Reactivating Yeast

• Yeast needs warmth, moisture and a food source to grow. The ingredients in bread provide the right growing environment for yeast. Warm water or milk provides the warmth and moisture while flour and sugar provide the food. As yeast begins to devour the sugars from the flour and sugar, it releases carbon dioxide. The yeast will continue to feed and grow until it runs out of food or is killed by high heat.

Fermentation

• As the yeast feeds, it begins the fermentation process, which means it releases both carbon dioxide and alcohol when it digests the proteins from flour. Wheat flour contains both glutenin and gliadin. When they combine with water, they form gluten, a sticky substance that holds the dough together. When the enzymes in the flour interact with the starch molecules, it releases more sugars to feed the yeast. When you knead bread, the dough becomes filled with the air bubbles released from the yeast.

Rising

• Yeast bread is typically left to rest in a warm place to encourage the dough to rise. This happens because the yeast continues to feed, releasing more carbon dioxide into the bread dough. These air bubbles create tiny pockets of air inside the dough. These pockets range in size, depending on the type of bread you are making, the temperature and how long you let the bread rise. When the bread is sliced, the air bubbles produce holes in the bread.

Baking

• Yeast continues to release carbon dioxide during the initial stages of baking, causing the loaf of bread to increase in size. As the temperature rises above 130 to 140 degrees Fahrenheit, the yeast dies. The alcohol the yeast has produced evaporates, leaving behind flavor. Yeast enhances the flavor and improves the texture of the bread.