Our Daily Bread 22 - Sourdough by Any Name http://ow.ly/QLnm30ltLNu Sourdough -- whatever you call it -- is the original leavening agent for breads around the world. At its simplest it is just a piece of the last batch of dough, set aside to ferment the current batch. But it can be so much more than that, a stable little ecosystem of species that support one another while keeping out intruders. It also makes the best bread, although I admit to being biassed. It needn't actually taste sour. In fact, except in a few countries, it need not even make use of a natural leaven.