What are the leaving agents in a loaf of bread?

There are no "leaving agents" in a loaf of bread. You're likely thinking of leavening agents.

Leavening agents are substances that create bubbles of gas within a batter or dough, causing it to rise. Here are the most common leavening agents in bread:

* Yeast: This is a living organism that feeds on sugars and releases carbon dioxide as a byproduct. This gas expands within the dough, causing it to rise.

* Baking soda (sodium bicarbonate): This is a chemical leavening agent that reacts with an acid in the recipe (like buttermilk, brown sugar, or lemon juice) to release carbon dioxide.

* Baking powder: This is a combination of baking soda, an acid, and a drying agent. It releases carbon dioxide when mixed with moisture.

So, instead of "leaving agents," bread relies on leavening agents to create its light and airy texture.