The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

longevity of yeast

Mini Oven's picture
Mini Oven

longevity of yeast

I've been slowly brewing away with some thoughts over the years....  Starters and their differences.  Why is it that sometimes a weak rising sourdough starter culture will bounce back quickly (too quickly) and suddenly "stabilize" after chilling or a near death experience?


I have a timing theory thinking the yeasts might have syncronized their life cycles through temperature control and also the idea that perhaps getting the desired yeasts to spore (hibernate) and then wake up the correct yeast using the same selected bacteria group to do the job.  I have always (still do hopefully) kept my ears and eyes open for explanations. 


I was pointed to a podcast on research extending life spans recently and the mention that yeasts were also affected perked up my ears.  Why not?  I began to think about it more and more and it made sense.  Maybe this was one explanation for what I was observing.  Longevity of yeast perhaps.  That the yeast were living longer budding more and producing more gas in their life spans before dying letting the next generations take over.  The peaks that stay peaked for longer periods of time after feeding the neglected starter.   Hmmm.  Puts the expression "never starve a starter" into question.


There is also lots of other information in the interview like a quick mention that 2% sugar intake shortened life span by 20% which also could be applied to yeasts.  I wonder what the details are there?  The BBC Podcast features Prof. Cynthia Kenyon, director for the Hillblom Center for Aging, Univ of Calif. San Fran.   Topic: Latent capability to extend lifespan.


http://downloads.bbc.co.uk/podcasts/worldservice/discovery/discovery_20101027-1032a.mp3


Toward the end of the interview, I was struck by our own TFL member diversity and how contributions from so many have enriched the site.   Listen and enjoy!


"Lay back and bake at TFL!"

Comments

Franko's picture
Franko

Hi Mini,


This is thought provoking stuff and relevant to what I've been seeing in my rye starter the last few times I've used it. The poor thing hasn't been fed in ages, sits in the fridge for weeks on end, but when I eventually get around to using it to inoculate a levain, it just goes gangbusters...much to my surprise. It's just amazing how resilient these starters can be considering how poorly we often treat them. Your theory seems like it may be on point, but it would be interesting to hear what Ms. Wink has to say on the matter, and hopefully she'll see your post and comment.


Franko

Mebake's picture
Mebake

So? I dread to say that we may come upon a time where a sourdough culture is Genetically modified to extend its yeast ripening longevity??!!


I still prefer an "organic" sourdough!


Thank mini for bringing this to our attention..

Mini Oven's picture
Mini Oven

accidentally?  If I understood it better, I could plan on it.  Use it like a tool.  No need to mess with any genes.  Knowing how to turn on and off switches would be helpful.  I would know that by tucking a peaked starter into the fridge mature would lead to a better starter with the next refreshing or If I tucked a just fed starter into the fridge , it will work better.  It would cut down on all the experimenting and frustration that can come with a weak starter.  Knowing that lack of food or being cold half starved would boost yeast activity (when I need them) would be a blessing.


Our goal as home bakers is to maintain a healthy sourdough culture/starter so that it responds well and raises our dough.  Keeping a healthy starter that can ward off invading organisms like mold and unwanted bacteria is important.  Prolonging life and helping our yeast to stay robust is a true goal.  Now if that means that the starter has to use up its food on a regular basis and go just a little bit hungry, so that we can maintain healthy starters, then I'm all for including it as part of a maintenance routine.  


Too much starving is not good, when the yeasts may be forced to go dormant...  or is it?  It takes patience to revive the culture but when this is done, many times (not all) the culture will come back with a health and fortitude that is amazing.   How does that affect us?  We become somewhat aware of what we are doing and repeat this maintenance behavior, after all, it works for us in bread preparation.


It is still organic.  Regulating the food for the yeast occurs naturally as well, with our starters we just supply the food on a regular basis.  It make sense that if a yeast in nature is deprived of food, it has some kind of mechanism that helps it survive longer when it becomes active again (when it comes in contact with food and moisture) ensuring that it survives longer to reproduce. 


Sourdough cultures (remember they're coming from the flour) not being organic?  I don't know where that fear is coming from.  In a lab, to find out what is going on, yes, genes are manipulated so that the experiments can be controlled.  Because nature doesn't always do what scientists want it to do  (like mutate or switch off a gene's working ability) when nature is being observed.  But when you combine water and flour in your own kitchen, any gene manipulating is only something that would occur in nature itself.  Turning on and off regulating switches in the genes happens all the time.  (That was a great discovery by the way finding out about switches.)

Syd's picture
Syd

This has fascinated me as well.  In fact I have begun to think, of late, that the best way to maintain my starter is to abuse it.  Once I  left it on top of the fridge in 31 degree C heat, unfed for two days.  When opened, it smelled like paint stripper.  I was sure it was ruined.  But no, it came tearing out of the stables and forced its way out of  the top of my wire clamp jar.  On numerous occassions I have left it unfed in the fridge for more than two months and when I re-feed it, you would swear it had spent 60 days at a health spa. 


 


For the past two weeks I have kept it out of the fridge.  I have pampered it with two regular feedings a day and how has it rewarded me?  With disappointing loaf after disappointing loaf.  I reckon it is time for neglect again.


 


Befuddling, thy name is sourdough.

Mini Oven's picture
Mini Oven

:)   (Friedrich Nietzsche)

dosidough's picture
dosidough

As an experiment after reading posts referencing starters kept out I tried it with mine (which is kept in the fridg) for a week. Then I baked using both just at their peak. The fridg stored starter was fed the night before as was the counter starter and left out 12 hours. The fridg starter rose better and definitely had a more robust sour flavor. So I abandoned the counter method and returned to fridg storage. Sometimes it just sits 4 to 6 weeks but with a Wed. night feed, then back to fridg, a Fri. night feed left out 12 hrs it's gangbuster for a Saturday bake.


Nice to hear a reason this this Mini. Thanks.


Oh...if I want a milder version I go to Susan's Ultimate Sourdough and build a stiff starter Wed. then do the same cold warm method. Just 2 feeds and it's good to go. It seems to me the cold storage promotes a more quickly convertible starter; white to rye or wheat, lower to higher hydration. Those yeasties are real survivalists :)   Also my basic is about 85% hydration and that seems more versatle than the wetter starter in my experience.


Good info Mini, and bake on...
Dosi

hanseata's picture
hanseata

but for me it works very well to keep my starters the whole time in the refrigerator and feed them only, when I used most of them and need to build a new mother starter with the leftovers.


Sometimes the starter, when I used a lot of it, is still at its peak, sometimes it dropped down quite a bit, and, at worst, it's concentrated at the bottom of the bowl and covered with a dark skin with liquid on top (that skin I scrape off, of course, before using).


In every case I could build up a strong new starter from those - therefore I don't really see why I should feed it all time (and throw a lot out).


A real difference in taste, though, especially in a rye bread without a lot of other ingredients, I achieve, when I feed the starter according to Martin Pöt's 3-step method (3 feedings at falling temperatures). Those starters are also very lively and smell very pleasant.


Karin