Sourdough

A description of a bread raised with a levain, a starter dough colonized by natural airborne yeasts. The lengthy fermentation of the starter dough imparts a distinct sour flavour to the bread baked using it as a raising agent rather than cultured brewer’s sugar fungus (see Yeast), the standard baker’s leavening. The name sourdough was first used by miners during the San Francisco gold rushes, which is why some bakers call sourdough loaves ‘San Francisco style’.