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Salvage yeast or ditch

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  • Salvage yeast or ditch

    Probrewers, we are up and running and our first lager was pitched at 48. I left and came back in the morning and the chiller crapped out sending temps up in the high 60's (tanks are single wall with internal coils). It stayed at that temp for 4-5 days until we could get it up and running. I slowly lowered the temp to low 50's and finished fermentation. Can I salvage this yeast? The beer isn't fit to serve but I'm wondering if it's risky to brink this yeast or dump it. 4 BBl system so not a huge loss but funds are tight etc. Thanks

  • #2
    You can rest assured the yeast will be fine. The beer would probably be fine too if you Lager it properly. It will likely have some higher esters still, however depending on the Lager this may not be an issue at all.

    Yeast is often propagated at much warmer temperatures than beer production ideals. We are looking to suppress or influence certain byproducts of metabolism during “beer making”. During propagation we are looking to increase cell numbers and vitality primarily. The yeast will be separated from the spent wort and any carryover flavors will be minimal at best. So basically decant your yeast harvest before repitching to help ensure minimal carryover. Check counts and vitability but they will likely be just fine.

    There are at least 4 commonly accepted fermentation schedules for lagering which I believe originally came out of a Vienna institute. They maybe listed in the Kunze. Basically warmer temperatures ferment faster and cause more flavor byproducts, however maturation also takes place at an increased rate allowing for quicker and more complete “clean up”.

    Condition the beer for a while and check back before dumping. Run forced VDK test to check it. Just my $0.02!


    • #3
      Sounds like a plan, thanks!


      • #4
        Depending on the yeast strain, the beer may be very sulphury, in which case the beer itself may not be considered drinkable. Some lager yeasts don't produce much H2S if fermentation temperature is above 16 C (about 60 F), others will make it stink. Either way, you should be OK to crop and re-use, but may have reduced yeast vitality / viability, and more to the point, may have to ditch this batch of beer.


        • #5
          Viability, Vitality, and cell density will not be negatively impacted by a 60*F fermentation. It will probably benefit those, if anything. You won’t be likely to see negative impacts on saccharomyces from temperature until you break over 82*F, and that is S Uvarum. S Cerevisiae will go up another 10-15*F before it hits the limit of effective growth and begins to have major issues. As stated earlier, by products can form, but if removed/decanted, you will not carry those over.

          I wouldn’t consider sulphur to be a major problem in most cases. You can add copper sulphate to to remove the compounds, or in the case of this finished beer you can probably just scrub the tank with CO2 to reduce the sulphur compounds. Obviously we know this won’t be the most exquisite batch ever produced, but I’d rather try scrubbing and running a sensory analysis before I just decided to dump it based on some sulphur. You can scrub quite a bit out, although you will admittedly loose other aromatic compounds as well. Probably won’t matter as much in the case of most Lager styles. Matters a lot more in estery ales and heavy hopped beers.

          But then again I actually prefer the slightest hint of sulphur in my lagers, so YMMV.