Why does bread rise when yeast is added?

Yeast is a type of fungus that consumes sugar and releases carbon dioxide and alcohol as byproducts of its metabolism. When yeast is added to bread dough, it begins to consume the sugar in the dough and produce carbon dioxide. The carbon dioxide bubbles get trapped in the dough, causing it to rise. This process is known as leavening.

The amount of yeast added to bread dough will affect how much it rises. If too much yeast is added, the dough will rise too quickly and may collapse. If too little yeast is added, the dough will not rise enough and the bread will be dense.

The temperature of the water or milk added to the bread dough will also affect how much the dough rises. Warm water or milk will encourage the yeast to grow and multiply more quickly, causing the dough to rise more. Cold water or milk will slow down the growth of the yeast and the dough will rise more slowly.

The presence of salt in bread dough will also affect how much the dough rises. Salt inhibits the growth of yeast, so if too much salt is added to the dough, it will not rise as much.

By controlling the amount of yeast, the temperature of the water or milk, and the amount of salt added to the bread dough, it is possible to produce bread that rises to the desired height and has the desired texture.