Sourdough controversy: Where do the microflora come from? Are they replaced over time?
The question recently posted about Ed Wood's (www.sourdo.com) starters brought to mind one of the great sourdough controversies: Do the original strains of yeast and lactobacilli in a purchased or gifted starter persist, or are they replaced over time by the yeast and lactobacilli strains native to the locality, or are they replaced by the flora on the flours used to feed the starter?
Ed is adamant about the flora in the starters he sells continuing forever. Others insist on one of the other theories.
Since most of the yeast and lactobacilli in grain supposedly adhere to the outer parts (bran) of the berries, does feeding a starter exclusively with "white" flour help preserve the original flora? Is it necessary to do this to prevent their replacement, or will the original flora continue to dominate in a healthy culture regardless of what kind of flour it is fed?
What do you all think? Does anyone know of data (not anecdotes!) that speak to these issues?
David
I posted in the other thread but to add to this one
there are the factors you stated dave but there is also this
since flour is a bland thing with very mild flavors as well as it's abilty to absorbe water from the air the flavors in the air due to moisture contant in a bakery are concentrated and constantly present as a result the flours absorb the flavors of the bakery and the sour starter (most of the time not being in the fridg or covered) absorbs thouse flavors as well. meny flavor compounts are present the constantly baking bread or other items the oders of other raw ingreadents , even the amount and type of wood used in the work tables will affect the started. (the wood tables get washed and scraped many times a day causing wood particals and other things on the moleculer level to be absorbed by the flour and starters)
when the starter is removed from the envoirment it starts to absorb the new flavors in the area of its new home or the lack of them as in a home kitchen where the air is not constantly saturated with flavor particals the starter will get blander.
this is why many people no mater how hard they try can not recreate the flavor of their favorit bakery's bread made with the 20 year old starter. Even if the baker gives them or sells them some starter while they first few bakes will give the flavor as the starter ages the flavors fade because the bactira yeast and the air is diferent.
I would question the usefulness of specific case data to answer this age-old question. Not least because I suspect it is incredibly difficult to identify and quantify all the microorganisms present in a sourdough culture. Even if it were possible, it would only be relevant for one particular culture.
Surely a more useful approach is to apply some logical deduction:
Is it possible for a new microorganism to be introduced to a culture? Yes, of course it is! It's also possible to grow all manner of moulds and lord-knows-what in a mixture of flour and water!
Is it likely? That depends on how you maintain your starter. Cast your mind back to when you were starting out with your sourdough culture. How did you feed it? Long feed cycle combined with large proportion of old starter carried through to the next cycle.
This allows a relatively low concentration bacteria/yeast population to increase to the point where it can be sustained through much lower inoculations.
In a healthy starter which is being fed, say once or twice daily or once weekly from the refrigerator - at relatively low inoculation - there simply is no scope or time for a new (relatively much lower population) organism* to establish itself before ingredients are refreshed and 'new native flora' are set back to low concentrations. In other words you are maintaining the existing organisms. and not really giving the new organisms a chance.
The conditions under which said starter is maintained WOULD affect the balance of the microorganisms already present. The plethora of wild yeast and bacteria will have differing metabolisms and each thrive under certain conditions (eg pH). In the extreme case, given time, sustained exposure to poor conditions could result in the death (or relative scarcity) of a particular microorganism. Such changes could certainly be reflected in different aroma and taste. For this reason, proper and careful maintenance of a starter is desirable if particular characteristics are valued. (refrigeration temperature, dechlorinated water etc.)
None of which is to say that it is impossible for a new microorganism to 'take hold' in a culture (after all they do exist, if in low concentration). However the process by which this could make a significant impact on the culture is not particularly 'easy'.
*An exception to this would be an aggressive organism such as Saccharomyces cerevisiae (commercial yeast) which would very rapidly metabolize available sugars and could quite easily become the dominant population.
Note: while the inoculation when feeding starters may be relatively low (say 1:7:7) - the concentration of established microorganisms in the newly mixed starter would still be greater than the 'native population'. It is possible for a very slow build-up of 'new native flora' (a v. v. small, but increasing amount carried through each feeding)...the cumulative effect eventually becoming significant enough to affect flavour.
Thanks for a great post, foolishpoolish!
In the online sourdough FAQ, the entire communication between Dan Wing (co-author of "The Bread Builders") and Dr. Michael Gaenzle can be found. In it, Dr. Gaenzle comments on some of the technical information contained in "The Bread Builders". Here's one relevant excerpt:
From this, I would conclude that although Wood's original culture may have a specific microflora, the microflora will, over time, adapt to altered living conditions (your specific maintenance routine (depending on flour, temperature, time, inoculation, etc.)). I'm a firm believer in Darwinism: The species that are best adapted to the current living conditions will prevail.
Peter Stolz, in Handbook of Dough Fermentations writes:
So although it's still not technically possible to determine the entire SD microflora, its composition will depend on the conditions.
Your quotations are very helpful to my understanding.
So, if one wants to maintain a particular sourdough culture, one must know what are the ideal conditions (feeding flour (?), feeding frequency, hydration, temperature) to give the resident yeast strain and bacterial species that give the culture its distinctive character the greatest advantage in competition with the other species which might also be present or might be introduced.
(Whew! That was sure one long sentence!)
Then, if I knew what those conditions were for Ed Woods' SF SD culture, I would certainly buy it again and strive to maintain it intact.
David
SpringerLink has a lot of scientific data covering sourdough. I thought the following was interesting, but I don't have the entire article and didn't want to purchase it.
"Abstract: Sourdough ferments were reconstitued in the laboratory according to three traditional procedures used in rural areas for building sourdough ferments. The ferments were subcultured on wheat flour to make four generations, which were then used to study the micro-organisms involved in the fermentation of sourdough bread and the characteristic flora that may remain in the ferment for a long time. The analyses carried out on the ferments of the four generations included determinations of lactic acid bacteria (LAB) and yeasts and physico-chemical characteristics (pH, titratable acidity and dough-rising capacity). The results showed thatLactobacillus plantarum, L. delbrückii, Leuconostoc mesenteroides andPediococcus pentosaceus were the most frequent species in all of the trials. Some other species includingLactobacillus buchneri, L. casei andL. sanfrancisco were also isolated in high proportions and in many samples. In some trials the microflora was dominated by LAB and the yeast counts decreased significantly in the fourth generation despite the leavening action of the ferments."
Here's the link to the site.
If Ed Wood is correct that his starter flora never change no matter where used, then I wonder why I've never seen a single loaf of bread labeled "San Francisco sourdough" on any bakery shelf in my state.
Thank you all for your input. Some first reactions:
Norm - Your perspective is very interesting. First, your time frame is decades, not weeks, months or years. Second, the atmosphere of the bakery must be different from that of a home kitchen, at least in the concentration of stuff that might get into a sour and add elements to its taste. Third, the sour is being refreshed so often with new flour, I would think that the stuff in the atmosphere would be present in miniscule amounts in the dough.
fp - Your contentions are consistent with Ed Wood's, and your conclusion is logical. However, there may be other variables in play, for example differences in growth rates for different species that might give some a competitive advantage, allowing them to take over a culture.
Lindy - Thanks for the link. The problem I have with this experiment is how short it is - four feedings.
I had Ed Wood's SF SD starter at one time. The taste of the breads I made with it changed over the first six months. At first, they had little character. After a few weeks, they had the wonderful characteristic SF SD flavor. After six months, they developed a different flavor - not bad, but not the SF SD balance of lactic and acetic acid.
I'm sure this was because of something I did, but I don't know what that was.
David
i do see your point but the time frame can be much shorter than you think try a little experment take some sour starter and place it (say in a small fridg away from other things) and in the same place place some strong oderous things like a cut onion of other vegies not close to each other but in the same place and see how long it takes the sour to get a flavor from the onion.
i think a change will be seen souner than you think. remember things like cooked and raw foods (chicken fish beef and other strong smelling foods are in the frigde constantly changing but there all the same.
the flour is being refreshed with clean flour but how is the flour stored in a bakery bags and bags are stored or silos all exposed to air with flavors. that is truly not the case in the home. also in the bakery the sour is out in the open in vats with no cover also a factor. but in the home even mild flavor componunits are traped in the fridg with no place to go and the sour is traped there as well.
if the sour is left out in the home thats another story
but what i am saying is that a small amount of transplanted sour no matter where it came from will within months will adapt and take om the elements of its new home. a sour started from scrach will also develop within the enviroment it resides in
heres an thought take two starters for the same kind of bread (both rye or both white) starter from a bakery or a forgen source like ed wood and one started from srach place them in the same enviroment for a few months feed them the same amount with the same flour stored in a connen bin, store them the same ( covered or uncovered plastic or the same wood containers) and see how long it takes for the starters to be come symbiotic or not.
it would be an intresting project the results would be (excuse me Mr. spock) fasanating.
To support Norm's theory, I have now had two white flour starters, kept in the refrigerator 5 days/ week in a crock with a loose-fitting lid, change over a period of about 3 months from producing a sweet wholesome-smelling ferment with overtones of citric acid to a much less pleasent ferment with different acids and an overall less good smell. One of these was grown from a King Arthur Vermont Sourdough sample, the other from scratch using the pineapple juice method. Both raise(d) the dough well, and the baked result tastes OK but not as good as it did when the starter was young.
I can only conclude that while the yeasts have remained strong, the orginal crop of bacteria were gradually replaced by the bacteria that live in our refrigerator - which admittedly is not as clean as our grandmothers would have liked. And while the new bacteria must still be sour-forming types, they don't produce the same output as the original set.
Interestingly, my white-rye mix starter, which is kept in the refrigerator in a mason jar with no gasket that is closed during the week, seems to have kept its original taste over time.
sPh
I've been experimenting with having several different cultures in the refrigerator at the same time with good results. There are 5 different cultures in the fridge (2 from Ed Wood (French & Giza), 1 from Carl, 1 I caught from scratch in SF over a decade ago (where I live), and 1 I caught from scratch in Mexico on a visit there. They all have very distinct flavors and properties. The Mexican has the most robust rising power, SF is the most flavorful, Carl seems bland these days but with strong structure. They are all fed all-purpose flour and water/milk every week or so. I hope to catch some Aussie creatures while Down Under next month. It is interesting that the regions with good wine/cheese also have nice sourdough bread (excellent yeast & bacteria!).
David and All,
I read this thread you started after I sent you a pm last night. I guess it answers some of my questions. But...
In addition to the characteristics of both crust and cumb that I find so appealing with SF sourdough bread that I enjoyed out west, the other feature that I found promising about Mr Wood's SF culture with regards to contamination is the supposed symbiotic relationship between the wild yeast Candida humilis and the bacteria Lactobacillus sanfrancisco.
Hamelman states in one of his books that due to the high production of glucose from maltose by L. sanfranciscensis as well as the high production of acetic acid which C.milleri is tolerant of, competing bacterial and yeast species are supposedly inhibited from developing which protects the conditions for the desired species to grow.
I ordered this particular culture from Ed Wood's website. I guess my open question to everybody who has used this starter is if you keep this starter separated and in as close to an aseptic environment as possible when using it, shouldn't it's characteristics in baking be preserved if all the above is true?
Darren
I have been curious about the microbiology of sourdough since it has many parallels to wine, I work at a winery. I remember reading on the net about a study of a sourdough used by a bakery in Germany. They claim that the microorganisms in it have been stable the whole 30 years of the study. The starter has been fed and maintained the same way for 30 years too. I still have questions like yours David but as long as the starter raises the bread and tastes good I'm happy.
Originally microflora comes from flour, there's not much question about it, but it doesn't necessarily mean that sourdough depends on it as a source of fresh bacteria. Flour has a diverse assortment of bacteria growing on it, but once sourdough matures the majority of them die off, leaving lactic acid bacteria. So once the culture is established and is stable it can last for a long time, and there's research following the composition of bakery sourdoughs for months and years which shows that it stays virtually unchanged. So on this count Wood is correct - it's quite possible to maintain the same culture for years.
But here's the thing. When we reconstitute dried sourdough we're not exactly dealing with the same culture. We're changing everything - flour, temperature, hydration, feeding schedule so the sourdough will readjust, benefitting the strains that are best suited to the new conditions and these may not be the ones that were present in the original culture. That is why Leader writes that every starter he'd been ever given always turns into the same thing after a while. There's a also a question about how well sourdoughs survive drying, and I don't know if it was ever studied - as Debra said in her paper - there's a whole lot of research on sourdough that's been done, but it is all in bits and pieces all over the place and needs both access and education to figure these things out.
Mike
...Agreed.
I have only been sourdough baking for 2 years. I began by creating my own rye based starter and have since bought 3 others.
From the start, I have kept my starters in 3/4 liter hermetic, wire-bail canning jars. I refrigerate them and feed irregularly unless I'm baking with them. I have always used filtered water and organic flours to feed and I keep roughly 150 grams (sometimes more) of each starter. I'm so anal about contamination, I even douse my stirring spoons with boiling water before I feed and elaborate for baking in a separate jar. I say this mostly to point out that other than what gets in from the flour and limited exposure to air, I like to believe I have avoided cross-contamination.
I bought the African Whole Wheat starter from Ed Wood and I also bought the Northwest Sourdough Desem. From my own experimenting, they proof at very different rates. The African one is very fast and remains so. The desem proofs faster than my white and rye starters. They both have distinct flavors that have persisted for 2 years and have not changed much that I can note. The African one has an unique tang that has not gone away.
On the other hand, my San Francisco starter story is similar to David's experience above, as its flavor has waned noticeably, much to my chagrin. I had thought because our refrigerator malfunctioned and the SF actually froze for a short period that it had killed off the relevant bacteria. While its leavening ability returned, the SF flavor did not. It has developed more of a sour of late as I have fed it more frequently, but it is definitely not the same.
Perhaps, as David notes, since the African and desem have faster growth rates, it is less susceptible to outside invaders while the SF, being a slower starter, can be overcome.
Along the lines of where do the flora come from. I have become convinced that it does not matter to the taste of the bread which starter I use to inoculate the sour levain for my rye breads. For a time I kept a dedicated rye starter for rye sour breads and they were wonderful. Then one day my white starter was looking so healthy I decided to try using it to start the elaboration. I started with 50 grams of white starter and fed it in 3 steps of progressively larger amounts until I had the needed amount. The breads were wonderful.In the case of rye breads, in most recipes using under 80% rye, we add white flour of some kind to help raise the dough.
I used some rye starter to preferment the biga in Mark Sinclair's Rustic White. You can see the rye in the larger amount of otherwise white flour so you know it's there but I don't think it influences the flavor IMHO.
If I feed my dog a tin of cat food, will it make him any less manly?
Eric
Eric,
I agree on the rye bread starter scenario. A couple of questions though...
Do you think the reverse is true? Did the Rustic White have a different taste having used a rye starter?
Does the amount of initial starter affect taste–i.e. using 250g of active starter from a larger pool of ongoing starter versus a build inoculated with only 30g of semi-dormant starter?
Does your dog know it's cat food? If not, it shouldn't affect his macho psyche.
John
John,
I suspect the percentage of starter used in the initial inoculation would raise the population in the preferment at the time of baking. I would assume there would be some influence on the flavor. I think what we have been hearing from Debra is that the larger amount of inoculation might raise the yeast but lower the LAB ratio causing a less sour flavor.
My dog is a Pomarainien and inclined to be psyco. Cat food, dog food, people food, he doesn't care.
Eric
I think it would make sense that some strains are weaker (and therefore more readily overcome) than others. I have three different starters, wholly different characteristics in each. Just like some bacteria will become more dominant in, say, someone's gut, it seems that the same would hold true for yeast.
I think this is also why we cannot get a firm hold on other sourdough questions (long and cool for sour vs long and hot, for example). Each strain acts differently. Perhaps the general consensus should be "It depends on YOUR particular starter, as each starter, like any other individual living thing, has varying degrees of stalwartness".
It SEEMS from what people are saying that SF is a bit weaker and tends to be overcome by more vigorous strains. I am not sure how one would overcome that. In fact, because there are so many different organisms on flour (even organic...or maybe ESPECIALLY organic), other painstaking efforts of lack of cross contamination are not going to be much good--perhaps either a yeast is spunky or it isn't? Perhaps if it survives the flour (with its millions of added yeasts, etc), it will survive other things. I do not know. I do know that I do not worry too much about water or flour, I just make sure not to use the same spoon to stir one starter as I do to stir another. I use plastic spoons for convenience and toss them after each feeding (which would not be that useful for really often feedings!).
Parenthetically, I have never had SF sourdough bread. I might need to see if I can get some shipped up here as it seems the one to which all others are measured.
I read somewhere about storing starter under 40°F for a couple of days "kills off" the sour producing bacteria. That is what stuck in my brain at least. To me that said storing my starter in the refrigerator wasn't the best place if wanted a more sour taste in my bread. I'm doing an experiment now by storing my starter out of the fridge now to see if it makes a difference.
Here is a quote that I found when I was looking around at sourdough microbiology "The lactobacilli also secrete an antibiotic cycloheximide which "sterilises" the dough since it kills many organisms but of course Candida milleri is resistant to cycloheximide." To me it looks like once you get your sourdough going the lactobacilli protect their food source by the antibiotic cycloheximide. There will be a yeast that will living with them also that is resistant to cycloheximide. I know from studying fermentation of wine that once a yeast is going and active it creates a hostile environment that keeps other yeasts from getting started. It seems to me there can be a similar environment in sourdough.
I have been wondering about this for quite a while. I have a starter I have been using for 3 or 4 years now. When I started it gave me a tangy bread. I maintained it according to the directions in C&C Reinharts book. I decided I was throwing away too much flour maintaining it in the quantitys he does. I divided it down to a very small but similar ratio for its feedings. I now have a starter that raises bread great but is very mild. I have since tried going back to the original feeding recommended in the book and still have a vigorous but mild starter. My question is can I bring back the componet of my starter that I assume has died by feedings, or do I need to make a new starter ? Its not that I don't like my starter but I do want to be able to control it flavorwise. This also makes me ask the question does a balanced starter need a certain volume to flourish, like some fish need a bigger tank? Thanks in advance for your answers.
Da Crumb Bum
Crumb Bumb,
I have about come to the conclusion that for as easy as it is to start up a new starter, you might as well start fresh. At least you will know that if you leave it on the counter it will probably make a sour bread. The other way you could waste a week or so and end up with the same thing only vigorous.
Eric
Here's a story of a mixed culture that might be analogous to our sourdoughs. I remember the story but not where it came from (maybe Bread Builders?):
The author wanted some lawn area on his new property. He started mowing an overgrown weedy area out back, treating it as if it were a lawn (no water or fertilizer, clearly not in Southern California). Within a short time the wild grasses that thrived on these new conditions dominated the other componets of the population, and he had a decent, low maintenance lawn. If he had watered it, other species would have flourished. If he had fertilized it, still others, and so on. If he stopped mowing it, he expected that it would revert to the weedy lot he started with. The other species didn't die, but they didn't thrive, and became a smaller part of the population.
If I insist on keeping my mother starter in the fridge, and refreshing it only monthly, then I should expect to get a different population than I would if I kept it on the counter and fed it daily, even starting with exactly the same starter. How many generation does it take? Maybe not so many, since I will be elaborating a 10g spoonful of the cold starter into maybe 200g of the active baking starter, and 2000g of dough. Twenty times the weight, presumably 20x the population of microbes in the starter (is that 4 generations? 2^4=~20), 200x for the dough (seven generations? 2^7=128). Now if my counter conditions favor LAB at the expense of yeast (say it's kept at 35 degrees C, which according to Ganzles graph is optimum for lb sf, but hostile to c. millerii yeast), I might see a much higher concentration of LAB than in my original starter. What I'm getting at is that the very conditions of elaboration may change the population profile. It may take more generations for a stable population to take hold, but it doesn't have to be stable to be different.
All this is speculation, of course, but if my weed patch doesn't contain fescue to begin with, I won't be growing fescue no matter what, unless I somehow get ahold of some seeds. And with that in mind, is there a good way to sterilize flour that is used to revive or refresh a starter? I would think baking the flour or boiling it would be candidates. I have a suspicion that the two Italian starters that I got from Sourdough Int'l actually never took hold, and the starters that I am using were products of the flour that I used. Especially when reviving an heirloom starter, it seems to me that sterilizing the medium would be the first step. A sterilized medium might make a favorite starter keep its character.
Thanks for starting this thread, David.
Stewart
Stewart,
I have some dry starters from Dr Woods also and was wondering the same thing. The times I have revived a dry starter, more times than not I get an outbreak of the nasty Leuconistic (sp). I know you should continue on feeding and it will eventually settle down but it IS raunchy.
I hope someone who knows the best way to sterilize flour will pipe in and show the way. It has to be a good idea and much less likely to corrupt the population with native species.
Eric
Stewart, good points and I think the reference you are looking for with "this grass in the empty lot" analogy is over at Mike Avery's website here.
FWIW, I've only used 3 starters in my brief 2.5 years of sourdough baking: a starter created from scratch at my home with rye flour that I maintained with rye for 2 years, a spin-off of that same starter maintained for 2 years only with wheat flour, and the Oregon trail starter reconstituted from dry flakes from the Friends of Carl. Although I only maintained them all for about 2 years (I am now down to only my homemade wheat starter), I noticed distinct differences in all 3 the entire time that did not seem to change:
Well, life got busy and I needed to simplify, so I decided to keep the wheat starter only, which I use to this day, although I still have some Carl's flakes stored and it was extremely easy to get that up and running quickly within 2 days. (I have also dried my wheat starter over a long period and sucessfully got it up and running in less than 2 days, where it seems to have the same characteristics as before.)
I maintained all 3 with the exact same feeding and storage schedule, more or less storing in frig for 4 days, out on counter and fed for the other 3 days per week while I prepared to bake or baked. 100% hydration fed at 1:2:2.
Just my observation: I expected the starters to be more similar than they actually were, and they surprised me with their prolonged differences, but 2.5 years is not that long a time in the life of many a starter, so who knows. --MD
Hey All
Eric, I will probably start a new starter at some point just to prove or disprove what is giong on. I hate to quit on it as it has not quit on me so we will see.
I was thinking about this thread today and also came up with the thought that maintaining a culture with just any flour especially organic might not be the way to go if you want to maintain the integrety of the original starter. I am not sure if heating or boiling would work as it might destroy some items the yeasties need. I was wondering about bleached flour and if it would be a more "sterile" if you can call it that, medium?
Lastly, We feed and maintain our starters to create the characteristics we want in bread. Thought being, depending on how we use this stuff in our builds : quantity,hydration,temp,and time etc. I think you could get results that are all over the map even though the intergrety of the original starter might still be fully intact? If we wanted our bread to mimic our starter it would have to be build exactly the same way as the starter. Just some random thoughts.
Da Crumb Bum
After whinning about the lack of sour in my naturally leavened bread and getting replies that said things like one must merely "put the loaves in the 'fridge overnight", it is wonderful to read this thread.
:-Paul