Topic summary
Leavened
Extracted from the Wikipedia article Bread.
Bread may be leavened by naturally occurring microbes (e.g. sourdough), chemicals (e.g. baking soda), industrially produced yeast, or high-pressure aeration, which creates the gas bubbles that fluff up bread. Bread may also be unleavened. In many countries, mass-produced bread often contains additives to improve flavor, texture, color, shelf life, nutrition, and ease of production.