About 34 years ago, Frank Sugihara recalls, he and Leo Kline, a fellow microbiologist, set out to "solve the mystery of San Francisco sourdough. Department of Agriculture, so perhaps it was inevitable they'd wind up studying San Francisco's signature bread. This crusty loaf, with its chewy bite and sharp acidulated tang, was a long way from Wonder Bread, and few tourists left the airport without a loaf. Local lore attributed the bread to Basque migrants from the Pyrenees who arrived in San Francisco during the gold rush.
About 34 years ago, Frank Sugihara recalls, he and Leo Kline, a fellow microbiologist, set out to "solve the mystery of San Francisco sourdough.
This crusty loaf, with its chewy bite and sharp acidulated tang, was a long way from Wonder Bread, and few tourists left the airport without a loaf. Local lore attributed the bread to Basque migrants from the Pyrenees who arrived in San Francisco during the gold rush.
Local bakers swore that no one could reproduce it outside a mile radius of the city. When they gave dough to bakeries elsewhere, it inexplicably lost its "sour.
For 5, years or more, humans have mixed flour and water, waited for the mixture to ferment, and when it was good and sour and full of gas, used it as leavening to make dough rise.
They found that they could propagate their leavening by saving a bit of unused dough to sow the seeds of foment in the next batch. It makes short work of pumping carbon dioxide into dough, and it always delivers.
Any Jack London reader knows that Alaska has a tradition of making pancakes with sourdough, but trappers also used it for tanning animal hides. They covered mink and muskrat skins with dough and let its acidity pickle the hides.
Then they kneaded the leather to buttery softness. Three ingredients, lots of taste, great texture. The difference is those fermenting bugs.
Almost all the bacteria are lactobacilli, cousins of the bacteria that curdle milk into yogurt and cheese. Not only that, say European researchers, the bacteria also contribute carbon dioxide as well as aromatic compounds that infuse bread with flavor and delicious smells.
Keeping a sourdough culture alive requires good time management and something like affection. An ecosystem begins to form as flour mixes with water to make a starter dough. Enzymes in the flour split starches into sugars. Not to worry, he says: The bugs will sort themselves out, and the "bread friendly" ones will come out on top.
Natural Gas A sourdough begins with only flour and water, left to ferment.
The resulting starter A is thick with wild yeasts and bacteria. A little starter is set aside for the next batch, then more flour is added to form a dough B.
The microorganisms feed on its sugars, forming carbon dioxide, acids, and ethanol. After fermenting at room temperature Cthe dough is chilled until use. As lactobacilli convert sugars to lactic and acetic acid, the dough noticeably sours, going down to the pH of mayonnaise, around 3.
Most microorganisms drop out of competition at this point, but yeasts that tolerate acid come into their own and convert sugars into carbon dioxide and ethanol.
Gas bubbles and fruity smells signal that fermentation is under way. By day six or so, the culture should teem with bugs and be ready to raise dough. Not all the culture is used, and the remainder is fed flour daily so it can live on to make bread another day.
A well-fed culture can last years. In their landmark San Francisco sourdough studies, Sugihara and Kline showed how nicely yeasts and lactobacilli live together. The principal yeast they found now goes under the name Candida milleri, and the principal bacterium, a species never found in nature before, is called Lactobacillus sanfranciscensis.
This is unusual for a yeast, and lucky for the bacterium. That tight, mutually helpful relationship may have allowed some San Francisco bakeries to keep their sourdoughs alive for more than years.
Once scientists knew what to look for, they started finding L. Will a San Francisco starter stay true to form in, say, New York? Many bakers contend the culture will lose its zip.Natural Gas A sourdough begins with only flour and water, left to ferment. The resulting starter (A) is thick with wild yeasts and bacteria.
A little starter is set aside for the next batch, then more flour is added to form a dough (B). Photojournalist Lena Mucha photographs the environmental and health impact of cobalt mining in the Congo.
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