Re-hydrating yeast kills?

[BansheeRider]

I have read mixed reviews about re-hydrating dry yeast and pitching yeast in cool temps. So, if pitching yeast in high temperature wort kills the yeast then how does re-hydrating yeast not kill, considering the water temp for hydrating yeast is 90-110 degrees? Sorry for the noob question

 

[menerdari]

Wort in that temp range doesn't kill yeast, it does cause the yeast to produce off flavors during fermentation.
I rehydrate at the lower end of that, about 90 deg.
I always rehydrate when using dry yeast.

 

[dlaramie08]

It doesn't necesarily kill the yeast; if you pitch that high the beer won't have time to cool enough before fermentation begins and off flavors will be produced. That being said, this situation may be favorable for some Belgian yeasts.


He beat me.

 

[BansheeRider]

Wort in that temp range doesn't kill yeast, it does cause the yeast to produce off flavors during fermentation.
I rehydrate at the lower end of that, about 90 deg.
I always rehydrate when using dry yeast.

I plan on doing that with my next batch, just wanted to make sure the high temps won't harm the yeast. I pitched dry yeast in my first batch and it was fermenting like crazy in under 8 hours.

 

[Golddiggie]

Rehydrating dry yeast is different than pitching it into HOT wort/must.

From the Lalvin Labs web site (applies to their strains, other strains can have different temperatures to rehydrate at)...

REHYDRATION
Dissolve the dry yeast in 50 mL (2 oz) of warm NOT HOT water (40°- 43°C / 104°-109°F).
Let stand 15 minutes without stirring, then stir well to suspend all the yeast.
Add to previously sulfited must. (The yeast should not be kept in the rehydration medium longer than recommended.)

The temperature delta between the prepared yeast and what it's going into is the same for both liquid and rehydrated yeast.

Most of us chill out wort/must at least to (if not below) the fermenting temperature before pitching the yeast so that things don't go ape-sheet right or give us nasty flavors. A small amount of higher temperature solution (~10C) will quickly be cooled to the same temperature of what it's going into. That's also why you don't want more than a 10C delta. You can easily shock/stress the yeast if they're suddenly put into a much cooler environment.

With dry yeast, the higher temperatures help with the rehydration process. Which is very different from the fermenting process.

 

[RM-MN]

Yeast are fine in warm water but there is a limit to how warm. I think that limit is about 140F. beyond which the yeast die.

 

[F250]

I plan on doing that with my next batch, just wanted to make sure the high temps won't harm the yeast. I pitched dry yeast in my first batch and it was fermenting like crazy in under 8 hours.

Um, aren't you "re-hydrating" when you pitch the dry yeast onto the wet wort?

Rick

 

[Satisfaction]

Awesome graphic, should just sticky that..

 

[Golddiggie]

Yeast are fine in warm water but there is a limit to how warm. I think that limit is about 140F. beyond which the yeast die.

Pretty sure that really only applies to dry yeast. I wouldn't want to put liquid yeast into anything even close to that. I have pitched a liquid yeast slurry into a wort that was about 10F lower than it's listed range. Fermented within a couple of degrees of the low end temperature for the duration. Batch came out great too.

 

[Golddiggie]

Awesome graphic, should just sticky that..

Found it here: http://www.lalvinyeast.com/strains.asp

 

[Satisfaction]

Um, aren't you "re-hydrating" when you pitch the dry yeast onto the wet wort?

Rick

Paraphrasing "Yeast"

The first few moments of a Re-hydrating yeasts life is very important, until the cell wall is completely reconstituted it cannot regulate what goes through it. If it is Re-hydrating in wort the cell takes in too much and can kill or damage it.

Re-hydrating the yeast properly will yield ~70-75% viability

Re-hydrating in wort will yield ~45-50% viability.

 

[F250]

Paraphrasing "Yeast"

The first few moments of a Re-hydrating yeasts life is very important, until the cell wall is completely reconstituted it cannot regulate what goes through it. If it is Re-hydrating in wort the cell takes in too much and can kill or damage it.

Re-hydrating the yeast properly will yield ~70-75% viability

Re-hydrating in word will yield ~45-50% viability.

Perhaps, but the manufacturers of dry yeast don't suggest re-hydrating, do they?

Rick

 

[Satisfaction]

Perhaps, but the manufacturers of dry yeast don't suggest re-hydrating, do they?

Rick

Well, they do but they figure most home brewers cannot handle it..

Check the spec sheet.

http://www.fermentis.com/wp-content/uploads/2012/02/SFA_US05.pdf

 

[jakenbacon]

Perhaps, but the manufacturers of dry yeast don't suggest re-hydrating, do they?

Rick

No they don't, and I trust the company that is making much more money than us and does this for a living. Read the manufactures instructions for the yeast your using, plain and simple.... That wasn't to you Rick, just quoted you for the 'yes or no' question....


.....Wow, appears fementis has changed the US-05 PDF, never had any hydrating options before, What the hell do I know...... (you do not have to answer that)....

 

[Satisfaction]

No they don't, and I trust the company that is making much more money than us and does this for a living. Read the manufactures instructions for the yeast your using, plain and simple.... That wasn't to you Rick, just quoted you for the 'yes or no' question....


.....Wow, appears fementis has changed the US-05 PDF, never had any hydrating options before, What the hell do I know...... (you do not have to answer that)....

I was just about to respond, but held back

The flame wars were about to begin :rockin:


The problem with not rehydrating is that the yeast kill can put you below optimal pitching rates and the only way to bring it back up is to throw in another package. If you like the KISS method just buy two packages.

For really big beers I buy two packages and rehydrate.


Just do a bit of research do not take my word for it.. you will find that lots of the top guys in homebrew preach rehydrating.

 

[dlaramie08]

I have tried both rehydrating and pitching dry and have had no discernible flavor difference between the two. This is just my experience and does not constitute a scientific experiment. However I also pitch at appropriate temperatures when available, ie not in the summer time.

 

[F250]

Well, they do but they figure most home brewers cannot handle it..

Check the spec sheet.

http://www.fermentis.com/wp-content/uploads/2012/02/SFA_US05.pdf

Interesting.

I usually use Fermentis or Danstar dry yeasts, as they happen to make good yeasts for the style of beers I like. To date I've always just sprinkled on top of the wort per the package instructions and not had issue, but the next time I brew something I'm familiar with I'll try re-hydrating and see if I notice a difference. I'm pretty familiar with Windsor and US-05, so they would be the logical candidates.

Rick

 

[jakenbacon]

I was just about to respond, but held back

The flame wars were about to begin :rockin:

Lucky you

 

[BansheeRider]

Um, aren't you "re-hydrating" when you pitch the dry yeast onto the wet wort?

Rick

No, we are talking about before pitching the yeast into the wort.

Perhaps, but the manufacturers of dry yeast don't suggest re-hydrating, do they?

Rick

Sometimes on the packet it will recommend hydrating before use.

 

[Satisfaction]

Lucky you

He edited the first post

 

[jakenbacon]

He edited the first post

 

[Demus]

Um, aren't you "re-hydrating" when you pitch the dry yeast onto the wet wort?

Rick

Yes, and the high gravity sugars burst the cell walls killing the yeast. It ferments much better when it's alive!

 

[BansheeRider]

Thanks for the replies! I will try hydrating my yeast for my next batch and see how my beer turns out.

 

[zeg]

.....Wow, appears fementis has changed the US-05 PDF, never had any hydrating options before, What the hell do I know...... (you do not have to answer that)....

Interesting. I've only been brewing a year, but every packet of dry yeast I've used (Danstar Nottingham, US-05, S-04, Lalvin 71b-1122) has suggested rehydration as the first option, with sprinkling as an alternative. The data sheets all give pretty detailed instructions on the rehydration procedures.

I had no idea they didn't used to recommend this.

 

[BansheeRider]

Why does the temperature have to be so high to hydrate the yeast? And what is the difference between rehydrating and making a starter with DME?

 

[logdrum]

Just to clarify: Danstar recommends rehydrating @ 80*F (+\- 6*) not 110*F

 

[F250]

Interesting. I've only been brewing a year, but every packet of dry yeast I've used (Danstar Nottingham, US-05, S-04, Lalvin 71b-1122) has suggested rehydration as the first option, with sprinkling as an alternative. The data sheets all give pretty detailed instructions on the rehydration procedures.

I had no idea they didn't used to recommend this.

On the yeast package itself?

I'm holding two packets of Fermentis yeast, one of Safale s-04, and one of Saflager s-23. Neither say anything about re-hydration, both say to "sprinkle into wort".



Rick

 

[zeg]

On the yeast package itself?

I'm holding two packets of Fermentis yeast, one of Safale s-04, and one of Saflager s-23. Neither say anything about re-hydration, both say to "sprinkle into wort".



Rick

Sorry, you're right. It's on the PDF instruction sheets for those.

 

[F250]

Sorry, you're right. It's on the PDF instruction sheets for those.

Gottcha.

I think after reading everything in this thread that I'll personally start re-hydrating my dry yeasts. If it's a better practice I'm all for it.

Rick

 

[zeg]

I think after reading everything in this thread that I'll personally start re-hydrating my dry yeasts. If it's a better practice I'm all for it.

Rick

I like to do it simply because I primary in Better Bottles, and it's a lot easier to pour a measuring cup of slurry in than to sprinkle a packet of yeast in through the small opening.