Life Span of Yeast Organism

Does anyone know the typical lifespan of a yeast organism in baking? I am also interested in knowing if sourdough yeasts and commercial baker's yeast have comparable birth-growth-death spans within conditions optimum for that particular yeast.

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[quote=Graham]Does anyone know the typical lifespan of a yeast organism in baking? I am also interested in knowing if sourdough yeasts and commercial baker's yeast have comparable birth-growth-death spans within conditions optimum for that particular yeast.
[/quote]

The "birth-growth-death" criteria is inadequate to quantify their life cycle because yeasts in bread dough reproduce by "budding", one cell divides to become two etc. so when does the original 'mother' cell cease to exist? When are daughter cells born or die? In dry conditions they can form spore packets and survive until favourable conditions once again prevail. 

Theoretically yeasts can live indeffinitely given the contiuation of optimum conditions. Specific reproductive conditions are slightly different to specific gas producing conditions for bakers and sourdough yeasts. "Sourdough yeasts" comprise of a mix of several species which may or may not have the same requirements.

Let me have a look around; however, you too can search, the main sourdough yeasts are as follows:

[quote]

(Spicher et al., 1979) isolated four sourdough yeasts and listed the sugars metabolised in two ways;

1. Fermentation (fer)
2. Assimilation   (ass)

The table is much as you would find in Bergies Manual with positives (+) and negatives (-) to indicate which, are or are not, metabilised. For the sake of simplicity I've not listed those sugars which are negative but where a sugar is omitted from the list below the specific yeast indicates a negative for that sugar;

  • Picia saitoi
Glucose - fer, ass
Athanol - ass

 

  • Candida Krusei
Glucose - fer, ass
Athanol - ass

 

  • Torulopsis holmii (Saccharomyces exiguus) if I remember correctly now classified as (Candida millerii)
Glucose - fer, ass
Galactose - fer, ass
Saccharose - fer, ass
Rafinose - 1/3fer, ass
Athanol - ass
 
  • Saccharomyces cerevisiae 
Glucose - fer, ass
Galactose - fer, ass
Saccharose - fer, ass
Maltose - fer, ass
Rafinose - 1/3fer, ass
Athanol - ass
 

From [url=http://sourdough.com.au/?q=forum/topic/1093#comment-8492][b]here[/b][/url] [/quote]

[quote=Danubian]

The "birth-growth-death" criteria is inadequate to quantify their life cycle because yeasts in bread dough reproduce by "budding", one cell divides to become two etc. so when does the original 'mother' cell cease to exist? When are daughter cells born or die? In dry conditions they can form spore packets and survive until favourable conditions once again prevail. 

Theoretically yeasts can live indefinitely given the continuation of optimum conditions. Specific reproductive conditions are slightly different to specific gas producing conditions for bakers and sourdough yeasts. "Sourdough yeasts" comprise of a mix of several species which may or may not have the same requirements.

[/quote]


Thank you Danubian. So yeasts are potentially immortal in optimum conditions.

You mentioned that forming 'spore packets' is a mechanism that helps the organism to survive in dry periods. I take it that the other threat to yeast is pollution, either produced by yeasts as a by-product of living (eg. alcohol), or introduced by humans and other external environmental influences (eg. heat from an oven).

What kind of physiological feedback occurs that makes yeast slow down the budding process as the pollution in the environment grows? Is there a mechanism that 'alerts' the yeast to stop reproducing for the survival of the colony?

Or is it just a case that new and developing buds are killed by the growing pollution and therefore there are less new and developing buds?

This is so Discovery Channel! :)

Seriously, they should make a documentary out of this.


In that respect.yeasts are like virus in that they will either mutate,or by selection,become immune to the effects of some toxins. On a simple level, yeasts becomes tolerant of chlorinated water for example...at first,inhibited by the chlorine,but slowly re-engineering resistance.

Yeasts are also aliens,because they can survive in a vacuum, ie space. This means they have already made us dependant on them, the next step,they will take control...we of the sourdough network are actually planet Earths last hope in the fight against this insidious alien species. 


 

We should make an animation film! I think we have all the talent (brains, comedy, drama) here in this forum.

Sorry, Graham, side-effects from the other thread....


Yes, I am thinking of the story-board now; a cluster of salamander balls floating through space, scorched by cosmic rays until they burst...releasing a cloud of mutant yeast organisms falling on the earth's moon and evolving into immortal single-cell creatures...launching baguettes at planet earth to destroy our ancient but more highly evolved cultures. Defend your leaven!
Maedi....start working on the theme song.

But....what rating shall we assign to it...you know...with the salamander parts and all...?


A rating? That's tricky. I needed to know more about salamanders, found this...

http://en.wikipedia.org/wiki/Salamander

...do these creatures really even have dangly bits?

John, where are they? Do tell.


You see,they have crossed threads on us....the salamanders are on the other thread,but their insidious evil genius,in league with the yeasts will probably spell the end of life as we know it. Graham must have been eating yeast bread,because they made him morph with the salamander thread, thereby demonstrating their power through their evil agents the salamanders....moonlighting as innocent creatures with a liking for (wood) fire(d) (ovens.)

The next thing they will do,this unholy league,is to get us making lists...beware anybody who starts making lists...you have been infected.


 


Sorry


John




Yes, some of us are vaccinated with sourdough leaven polycultures so we are protected! The polycultures reek of compounds antibiotic to the malignants.

A group of free thinking citizens have set up The Polyculture Foundation to coordinate the distribution of this vaccine for the populations of the west, espcially in densely populated urban areas with success spreading. However, The Polyculture Foundation has been approached by some of the well connected and well funded international foundations and banks who are keen to assist, they pay lipservice, but their assistance has been declined as we have evidence they were planning to replace the vaccine in the field with the malignant.

Since our investigation we have found evidence that other vaccine tampering has been rife in the East and Africa and the malignant is gaining ground in those areas.

     


Gotta nitpick it in the bud while the list is short! Together, now.....

* * * REFRESH!!! ** *


Being totally serious as always, ummm John now that you are a sourdough geek, have you torn out the pages of your book, I mean the yeasted parts?
Another query regarding the natural Tucker book, a fellow I found on the net said your rye recipe only called for shaping the dough after a short mix then a long ferment, is that a style you came up with?

I like my salamander oysters out of my loaf, fry em up I say and slap some of that vegamite, ooops that is yeast isn't it!

Have you heard the term "Murray oysters"? I remember the first time I went to visit a bloke I was hoping to introduce myself to - I was 22 years of age at the time and a city slicker at that - I went out to his farm in the back blocks between Bourke and Nyngan. He was mulsing (I think that's the correct spelling) and knackering his sheep. (it was common practice back then) The young ram is held on its back in a steel cradle with its back legs splayed out and pinned down. But the front legs require one arm held over them which means the cocky has only the other holding a knife to perform the task.

I walked over to where he was working, as I got close I noticed him bend and put his face in the rams crutch. He then straightened up truned, spitting to the side then held out his hand. I couldn't concentrate on what he said because an oyster was hanging from his chin. He could see I was stunned but chipped in that removing murray oysters was hard unpleasant work. At the time it took a few minutes to understand what I saw. But I'll never forget it. 

Apparently teeth are used to remove the oysters after the cut has been made so the knife doesn't need to be put down and taken up again.  

 


A good read on yeast including the yeast reproductive cycle:

http://en.wikipedia.org/wiki/Yeast


Interesting quote from 2nd paragraph:

"The yeast species Saccharomyces cerevisiae has been used in baking and fermenting alcoholic beverages for thousands of years."


Well...this sounds a little bit odd! Saccharomyces cerevisiae may have been a part of the process...but this statement does not credit other yeasts with making a contribution to baking over that period.


For the record...

http://en.wikipedia.org/wiki/Bacteria

Bacteria sound more advanced than yeasts in terms of reproduction and their ability to adapt/survive in different environments.

that was deffinitely a hijack, unintentional as it was.

I'll get back to the yeast question over the next few days, I've got stuff in books but I'd rather post links from the web.

I don't even know how relevant the 'hijack' concept is on this site. If we are inspired to talk isn't that what counts?
Besides, I had heard the term 'Murray Oyster' and not known what it meant. Now that I do know I am so much happier and am certain that it will improve my baking process.
I'll never forget it. I have a vivid imagination. But, I can't imagine, Graham, how you'll use your teeth in your baking process.

More yeasty beasty info, Boris? Can't wait.

Oops. Just saw my shiny new badge. I promise to behave hereafter.


That Rye recipe,yes it works well for dead soft rye but i developed different tech later,which isnt that different but faster.Rye tech often depends on the rye,because it can vary a lot..........geek schmeek, i would love to have the time to make good yeast bread commercially,as i did in the late 70`s...long ferments using malt...starting it all with a teaspoon of yeast the day before, just as another style of bread in a bakery....but i rapidly tire of eating yeast bread, no matter how well made....hatcho miso is like "sourdough vegemite"!.........the book, um that was 1982-3,talking sourdough was like talking quantum physics, the yeast stuff is really to provide a medium for translation of yeast based(alien) headspace to the transcendental one of sourdough...u know rosetta stone lol.


 


I meant to tell you a fellow on the site called foldingpain http://foldingpain.blogspot.com/ mentions you and I and bought your book NTB and tried the said receptte with some changes!

 

Cheers!

This book really has it all in terms of industrial and commercial, except sourdough yeasts. However, you can read through the text of the selected pages and come away very much informed on yeast in food production.

Just a few points on reproduction; yeast - Saccharomyces cerevisiae - can function in aerobic and anaerobic (in the presence of oxygen and the absence of oxygen, respectively) conditions but reproduces more efficently in aerobic conditions. Dough conditions are largely anerobic which means more alcohol and Co2 is produced and daughter cells take longer to synthesise.

The yeast organism, although a single cell does have a finite lifespan which could be measured by the number of times it buds producing daughter cells; 12-15 times if I remember correctly, but I'm sure it'll be somewhere in this book. However, I believe as a colony given the optimum conditions could grow indeffinately.

[url=http://books.google.com.au/books?id=xbZRt2pKwqUC&pg=PA180&lpg=PA180&dq=yeast+manufacture&source=web&ots=p-pTr_fD1a&sig=fpXO1s812e7SM95kEXuXWqLrmK0&hl=en#PPA12,M1]Use of Yeast Biomass in Food production[/url]


[quote=Danubian]

The yeast organism, although a single cell does have a finite lifespan which could be measured by the number of times it buds producing daughter cells; 12-15 times if I remember correctly, but I'm sure it'll be somewhere in this book. However, I believe as a colony given the optimum conditions could grow indefinitely.

[/quote]

Danubian this book is a very important find, and your quote above goes straight to what my original query was all about. Thank you.

That is interesting that individual yeast cells are finite and that the amount of daughter cells produced is a potential measure of life expectancy. Without citing the complete book directly we do not have a concrete source, though having observed your similar recollections of baking knowledge, I give your memory a 97% or higher chance of absolute accuracy.

Similar to humans, both nature and nurture determine the life span of a yeast cell. The baker is in a position to nurture the yeast by controlling the environment it lives in. The way the baker nurtures yeast will affect the behavior of the yeast colony and many characteristics of the baker's dough.

Quote from Use of Yeast Biomass in Food Production:

"The taxonomy of yeasts is in a continual state of flux as new microorganisms are discovered and increasing knowledge about microorganisms results in the yeasts being shifted within subgroups".

Yeast and yeast knowledge is evolving. What an exciting prospect! Yet some styles of baking choose to use only quantifiable yeasts with known performance characteristics. These are not just the 'baker's yeast' styles, but also the industrialised sourdough systems of larger manufacturers; The nature of the microorganisms is known, the nurture is tightly controlled, and the outcome (bread) is highly predictable.

There is obviously a commercial place for extreme predictability in baking. But personally I find the idea of working in a tightly controlled 'closed loop' very boring and uninspiring. Bakers outside the loop have much more fun!