From Flat Dough to Fluffy Loaf
One of the small wonders of baking is watching a dense lump of dough slowly grow into a soft, airy loaf of bread. It seems almost magical that simple ingredients like flour, water, and yeast can transform into something so light. But the rise of bread is not magic at all. It is the result of a living organism quietly working inside the dough, producing gas that gives bread its familiar texture.
The Living Ingredient: Yeast
The key to rising bread is yeast, a tiny single-celled organism that is actually a type of fungus. Although it is often sold as a dry powder, yeast is alive, simply dormant until it is mixed with water and flour. Once activated, yeast becomes hungry and begins to feed. The dough provides it with plenty of food in the form of sugars, some of which are present in the flour and some of which are created as the flour breaks down. This feeding process is what sets the whole rising in motion.
Fermentation and Carbon Dioxide
As yeast feeds on the sugars in the dough, it carries out a process called fermentation. During fermentation, the yeast breaks the sugars down and produces two main byproducts: carbon dioxide gas and a small amount of alcohol called ethanol. The carbon dioxide is the crucial part for rising bread. As the yeast keeps feeding, it keeps releasing this gas, and the gas slowly builds up throughout the dough. This is why bakers leave dough to rest in a warm place, often called proofing, allowing time for the gas to accumulate.
Trapping the Gas
Producing gas alone would not be enough if the gas could simply escape. What makes bread rise properly is that the dough traps the carbon dioxide. When flour is mixed and kneaded with water, it develops gluten, a stretchy network of proteins. This gluten network acts like a web of tiny balloons, capturing the carbon dioxide bubbles and holding them in place, which expands the dough. When the bread goes into the oven, the heat makes the trapped gas expand even more and the alcohol evaporates, giving the loaf a final burst of rising before the structure sets firm.
Source
This article was written using information from Wikipedia.