Bread Making Leavening Agents
Yeast, through a fermentation process, produces gas (carbon dioxide) necessary to make the bread rise. Yeast feeds on sugar and flour carbohydrates to produce this gas. Traditional active dry granular yeast is used in all recipes that call for yeast. Three different types of yeast are available: fresh (cake), dry, and quick acting. Bread machine yeast is quick acting. For best results, use traditional dry yeast. However, quick rising yeast can also be used in smaller amounts in ultra fast cycle bread machine recipes.
Always store yeast in a refrigerator to keep it fresh as heat will kill it. Ensure your yeast is fresh by checking its expiration date. Once a package or jar of yeast is opened, it is important that the remaining contents be immediately resealed and refrigerated for future use. Often, bread or dough that fails to rise is due to stale yeast.
To test your yeast to determine if it is stale or inactive: Place 1/2 cup of lukewarm (110°F to 115°F/43°C to 46°C) water into a liquid measuring cup. Stir 1 teaspoon of sugar into the water and sprinkle 2 1/4 teaspoons (1 package) of yeast over the surface. Place the cup in a warm area and allow to sit for 10 minutes undisturbed. The mixture should foam and rise to the 1 cup mark. If this does not occur, discard this yeast and purchase fresh yeast. You can then use this mixture in your dough; just be certain to reduce the amount of liquid in your recipe by 1/2 cup.
Active dry yeast
A highly stable yeast in dry form, this yeast is perfect for making bread either the traditional method or in bread machines. Fed by sugar, warm liquid (about 80°F/27°C), and a pleasantly warm environment, yeast will multiply effectively, allowing bread to rise. One packet of active dry yeast contains 2 1/4 teaspoons yeast.
Bread machine yeast
A strain of active dry yeast developed and packaged especially for bread machines. It comes in handy 4-ounce jars and is interchangeable with active dry yeast.
Fresh or compressed yeast
A fresh yeast compressed into very small blocks that is made from cream yeast, from which a good deal of the water is drained off by centrifugal force. It is moist (about 70% moisture), crumbly and creamy-white. Available in a refrigerated package. This highly perishable yeast is not recommended for use in bread machines.
This is a fast-acting strain of dry yeast that requires only one rise, so it significantly shortens the entire bread-baking cycle. It is interchangeable with active dry yeast, but must be used in conjunction with the rapid-bake cycle in bread machines. If you choose to use quick-rise yeast, follow the directions on the package for the recommended temperature needed for the liquid in your recipe. It is not recommended using quick-rise yeast in sourdough breads, or in breads containing eggs, cheese, or two or more whole-grain flours, because these breads really need longer rising times to be successful, especially in bread machines.
A mixture of flour, water, sugar, and yeast. The starter is a mixture that is left to "sour," or ferment, for two to four days. During this time, it develops a sour flavor and a bubbly effervescence. Used as a leavener for yeast bread, a starter imparts a sour flavor and an open texture to bread.
Used in quick breads, not yeast breads, this is a type of chemical leavening that does not require a rising time. Quick breads and cakes made with baking powder can simply be mixed and baked.
Another type of chemical leavening used in quick breads, cakes, and muffins. Baking soda activates when it comes in contact with liquid ingredients. It cannot be substituted for baking powder, but is sometimes used together with it.