I usually use liquid yeast so this is process is new to me. Both How to Brew and the Fermentis website say to rehydrate in warm water (95-100F in HtB, 77-84F for ale and 69-77F for lager on Fermentis). Okay, got that. Both sources say wait 30 min then pitch. So the question is, do I pitch the still warm yeast into a much cooler wort? If I just pitch as is, it’s going experience a roughly 30F drop in temp. Will this not shock the yeast and cause more harm than good? Or, should I wait the prescribed 30 minutes then cool the yeast down closer to the temp of the wort?
The instructions used to say (not able to look now) to cool it down by slowly mixing in some of the wort with it before pitching. Kara Taylor from White Labs mentioned during her yeast talk that it’s critical to get the yeast within 10F of the wort prior to pitching. Obviously that was for liquid yeast but I would apply the same logic… I am often guilty of being impatient and just pitching the warm rehydrated yeast. I will be making an effort to add a few spoonfuls of wort to it next time to see if it makes a difference.
I usually rehydrate between 80 and 84 F. Usually after 1/2 an hour, I pitch to wort without additional cooling expecting the sample to have cooled off anyway. If the starter takes off, I often add some cooled wort primarily to feed the starter. I suspect that I may have checked starter temps before pitching a few times and concluded it wasn’t necessary to cool down.
If I rehydrated at ~100 F, I would probably cool the starter down.
Dan, I didn’t hear that talk, so bear with me please…is that 10F in either direction? For years I’ve been pitching yeast into wort that was maybe as much as 20-25F warmer than the yeast. I get great results doing that. But I’ve also heard that it’s not a good idea to pitch warmer yeast into cooler wort, so I would guess that’s the direction where it should be 10F. Did she differentiate at all?
I don’t recall her specifying. I’ve also never noticed anything ‘off’ with having a bit of a temp variance but I figured it’s an easy enough thing to do I would give it a try and see. If it’s colder I guess you would have to have some cold water or something to add in to the yeast to bring the temp down? Adding wort back to it would always leave it in the slightly ‘warmer’ side since the wort itself couldn’t cool it below it’s own temp…
The instructions for Nottingham say to get the rehydrated yeast within 10C (or 18F) of wort prior to pitching. I find that by the time I finish the rehydration process the temp is within, or close to, 18F of the wort.
Maybe that’s what I was thinking… It was a long weekend 