During the formation of bread it becomes porous due to the release of CO ₂ by the action of:

Step-by-step solution

Yeast Saccharomyces cerevisiae is also known baker's yeast. Upon fermentation, yeast release ethanol and carbon dioxide as byproducts. CO ₂ forms bubbles which give the dough the perfect consistency and structure for it to rise and porous. Related Theory During the baking process, most of the alcohol in the dough evaporates into the atmosphere. This is basically the same thing that happens to much of the water in the dough as well. And it has long been known that bread contains residual alcohol, up to 1.9 % of it.