RmikeVT

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I recently siphoned my beer into a keg from my fermentation vessel. I left behind the yeast/trub. I was planning on washing some yeast but it was getting late and playoff baseball was on, so I put it off and snapped the lid back on the bucket. So, for my questions:

Can I come back 3-4 days later and wash the yeast and re-use, or should I toss and just buy the yeast again and in the future plan on washing immediately after I remove the beer?

osagedr

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People will come on here and say "Sure, just use it! I use my ___ day/week old yeast all the time and my beer turns out great!"

A local brewery owner/brew master says he won't use yeast slurry stored any longer than a day at 34 degrees.

It really comes down to how much you care about the quality of your beer.

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Minjin

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As long as there is still beer on top it should be good for a day or two, any more and I wouldn't risk it.

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kingwood-kid

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3-4 days is a long time. Not that it can't work, but it might not work exactly how you want. However, there should be more than enough yeast at the bottom of the keg, assuming the keg was thoroughly cleaned and sanitized.

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dawgmatic

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You can use chlorine dioxide to kill the bacteria if that bothers you. But that won't kill any wild yeast that got in there.

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KBentley57

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4 days is too long to leave it set, basically open to the air, and not expect anything bad to happen. It would probably ferment, but who knows what it would be like. I would collect the yeast/trub and wash right after racking, and immediately put in the fridge, personally. I would hate to see you waste all the effort on brewing a batch, only to be ruined because of your own laziness

RmikeVT

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Thanks for all the feedback. I decided not to use the yeast as I would hate to ruin a batch of beer. I do have a follow up questions, though.

Why does removing lets say 5 gallons of the 5.5 gallons in the fermentation bucket have such an impact on the ability to wash and re-use the yeast? Assuming I remove the lid to rack and then snap the lid right back on.

I can leave the full amount in for lets say 4 weeks and 4 days and the yeast will be fine; but I rack after 4 weeks and leave 0.5g of beer behind for 4 days and it is at least debatable to re-use the yeast. Do you see where I am going with this?

KBentley57

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Yes, I can see the logic - its enveloped by beer either way. However, in one situation you've already opened the fermenter, siphoned the beer out, and replaced 5 gallons of volume with "dirty air", that has 4 days to inflict any damage it can. We're not saying it will, we're just saying it might.

william_shakes_beer

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When the fermenter sits full of beer and unopened it creates a slight positive pressure from the co2 generated by fermentation. Venting the excess co2 is the reason we use an airlock. Once you open the fermenter and pull the beer out you loose the positive pressure and co2 blanket and bacteria can get back in. Next time, if you want to keep the cake a few days, try adding a starter mix and put the airlock back on. You will begin a brief fermentation and re-establish the pressure and co2 blanket. Its easier still to just wash at the end of the bottling session or, like I do, harvest from the starter and pour the cake down the drain..

Zacher

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If you didn't swirl it up it probably would have been fine so long as it had a coating of beer on it.