Sourdough is a bread product made by a long fermentation of dough using naturally occurring lactobacilli and yeasts. In comparison with breads made quickly with cultivated yeast it usually has a mildly sour taste because of the lactic acid produced by the lactobacilli.
This page contains content from the copyrighted Wikipedia article "Sourdough"; that content is used under the GNU Free Documentation License (GFDL). You may redistribute it, verbatim or modified, providing that you comply with the terms of the GFDL.