White Labs yeast viability vs brewers friend discrepancy

[Noob_Brewer]

I am getting ready to make a yeast starter with WLP530. I used yeast man.com to show me the manufacturing date was 4/16/20. In brewers friend, with this date, it was estimated to have 50% viability. However, the white labs website shows that pure pitch viability of yeast at ~2.5months after the manufacturing release date to be ~94%. So this is a big discrepancy. Wanting to make sure I pitch the right amount of yeast at a pitch rate of 0.75. Which estimate of yeast viability do peeps use with WLP pure pitch yeast packs? Thanks.

 

[Qhrumphf]

When in doubt, assume it's less viable. Unless you're deliberately trying to pitch at a very low rate (Hefe or Kveik), you'll be better served pitching more than less.

 

[Oginme]

The yeast calculators were developed before White Labs went to their new packaging. Additionally, they err to the low side of viability as a matter of practice.

I did cell counts on many packages of varying ages of both Wyeast and White labs (vials back then), just to get myself trained. From my experience, I always had a much higher count of viable cells than the calculators estimated.

 

[Noob_Brewer]

Thanks all! I think Im going to split the difference and assume viability of 70% Even if viability is less, that should still get me in the 0.75 pitch rate ball park.

 

[IslandLizard]

Thanks all! I think Im going to split the difference and assume viability of 70% Even if viability is less, that should still get me in the 0.75 pitch rate ball park.

No need to split the difference.
Viability rates with WLP PurePitch sleeves is much better than any other yeast packaging.
https://www.whitelabs.com/news/purepitch-shelf-life
Now if you suspect the yeast was mishandled since manufacturing, such as shipping during extreme weather, make applicable corrections or estimates.

 

[Qhrumphf]

That's a decent approach. I generally figure the pitching rate calculators are conservative while the labs are generous with viability and growth. But I'll aim to the conservative more than not because overpitching is safer than underpitching.

 

[Noob_Brewer]

No need to split the difference.
Viability rates with WLP PurePitch sleeves is much better than any other yeast packaging.
https://www.whitelabs.com/news/purepitch-shelf-life
Now if you suspect the yeast was mishandled since manufacturing, such as shipping during extreme weather, make applicable corrections or estimates.

I thought of this actually. I got the WLP530 pack during a week in May where weather was unexpectedly hot (80-90s) on the shipment from PA to here in eastern NC. When I got it delivered, the two cold packs weren’t warm but you could tell they were barely cool and the yeast was “room temp” ie 70s but not hot. So I just started the starter estimating 70% viability which according to brewers friend should higher than 0.75 (about 0.83) pitch rate based on my volume and DME added. So even if it’s at 50% viable I should be safe for a healthy pitch.

 

[Gozie Boy]

I thought of this actually. I got the WLP530 pack during a week in May where weather was unexpectedly hot (80-90s) on the shipment from PA to here in eastern NC. When I got it delivered, the two cold packs weren’t warm but you could tell they were barely cool and the yeast was “room temp” ie 70s but not hot. So I just started the starter estimating 70% viability which according to brewers friend should higher than 0.75 (about 0.83) pitch rate based on my volume and DME added. So even if it’s at 50% viable I should be safe for a healthy pitch.

Yep, shipping enviro is the real wild card for viability during the shoulder seasons if you're in areas that can have warm/hot spells. I'm erring on the conservative side on a batch right now for this reason (Wyeast, mid Apr), and upsizing my starter. Little downside in doing so.

 

[VikeMan]

It's think very important to realize that the White Labs published viability data is under, well, laboratory storage conditions.