"Do not rehydrate yeast"

[Konn]

Would argue you should always use a starter for liquid least and always rehydrate dry yeast. For rehydration, I just boil about a half a bottle of water, put 4 ounces in a pyrex cup, wait 20-25 mins (or until the temp is about 95), add the yeast, wait 15 mins, stir, wait 15 more, stir and pitch. As long as you clean and sanitize your pyrex glass and stirring spoon you shouldn't have to worry about infection. Total process takes about an hour vs. a day for a liquid starter which is one of the reasons I've been using dry yeast for most of my brews lately.

Here's the video I used to come up w/ my method:

 

[Bottoms_Up]

After looking at the data in Zepth's link, do you still support wort over water for rehydration? I.e., how will you rehydrate the next time you brew?

I have been told that adding the yeast to wort is not considered "rehydration" but is rather a type of "yeast starter". As mentioned earlier, I have added dry yeast to a smaller amounts of wort many times before with great results. Also as mentioned earlier, the experiment in Zeph's link does not address whether or not the extra amount of active yeast (as compared to adding it to cooler water or wort) is largely a result of activating the existent weak yeast or not. It only talks about the 'quantity' of yeast, not the average 'quality'. I haven't had a chance to review some of the other information that was mentioned in other posts as I was away much of this weekend attending to my 92 year old mother who suffered a major heart attack yesterday. Perhaps some of this other information addresses this question more directly. Until more information on this specific issue is available, I cannot support one process over the other - it is still just conjecture.

 

[Bottoms_Up]

It kills yeast cells non-preferentially. The yeast can't control what enters the cell wall and can't control what leaches out. Some survive, but they are stressed and left in a weakened state (important nutrients have leached out and need to be restored or cell vitality is reduced), then need to work double time just to restore the colony to the original size. Why would someone knowingly do that? You wouldn't wait for a White Labs vial to reach 50% viability on purpose on the premise that "only the weaker cells will die," would you?

Ah! Now I see where our differences are. You are assuming that the package of dried yeast is as healthy and active as possible. The experiment, however, was not with a healthy package of yeast, but with an old package that contained much dead and weak yeast, as was sen through the microscopic analysis.

 

[Bottoms_Up]

The results I quoted above are from experiments that start with a very healthy colony, so it kills more than just weak cells.

Sorry, Juan, I haven't had a chance to review the results you posted yet. This has been a bad weekend for me as mentioned in one of my previous messages, and I was away for much of the weekend. Give me a chance to review it and I'll past again later.

 

[Bottoms_Up]

Here's IMO a better source on the subject than the one posted above. This is a quote from a doctor in biology who works for Lallemand yeast-

Thank you Juan - that's an excellent overview, and addresses my question much better than the other source. Now that I understand the rehydration process better, I agree that it is indeed beneficial to rehydrate dried yeast in warm water. However...

In the future, I plan to combine the rehydration AND add it to a small amount of wort before adding it to the main wort. This takes advantage of both processes and hopefully ends up with an improved overall result. Here is the proposed process:

1. Take about a liter (2 pints) of wort from the main wort after it has boiled for at least 15 minutes. Put it in a sterlized container.

2. Cool the liter (2 pints) of wort in a sink of cool water until it reaches fermentation temperature.

3. Then take the package of dried yeast and add it to warm water (95-105 F) to rehydrate for 15-30 minutes.

4. After 15-30 minutes, cool the warm water/yeast to close to fermentation temperature (within 15 F), and immediately add it to the liter (2 pints) of wort.

5. Allow the liter (2 pints) of wort and yeast to stand for about two hours at fermentation temperature, while the main wort has finished its boiling/hop addition schedule, has been cooled to fermentation temperature, and has been transferred to the primary and aerated.

6. Add the liter of wort/yeast to the main wort.

 

[boydster]

Ah! Now I see where our differences are. You are assuming that the package of dried yeast is as healthy and active as possible. The experiment, however, was not with a healthy package of yeast, but with an old package that contained much dead and weak yeast, as was sen through the microscopic analysis.

When did I make that assumption? You are referencing just one experiment, and it's not even the one I pointed out to you. Did you look at Sean Terrill's website? Did you check out any of the references listed at the bottom of the first post of the Dry Yeast FAQ sticky that I originally pointed you in the direction of? I think not, because the quote from Clayton Cone that JuanMoore added is also linked there so had you done some legwork, you would have already encountered that info.

What do you hope to gain by throwing 150+ billion cells into 1 liter of wort for a couple hours? The yeast is packaged to have an energy boost during the first 30 minutes after rehydration to help kick it into the reproductive phase (again, this is from Clayton Cone), but in 1 liter of wort it will have no reason to reproduce at all, so basically you would be wasting that energy boost.

 

[Bottoms_Up]

but in 1 liter of wort it will have no reason to reproduce at all.

Source?

 

[boydster]

Yeast, pg 140. Chart of inoculation rate and cell growth. 150 billion cells in 1 liter of wort is an inoculation rate of 150 million cells per ml, which based on the chart would mean you get 0.3 doublings - and that's if you let the starter go at least to high krausen, forget about just leaving the yeast in there for a couple hours. That means most of the yeast cells won't divide, they will just consume the sugar around them. Your method is basically proofing with wort instead of plain sugar - a practice that was written about by Palmer in the original How to Brew but has since been deemed unnecessary because of the high quality of dry yeast available today. It's also worth mentioning that every additional step you add into the process is another potential avenue for contamination.

Why do you want to add this process to your brew day? If it is to put the yeast at more of an advantage, I urge you to read more from some of the resources you have already been pointed towards, or alternatively, follow the good advice from your fellow members here and trust in the collective knowledge and experience. If you want to do this to eat up some down time on your brew day and play with the yeast, go for it, it's probably not going to ruin your beer (barring an unexpected infection).

 

[Bottoms_Up]

Yeast, pg 140. Chart of inoculation rate and cell growth. 150 billion cells in 1 liter of wort is an inoculation rate of 150 million cells per ml, which based on the chart would mean you get 0.3 doublings - and that's if you let the starter go its full course, forget about just leaving the yeast in there for a couple hours. That means most of the yeast cells won't divide, they will just consume the sugar around them. Your method is basically proofing with wort instead of plain sugar - a practice that was written about by Palmer in the original How to Brew but has since been deemed unnecessary because of the high quality of dry yeast available today.

Thank you - time to throw my old beer books out! I even have Papazian's first book (1984)

 

[Zuljin]

On brew day, I pour my dry yeast into a clean Jagermeister bottle, add some warm water and a little DME, sugar or honey. Cap. Shake. Put a bung and airlock in the bottle. Put the bottle in a cabinet. By the time I'm ready to pitch, the bugs are twerking their asses off. I win every time.

I've also dissolved whatever I was going to use as food into water and then added it to the yeast.

I used to start my dry yeast a full day ahead or at least overnight. Then, a homebrew shop told me that could cause unwanted cell mutations and some other potential issues. I read the same on an HBT wiki. I stopped doing that. Can't say I've noticed a difference either way.

What I have noticed is that my fermentation is more vigorous, more sooner, when I get the bugs going first. Pitching dry yeast, dry, into the wort has always been the slowest.

Use clean gear, of course.

 

[BowAholic]

I know this is an older thread and probably a stupid newbie question, but... if yeasts optimal temp is between 95 F to 105F(Most of them closer to 105F) and you get 100% recovery at this temp, what would happen if you pitched the dry yeast into the cooling down wort when it hit 105, let it do it's thing, and then continue dropping the wort to fermentation temperature?

 

[boydster]

A large percentage of the cells would still die. Regardless of temperature, pitching dry yeast into a sugary substrate kills them. They can't regulate the sugar or other chemicals coming into the cell, so even things that would be considered nutrients or food for the yeast can quickly become toxic until the semipermeable cell membrane is reconstituted. Would you get more viable cells than if you hydrated in cool wort? Perhaps. But hydrating in warm water (vs cool water, cool wort, or warm wort) will get you the highest number of viable cells, all other things equal.

 

[BowAholic]

thanks! I'm making my first all grain tomorrow... a Buried Hatchet clone...and I want to get the yeast right. Warm water it is...
Bob

 

[boydster]

Good luck!

 

[govner1]

I know this is an older thread and probably a stupid newbie question, but... if yeasts optimal temp is between 95 F to 105F(Most of them closer to 105F) and you get 100% recovery at this temp, what would happen if you pitched the dry yeast into the cooling down wort when it hit 105, let it do it's thing, and then continue dropping the wort to fermentation temperature?

What yeast are you using that has an optimal temp of 95°-105°? And, what are you brewing? Most ale yeasts have ideal ranges from the mid to upper 50's going to the lower 70's. Ideally you want to pitch low and let your temp rise to your target ferM temp (66-68 is common) and you want to keep it consistent for at least the first 5 days or so during really active fermentation.

 

[JuanMoore]

A large percentage of the cells would still die. Regardless of temperature, pitching dry yeast into a sugary substrate kills them. They can't regulate the sugar or other chemicals coming into the cell, so even things that would be considered nutrients or food for the yeast can quickly become toxic until the semipermeable cell membrane is reconstituted. Would you get more viable cells than if you hydrated in cool wort? Perhaps. But hydrating in warm water (vs cool water, cool wort, or warm wort) will get you the highest number of viable cells, all other things equal.

Not only that, but pitching warm also has the potential the create some nasty off flavors as temperature control is most critical in the initial stages.

What yeast are you using that has an optimal temp of 95°-105°? And, what are you brewing? Most ale yeasts have ideal ranges from the mid to upper 50's going to the lower 70's. Ideally you want to pitch low and let your temp rise to your target ferM temp (66-68 is common) and you want to keep it consistent for at least the first 5 days or so during really active fermentation.

They were referencing the optimum re-hydration temperature, not the fermentation temperature.

 

[soccerdad]

U guys might be talking apples and goats here. Rehydrate at 95 to 105. Pitch at 65 or cooler.