How does a yeast makes bread to expand?

Yeasts are fungi that consume sugar and produce carbon dioxide gas as a byproduct of their metabolism. In bread making, yeast is added to the dough, and as it ferments and multiplies, it produces carbon dioxide gas. This gas gets trapped in the dough, causing it to rise or "expand." The bread continues to rise until it is baked and the yeast dies, at which point it reaches its final size.

Here are the steps involved in how yeast makes bread to expand:

1. Mixing: Yeast is added to the dough, along with other ingredients like flour, water, salt, and sometimes sugar.

2. Fermentation: Yeast begins to feed on the sugars present in the dough, breaking them down and converting them into carbon dioxide gas. This process of fermentation is what causes the dough to rise.

3. Kneading: Kneading helps distribute the yeast evenly throughout the dough and strengthens the gluten network. Gluten is a protein found in wheat flour, which helps trap the carbon dioxide gas produced by yeast, leading to a better rise in the bread.

4. Resting: After kneading, the dough is left to rest or "proof" in a warm place, allowing the yeast to continue fermenting and the dough to rise further.

5. Baking: Once the dough has reached its desired size, it is placed in the oven to bake. The heat in the oven causes the yeast to die and the carbon dioxide gas to expand rapidly, resulting in the bread expanding further and becoming light and airy.

It is important to note that the amount of yeast used, the fermentation temperature, and the baking time all play a role in how much the bread expands and its final texture.