Leavening with yeast is a process based on fermentation, biologically changing the chemistry of the dough or batter as the yeast works. Unlike chemical leavening, which usually activates as soon as the water combines the acid and base chemicals, yeast leavening requires proofing, which allows the yeast time to reproduce and consume carbohydrates in the flour.
Yeast can also be used to make alcoholic beverages like beer. The resulting cast-off yeast, known as barm, can be used as a leavener and was probably ancestral to the use of modern pure-cultured yeast.
While not as widely used, bacterial fermentation is sometimes used, occasionally providing a drastically changed flavor profile from a yeast fermentation; salt rising bread, which uses a culture of the Clostridium perfringens bacterium, is a well-known example.
Some typical biological leaveners are:
Since chemical expertise is required to create a functional chemical leaven without leaving behind off-flavors from the chemical precursors involved, such substances are often mixed into premeasured combinations for maximum results. These are generally referred to as baking powders.
Chemical leavening agents include:
Using a whisk on certain liquids, notably cream or egg whites, can also create foams through mechanical action. This is the method employed in the making of sponge cakes, where an egg protein matrix produced by vigorous whipping provides almost all the structure of the finished product.
The Chorleywood Bread Process uses a mix of biological and mechanical leavening to produce bread; while it is considered by food processors to be an effective way to deal with the soft wheat flours characteristic of British Isles agriculture, it is controversial due to a perceived lack of quality in the final product. The process has nevertheless been adapted by industrial bakers in other parts of the world.
Nitrous oxide is used as a propellant in aerosol whip cream cans. When the gas boils out of the cream, it also instantly creates a foam.
Building baked goods and snacks: Prepared Foods' 2006 R&D Applications Seminar delivers tips on leavening agents and a calcium fortifier.(R&D Applications Seminar)
Dec 01, 2006; Sodium Down, Calcium Up Media attention has been focusing on dietary sodium levels and calcium intake. Consumers are responding...