Today, April 1, 2014, is National Sourdough Bread Day. 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. Sourdough likely originated in Ancient Egyptian times around 1500 BC and was likely the first form of leavening available to bakers. Sourdough remained the usual form of leavening down into the European Middle Ages until being replaced by barm from the beer brewing process, and then later purpose-cultured yeast.
