Life Span of Yeast Organism

[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
  

• Candida Krusei

• Torulopsis holmii (Saccharomyces exiguus) if I remember correctly now classified as (Candida millerii)
  

• Saccharomyces cerevisiae 

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

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. 

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.

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.

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.  

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 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!