Harvesting yeast from bottom of keg

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

  1. Seany

    Seany Initiate (183) Sep 27, 2005 Quebec (Canada)
    Beer Trader

    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 Aspirant (275) Dec 22, 2011 Tajikistan

    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. Seany

    Seany Initiate (183) Sep 27, 2005 Quebec (Canada)
    Beer Trader

    Now that you mention it, that sounds familiar. I'll have to look into that. Anyone else know about this?
  4. WickedSluggy

    WickedSluggy Devotee (400) Nov 21, 2008 Texas
    Beer Trader

    If the source beer is still available, I would just repeat the propagation from bottle. After all, you successfully propagated for the first batch.
    jbakajust1 likes this.
  5. darknova306

    darknova306 Initiate (0) Jan 13, 2005 New York

    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 Poo-Bah (1,587) Aug 13, 2005 Wisconsin
    Supporter Subscriber

    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,
    jbakajust1 likes this.
  7. mugs1789

    mugs1789 Initiate (184) Dec 6, 2005 Maryland

    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 Aspirant (268) Jan 13, 2006 New Mexico

    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. kjyost

    kjyost Initiate (0) May 4, 2008 Manitoba (Canada)

    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...
    Lukass and ChrisMyhre like this.
  10. skivtjerry

    skivtjerry Zealot (523) Mar 10, 2006 Vermont

    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).
    Lukass and ChrisMyhre like this.
  11. VikeMan

    VikeMan Meyvn (1,386) Jul 12, 2009 Pennsylvania
    Beer Trader

    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.
    ChrisMyhre likes this.
  12. NiceFly

    NiceFly Aspirant (275) Dec 22, 2011 Tajikistan

    I just looked it up. Paragraph 5 states toxicity begins at 35 PSI. So not the 20 PSI I stated above.
    ChrisMyhre likes this.
  13. Seany

    Seany Initiate (183) Sep 27, 2005 Quebec (Canada)
    Beer Trader

    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. clearbrew

    clearbrew Initiate (0) Nov 3, 2009 Louisiana

    "They can't put anything on the internet that isn't true."
    ChrisMyhre and NiceFly like this.
  15. skivtjerry

    skivtjerry Zealot (523) Mar 10, 2006 Vermont

    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 Initiate (0) May 11, 2007 Minnesota

    I don't see why you can't make a starter to find out either way.
  17. Seany

    Seany Initiate (183) Sep 27, 2005 Quebec (Canada)
    Beer Trader

    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. Jaysus

    Jaysus Initiate (154) Jan 16, 2003 Pennsylvania

    I'm curious how to best to that as well :wink:
  19. chavinparty

    chavinparty Initiate (189) Jan 4, 2015 New Hampshire

    Sounds like an awesome plan let us know how it goes. The more saved yeast the better
  20. VikeMan

    VikeMan Meyvn (1,386) Jul 12, 2009 Pennsylvania
    Beer Trader

    I think you mean how it went.
  21. chavinparty

    chavinparty Initiate (189) Jan 4, 2015 New Hampshire

    Alright captain grammar
    Oh I see it was years ago... Lol my bad
    Lukass likes this.
  22. AngryDutchman

    AngryDutchman Aspirant (260) Aug 8, 2015 Pennsylvania

    Life finds a way. Feed them graciously and give them time.
  23. Mitchellrhen

    Mitchellrhen Initiate (0) Jan 2, 2016 Colorado

    I've done this once actually. It's gonna sound strange but what I did was shake my keg(softly) to rustle up as much yeast as I could. Draughted out some beer from the keg into a sanitary mason jar and closed it up and chilled it. (albeit this beer was not carbed yet, only pressurized) the result was a nice thin yeast cake at the bottom, just enough for a starter, and it worked great the next time around. The yeast was from a propagated Trappist strain that I had built slowly from a bottle fermented beer, and it was the first time I had used it to fully ferment a 10 gal batch. It tasted great and fermented quickly, the 1st, 2nd, and 3rd time around, but after that, seemed to lose its complexity and I retired it. Currently I am repropogsting the strain in hopes to start again:slight_smile:
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