The primary ingredient in sourdough bread is flour, specifically bread flour or all-purpose flour. Sourdough is unique due to its leavening process, which involves natural fermentation. This occurs when wild yeast and lactic acid bacteria present in the environment interact with the flour and water mixture. The fermentation process enhances the bread's flavor and texture, resulting in a distinctive tangy taste and chewy crust. Typically, whole wheat or rye flour can also be used in combination with white flour to enrich the sourdough flavor profile. The simplicity of flour, water, and salt creates a beloved artisan bread.