To use harvested yeast or not

[rmr9]

I brewed a nice SMaSH lager all the way back in April. I decided to overbuild my starter and save some yeast that I split into 2 mason jars each with about 100B cells. Away it went into my fridge where I sort of forgot about it. I’m hoping to brew a batch sometime in September and I’m wondering if it’s worth using this slurry or if it’s just past its prime and ready to start fresh. Thoughts?

 

[odie]

I've used year old saved slurry without issues. Just direct pitch into the wort and it will wake up.

 

[rmr9]

Thanks for the feedback! I don’t brew as much as I would like to so I obsess over the details of each batch. I’ve never saved yeast before so it’s sort of taking a chance in something new for me. Maybe I’ll throw together a 2 liter starter using both slurries to build up a big pitch.

 

[CascadesBrewer]

Maybe I’ll throw together a 2 liter starter using both slurries to build up a big pitch.

That is what I would do.

 

[Jeroen79]

I would also create a starter, and if it then smells ok pitch it!

 

[DBhomebrew]

I'd build a starter too. But not with all of the slurry. Much of it is old, tired if not dead yeast. You don't need much to start a new colony and that new colony will be... New.

There are starter calculators if you want to get fancy.

 

[IslandLizard]

Definitely build a starter.
If you started out with and est. 100 billion cells in each jar, after 4 months there's probably around 40-50% viable, say 50 billion in each.
http://www.brewunited.com/yeast_calculator.php
BTW, how large are those 2 jars?
How much slurry (volume) do you think is on the bottom of each jar?

 

[IslandLizard]

I'd build a starter too. But not with all of the slurry. Much of it is old, tired if not dead yeast. You don't need much to start a new colony and that new colony will be... New.

I've often made starters with much older slurries, never thought much of the dead yeast present being a problem.
Is it?

 

[DBhomebrew]

I've often made starters with much older slurries, never thought much of the dead yeast present being a problem.
Is it?

At the minimum, I scrape off and discard any grayish matter on top. Since I've moved away from harvested yeast cake to top-cropped barm, I don't have that problem and often use the whole thing.

I reread the OP just now. Overbuilt starter is probably just as good.

 

[rmr9]

Definitely build a starter.
If you started out with and est. 100 billion cells in each jar, after 4 months there's probably around 40-50% viable, say 50 billion in each.
http://www.brewunited.com/yeast_calculator.php
BTW, how large are those 2 jars?
How much slurry (volume) do you think is on the bottom of each jar?

My rough conservative guess would be about 30-40mL per jar. Given a pretty steep loss of viability I may have to build a 2 step starter….or invest in a 4L flask. I plan to use this in a mid-range märzen.

 

[Conehead]

When I buy supposedly new yeast it is usually around 4 months old anyway. I bought a 500 ml and a 1 L flask to build it up. Same thing with your over build.

 

[odie]

isn't dead yeast cells basically nutrianet for live yeast cells?

 

[IslandLizard]

isn't dead yeast cells basically nutrianet for live yeast cells?

To some extent dead yeast can provide nutrients to the live yeast, yes.
Dead yeast in large amounts can cause off flavors associated with (yeast) autolysis.