Liquid Yeast: post refrigeration acclimation/incubation time – why so long?

Reading liquid yeast labels for both White Labs and Wyeast, it seems you’re supposed to let yeast sit out at room temp (say ~72°) 3 hours minimum before pitching. Why? It seems to me it takes only maybe 1 hour to get to room temp, and perhaps the yeast would best be served acclimating further within the starter’s lag phase. But that’s not what the labels say. Surely they know better, but WHY?

I regularly shave off that 2-5 hours from my starter day. I pull the yeast out of the fridge and shake until the cake is liquefied and set on the counter. It sits there for 1.5 hours until my flask is baked and cooled (10min for oven to heat up, 60min at 350°, 20min to cool.) During the 20min I’ll boil DME for 10min and have a set 9min ice bath that lands me at ~70°. During the 9min my stir-bar, tongs, yeast package, (scissors if Wyeast), and funnel get sanitized.

Is there any possible benefit to letting the yeast package sit out another couple hours before pitching? I say “no”.

…but that’s not what the labels say.

I assume 350 is overkill, only 250 is needed. I assume 10min boil is overkill, only 3min is needed. Etc. And I assume said yeast companies suffer the same ~needless~ caution and put on their labels “3 to 6 hours”, or “3 hours or more” when only 1 is needed.

Or is there some metabolism benefit, or cell wall strength benefit, from resting in the same medium before inoculation?


(Note: I’m not stressed; nothing is wrong with my beer; I’m not worried about anything, nor am I over thinking it - I’m just curious. “Rdwhahb” need not reply.

Clayton Cone at Lallemand actually recommends pitching the yeast while it is cold.
http://www.danstaryeast.com/articles/pitching-temperature-and-nutrients

In theory, microbiologically, the reasoning behind it is that the yeast are "dormant" while in the fridge. If they immediately get tossed into some wort, all of a sudden the osmotic stress is acting upon them while they're still trying to wake up and make the proteins and carbohydrates necessary for survival. If you give them a chance to warm up, they can make those before getting bombarded, allowing more to survive stress-free.

I like the Danstar theory though, with the buildup of trehalose within the cold yeast. I don't know enough about trehalose formation to know the preferred conditions for optimal concentrations of trehalose, but there might be some work out there that could shed some light. Wyeast packets might not be optimized for trehalose generation?

Also, at least the last time I bothered to read them, the instructions were all for pitching directly into a batch of wort, rather than a starter. The starter wort is going to likely be lower gravity, little to no hops (and thereby no alpha acids, antimicrobials, etc.), and very well oxygenated (assuming you toss it on a stir plate). You're already giving the yeast anything they could ask for in a starter, besides the fact that you don't particularly care about ester generation if you're decanting anyways.

I definitely don't give them a full three hours and, like you, just pull it out before boiling the wort and pitch once its cool (maybe an hour, tops). Although, I do toss the starter into the fridge for a day or two before decanting, and I do let that warm up for a few hours before pitching into that day's batch. Maybe next time I'll leave it in the fridge until right up to pitching, see if it affects anything!

MalFet said:

Clayton Cone at Lallemand actually recommends pitching the yeast while it is cold.
http://www.danstaryeast.com/articles/pitching-temperature-and-nutrients

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Very interesting. Completely counter intuitive. But then, for me, yeast are still the minions of “the little people”. What do I know?

Wait – isn’t this a typo in the link?

“…cooler temperature near the end may be needed for full attenuation.”

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He’s talking about an ale yeast. I think he meant “warmer”, right? Cooling will induce flocculation – and if yeasts fall out they can’t fully attenuate. I thought you want to warm up your ale at the end for full attenuation.

erikpete18 said:

..Also, at least the last time I bothered to read them, the instructions were all for pitching directly into a batch of wort, rather than a starter. The starter wort is going to likely be lower gravity, little to no hops (and thereby no alpha acids, antimicrobials, etc.), and very well oxygenated (assuming you toss it on a stir plate). You're already giving the yeast anything they could ask for in a starter, besides the fact that you don't particularly care about ester generation if you're decanting anyways….

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Good point. Great overall reply.

But of course I want more info. You guys are going to force me to go buy the Jamil yeast book, unless a better one is recommended.

With WLP007 the yeast are huge and just drop to the bottom as soon as I take it off the stir plate – no refrigeration needed – but with WLP001 it requires an hour in the fridge for a yeast cake to form good and proper. I’ve always wondered if banging them dormant was detrimental vs. say letting the starter sit off the stir plate for 3 hours or whatever and just let them settle. Too many questions. 12 hours vs. 24 hours - etc. etc.

I’m sitting here looking at 3 kegs full of great homebrew, but I’m always shocked at how much I don’t know. Thanks for the replies!