Quick question: the ingredients on one of my packets of Safale Dry Yeast says to activate: sprinkle in wort. I just read ‘Yeast’ by Chris White and he talks about why not to do that. Would it be better to activate it in water even though the instructions say wort? I was wondering if the dry yeast packet has enough yeast that it can afford to lose some when activated in wort instead of water.
Rehydrating the yeast per the manufacturers instructions is recommended but not necessary for most beer recipes below 1.070
I just sprinkle the dry yeast across the top of the properly chilled and aerated wort and let it do it’s thing. Works like a charm every time.
I rehydrate in water with a little GO-FERM. Can you use wort? Sure. You can also use more packets of yeast if you are concerned about viability. I guess the rehydrating thing with dry yeast is still way less hassle than what you’d do to make a starter for liquid yeast that I think it isn’t a big deal. It only takes 15 minutes. If it helps the yeast acclimatize faster and get going quicker, it’s worth it.
As with most brewing choices, it’s not a yes it will work/no it won’t question. You’re dealing with probabilities. Chances are it will work. Chances are better if you rehydrate properly. Is the difference significant? Really hard to tell except after the fact. In my way of thinking, I’ll always go the “cheap insurance” route if it isn’t a lot of extra work. If I get an inferior batch and then tie it to not taking an extra 15 minutes (of which only about 30 seconds are actual work), then I’d feel like a putz.
If you go to Fermentis’ website (http://www.fermentis.com/FO/10-Home/home.asp) they have fairly detailed activation instructions. I have read that pitching dry yeast directly into the wort, especially high gravity wort, runs the risk of inefficient or reduced rehydration of the yeast. When going from a dry state to a sugary starter it can blow out the cell walls of the yeast as they try to rehyrdrate. This can cause slow/stuck fermentations due to low cell count. I have been using much more dry yeast lately and have been extremely happy with the results I get by using 1/2 cup boiled and cooled water per 11.5g packet of dried yeast. I sprinkle the yeast on the water and let it sit for 30 minutes, then stir gently every few minutes for 15 to 30 minutes after that.
I havn’t had a stuck fermentation since I started rehydrating per manufacturer recommendations following the pitch rate guidelines on MrMalty.com. I’ve also been using yeast hulls 3 days after fermentation takes off just to hedge my bets. Call me paranoid, but i have a very poorly attenuated batch of american wheat in my cellar that reminds me to take good care of my yeast every time i see it!
Edit: This is my first attempt at a helpful reply to a question since I’ve joined the forum, take what I say with a grain of salt. 
+1
My real question is about the instructions on the packet of dry yeast. Even though it says to sprinkle into wort, I am assuming that it is better to activate in 85-95 degree water first, not wort. Is this safe to assume, even though the instructions don’t say to do this?
In a word . . . yes.
I’ve never understood why the directions on the packets is so much different than the more detailed directions provided on the manufacturers website. I guess they just ran out of space on the packet?
At any rate, I’d go to http://www.fermentis.com/FO/10-Home/home.asp and follow the instructions there.
If you are going to use wort you may as well just sprinkle it on the top of the beer, no? The whole point about rehydrating is to ensure the cells “pop” back into shape, and that is theoretically better with plain H2O.
That said, curious about this “GO-FERM” - any info on that?
It’s not beer until you pitch the yeast, eh? Yeah, I meant sprinkling the yeast on the wort in the carboy.
GO-FERM is a Lallemand product designed to rehydrate yeast and get them back into action. See http://www.lallemandwine.us/products/nutrient_strains.php.
Rehydrating isn’t just about popping the cells back into shape. It’s about making sure they can actually function properly once they are in shape.
Like I said in an earlier post, this isn’t a yes/no issue. Will it work/won’t it work. It’s more of a “will it work better” issue. When it comes to fermentation, I’d like to have the deck stacked in my favor whenever possible. If you provide the best possible environment for your yeast, you will have a superior fermentation. If you give a substandard environment, it might work, or it might not. It’s like Jenga – you never know which piece you remove will cause the whole structure to come crashing down. So try to avoid putting yourself in that position.
Lallemand also recommends re-hydrating in water. They also claim that you do not need to aerate your wort when you use their dry yeast, as it has been given sufficient sterols for sufficient growth prior to drying. Not sure if Fermentis makes that same claim.
Weirdly enough, when I was studying at Doemens in Munich we used dry yeast for a couple batches in the pilot brewery and re-hydrated the yeast in first runnings. The brewmaster overseeing the brew was adamant that it was completely fine, and this guy had a phd from Weihenstephan. The fermentations were fine, so it looked like the yeast at least tolerated it.
Not that this is definitive or anything but I recently decided to finally make a mead. As I was researching mead making, it appeared that proper rehydration in the mead community was MUCH more strongly adhered to. And since the yeast are being pushed closer to their limits it sort of follows that they tend to treat their yeast as well as possible.
I also read that 105* F was actually the best rehydration temp and that you really do need to pitch it relatively soon after rehydration (within 30 minutes, preferably less) or the yeast tends to use up stored glycogen and trehalose. Get it in the wort/must quick enough and it starts using the energy/nutrients it gets from the wort/must instead of stored glycogen/trehalose.
FWIW, Dr. Clayton Cone speculated that this usage (or not) of stored glycogen/trehalose may be why cold-pitching seems to work so well. But that’s for another thread. 
We had a good thread about this on the NB forum which culminated in an experiment performed by Sean Terrill, I hope he won’t mind my posting it here.
That’s a cool experiment. At the same time I would hope that it’s obvious that Lallemand and Fermentis have already done extensive experimentation to arrive at their re-hydration instructions.
The commercial instructions? Yes. I don’t think any of the manufacturers give best practices on homebrew packaging, any general.
Sure, but it’s nice to see some data from an actual homebrew setting.
I posted links to a couple of research papers I thought were relevant and interesting in the NB thread, here’s the link if you’re interested (they are all on the second page): http://forum.northernbrewer.com/viewtopic.php?f=26&t=100629
Oddly enough, the paper hosted on the Fermentis site was the one that found no difference in viability between the sample rehydrated in wort vs the sample rehydrated in water (this was in opposition to every other paper I was able to find on the subject and to Sean’s results).