Leavening process

Leaven means a substance (such as yeast) used to produce fermentation in dough or a liquid. In baking, leavening is the process of adding a substance to bread dough (and other baked goods) that enables the dough to rise. Risen breads rely on a means of producing carbon dioxide gas that becomes trapped in the batter or dough causing the rising action. The carbon dioxide gas is produced either as a byproduct of fermentation or through the use of chemical agents.

Mixing dough or batter causes the proteins gliadin and glutenin to combine and form a protein called gluten. The gluten builds an elastic chain, which allows the dough to expand and contract. The gas produced by the leavening agent use forms thousands of little bubbles in the dough, which causes it to inflate. Leavening agents create air pockets into the batter by producing a gas. This makes the batter to rise & become fluffy.

The use of a starter is a traditional method of leavening requiring only a flour, water, and yeast mixture, which is allowed to ferment for varying periods depending on the type of bread being prepared. A starter may contain additional ingredients, such as milk, sugar, or honey, depending on the recipe.

The main biological leavening agent is yeast. The most common chemical leavening agent is baking soda. Steam can be used as leavening agents for cooking that is done at very high temperatures. The batter must be capable of holding in the steam until it is set.
Leavening process