Storing Yeast

[12stones]

Hey y'all... I'm wondering how long yeast can be stored once washed and placed in sanitized jars. I've heard anywhere from a couple of weeks to up to a year. What's the best way to store it for best longevity? Should it just be washed or rinsed or both prior to storage? Never harvested my own yeast yet, but I'd like to. There's also some local craft brewers that will share theirs and I'd like to take advantage of that as well.

[philbrasil]

That´s also a question I have. In Jamil´s book "Yeast: Practical Guide..." he says to use this harvested yeast in no more than 1 or 2 weeks. I think it´s because the active population is healthy and ready-to-go. Once the weeks/months have passed, they go into dormancy and won´t be as healthy as they were.

I know that to pitch this old yeast into a new beer won´t be good, exactly because of the unhealthy aspect, but my question is if I can maybe re-use that yeast, by doing a new starter, without worrying about off-flavors or mutation. Or in extreme cases, if I plate this harvested yeast, select a good colony and grow from that, will I have a good non-mutated source of yeast?

[spiderwrangler]

Hey y'all... I'm wondering how long yeast can be stored once washed and placed in sanitized jars.

Uhhhh... It depends.

Assuming you are talking rinsing and not acid washing? Check out Ozwald's sticky post on the subject of yeast rinsing.

[Ozwald]

That´s also a question I have. In Jamil´s book "Yeast: Practical Guide..." he says to use this harvested yeast in no more than 1 or 2 weeks. I think it´s because the active population is healthy and ready-to-go. Once the weeks/months have passed, they go into dormancy and won´t be as healthy as they were.

I know that to pitch this old yeast into a new beer won´t be good, exactly because of the unhealthy aspect, but my question is if I can maybe re-use that yeast, by doing a new starter, without worrying about off-flavors or mutation. Or in extreme cases, if I plate this harvested yeast, select a good colony and grow from that, will I have a good non-mutated source of yeast?

This I really didn't cover in the rinsing post. I have jars in the back of my fridge that are years old with plenty of viable cells. I haven't put them under the microscope yet, mostly cause I don't need those strains for anything at the moment, but they'll get there soon enough. Throw that 1-2 weeks garbage out the window, it's simply not true what-so-ever. Regarding off-flavors, this goes hand in hand with how clean you are while rinsing. Some mutations can do it to, but be more worried about contaminants.

As for the mutation aspect, first remember mutations aren't necessarily bad. If the yeast didn't mutate, we wouldn't have brewers yeast at all, let alone the multitude of strain options. You're exactly on track by growing up a new colony. The most important thing to remember is this yeast has been dormant for a while & is going to be very fragile as well as very susceptible to shock. They're not going to have much in the line of reserves left. Do very very very small starters to nurse them back to health before trying to get them to propagate. This would mean starting out with a 1.010-1.015 wort in a volume that's about half of what you'd be using for propagation. You can take that starter & step it up to a 1.020-1.025 wort of that same small volume. Then you could start to propagate, but again, keep it light & small. Don't step right to a 2L 1.040. This is along the lines of how you treat washed yeast & part of it's higher expense. If you're trying to resurrect yeast more than a couple months old just to save some money, go buy a vial.

[philbrasil]

Thanks. I guess that slants would be in even better condition than a 3 quart jug of yeast, right? Personally I would like to have a few strains on hand because:

1) can´t brew a particular style with dry yeast.
2) not always available, and when they are, they are not in the best of shapes. Plus at $15 a pop, they are kind of expensive.

I have kept in the past some slurries for 2-3 months, but never past that. Maybe I should do some experimenting now that you said that..

[12stones]

Thanks for the responses y'all. This helps. And, I guess I did mean rinsing.

[WoodlandBrew]

Yeast will maintain it's viability for months in the refrigerator, and according to "The Practical Brewer" if stored correctly can be used after six months. Some people have successfully used yeast that has been in the refrigerator for more than a year.

That said, there is more to yeast health than viability. After a short period of time the sterol reserves of the yeast are depleted. To get the yeast going you will need to oxygenate your wort well, or use a starter.

To see the details of yeast viability stored in the fridge see this:
http://woodlandbrew.blogspot.com/2012/1 ... ility.html

[maltseeker]

To add to this, for yeast that has been stored for 2 weeks the Mr. Malty calculator says the viability would be around 80%. The "Yeast" book suggests not pitching below 90%. To get the best beer would you recommend: 1) pitching more slurry to account for the viability - per the caclulator, 2) doing a "Revitalization" step as explained in the book, or 3) using the yeast slurry to make a starter and then pitching?