What ingredient in bread produces carbon dioxide?

The ingredient in bread that produces carbon dioxide is yeast.

Here's how it works:

* Yeast is a single-celled fungus that consumes sugar (from the flour in bread) as its food source.

* As a byproduct of its metabolism, yeast releases carbon dioxide and alcohol.

* The carbon dioxide gas gets trapped within the dough, causing it to rise.

* The alcohol evaporates during baking.

So, while other ingredients like flour, water, and salt are essential for bread, it's the yeast that's directly responsible for the carbon dioxide that gives bread its airy texture.