Author Topic: Over pitching/under pitching experiment  (Read 9077 times)

Online euge

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Re: Over pitching/under pitching experiment
« Reply #30 on: October 22, 2012, 06:54:39 PM »
I expect no less from Dr Schmidlin. Only wish this sort of insight was more frequent.
The first principle is that you must not fool yourself, and you are the easiest person to fool. -Richard P. Feynman

Offline nateo

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Re: Over pitching/under pitching experiment
« Reply #31 on: October 22, 2012, 06:57:40 PM »
Tom - So if someone says "budding scars inhibit yeast performance in beer fermentations," that's probably specious reasoning?
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Re: Over pitching/under pitching experiment
« Reply #32 on: October 22, 2012, 07:00:53 PM »
older mothers don't perform as well as younger mothers.
Tell me about it...

Online yso191

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Re: Over pitching/under pitching experiment
« Reply #33 on: October 22, 2012, 08:13:29 PM »
older mothers don't perform as well as younger mothers.
Tell me about it...

Ha!
Steve

Offline tschmidlin

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Re: Over pitching/under pitching experiment
« Reply #34 on: October 22, 2012, 11:02:03 PM »
THAT, Sir, was probably the most interesting thing I've ever read on any brewing forum. Very nice!
I expect no less from Dr Schmidlin. Only wish this sort of insight was more frequent.
Thanks :)

older mothers don't perform as well as younger mothers.
Tell me about it...
;D

Tom - So if someone says "budding scars inhibit yeast performance in beer fermentations," that's probably specious reasoning?
Maybe, maybe not.  Bud scars do affect cell flexibility and will likely affect the ability of cell surface proteins to do their jobs.  But there are many changes to yeast cells as they age replicatively, including alterations in gene expression and decreased protein synthesis, so to attribute poor performance to bud scars is wrong in my opinion.  Bud scars are an indication of replicative age, and replicatively older cells perform worse - that doesn't mean that the scars are the cause.  The data I am familiar with indicates mixed results on the ability of scarred cells to get the nutrients they need effectively so that doesn't seem to be the case, but there may be more recent data that proves me wrong on that.

I should also point out that the end of a yeast "lifespan" is not death, it is senescence - the cell does not divide.  Whether it is alive and consuming nutrients or not can be hard to tell on a cell to cell basis, and I am not aware of any studies that came up with an definitive answer for that.
Tom Schmidlin

Offline phillamb168

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Re: Over pitching/under pitching experiment
« Reply #35 on: October 23, 2012, 02:27:12 AM »
So, old yeasts never die, they just produce more phenols?
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Offline tschmidlin

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Re: Over pitching/under pitching experiment
« Reply #36 on: October 23, 2012, 09:22:38 AM »
So, old yeasts never die, they just produce more phenols?
;D

They die of course, I'm just saying the experiments don't test for cell death.
Tom Schmidlin

Offline bluesman

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Re: Over pitching/under pitching experiment
« Reply #37 on: October 23, 2012, 09:35:59 AM »
Great info Tom!

How would you explain yeast cells recovered from King Midas' tomb to produce DFH Midas Touch. Were they dead cells that were somehow rejuvenated or do the cells go into some sort of hibernation? Inquiring minds would like to know!
Ron Price

Online euge

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Re: Over pitching/under pitching experiment
« Reply #38 on: October 23, 2012, 10:17:54 AM »
Obviously some yeast are able to dehydrate and maintain some sort of suspended animation for lengthy periods. Also, I wouldn't expect all of them to survive- but the billions ought to be able produce a few that the scientists could culture. That would just be a statistical outcome.

Think about the yeasts found in the millions of years old piece of amber that have been grown- amazingly this particular strain shares the same DNA found in lager yeast.
The first principle is that you must not fool yourself, and you are the easiest person to fool. -Richard P. Feynman

Offline denny

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Re: Over pitching/under pitching experiment
« Reply #39 on: October 23, 2012, 10:21:09 AM »
Obviously some yeast are able to dehydrate and maintain some sort of suspended animation for lengthy periods. Also, I wouldn't expect all of them to survive- but the billions ought to be able produce a few that the scientists could culture. That would just be a statistical outcome.

Or it's a great publicity vehicle....
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Offline tschmidlin

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Re: Over pitching/under pitching experiment
« Reply #40 on: October 23, 2012, 10:35:06 AM »
Assuming it was actually an ancient strain and not some modern contaminant, the most likely explanation is that the yeast sporulated, which would protect them.  The revived strain would not be exactly the same as the parent strain, but there would be some strong similarities.

I don't know the circumstances behind the discovery, but there are many things that could have contributed to the cells' ability to survive even without sporulating.  pH of the liquid over time, if it ever dried out and when and how, temperature stability, O2 levels, really just a host of factors that play into it.  And remember, viability of cultures depends a lot on the media used and is determined in research papers by growing them for a certain period of time after chronological aging and then measuring growth in some way.  These methods may be sensitive enough to note that a single cell is growing (they may not), but when the data are presented they are shown as a fraction of full viability and the plots trail downward over time.  So it goes form 100% to 0% on a single plot - anything below 5% is pretty close to 0% due to the size of the plot and the line thickness.  Anything at 1% is virtually indistinguishable from 0%.  Imagine what 0.0001% looks like - that's still a lot of viable cells :)

Finally, there is the phenomenon of "gasping".  Some cultures will start to grow again, long after the nutrients are depleted and when the plots show they are "0% viable".  This is not well studied, but I would speculate that the viable cells are scavenging from the dead cells, and this could create new cells in preparation for sporulation.
Tom Schmidlin

Offline davidgzach

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Re: Over pitching/under pitching experiment
« Reply #41 on: October 23, 2012, 10:55:27 AM »
I expect no less from Dr Schmidlin. Only wish this sort of insight was more frequent.

+1 to that!
Dave Zach

Offline phillamb168

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Re: Over pitching/under pitching experiment
« Reply #42 on: October 25, 2012, 12:57:05 AM »
Do Wyeast or White Labs carry any of these paleontological yeasts? As you say Denny, it's a great publicity vehicle...
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Offline denny

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Re: Over pitching/under pitching experiment
« Reply #43 on: October 25, 2012, 08:48:29 AM »
Do Wyeast or White Labs carry any of these paleontological yeasts? As you say Denny, it's a great publicity vehicle...

Although I have no evidence, I tend to believe it's as Tom suggested...some more recent contamination rather than a truly ancient yeast that's been magically revived.   But that just might be my inner curmudgeon coming out.....
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Offline bluesman

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Over pitching/under pitching experiment
« Reply #44 on: October 25, 2012, 12:49:58 PM »
Thanks for the insight Tom. Perhaps we'll never really know but believe as we may desire. It's at the very least an interesting story, not to mention a really fine beer. :)

Ron Price