How long will refrigerated yeast last?

I was preparing to brew and made my starter; ran out of time and put the ready starter in the fridge until the next weekend.

Now, due to way too many unforseen circumstances... It's been in there for over a month now. Is this yeast still viable if I make a new starter? How long will yeast last after used in a starter and refrigerated?

Thanks!

If your yeast was not contaminated and it has been stored well it should be fine. The viability will be lower than if it was fresh but it will be high enough, especially if you give it overnight in fresh wort. People store washed yeast in the refrigerator for many months. Having it in wort is fine as long as other things aren't growing. The more spent the wort the better in terms of preventing other intruders.

I've possibly run up against a similar issue. Starter is going now for 24 hours, but I may have to shelve my plans for brewing saturday. Should I simply pour the starter back into sanitized tubes and put back in the fridge and use them like I would just starting the whole process over again when I'm ready to brew next?

I don't have much experience with yeast ranching. That said assuming you took the same precautions as if you had been washing yeast for storage I don't see a problem with dividing the starter up for long term storage. I'd count that as a generation towards the generally accepted 5 generation limit*. Or just decant and send the whole batch through a double round of step ups and use it as is. If you were really concerned with viability you could wash them before stepping back up or storing.

* The 5 generation limit I feel is heavily dependent on sanitation practices, ABV, and the amount of equipment the brewer has invested in being able to determine/count cell viability. If you can plate out healthy/ideal cells there's theoretically no generation limit. Microbiologists and practiced ranchers please correct/educate me if I'm wrong.

ctranchina said:

I've possibly run up against a similar issue. Starter is going now for 24 hours, but I may have to shelve my plans for brewing saturday. Should I simply pour the starter back into sanitized tubes and put back in the fridge and use them like I would just starting the whole process over again when I'm ready to brew next?

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Just keep the starter in what it's in now. If you can fit it in the fridge after covering it tightly I'd do that, but it won't be a big deal if the whole thing sits at room temp for a week or two. Yeast don't mind room temps too much, they just don't stay viable quite as long as they would at fridge temps.

Thanks everyone! I successfully brought the 2+month old yeast back thanks to you guys.

I brewed a full 1 liter starter; and put about 1/4 of it on top of the warmed yeast cake in a little 500ml flask. I tightly sealed and refrigerated the rest as I figured if it worked it wouldn't take long.

They were busily frothing up the flask within an hour or so so I knew they'd come back. Gave them a full day in there, then added the whole thing into the rest of the cold wort and gave them 3 more days. I cold crashed them overnight and brewed my ale today so let's hope they are happy and active in their new "home"

ctranchina said:

I've possibly run up against a similar issue. Starter is going now for 24 hours, but I may have to shelve my plans for brewing saturday. Should I simply pour the starter back into sanitized tubes and put back in the fridge and use them like I would just starting the whole process over again when I'm ready to brew next?

Click to expand...

I had the same problem. Simply cold crash the starter, when ready to use just let sit at ferm temp for two to three hours, then add some sanitized wort as if you were stepping it up. Proceed as usual.
Did that to my starter - had to put it in the fridge cause I couldn't brew when planned. Brewday was saturday, crazy activity mere hours after pitching.

I just had the same; after brewing as I stated above I pitched the still slightly cool yeast and I had it blowing out the airlock by morning about 5 hours later.