Old yeast from LHBS

[rmr9]

Just picked up an order from my LHBS and noticed when I got home (of course) that the manufacture date of my yeast is March 15 2023….which is a lot older than I would like. I wasn’t planning to brew with it until next month on top of that.

Is it worth trying to grow a starter to save back? It’s omega Bayern yeast if that changes anything.

 

[mashdar]

Personally, unless I know liquid yeast has has a short and immaculate chain of custody, I always make a starter.

I would wager your yeast is fine but cell count is a little lower. Probably fine after a starter.

 

[rmr9]

I was between contacting the LHBS for a replacement or building a 1 liter starter then saving down the slurry until I plan to brew next month, then use that slurry for a bigger starter.

My only concern is that if it doesn’t take off I’m up a creek and I think I’d have a less accurate idea of how much yeast I’d be pitching. I’d hate to underpitch my first crack at a helles.

 

[gewehr43sniper]

its fine

 

[mashdar]

IMO don't do the first starter until the week before, to limit time sitting around after breaking the sanitary packaging seal.

You could always ask the LHBS. Personally my LHBS is too far away for a pop-in, and I wouldn't want the owner to eat the wholesale price of the yeast. Maybe I'm too nice, though. (edit: maybe a discount/credit though?)

 

[rmr9]

Yeah it’s a 40 minute drive one way for me so definitely not a drive I’d like to make on any old day. I’d happily pay for the shipping though.

Any idea for how much viable yeast would be a reasonable estimate? All the calculators put it at 0%

 

[Bobby_M]

You didn't say what kind of beer it was going into. What's the batch size, OG target and fermentation temp you plan on?

 

[rmr9]

Good point. My thought was to brew a 5 gallon batch of helles at an OG of 1.050 and ferment at 50. I had I always intended to build a starter and aim for a pitch rate of 1.75M/mL/degree plato.

 

[Bobby_M]

The brewfather calculator puts it at 5% viable or 10B cells requiring 45 of those packs. The bigger issue though is that if you make the recommended 3 liter starter, the inoculation rate is WAY too low. The pack needs to be less than 3 months old to be ideal for a direct starter pitch. If getting a fresher pack can't happen, I would make a 500ml starter first, then decant and pitch the slurry into 3 liters after.

 

[rmr9]

Thanks Bobby! I think I’ll contact the LHBS to see if I can get a replacement. I imagine those 10B cells won’t all be alive when I get to brewing in another month, which only compounds the problem. Mashdar has a good point about keeping a sanitary culture as well.

 

[mashdar]

Out of curiosity, does (edit:brewfather) assume linear decay? I would imagine it's probably more geometric in reality? E.g. think half life, if half life is 3 months, then 12 mo = 0.5 ^4 = 6.25%. But I know nothing.

 

[Bobby_M]

I have no idea how viability decay is calculated.