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32. What is San Francisco Sourdough?

Subject: 32. What is San Francisco Sourdough?

As I understand it, all stable "sourdough" starters are a symbiotic mixture of yeasts and bacteria, that, through their mutual liking of the other's by-products, cause the mixture to remain stable over time, relatively unaffected by other wild yeasts & bacteria that may, by chance, settle into the mix.

In the case of "San Francisco Sourdough" the protagonists have been identified as Lactobacillus sanfrancisco (the bacteria) and Saccharomyces Exiguus (the yeast).

These two players seem to be common in the air in the San Francisco bay area, and hence, starter started there contains them in abundance. Their mutual relationship gives bread made therefrom a singular tang.

In 1995, I toured the bay area stopping at many bakeries to sample their "sourdough". Parisian was the most bland, though most widely distributed; Le Bolangerie was the most tangy and "sanfranciscian"; the Village Baker, in Petaluma, was the most interesting. I did not get to Acme in Oakland, which is deemed by some to be, well, the acme.

I, like others on this list, have attempted to duplicate the taste I had tasted in SF, here in eastern Mass., with little success. I have tried inoculating commercial "San Francisco Sourdough" starter with Lactobacillus sanfrancisco, obtained from a baking industry contact, to little avail. The resulting loaf _was_ "sanfranciscian" but the starter did not retain that quality for the next batch. I believe both Lac. SF. and Sacc. Ex. must be in the air & the flour, or the symbiosis will not survive in the starter.

Troy Boutte, of this list, wrote in 1995:

"Lactobacillus san francisco, when fermented by itself from a pure culture, has an odor of canned corn early in the fermentation. After about 17-20 hours of fermentation under good conditions, the pH of the ferment will drop to about 3.6 - 3.8. At that time the odor will have changed to a very complex and unique odor which of course makes it impossible to compare it to anything else.

Most people say it smells like sweaty sneakers or old socks, but not in an unpleasant way. ... The odor comes from 40-50 small volatile compounds that have been identified in these ferments. Besides lactic acid, the most abundant compounds are acetic acid (vinegar), ethyl acetate (cross between vinegar and alcohol), and ethanol. Other compounds are esters of short chain fatty acids that give goat cheese and butter their respective odors and flavors.

I've found that the odor of this ferment bears little relationship with the flavor of the bread produced. Baking seems to mellow out the flavor, leaving what many people consider to be an excellent flavor to the bread."



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