Trockenhefe, or dry yeast, is a type of yeast that is dehydrated and sold in granulated form. It is commonly used in baking to help dough rise, producing light and fluffy bread and pastries. When mixed with warm water and sugar, it becomes active and can ferment, releasing carbon dioxide gas that causes the dough to expand. This yeast is convenient and has a long shelf life, making it a popular choice for home bakers. Unlike fresh yeast, Trockenhefe does not require refrigeration and can be stored in a cool, dry place until needed.