Can I collect local San Fran yeast when I visit?

If you buy the flour in SF and use the water from SF to start a culture in SF, you will have a SF culture. But, how long will you be there? If you don't stay long enough to get a good strong culture, it may be for naught. As long as the culture is in initial development stages, there is always a chance for changes, even major ones. Once you get an established starter, do what the big SF bakeries purportedly do - feed your starter in a way that keeps the culture dominant. That means, your inoculation amount has to be greater than the new food you give it. Something like 1.x or more starter to one flour and one water by weight. The starter will need to be cared for very diligently to keep it that way indefinitely. But, if that's what you want, there's no harm In trying it. If you decide later that it's not worth that much effort, then you don't have to do anything but just start maintaining it like a regular, non-special starter, or just mix it in with another starter you already have or bake it all away, or whatever.

about a SF starter.  I started mine there in 1973. moved it all over the place in 40 plus years and I'm sure it is different today but my palate just isn't good enough to tell any difference in the bread it made over those years.   Where ever you go it will just adapt to what ever flour and water you feed it.

I wouldn't let the hype and hyperbole of SFSD and starters from there get in the way of the facts.  Their bread isn't any better then anyone elses and, for me, it isn't as sour as it was 40 years ago.   They have modified the taste to be less sour on purpose to sell more bread - good for them -  because most people don't like sour bread.  At least I can still make the real '0ld Time' SFSD in Arizona.......and make the new version too from my 'old time' starter that isn't anything like it was 40 years ago. 

It is just plain fun to make a starter in SF though and I bet I will be doing so the next time I am there:-)

My understanding of sourdough cultures is that the microflora come from the grain rather than the air, and on most grains, l. sanfranciscensis (the lactobacillis that produces acid) grows naturally.  That said, I live in San Francisco and would be happy to share some of my culture with you. Contact me by private message if you would like to set something up.

-Brad

... from the BBC article:

Andrew Whitley of the Bread Matters baking school near Edinburgh considers his sourdough starter, brought back from Russia in 1990, to have retained its essential properties. "In 22 years of using and refreshing my Russian starter I have never once had a 'failure', nor have I been able to detect any drift of flavour,"

"Laboratory analysis might tell a different story, but bakers live in the real world of daily production and over the millions of loaves I (and others) made with my Russian starter no-one complained about any change attributable to the sourdough."

"my starter, despite being refreshed with UK flour, didn't seem to have changed much."

"I learned my craft out in San Francisco and had considered bringing back my starter and using it as a selling point for my bakery. But I decided against it as I knew it would be a bit of a lie,"

From what i have read and in talking to others a starter from any location will change over time. I am not doubting the person from Edinburgh who says his has not changed in 22 years. it just stands to reason in my thinking that it will pick up the local wild yeast and flour and water changes would change it over time.

More likely than not, people keep their starters in a closed container or under some kind of cover so that it will not dry out, rather than exposed to the air where local yeast could settle on it in any significant quantity. Even so, the local airborne yeast would have to be somehow different from what's already in the flour and settle on the starter in a significant quantity in order to change the flavor.

I would give much more weight to the idea that changes in flour would contribute to a starter changing over time, or if there were something drastically different about the water such as impurities or excessive chlorination.

The notion that special properties of the local yeast in San Francisco are what make the local bread unique doesn't really stand up to scrutiny and can probably be dismissed as so much marketing hype from one particular bakery. Still, if someone wants to take his jar of starter to San Francisco and wave it around in the air to capture some of the local yeast, I hope they have fun doing so.

mature, other local invading yeast and LAB have a hard time taking over a stable culture if it is well maintained and full of strong competitors   Those wee beasties are almost impossible to kill  even if you try to do so..   i cant really tell the difference in m starter's bread over 40 years but I just chalked it up to having an insensitive palate and smoking for 35 years:-)    i can make it more or less sour when ever I want but it tastes the same to me. 

I know that Ian's bread tastes totally different too sine he sent me a couple of loaves last Holiday season.  I was amazed at the difference in taste.

This idea of picking up local strains of yeast from the air seems a bit dubious to me. I'm sure there's plenty of yeast living in my kitchen, but after baking several times a week for three or four years, the commonest strain is likely to be Allinson's Easy Bake!

Also, isn't yeast metabolism pretty basic, giving rise to fairly simple byproducts (CO2, alcohol)? Seems to me the flavour is more likely down to the relative proportions of the beasties and the type of flour, rather than the specific strain of yeast.

See also http://www.intechopen.com/books/food-industry/yeast-world-s-finest-chef for some descriptions of different yeast metabolic pathways.  It is not as simple as sugar in, Alcohol/CO2 out, there is many sub and by products, in the form of esters (fruity),aldehydes (astringant, biting), and many others.

Fair enough.

I suppose the question then would be, how much do these byproducts (and their proportions)  vary as a function of yeast strain, versus feeding schedule, hydration and flour type. Do different strains of the same species react significantly differently to the same feeding? 

Am I right in thinking that most sourdough starters are s. Sanfranciscencis? How common is s. Cervisei (baker's yeast) in sourdough starters? My 'Allinson's Easy Bake' comment was only half joking - the air in my kitchen must be thick with the stuff. And that's an entirely different species.