Year Old Wyeast

After brewing this weekend I noticed the smack pack I purchased hadn't swollen 5-6 hours after being smacked. It was time to pitch the yeast so I sanitized the package and pitched like I normally would.

I never thought to check the date... The package has a date of March 2012. I figured I would give it 72+ hours and pick up another package (checking the date this time). This afternoon would have been 72 hours, so when I got home I verified no airlock activity or krausen formation and went back to the LHBS and picked up another 3638 with a mfg date only 15 days old. I popped the pouch on the way home.

Of course now that I am home the original 3638 took off... Should I just save the new package, or pitch it in anyway?

I think after a year you're at 10% viability on that pack. I'd pitch the new pack.

I think after a year you're at 10% viability on that pack. I'd pitch the new pack.

Click to expand...

+1

If it's a year old, it's doubtful there's enough viable yeast there...especially without making a starter. That is, unless it's a one gallon batch of 1.030 beer. Even if it ferments, the stress on the yeast might cause unwanted flavors. I'd pitch the new pack to be safe.

If you are worried about losing money, just wash the yeast after you're done, you'll get back more than you put in. Search for "washing yeast" if you haven't read about it yet.

You actually don't loose nearly as much viability as the popular calculators indicate. It was probably closer to 50%. The down side is that the yeast are more likely to mutate after a long period of stress, so it might not taste quite the same as you would expect, but it will make fine beer.

Here is some data on viability of refrigerated yeast:
http://woodlandbrew.blogspot.com/2012/12/refrigeration-effects-on-yeast-viability.html

Also, I don't recommend washing the yeast. Save it from the slurry, but washing just throws our 95% of the viable cells and selects the low flocculators.

Yeast washing:
http://woodlandbrew.blogspot.com/2013/01/yeast-washing-revisited.html

And how I save yeast:
http://woodlandbrew.blogspot.com/2013/01/yeast-storage.html