What makes sourdough special?
Sourdough is made using sourdough starter, which is a fermented flour and water mixture that contains natural yeast. This gives the bread a distinct "sour" flavor which is different than breads made with commercial yeast.
Instruction: What makes sourdough special?
Context: 
Response: Sourdough is made using sourdough starter, which is a fermented flour and water mixture that contains natural yeast. This gives the bread a distinct "sour" flavor which is different than breads made with commercial yeast.