Why does yeast make bread dough rise?

Yeast makes bread dough rise due to a fascinating process involving fermentation and the production of carbon dioxide. Here's a breakdown:

1. Yeast eats sugar: Yeast is a single-celled organism that feeds on sugars. In bread dough, yeast consumes sugars from the flour.

2. Fermentation: During this process, yeast breaks down sugars into simpler molecules, releasing carbon dioxide (CO2) and ethanol as byproducts.

3. Trapped bubbles: The CO2 gas produced by the yeast gets trapped within the gluten network formed by the flour and water in the dough.

4. Dough expansion: As more and more CO2 bubbles form and expand, they push the dough outward, causing it to rise.

5. Baking and expansion: The heat of the oven further expands the CO2 bubbles, giving the bread its characteristic airy texture. The ethanol produced during fermentation evaporates during baking.

In summary, the rising of bread dough is a result of the yeast's consumption of sugar, which leads to the production of carbon dioxide gas. This gas becomes trapped in the dough, causing it to expand.