How long can you leave liquid yeast after the best-before date?

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Northern_Brewer

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It seems to be a regular question, how long before liquid yeast is dead or unusable. Well here's proof that you can revive liquid yeast that's nearly 5 years old, this was an out-of-date pack of WLP540 that I got from the old Hop & Grape ages ago, then with one thing and another I didn't get round to using it, then I was locked down the other end of the country to the fridge where it was, and so on. Anyway, last week I tipped it into a little 5% DME, then into 200ml of 10% DME, then this was a vitality starter again of 10% DME and within a few hours it was ripping through a small test batch of pale ale.

It's not ideal, don't do this - but it can be done.

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smcinco

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Yah I've only had one true DOA on a way out of date white labs older style tube. There's usually something in there unless it's been cooked, just gotta bring it back to life slowly!
 

McMullan

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I recently did an annual viability check on yeast stored on cryobeads at -20 for 5 years. Dead as dodos. I suspect storing at fridge temp is better than -20 long-term. I wish I'd stored some cryobeads in the fridge 5 years ago for comparison 🙄
 

odie

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those dates are uber conservative. Dry yeast several years old is often viable. Liquid if kept in the fridge is also likely to last long beyond the date.

But either way, unless it was in the 99 cent bin I would pass.
 

Pablo 54

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I have no problem using yeast that is several months beyond the "best by" date but 2017 is a little extreme. If you really wanted to play around with it, I would do 2 or 3 builds on it, 2L at a time. Just my $0.02
 
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