The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

San Francisco starter

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Crumbly Baker's picture
Crumbly Baker

San Francisco starter

Ok, I do hope this hasn't already been asked, but I expect it might...


However, the question is this.  If you have a starter, could be from SF, could be from Timbucktu, at what point after refreshment does it no longer have the right to be called, 'SF sourdough' or 'Timbucktu sourdough' starter?


If I keep adding a floour and water from anohter place on the planet, does that corrupt the original?



wmtimm627's picture

My understanding is that what makes a San Fran sourdough so unique is the airborne yeast in the area. You could get a starter from there, but as you feed it, over time, it just turns into a "wherever you live" starter. This may not be so bad. San Fran sourdough is certainly unique, but that doesn't mean that it tastes any better than what you make at home.

RonRay's picture

And I been told what makes a San Fran sourdough is the wee beasties in the mountain waters that feed the area.
However, I have often read that about 2 months is as long as it takes for aquired starter to be "your" starter, in the sense that your water and airbourne yeast will have joined the party, if not completely taken over by then. I would imagine, that there are so many variables that any difinitive answer would need to be on a case by case basis.

Daisy_A's picture

Hi Crumbly Baker,

Seems like a good question and one I'm interested in, having just purchased a 'San Francisco' starter.

I'd go along with RonRay's point that a case by case basis is a sound approach. All starters contain a range of micro-organisms and the San Franscisco lactobacillus can be identified in other parts of the world and is present in starters that don't originate in San Francisco.

I've read informal reports that say that starters are colonised by local yeasts no matter where they are imported from and others that say that certain strong strains will survive transplantation. However there may be some confusion about the San Francisco lactobacillus. Given that is it both distinct to San Franscisco but also traceable in other places does a continued presence of this bacteria in starters exported from the city show that the original bacteria are dominant or that they are also present in the local colonies, which ultimately take over the starter?

Interestingly a group of Belgian scientists has tested sourdough starters from 11 artisan bakeries in Belgian and reported back. Their tests included bakeries where lactobacillus sanfransiscensis were present. A full and quite serious report is available on this link.

Their main conclusion is summarized as follows:  "These results may indicate that the “in-house microbiota” of the bakery setting largely determines the microbial diversity in sourdoughs".

According to the provisonal findings of the study it isn't the flour or the original starter that determines the long term character of the sourdough starter, rather it's the bugs in the bakery (and by implication our homes), which tend to do that.

The tests showed that both new flours and original starter cultures introduced new elements to the local mix but I couldn't find any reference to how long it took for local cultures to dominate.

However among the finer details of the study are findings about what helps San Francisco bacteria to survive or flourish long term. They were found in greatest strength in Type 1 starters, those which were fed continuously and kept at room temperature. Their growth was inhibited in cultures which also contained lactobacillus paralimentarius, as both strains seemed to compete as to which would be 'lead bug'.

Obviously it is hard to tell if you have both the sanfranciscensis and paralimentarius strains without a lab test. However the latter is apparently a major feature of Greek sourdough starters and possibly also wheats. Both strains flavour bread well apparently but don't mix well. So probably best for those with Greek starters to avoid San Francisco-based starters and vice versa!

Kind regards,  Daisy_A

EvaGal's picture

How do I know if I have Greek Parliament starter? I live much closer to San Francisco than the Mediterranean, alas!

I started mine at home by using potato water, flour and a warm,dark boiler room closet for a few days. What kind of lab kit do I need? My teenagers are doing biology and chemistry and I homeschool, so how hard would it be to ID these little critters in my starter?


Daisy_A's picture

Hi EvaGal,

That's an interesting question! The Belgian tests were sent to a lab. in the UK, and apparently both San Fran and Greek strains were found in some of the 11 Belgian starters tested. Not sure what it would take to do it and do it safely at home. Would need the biochemists and lab people to chip in on that.

Looking at the link on how they did it, they start with Agar jelly but then it gets rapidly much more complicated (is under Sourdough sampling and isolation of LAB and yeasts). Not only do they have to isolate each strain but they have to identify it against a valid example that they have to get from a university lab. I do know of people having their starters tested in labs. to see what is in them but I think it can be dear. Still I'm sure there's a homeschooling lesson in there somewhere, 'cos it's such an interesting subject.

I think if your starter is doing fine there probably isn't any problem with clashing critter strains. It's only if the Greek strain gets in with San Fran that they start a struggle to take over the jar, apparently. I don't know how often that happens. Perhaps it's particular to Belgium? I don't know but think there might be more of the San Fran strain in the U.S.A. Apparently both work well so the starter wouldn't fail even if the dominant bacteria changed. It's just a problem for bakers who would want the same mix to last.

Could be problems though when people travel and take their starters to places where they could take on local bugs. Greek bakers going to San Francisco and coming back with flours in their hair, maybe, or bakers from San Francisco going to Greece and bringing back the Greek Parliament?

A baker I know took her starter with her to South Africa from the UK while on a family visit and work trip and did say it became different while over there. However she was over there for several months, which might be how long a starter takes to change. It's all worth a wonder.

Kind regards, Daisy_A



copyu's picture

I've wondered about this same issue for a long time

Abstract from a science paper:

"Yeasts are commonly identified from either phenotype or, more recently, from diagnostic gene sequences. Methods based on phenotype include fermentation reactions on a select set of sugars and growth responses on various carbon and nitrogen sources or on other diagnostic compounds. Isolates are further characterized phenotypically from the microscopic appearance of vegetative cells as well as sexual states because this information often gives clues to the identity of a strain. Molecular methods for yeast identification include nuclear DNA reassociation as well as the more recent and faster procedure of sequencing species-specific genes or the use of oligonucleotide sequences that react to a species-specific region of genomic DNA. These so-called "molecular probes" may have a marker molecule attached or they may be used in pairs, that when employed in a PCR reaction, amplify a species-specific region of DNA. The DNA-based identifications are far more reliable than those from phenotypic tests, and much faster. Nonetheless, in the absence of facilities for molecular comparisons, satisfactory identifications can often be made from phenotype. For this reason, both phenotype-based methods, as well as molecular techniques are given in this chapter."

After reading this, I think 'Voodoo', or some other magic, would be easier for the home baker...       ;-)

As a rank amateur, I'm fairly sure that, with my 'average' quality trinocular lab microscope, I could probably tell a bacterium from a fungal cell or spore...but no promises. I might still have to take a photo and send it to a lab, or spend months on the internet to be 100% sure of what I'd seen. I didn't even know, before, that yeasts HAD a 'sexual state'...identifying THAT would be beyond my humble facilities and even poorer skills

I'm still very interested in the question, but not too hopeful of an easy answer