Sourdough

Sourdough bread is made using a 'starter' of flour, water, lactobacilli and yeasts that is allowed to ferment and become the leavening agent for the bread. A small amount of the starter dough (making up about a quarter of the final dough) is added to new flour and water, part of which is saved to use as the starter next time. Sourdough bread has a distinctive taste, due mainly to the lactic acid and acetic acid produced by the lactobacilli.

This variety of bread originated in France, and has spread to many other parts of Europe and the world. It is most commonly used in France to make Pain de Campagne (country bread), a chewy, crusty, bread with an open crumb.