Understanding Sourdough
Sourdough is a culture of wild yeast and bacteria in a mixture of flour and water. When people mention sourdough, it often refers to the bread and starter used to make it.
Sourdough bread is made by fermentation of dough using wild yeast and bacteria found in the flour and environment. This mix of wild yeast, bacteria, flour and water used to make sourdough bread is called a “starter.” During the bread-making process, the starter ferments the sugars in the dough, helping the bread rise and acquire its unique complex and tangy flavour.
The Science Behind Sourdough
A starter is created when flour and water is mixed and left to ferment. The wild yeast and bacteria will begin feeding on the sugars in the flour. With proper care and feeding, the wild yeasts and bacteria from the environment and the flour will multiply and grow vigorously over seven to ten days into a stable culture. When the starter is stable, it is time to mix the starter into the dough to bake some bread!
The wild yeast produces carbon dioxide that is trapped by gluten within the dough that creates air pockets, and makes the bread rise and excrete carbon dioxide and alcohol as byproducts, which also contribute to the complex flavours in the bread.
On the other hand, the bacteria (Lactic acid and Acetic acid) provides flavour and also keeps microbes from growing. Lactic acid is more mellow flavoured whereas the acetic acid is more vinegary, giving its characteristic tang.