. Thanks everyone for your input. My keg should "kick" within the next couple of weeks which will make about 6 weeks total and I do not force carb at extremely high pressure, so I will certainly give this a go. Do you think I could go right to a 1.5 liter starter since there should be a good amount of yeasties in there? Thanks again.
  14. "They can't put anything on the internet that isn't true."
    NiceFly likes this.
  15. skivtjerry

    skivtjerry Advocate (540) Vermont Mar 10, 2006

    There will be a lot of yeast but not all of it will be alive/healthy. I'd maybe start with 500ml and step it up when I saw activity.
  16. mnstorm99

    mnstorm99 Advocate (535) Minnesota May 11, 2007

    I don't see why you can't make a starter to find out either way.
  17. Thanks again guys. I will start at 500ml. Look forward to trying this. I thought maybe I would prepare starter wort, cool and dump into keg, swirl around, then pour out the sanitized dip tube hole into mason jar. What do you think?
  18. I'm curious how to best to that as well ;)

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