The pioneers who marched west in America, who followed the trail into the prairie vastness, or eagerly set forth to pan for gold in California or the Yukon, were hardly able to rely on bakers and grocery stores for an ounce or two of yeast. They took their own leavening: a smidgeon of dough kept back from the last baking which could be reactivated for the next. If it was stored deep inside a sack of flour, it was proof against frosts, heatwaves, even Indian attacks!
So it was that they were called ‘sourdoughs’, but it was only those who got as far as San Francisco who were to be able to make this very specific sourdough, which develops its tang from the particular bacilli that seem partial to the air in the Bay. Everyone’s air is different, so a true San Francisco sourdough may be impossible to repeat elsewhere, as the leaven will take on different microbes and wild yeasts, depending on the kitchen, bakery and climate.
If you have no leaven from previous baking, see To make a sourdough leaven.
© 2005 Tom Jaine. All rights reserved.