Viability of harvested yeast

I have a California Common fermenting and am considering harvesting the yeast for another batch. I may not get back to this style for several months, though. If I harvest the yeast, how long will it be viable?

Thanks, Pulse. That is exactly the method I plan to use, but I didn't see any info on how long it will keep. I don't want to waste time harvesting if the yeast won't be good to use months from now.

I see one guy that used one that was 3 months old. I don't know if it would "go bad" if it was stored. You want to adjust your pitching rate for how old it is though. Mr. Malty's pitching Calculator allows for this variable.

The rate of loss of yeast viability varies with several factors including yeast strain, environmental stress on the yeast, storage conditions, etc. Unless you can do a viability test (stained cells under a microscope) its hard to tell. I use just a rule of thumb that if I need to reused stored yeast (this is refrigerator stored yeast) within 4 - 6 weeks. Much longer than that and I just buy a new starter. When I do use refrigerated yeast, I use it for making a starter so I am pitching viable, actively growing yeast.

Dr Malt

I've seen a few folks talking about harvesting from a starter. That is to say, they make a large starter and pitch half and save the other half. If this is a special yeat (hard to find or one that you've been using for generations) you could store it for few months then make a starter and save yeast harvested from that. It's more work than just letting it sit, but I would think that this way you would be able to know that the yeast in storage is still viable since it's new yeast every few months.

I've used washed yeast that was 6 months old with no major problems. There is no doubt that yeast viability suffers with age, but at 6 months there were still viable cells in there & the fermented beer tasted great. The only think that's important to remember is that because viable is knocked way down, you'll have to build it back up. When I used the 6 month old washed yeast, I built it back up by increasing the size of my starter a couple times. I have one more jar of that washed yeast that I'll use at 8 months old next month. I'll be sure to make sure that the yeast starter smells & taste normal so I know nothing funky has happened to my yeast, but if it does start, I'll know that there were still viable cells.

Bobby M recently did a test on year old stored yeast here; https://www.homebrewtalk.com/f13/testing-limits-yeast-viability-126707/

And my LHBS cells outdated tubes and packs of yeast dirt cheap 2-3 dollars each and I usually grab a couple tubes of belgian or other interesting yeast when I am there and shove it in my fridge. and I have never had a problem with one of those tubes. I usually make a starter but I once pitched a year old tube of Belgian High Gravity yeast directly into a 2.5 gallon batch of a Belgian Dark Strong, and after about 4 days it took off beautifully.

Same with jarred yeast.

With any stored, old yeast you just need first to apply the "sniff test" if it smell bad, especially if it smells like week old gorilla poop in a diaper left on the side of the road in the heat of summer.

Then make a starter, and if it takes off you are fine. The purpose of a starter is to reproduce any viable cells in a batch of yeast....that;s how we can grow a starter form the dregs in a bottle of beer incrementally...and that beer may be months old.

Even if you have a few still living cells, you can grow them....That's how we can harvest a huge starter (incrementally) from the dregs in a bottle of some commercial beers. You take those few living cells and grow them into more.

If yeast can be grown from a tiny amount that has been encased in amber for 45 million years, 45 million year old yeast ferments amber ale we really don't need to sweat too much about yeast viability....

we just need to think in terms of making starters. Viability isn't really an issue if you are reproducing a lot of healthy cells.

Revvy said:

If yeast can be grown from a tiny amount that has been encased in amber for 45 million years, 45 million year old yeast ferments amber ale we really don't need to sweat too much about yeast viability....

we just need to think in terms of making starters. Viability isn't really an issue if you are reproducing a lot of healthy cells.

Click to expand...

Thanks for the link Revvy! I always knew that the yeasts were much more hardy than most folks give them credit for, and this just proves the case. Handle with care and treat them like a beloved pet and they will work for you every time.

I searched around a little, could not find a definite answer, so not wanting to start a new thread, this thread seemed a good place to start.

I brewed on Sunday, and not planning to do so, I did not make a starter for my 2 month old wyeast 1056 harvested yeast. Now Tuesday, I have no visible activity in my carboy. Should I wait a while longer? Should I take my two other mason jars with harvested yeast and pitch them? It is a lower gravity pale ale, around 1.050 og.
Thanks

What if you don't do a yeast starter? I pitched about 1-1 1/2 old yeast without yeast starter! Do u think I'll run into problems of yeast not kicking off?