Contrary to what some in the foodie culture may think, San Francisco did not invent sourdough bread. The city does have a lactobacillus named after it: Lactobacillus sanfranciscensis, a key player yet only one of many species found percolating in sourdough bread.
In fact, sourdough bread has been a delicious staple since agriculture began, many thousands of years ago in the villages of the fertile crescent.
A little background:
- Sourdough is a blend of cereals and water which spontaneously ferment.
- Sourdough breads taste good and last longer—staleness and spoilage are delayed—than most other breads. No artificial preservatives are required.
Lactic acid bacteria (LAB) are the stars in sourdough fermentation. But they work their magic by linking up with yeasts.
Researchers led by Gino Vrancken at Vrije Universiteit in Brussels provide us with an excellent treatise on sourdough fermentation in their article Influence of Temperature and Backslopping Time on the Microbiota of a Type I Propagated Laboratory Wheat Sourdough Fermentation which appeared in Applied and Environmental Microbiology journal.
Lactobacillus plantarum, Lactobacillus fermentum, Lactobacillus paralimentarius, Lactobacillus brevis, and Lactobacillus sanfranciscensis are commonly reported.
The Belgian researchers wondered how different conditions would affect the types of LAB produced.
Temperature made a huge difference, showing how some LAB thrived and competed better in varying
- 23 degrees– Leuconostoc citreum dominated
- 30 and 37– Lactobacillus fermentum dominated
But this is an odd finding:
The sourdough-typical species Lactobacillus sanfranciscensis was missing in action.
The authors have a hypothesis:
Sourdough flour may come enriched with microbes from vertebrate gastrointestinal tracts (feces or droppings) swept in from the mill floor.
Lactobacillus sanfranciscensis may have crept into sourdough bread compliments of mouse droppings.
While not a very palatable public relations campaign for the tasty sourdough, the probability of such humble beginnings would have put a smile on the face of St Francis, the namesake of the city by the bay.