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Can a starter be taken over by local mircoorganisms?

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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?

Daisy_A's picture
Daisy_A

Hi Plasticookies,


Funnily enough this is a popular discussion right now. Information on this link might be helpful.


Basically, as I understand it lactobacillus sanfranciscensis is present in San Franscisco but also in other parts of the world, including in starters that neither came from nor went to that area.


If you got a starter from there it would change but the San Fran bac. would not necessarily die out if your local environment also contained the bac. or was hospitable to it.


In the Belgian lab. tests cited on the other thread, long term presence of the San Fran. bac. was influenced by the way in which starters were kept. Those kept out at room temperature and fed regularly (Type 1), seemed to support the bac. for longer. This would be one of the keys to promoting the San Fran bac. whether your culture was started at home or abroad.


Kind regards, Daisy_A

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

Daisy_A's picture
Daisy_A

Hi Ben,


Thanks for the thumbs up! You mention papers on lab. tests. The paper I was reading is this one from a test on 11 sourdoughs from Belgian bakeries, some of which contained the San. Fran. bac. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2075033/


It's stiff reading but the conclusion is not too impenetrable! It has the local environment as the main influence but does say that flour is important, stating that 'it is known that the type of flour, process technology, and other factors strongly influence the composition of the sourdough microbiota'.


The question it doesn't really answer is how the local groups come to be there and to dominate in the first place. Food for thought...


Kind regards, Daisy_A

Debra Wink's picture
Debra Wink

Daisy_A, you deserve a commendation for slogging through a paper like that. Not an easy task, so please don't be disheartened by my saying that I think you misunderstood the conclusions. The findings actually showed no correlation between the microbial profiles and local environment, but a strong correlation to the bakery in which the starter lives. And, in these bakeries, it didn't appear to matter what flour(s) the starters were fed---wheat, rye, spelt, or any combination---multiple starters in the same bakery, were found to be growing the same organisms. The theory is that the bakery environment is so heavily contaminated with these organisms owing to the shear volume of flour and dough manipulated on a daily basis, that the bakery itself plays a big role in the stabiliy of the starters (rather than flour type). This is very different from the typical home kitchen, however.


Best,
-dw

Daisy_A's picture
Daisy_A

Hi Debra,


Many thanks for your feedback. This clarifies things greatly. It was no problem reading the paper. I quite enjoyed it actually. I read academic papers regularly in Humanities, and although a different field I thought this much more clearly written than many!


I wasn't clear, however, about how I defined local environment. I did actually mean the immediate micro-environment, i.e. the bakery, but didn't say this clearly enough.


What you highlight here makes a lot of sense as the bakery would be very high in microflora. Still leaves me wondering, however, how particular microflora come to dominate any given bakery.


I also wonder in general why lactobacillus sanfranciscensis tends to be found in the San Francisco area. Surely it can't be flour alone, when bakers there must surely use similar flours to bakers across America? If it's the bakery environments, what is distinct about those? So complex but also fascinating.


I take the really good point about the home kitchen not having the historic dough traffic that creates such a wealth of organisms in the commerical bakery. Still complex though as your other posts on starter management show. I have enough to think about sometimes managing my few jars of starter, but the bigger picture is still interesting, particularly as I just added a 'San Francisco' starter to my collection!


My guess from the information here is that it may not keep its distinctive characteristics over time. Still my Cultural Studies training prepares me for that, telling me that cultures that are sometimes represented as distinct are in reality often already becoming mixed, a notion that was developed in part from Biology!


Kind regards, Daisy_A


 


 


 

Debra Wink's picture
Debra Wink

Hi Daisy,


I should say at the top here, that I feel the design of that study is flawed, and I'm not at all convinced the data support some of the conclusions that were made. They failed to collect and consider some important pieces of information, in my opinion, and they didn't take the organism counts and pH readings at times which make sense for comparison purposes. So, it's no real surprise to me that when they fed their data into the software program, it couldn't find any clear relationships. But, they're there if you really look. The article is still very interesting when taken into the overall progression of scientific investigation, but I would recommend others for your purposes:


The sourdough microflora: biodiversity and metabolic interactions, 2005. Luc De Vuyst and Patricia Neysens


Biodiversity and identification of sourdough lactic acid bacteria, 2007. Luc De Vuyst and Marc Vancanneyt


Biodiversity, ecological determinants, and metabolic exploitation of sourdough microbiota, 2009. L. De Vuyst et al.  


the bakery would be very high in microflora. Still leaves me wondering, however, how particular microflora come to dominate any given bakery.

"Due to their artisan and region-dependent handling, sourdoughs are an immense source of diverse LAB and yeast species and strains... In practice, strong effects are exerted by process parameters such as dough yield (water activity), addition of salt, amount and composition of the starter, number of propagation steps, and fermentation time. The impact of these parameters during continuous propagation of sourdough causes the selection of the characteristic LAB and yeast microflora..."   ~2005


"The microbial ecology of a sourdough is not a result of geography itself, but it is the result of traditional practices in specific geographical regions, which certainly affect the processes themselves... The eventually established LAB consortia commonly reflect the media resources (carbohydrates, amino acids, vitamins), environmental conditions (temperature, pH, redox potential) and technology applied [process parameters, use of (a) starter(s), use of baker's yeast]."   ~2007  


I also wonder in general why /lactobacillus sanfranciscensis/ tends to be found in the San Francisco area... If it's the bakery environments, what is distinct about those?

Actually, L. sanfranciscensis isn't found in San Francisco, any more than it is found anywhere. But it has been found to be common in traditional sourdough starters all around the world, even if an environmental source has never been found. Not even in San Francisco, where it just happened to be discovered (in starters) first. One of many myths surrounding sourdough.


Note that traditional (type I) sourdoughs are characterized by frequent refreshment at ambient temperatures, in order to keep leavening strong. Frequent refreshment is the key for L.sf. too, because it keeps a starter from getting too acidic. Low pH is difficult for L. sf., but so long as it's kept comfortable, it is very successful, even with many other Lactobacillus species, which is probably why it is found so often.


"The major part of the microflora of type Ib sourdough preparations consists of obligate heterofermentative strains of L. sanfranciscensis, selected only by the environmental conditions induced by the sourdough fermentation technology applied. Depending on the fermentation conditions, other species... occur in relevant cell counts."   ~2005


"L. sanfranciscensis is very abundant in type I wheat sourdoughs. As mentioned above, this species is characteristic for and dominates type I sourdough fermentations, because it is probably selected only by the environmental conditions induced by the sourdough fermentation technology applied."   ~2005



My guess from the information here is that it may not keep its distinctive characteristics over time. Still my Cultural Studies training prepares me for that, telling me that cultures that are sometimes represented as distinct are in reality often already becoming mixed



Because it's all about the conditions, it is possible for a transplanted starter to keep its characteristics, and it's also possible (and more likely) that it will transform sooner or later. It can go either way, but the microbial profile is only partly responsible for the character of the bread made from it. The rest comes from "process parameters" and "artisan-dependent handling."


Hope that helps :-)
-dw

Daisy_A's picture
Daisy_A

Hi Debra,


That's brilliant. Many thanks for this detailed and expert feedback. Thanks in particular for the critique of the study quoted initially and recommendations for further reading. I will try to follow these up. Obviously I won't be able to understand these as a scientist would. However this is the general way I am used to working in the Humanities, i.e not relying on one paper and hearing experts in the field outlining the strengths and limits of particular approaches and recommending and citing further studies :-)


Thanks also for the feedback on lactobacillus sanfranciscensis and Type 1 sourdoughs. I may be wrong but am hoping that this tends to confirm my growing understanding, as expressed in the earlier message to plasticookies:


 


Basically, as I understand it lactobacillus sanfranciscensis is present in San Franscisco but also in other parts of the world, including in starters that neither came from nor went to that area [...] [Starters] kept out at room temperature and fed regularly (Type 1), seemed to support the bac. for longer [if present]. This would be one of the keys to promoting the San Fran bac. whether your culture was started at home or abroad.

 


The quotations that you give from further studies really help to provide an insight into the next level parameters. Thank you.  "Artisan-dependent handling" - let me take that back into the kitchen. Down to me to keep my starters healthy then!


The starter I cultured myself is quite young. After a strong start and several weeks on the bench it seemed to weaken after a short stint in the fridge and started producing inelastic dough. Your postings on that problem did help me to get it back in line. At the moment I have my starters as 'Type 1' - on the bench and fed regularly with a generous and consistent amount of flour. They are now looking strong, rising well and are well aerated.


I am interested too in the fact that fermentation time is one of the parameters. Like a lot of bakers who use sourdough I mostly ferment my doughts over a relatively long time, up to 24 hours in some cases. 


In addition, the interplay of 'traditional practices in specific geographical regions', seems like it might be a very interesting focus for future as well as current research.


Thanks again for taking the time to respond in such detail.


With best wishes, Daisy_A


 

Debra Wink's picture
Debra Wink

You're welcome, and thank you :-)



the interplay of 'traditional practices in specific geographical regions', seems like it might be a very interesting focus for future as well as current research



You should read Local Breads by Daniel Leader, for real-life examples of "artisan and region-dependent handling" across various regions of France, Italy, Germany and the Czech Republic.

Daisy_A's picture
Daisy_A

Hi Debra,


Many thanks for recommending the Leader book. I look forward to following this up.


With kind regards, Daisy_A

La masa's picture
La masa

A friend sent me some dried starter about a year and a half ago. It was made in a very different climate than mine, Atlantic vs. Mediterranean.


I brought it back to life and have been using it since then.


About six months ago I grew a new starter keeping it into a proofing box while I was trying a Detmolder process, so it was at a fairly high temperature, unlike the first one.


I've been using both starters since then and now I can't tell the difference between them.


Same behaviour and same smell.


Actually, I've thrown the latest one away, as mantaining two identical starters makes no sense.


Even more: during my holidays this month I went to see my friend and we made a few loaves together. I was surprised to see that her starter was completely different from mine despite originally being the same.


We both feed our starters a bit chaotically, using different flours and shedules. We both make bread at least once a week.


Some of the flours we use are the same brand, some aren't, sometimes wheat, sometimes rye.


So, IMHO, environment matters a lot, but I'm open to correction.

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.