How does yeast act as a raising agent in bread?

Yeast acts as a raising agent in bread through a process called fermentation. Here's how it works:

1. Yeast consumes sugar: Yeast is a single-celled fungus that feeds on sugars. When you mix yeast with water and flour (which contains starch, which can be broken down into sugars), the yeast starts to consume the sugars.

2. Yeast produces carbon dioxide and alcohol: As the yeast consumes sugars, it produces carbon dioxide (CO2) gas and alcohol as byproducts of its metabolic processes.

3. Carbon dioxide expands the dough: The CO2 gas gets trapped within the gluten structure of the dough. This trapped gas causes the dough to expand and rise, creating the airy texture we see in bread.

4. Alcohol evaporates during baking: The alcohol produced by the yeast is volatile and evaporates during the baking process, leaving behind the airy bread structure created by the CO2.

Key Points:

* Active yeast is essential: The yeast must be alive and active to produce CO2 and alcohol.

* Temperature matters: Yeast works best at warm temperatures, typically between 70°F and 95°F (21°C and 35°C).

* Other ingredients contribute: Flour provides the starch, water provides hydration, and other ingredients (sugar, salt) can influence the fermentation process.

In essence, yeast transforms simple sugars into CO2 gas, which inflates the dough and gives bread its characteristic texture.