Author Topic: Pitching dry yeast without rehydrating  (Read 5815 times)

Offline liquidbrewing

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Pitching dry yeast without rehydrating
« on: May 24, 2012, 03:44:21 PM »
So, I'm trying to draw Mr. Denny Conn out here.  Have you noticed any thing different (off flavors, etc...) just pitching the dry yeast pack without rehydrating?  Anything over 1.060 I just pitch two packs, but is the rumor true that if you pitch dry yeast, without rehydrating,  it kills half the cells instantly?  This doesn't really make any sense to me, as I usually rehydrate in around 85 degree water.  Wouldn't that kill some cells too?  Why does it make a difference when you pitch into wort, is it because of the sugar content, like it's such a shock to the yeast?  Just need a little food for thought.
Justin
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Offline gymrat

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Re: Pitching dry yeast without rehydrating
« Reply #1 on: May 24, 2012, 04:04:29 PM »
I am not Denny. But I did read an article on this several weeks ago. I don't remember where I read it. Someone researched this and came to the conclusion that rehydrating makes no difference. However in my own personal experience when I do rehydrated my airlock starts bubbling a lot sooner. I have never been able to detect any difference in the finished product though.
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Offline hokerer

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Re: Pitching dry yeast without rehydrating
« Reply #2 on: May 24, 2012, 05:41:33 PM »
As I've heard it, it has to do with the permeability of the yeast cell walls.  The process of drying leaves the cell walls in a somewhat compromised state.  Part of their function is to allow some things to pass into the cell but keep others out.  It the "keep others out" skill that's compromised.  When you rehydrate in water, there's no "baddies" in the water and, once rehydrated, everything works as normal.  If instead, you pitch directly into wort, there are "baddies" and the cell walls can't keep them out.  About half the cells don't survive the invasion of the baddies.
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Offline liquidbrewing

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Re: Pitching dry yeast without rehydrating
« Reply #3 on: May 24, 2012, 07:58:50 PM »
As I've heard it, it has to do with the permeability of the yeast cell walls.  The process of drying leaves the cell walls in a somewhat compromised state.  Part of their function is to allow some things to pass into the cell but keep others out.  It the "keep others out" skill that's compromised.  When you rehydrate in water, there's no "baddies" in the water and, once rehydrated, everything works as normal.  If instead, you pitch directly into wort, there are "baddies" and the cell walls can't keep them out.  About half the cells don't survive the invasion of the baddies.

But boiled wort should be sanitary for a few days right?  Even though it's structure is different than water, sanitary is sanitary, right?
Justin
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Offline anthony

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Re: Pitching dry yeast without rehydrating
« Reply #4 on: May 24, 2012, 08:12:41 PM »
Those aren't the "baddies".

Hop oils, sugars, and other such things can freely enter the cell before the wall has been completely rehydrated, damaging the cell. There is a lot of variance in the estimates of how many yeast cells this process kills when you aren't using plain water at the correct temperature, but most seem to hover in the 40-60% range. Fermentation still takes place though, just as fermentation most often takes place when you just toss a single vial or smack pack into a beer too.

Offline erockrph

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Re: Pitching dry yeast without rehydrating
« Reply #5 on: May 24, 2012, 09:15:00 PM »
Here's a good article/experiment pitting rehydrated vs dry/sprinkled yeast. My takehome from it is that the effects on fermentation and taste vary from strain to strain, but the differences don't seem to be too significant.

http://hw.libsyn.com/p/1/a/e/1aeeb08f8db636f1/Verslag_hydratatie_experimenen.pdf?sid=6af016d2e83556038c0f9b3c0539b4d0&l_sid=18257&l_eid=&l_mid=2665804&expiration=1337919770&hwt=a2139bdfabe76df3bc4385d00ec142fc

In the end, I personally think of it as the decision whether to rehydrate or not equates most closely to pitching rate. I've always been a rehydrator, but I think I'm going to switch to sprinkling dry for lower gravity beers. I will probably continue to rehydrate for beers in the 1.060 and up range, especially in beers where I want a clean fermentation (although I'd probably still sprinkle something like T-58 if I'm looking for more esters).
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Re: Pitching dry yeast without rehydrating
« Reply #6 on: May 24, 2012, 09:46:15 PM »
I've done several methylene blue viability studies on yeast rehydrated in wort and in water, and I'm confident that there is in fact a substantial reduction in viability after rehydrating in wort. So if you accept that a reduction in pitching rate promotes off-flavors, then there you have it.

On the other hand, I've only conducted one (blind) tasting of beers that were actually fermented using yeast rehydrated in water vs. those rehydrated in wort. http://seanterrill.com/2011/07/29/dry-yeast-viability-take-two/

The results are not exactly unambiguous, but for what it's worth, I was the only one who tasted them*.


*That's not true. My non-beer-drinking roommate, who randomized the samples for me, described the rehydrated yeast beer as being the "fluffiest".
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Offline gymrat

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Re: Pitching dry yeast without rehydrating
« Reply #7 on: May 24, 2012, 10:02:10 PM »
Here's a good article/experiment pitting rehydrated vs dry/sprinkled yeast. My takehome from it is that the effects on fermentation and taste vary from strain to strain, but the differences don't seem to be too significant.

http://hw.libsyn.com/p/1/a/e/1aeeb08f8db636f1/Verslag_hydratatie_experimenen.pdf?sid=6af016d2e83556038c0f9b3c0539b4d0&l_sid=18257&l_eid=&l_mid=2665804&expiration=1337919770&hwt=a2139bdfabe76df3bc4385d00ec142fc

In the end, I personally think of it as the decision whether to rehydrate or not equates most closely to pitching rate. I've always been a rehydrator, but I think I'm going to switch to sprinkling dry for lower gravity beers. I will probably continue to rehydrate for beers in the 1.060 and up range, especially in beers where I want a clean fermentation (although I'd probably still sprinkle something like T-58 if I'm looking for more esters).

This is what I had read and commented on earlier. I didn't remember where I had read it.
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Offline anthony

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Re: Pitching dry yeast without rehydrating
« Reply #8 on: May 24, 2012, 10:24:07 PM »
I've done several methylene blue viability studies on yeast rehydrated in wort and in water, and I'm confident that there is in fact a substantial reduction in viability after rehydrating in wort. So if you accept that a reduction in pitching rate promotes off-flavors, then there you have it.

On the other hand, I've only conducted one (blind) tasting of beers that were actually fermented using yeast rehydrated in water vs. those rehydrated in wort. http://seanterrill.com/2011/07/29/dry-yeast-viability-take-two/

The results are not exactly unambiguous, but for what it's worth, I was the only one who tasted them*.


*That's not true. My non-beer-drinking roommate, who randomized the samples for me, described the rehydrated yeast beer as being the "fluffiest".

I would be curious to see if you rehydrated in even warmer water than your first experiment, more on the order of 90-100F, would you improve your viability even further.

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Re: Pitching dry yeast without rehydrating
« Reply #9 on: May 24, 2012, 10:31:20 PM »
I would be curious to see if you rehydrated in even warmer water than your first experiment, more on the order of 90-100F, would you improve your viability even further.

In my experience, temperature doesn't have a statistically significant effect.
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Offline euge

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Re: Pitching dry yeast without rehydrating
« Reply #10 on: May 24, 2012, 10:35:49 PM »
Do what you want but I always rehydrate my dry yeast. It just doesn't make sense to do all that work- carefully measuring and sanitizing etc and then cavalierly toss the dry yeast in. It seems that dry yeast is considered to be so substandard that any extra effort is deemed worthless.

Well, I hydrate even on lower gravity beers. It works well for me and suggest that you use plain boiled and cooled tap water to do so. Hydrate at 85-90F. Never use RO or distilled to hydrate the yeast.

Good luck.
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Offline tygo

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Re: Pitching dry yeast without rehydrating
« Reply #11 on: May 25, 2012, 04:08:23 AM »
I don't use dry yeast that often but I rehydrate it when I do.  From everything I've seen it certainly doesn't hurt and it's easy to do.  As Euge pointed out, with all the time and effort you spend on a batch what's a couple extra minutes?
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Re: Pitching dry yeast without rehydrating
« Reply #12 on: May 25, 2012, 04:20:46 AM »
Tried it numerous times sued by side and there is no perceivable difference. Try it for yourself. That's the ultimate test.
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Offline davidgzach

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Re: Pitching dry yeast without rehydrating
« Reply #13 on: May 25, 2012, 05:12:27 AM »
+1 to taking an extra 5 minutes to rehydrate.....
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Pitching dry yeast without rehydrating
« Reply #14 on: May 25, 2012, 05:32:08 AM »
I've also done it both ways with no significant or noticeable flaws that I could detect, but that being said, I do rehydrate dry yeast for "cheap" insurance purposes. I've read about the potential toxic effects of wort (sugar solution), specifically the rehydration effect on the cell walls can be detrimental to the integrity of the cell wall layer.
Ron Price