In breadmaking, yeast plays three key roles:
1. Yeast makes dough rise
Yeast works by consuming sugar and generating carbon dioxide and alcohol as by products. The basic ingredients for bread dough are flour, water, and of course yeast. When these ingredients are mixed together, enzymes in the yeast and the flour cause large starch molecules to break down into simple sugars. Yeast cells thrive on simple sugars. As the sugars are metabolised, carbon dioxide and alcohol are released into the bread dough, making it rise.
2. Yeast strengthens bread dough
When you mix flour and water, the proteins in the flour absorb the water to form an elastic mass of molecules that we call gluten. In bread making, we want to develop as much gluten as we can because it strengthens the dough and holds in gases that will make the bread rise.
3. Yeast produces flavour
Yeast imparts the characteristic flavour of bread by producing aromatic compounds that contribute to the aroma and taste of bread. These reactions occur primarily in the crust and the resultant flavour diffuses into the crumb of the baked bread.