Re-hydrating yeast kills?

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BansheeRider

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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 :eek:
 
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.
 
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.
 
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.
 
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.)
mode_emploi_web.gif


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.
 
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.
 
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
 
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. :D
 
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.
 
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
 
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)....
 
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 :D

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

:drunk:

Rick
 
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".

:drunk:

Rick

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

Gottcha. :mug:

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 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.
 
Man this thread had slow start but eventually got to good info. Just to reiterate, yeast rehydrate at nearly 100% viability in warm water while rehydration in a sugar dense liquid may yield 60% (IOW, 40% of the cells die).

From the Danstar FAQ:
Why is rehydrating the dry yeast before pitching important?

Dry beer yeast needs to be reconstituted in a gentle way. During rehydration the cell membrane undergoes changes which can be lethal to yeast. In order to reconstitute the yeast as gently as possible (and minimize/avoid any damage) yeast producers developed specific rehydration procedures. Although most dry beer yeast will work if pitched directly into wort, it is recommended to follow the rehydration instructions to insure the optimum performance of the yeast.

rehydration instructions for Safalel US05
Sprinkle the yeast in minimum 10 times its weight of sterile water or wort at 27°C ± 3°C (80°F ± 6°F). Leave to rest 15 to 30 minutes.
Gently stir for 30 minutes, and pitch the resultant cream into the fermentation vessel.
Alternatively, pitch the yeast directly in the fermentation vessel providing the temperature of the wort is above 20°C (68°F). 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, then mix the
wort using aeration or by wort addition.
 
Man this thread had slow start but eventually got to good info. Just to reiterate, yeast rehydrate at nearly 100% viability in warm water while rehydration in a sugar dense liquid may yield 60% (IOW, 40% of the cells die).

From the Danstar FAQ:


rehydration instructions for Safalel US05

Good info! So as long as the wort is above 68 degrees then the yeast won't go into shock? I can see how pitching yeast from 80 degree water to below 68 degree wort can possibly shock the yeast.
 
The rule I've seen is that you don't want more than a 10°F (5°C) jump in temperature between the yeast being pitched and the wort it's being added to. From other threads and the 71b-1122 data sheet, rehydrated yeast lose viability about 45 minutes after rehydration because they deplete the reserves that were stored with them.

Because of this, waiting for the rehydrated slurry to drop to the pitching temperature can be too slow. For some yeasts, the advice is to add small quantities of wort and mix them, wait a couple minutes, and repeat. This can bring the slurry to pitching temperature faster than waiting, but slow enough to avoid a thermal shock.

In most cases, the pitch rates are high enough with dry yeast that we're picking at details with a lot of these concerns, though. Other than major errors (like cooking the yeast), more than likely enough yeast will survive that you'll be within a factor of a few of the pitch rate you're after. I think for most of us, that's close enough that it's unlikely to be the difference between a good and a bad beer.
 
The rule I've seen is that you don't want more than a 10°F (5°C) jump in temperature between the yeast being pitched and the wort it's being added to. From other threads and the 71b-1122 data sheet, rehydrated yeast lose viability about 45 minutes after rehydration because they deplete the reserves that were stored with them.

Because of this, waiting for the rehydrated slurry to drop to the pitching temperature can be too slow. For some yeasts, the advice is to add small quantities of wort and mix them, wait a couple minutes, and repeat. This can bring the slurry to pitching temperature faster than waiting, but slow enough to avoid a thermal shock.

In most cases, the pitch rates are high enough with dry yeast that we're picking at details with a lot of these concerns, though. Other than major errors (like cooking the yeast), more than likely enough yeast will survive that you'll be within a factor of a few of the pitch rate you're after. I think for most of us, that's close enough that it's unlikely to be the difference between a good and a bad beer.


Ok sounds good. I normally cool my wort to just below 80 degrees before pitching the yeast. If I hydrate the yeast in 90 degree water then it shouldn't be an issue regarding pitching temperature.
 
Ok sounds good. I normally cool my wort to just below 80 degrees before pitching the yeast. If I hydrate the yeast in 90 degree water then it shouldn't be an issue regarding pitching temperature.

Ive had pretty fruity beers pitching at that temp,if you like it then have at. I havent done that since my first few beers,which I think is way to high. You could get too fast a ferment as well as alot of esters. Ive always had good beers with nothing off hydrating at recommended temps then pitching at ferm temps. It does seem that you should add some wort after 15 min to ease it into your main pitch wort temp. Its really only about viability loss. So if you pitch more than enough dry yeast then you can pitch dry or hydrate and pitch the 20 degree difference and still afford some of the viability loss. Although it does stress and add loss of viability but again, if you overpitch you shouldnt have to worry too much about the temp difference. Although its better to strive for optimum yeast viability.:mug:
Also if your pitching just below 80 what temps does that mean your fermenting at? More than 10 deg drops can stress yeast(maybe more?) that way if you ferment in the mid low 60's that way. And its generally more estery fermenting above 70 to ferment in most yeast it seems anyway if your primarily fermenting that high.
So long story short: you may be getting more stressed yeast pitching @ 80 and fermenting above 70.

I dont generally hydrate- then add cooled(primary temp) wort- then pitch to main wort. I generally overpitch-hydrate, then just throw the hydrated yeast in to wort below or close to 70. If I knew I wasnt overpitching then I would add wort after hydration to get it closer to primary pitch temps.
 
I use tepid tap water with a little table sugar mixed in.

I pour the dry yeast on top and let it sit there. I do not stir it in. I let it do its thing for a few hours.

I swirl it around and dump it into my wort when it is ready.

https://www.homebrewtalk.com/f39/fermentor-experiment-one-yeast-substitution-365182/

I don't stir it once it is in the wort.

You dont really want to "proof" it like bread yeast. Just hydrate it first. Shure that will work but you will get loss from that as discussed previously. :mug:
 
Ive had pretty fruity beers pitching at that temp,if you like it then have at. I havent done that since my first few beers,which I think is way to high. You could get too fast a ferment as well as alot of esters. Ive always had good beers with nothing off hydrating at recommended temps then pitching at ferm temps. It does seem that you should add some wort after 15 min to ease it into your main pitch wort temp. Its really only about viability loss. So if you pitch more than enough dry yeast then you can pitch dry or hydrate and pitch the 20 degree difference and still afford some of the viability loss. Although it does stress and add loss of viability but again, if you overpitch you shouldnt have to worry too much about the temp difference. Although its better to strive for optimum yeast viability.:mug:
Also if your pitching just below 80 what temps does that mean your fermenting at? More than 10 deg drops can stress yeast(maybe more?) that way if you ferment in the mid low 60's that way. And its generally more estery fermenting above 70 to ferment in most yeast it seems anyway if your primarily fermenting that high.
So long story short: you may be getting more stressed yeast pitching @ 80 and fermenting above 70.

I dont generally hydrate- then add cooled(primary temp) wort- then pitch to main wort. I generally overpitch-hydrate, then just throw the hydrated yeast in to wort below or close to 70. If I knew I wasnt overpitching then I would add wort after hydration to get it closer to primary pitch temps.

My fermenting temps fluctuate between 68-72 degrees. I have only done one batch of beer (currently in secondary carboy). I pitched the dry yeast at 80 degrees. The next morning the beer was fermenting like crazy at about 70 degrees. Are you saying this will create off flavors? I just ordered a recipe kit, I will try to get my wort to about 70 degrees this time before pitching the yeast.
 
My fermenting temps fluctuate between 68-72 degrees. I have only done one batch of beer (currently in secondary carboy). I pitched the dry yeast at 80 degrees. The next morning the beer was fermenting like crazy at about 70 degrees. Are you saying this will create off flavors? I just ordered a recipe kit, I will try to get my wort to about 70 degrees this time before pitching the yeast.

It can. And depends what yeast if you want that or not. Its just something I learned and didnt know even with months of research before brewing,its just something that I didnt come across. Especially when directions say pitch below 80 deg. Yes,but generally that is still to high. JUst give your beer longer and it could still and may turn out very good right away, if its not give it more time and it may get better. There are alot of other things that can account for many different characters that may even be misleading at first when starting out. I was a little frustrated at first and just thought that homebrew may not be good or something.It was only a few things I happed to overlook which took experience and time to figure out.
Is your actuall beer 70 deg or your ambient temps 70? If you feel your fermenter and its pretty warm then you may have somewhat an estery beer.
 
For my first few batches, I pitched in the low 80s or high 70s simply because I didn't yet have a good way to cool the wort and I got tired of waiting. I've not had what I'd call any fruity off flavors. In my case, I used Nottingham dry yeast, pitching two 11g packets. That should be a pretty generous pitch, although it's in line with the recommended numbers that were either on the packet or on the datasheet. That's a yeast that, especially at fermentation temps in the low 60s, tends to be pretty clean. So it's possible I did get some esters but the rest of the fermentation was so clean that they weren't enough to be prominent.

Now that I've got an immersion chiller, I can get down to proper ale temperatures very quickly. For lagers, I just chill it to room temperature, then stick it in the fridge overnight and pitch the next evening in the upper 40s.
 
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