Re-hydrating dry yeast and wort temp, a critical consideration?

[diannotti]

So I apologize for bringing this topic up as I have read numerous posts on the topic of "to re-hydrate, or not" and just as many answers. But what I never found discussed is the concept that re-hydrating allows you to pitch into lower temperature wort. What I mean is typically if you direct pitch you need to pitch into a higher temp wort ( 68 or so ). This seems to me, and I am no expert - I am asking, a major consideration when deciding to re-hydrate or not. Example in mind is you can re-hydrate and pitch on 63 degree wort to lessen esters and diacetyl.

Anyone agree , disagree?

 

[Daybis]

When using dry or liquid yeast, I always try to get my wort temps close to the fermentation temperature as possible before I pitch. So if I plan on fermenting at 63 degrees, I will usually wait for my wort to get to 63 before I pitch. You shouldn't have any issues pitching at 63 degrees.

 

[diannotti]

Interesting. I just note that manufacturers typically instruct when "dry pitching" to pitch at higher temp:

Example Safale US05 68
"Alternatively, pitch dry yeast directly in the fermentation vessel providing the temperature of
the wort is above 20C (68F)."
http://www.fermentis.com/fo/pdf/HB/EN/Safale_US-05_HB.pdf

Yet the fermentation range is stated as 59 to 75.

It seems to me the manufacturer in this case is recommending re-hydration if you want to pitch into wort cooler than 68, no?

 

[Daybis]

Interesting. That's what it sounds like after reading that pdf. I wonder if you are pitching directly into the wort if the wort needs to be warmer to "wake" the yeast up a bit. I use liquid yeast for the most part, but I've never had issues with pitching temps when re-hydrating or pitching the dry yeast directly into the wort. What you could always do, is split a batch, use one where you re-hydrate and pitch at the temperature you want to ferment at. Then in the second batch, toss in the dry yeast into a warmer wort, then bring the temps down to your fermentation temps.

 

[diannotti]

Basically looking for anyone who knows the answer to this. Is re-hydrating dry yeast most critical when pitching onto a lower temp wort. I realize I can direct pitch onto 68 degree wort. What I really want to know is will re-hydrating dry yeast be particularly beneficial when pitching the re-hydrated yeast onto a cooler wort.

Does any one do this? re-hydrate at 80 or per instruction temp range and pitch onto cooler wort ( say below 65 )? Of those people who re-hydrate what temp is your wort when you pitch? Do you allow the re-hydrated yeast to drop down to wort temp before pitching?

 

[Anacrusis]

When I rehydrate with say US-05, I rehydrate with ~86F water. I then let it sit until it has gotten closer in temp to my wort, usually around 70. I then wait a couple of hours after pitching and then bring down the temp depending on the style and yeast. Never had any problems doing it this way. But that's just me.

 

[diannotti]

I then wait a couple of hours after pitching and then bring down the temp depending on the style and yeast. Never had any problems doing it this way. But that's just me.

I'm sure you haven't had any problems but I am just trying to determine what would be considered "ideal". I would not think starting fermentation at one temp and then bringing it to a lower temp within a couple hours would be ideal for the yeast. I would think you would want to start at the temp you intend to complete initial fermentation at. Then raise temp at end of fermentation for diacetyl re-absorption.

 

[periwinkle1239]

I'm sure you haven't had any problems but I am just trying to determine what would be considered "ideal". I would not think starting fermentation at one temp and then bringing it to a lower temp within a couple hours would be ideal for the yeast. I would think you would want to start at the temp you intend to complete initial fermentation at. Then raise temp at end of fermentation for diacetyl re-absorption.

I think I've read that pitching yeast before it's completely down to your target fermentation temperature is ok because fermentation doesn't happen instantaneously. If I recall, the initial hours are when reproduction takes place and so the temp is not as critical because there really are no 'flavors' being developed? I may have this understanding wrong.

So you could pitch at say 75-80 and then it might take a few hours to bring it completely down to 60-65. This is basically what I do, no complaints thus far...