Which is worse?

[aagiv]

For this morning's brew, I rehydrated my dry yeast for the first time. I know people disagree on the necessity of doing so, but I figure what's good for the yeast is good for my beer. However, after rehydrating my yeast, I pitched 80-90 degree yeast (didn't actually measure) in to my 66 degree wort instead of getting them to the same temp for pitching. Oops...

So my question is which is likely to kill more yeast: pitching dry into the wort, or rehydrating and then subjecting them to temperature shock? And as far as RDWHAHB, I will be doing that as soon as I get back home from an afternoon meeting. I am not worried about this batch, just curious about which scenario is worse for the yeast.

 

[Homercidal]

Temperature shock is not likely to kill the yeast (unless it's too high). But it might cause them to process their stuff differently, leading to off-flavors or perhaps just causing some lag time.

I would be more worried about a constant cycle of higher and lower temp changes, than a single sudden change.

 

[samc]

Fermentis (SO5, etc.) recommends rehydrating. I would have voted for pitching dry into the wort but I think you will do fine either way.

Re-hydrate the dry yeast into yeast cream in a stirred vessel prior to pitching. Sprinkle the dry yeast in 10 times its own weight of sterile water or wort at 27C ± 3C (80F ± 6F). Once the expected weight of dry yeast is reconstituted into cream by this method (this takes about 15 to 30 minutes), maintain a gentle stirring for another 30 minutes. Then pitch the resultant cream into the fermentation vessel.

Alternatively, pitch dry yeast directly in the fermentation vessel providing the temperature of the wort is above 20C (68F). Progressively sprinkle the dry yeast into the wort ensuring the yeast covers all the surface of wort available in order to avoid clumps. Leave for 30 minutes and then mix the wort e.g. using aeration.

 

[springer]

it will be fine may have some lag time as the yeast is most likely a little shocked but it wont kill it. What I do is add a small amounts of wort to my hydrated yeast aver a period of like a 1/2 hour to get it down to the worts temp or very close .