The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Can a starter be taken over by local mircoorganisms?

plasticookies's picture
plasticookies

Can a starter be taken over by local mircoorganisms?

I had this ridiculous idea of starting a culture during my trip to San Francisco, but soon scrapped that idea after realizing *how* ridiculous that idea actually was. Anyhow, that got me thinking: If I could actually bring a San Francisco sourdough starter (dried) back to my home in Toronto, would the original SF bacteria and yeast be maintained in the starter?

I've taken microbiology courses, so I understand that the existing population of microbes will generally restrict the growth of any foreign microbes. However, if I maintain this starter over a long period of time, and it is exposed each time I use it, wouldn't the population of microbes eventually change?

Maybe I'm just looking into this too much. I haven't had a chance to really experiment with sourdough starters, so does anyone else have any input on this?

BakerBen's picture
BakerBen

Hello,

I have been interested in this topic too.  There are some places that sell dried starters - you can buy starters that come from many different locations in the world.  Now, that would lead one to believe that the starter would not change or else why would you buy it.  I agree with everything Daisy_A said and have just a little more to add - a lot of sources state that you really are not catching wild yeast from the air as much as the wild yeast that innoculates a starter when it is initially started come from the actual flour that you are using to feed the starter with.  This kind of supports the statement of "starters are influenced to a great degree by the way they are cared for" -I would think that most people have a loyalty to a specific brand of flour and thus continue to buy it over a long period of time and thus the starter gets fed the same type flour over a long period of time.  It would be interesting to see studies that take a well established and healthy starter and see how long it takes to feed it with a flour that contained a different type of yeast to see how long it would take for that yeast to influence and become established in the starter - that is, how long before the starter changed.  I would think there would be varying results based on the types of yeasts - both established yeast and yeast that would be contained in the feeding flour.  There are some really technical papers available from Colleges and Universities that study this type thing - you need to be part biologist and part chemist to really understand them and I am neither.

Ben

Frequent Flyer's picture
Frequent Flyer

My wild yeast starter which I grew with rye and white flours tends to be more sour than I like. When I mentioned that to my friends and said I was going to stop using sourdough starters, they offered some mild starter they have had for quite a while that originally began with cultures from near the Red Sea.  This new starter was very mild and had a distinctly different texture.  I've been using this weekly now for over 6 months and it may be slightly sour now, but still primarily mild.  It doesn't answer the question for me as to whether the yeasts are contributed primarily from the air or from the flour being fed to the starter, but certainly any transformation is very slow.

To further my so-called research, I've begun a new starter (now on day 3) with heirloom wheat grown in my region of the country (South Carolina).  The yeasts present initially should be native to the South.  I'll see how the starter acts and tastes initially and over time. 

Lastly, I'll ask a question.  Is there a way to sterilize the flour used to feed the starters?  I assume heating the flour to 140F would do that but I don't know what other attributes of the flour would be affected.  Using sterile flour should eliminate from the equation the yeast on the flour being fed and would leave any new yeasts contributed to be from the air.

FF

BakerBen's picture
BakerBen

Hello FF,

The study I saw - can find now - was where the scientists irradiated flour and then tried to use it as the basis, and subsequent food, for developing a sourdough starter.  I believe they hand 10 control samples (non irradiated flour) and 10 irradiated samples.  The test result was that 90% of the control samples were successful and only 10% of the irradiated samples were successful.  Based on this the conclusion was that the yeast did not come from the air but rather the source was the flour.  I am sure if you searched you could find this somewhere. 

Food irradiation is very questionable as to its safety for food consumed by humans or other animals and also to possible mutation which it may cause.  I have studied wine a bit and I know that the wine making process starts by killing any wild yiest on the grapes and then introducing a "known" and "desired" yeast.  I was told that this process was done to get to a known starting point so that a known result would occur (i.e. kill the unknown and start with a yeast that has known and predictable characteristic).

Now this does not answer the question "does feeding a healthy well established starter with a flour that contains a different yeast strain cause a change in the sourdough starter?".  I have read the analogy that a healthy starter is kind of like a healthy lawn - it will not let a different type grass come in.  Now, obviously who ever said this is not from SC, but you get the drift.  I would tend to believe that when you abid by the principle of a 2:1 1 ratio that you are only instroducing 25% new flour into an established yeast colony and that the differring new yeast don't get a chance to really get a foothold. 

This is an interesting because there is so much information on the web that give such varied information with such authority.  There are a few really scientific bakers that could possibly provide more information than I have for sure. Hopefully they may enter in to this conversation.

Different topic. I was born and grew up in SC - small town named Lancaster about 40 miles south of Charlotte, NC.  I live in Raleigh, NC now.  Just curious where you may be in SC?

Ben

Frequent Flyer's picture
Frequent Flyer

I'm near Atlanta.  South Carolina is the only place I could find near here that grows hard wheat.  It's in the same region and as local as I'm going to find.