What About San Francisco Sourdough?

So asks reader Rainey, who points out very rightly that San Francisco sourdoughs use flour from Kansas and other places, yet they have very distinctive flavor profiles. That’s an excellent question. The reason San Francisco sourdough breads taste the way they do isn’t a result of the yeast so much as it is the lactic acid bacteria that thrive in that area. All starters are tag teams of various yeasts, which consume the simplest sugars in the flour slurry (glucose and fructose), and bacteria which generally consume the more complex sugars (like maltose). The yeast are primarily responsible for the CO2 and alcohol in the dough, and the bacteria — as their name implies — the flavor-giving acid.

The interesting thing about lactic acid bacteria is there are thousands of different kinds in nature. A unique species may live in your water supply, or in your back yard. Assuming those bacteria are capable of thriving in your homemade starter, they just might give your bread a taste that’s completely unique. Speaking for myself, I’ve never managed to culture any critters that deliver anywhere near the tang of L. sanfranciscensis and L. pontis, which are the bacteria that give San Francisco sourdough its unusual taste. These two bugs produce unusually high amounts of acid, and not just lactic acid. Under the right conditions L. pontis will produce large amounts of acetic acid, an acid with a very strong taste that’s most commonly found in vinegar.

But while my starters have never yet delivered the same acid bang for the buck as some San Francisco starters do, they have a nice subtle character that they pass to my breads. Is that character unique? On the microbial level my starter probably is unique to some extent. Flavor-wise I’m not so sure, but then it doesn’t really have to be. Homemade bread in itself is a rarity. Even without the San Francisco tang I get plenty of points for the effort!

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14 Responses to What About San Francisco Sourdough?

  1. rainey says:

    Thanks! Now that pulls everything into focus.

  2. Liz says:

    Hi Joe,

    I have a related question. Does the age of the starter have anything to do with the sourdough flavor? It seems like old starters are always highly touted – is that just because it’s impressive to have maintained a culture for so long or is it possible that the conditions of the starter will, over time, become more hospitable for the more flavorful, higher acid-producing lactobacilli? Thanks!

  3. Devon says:

    Technique, not geography, is what give ‘San Francisco’ sourdough its flavour. Both L. pontis and L. sanfranciscensis are ubiquitous and not indigenous to San Francisco. L. pontis is most active in cooler, drier environments, and L. sanfranciscensis prefers to be wetter and warmer. Therefore, long, cool fermentations with lower hydration preferments encourage acetic acid production, yielding the sharp, tangy sour of San Francisco-style sourdough. Those results can be replicated anywhere.

    • joepastry says:

      Good to know, Devon! Thanks very much for writing in with this. For those truly interested in exploring the potential of starters, it’s nice to know they can do it in their kitchens. I’ve experimented with drier starters and have noticed a difference in flavor. Perhaps there’s a future project in this!

      Thanks again,

      - Joe

      • Devon says:

        My pleasure, Joe. Natural starters can be intimidating to start, but they’re incredibly rewarding. Exploring how ferment time, temperature, and hydration affect structure and flavour is all part of the pleasure of naturally leavened bread baking.

        • joepastry says:

          I think I will have to make a project out of this sometime soon. It’s too interesting!


          - Joe

  4. Darren says:

    So could someone cheat and get a sourdough-like flavor by adding a small amount of vinegar to a dough? Maybe even use acid blend you get at a wine makers supply store? That’s usually a mix of citric, malic, and tartaric acid. I might have to give that a go.

  5. Susan says:

    Jim Lahey, in his faster version of his no knead bread, advised adding a few drops of vinegar to the batter. I assume it was to effect the more fermented flavor of the longer rise. I’ve used that technique in other bread recipes when I don’t have time for a long fermentation. Just a few drops…

  6. rainey says:

    I just ordered some ascorbic acid but I’m concerned that at least one report says it will improve the flavor and volume of bread but give it a finer crumb. I’m looking for the big, open, irregular crumb of a proper sourdough. …hopefully, without the flounder-like spread of a wet dough ciabatta.

    The same item said that citric acid wouldn’t have much effect on the dough.

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