Sourdough is assumed to originate in ancient Egypt, roughly 6000 years ago. In its original form, bread was only known in form of a hard disk. Flour and water were mixed and dried in the sun or over the fire. In the process, spontaneous acidification was discovered coincidentally. This was the birth of sourdough. Naturally occurring enzymes and lactobacteria convert the starch in the flour to lactic acid, alcohol and carbon dioxide. These substances, in combination with the yeast fungi residing in the sourdough, make the dough taste sour and cause it to rise during baking. A crust is formed on the outside and the inside remains moist and fluffy.
Over the course of time, many procedures for dough fermentation were developed. Sourdough with a multilevel dough process is the most complex procedure and allows for making bread without artificially adding yeast. Commonly, however, a more time efficient method is employed, using artificially cultivated high performance yeasts and synthetic leavening agents.
Aside from its aroma, sourdough bread is especially popular due to its enhanced health benefits. As early as 79 A.D., Pliny’s Natural History reads that „bodies nurtured with sour bread are stronger“.