leaveners

Leaveners are substances used in baking to generate gas within doughs or batters, producing a light, porous crumb as heat sets the product. The gas expands the mixture, causing it to rise above its dense, unleavened state. Leavening can occur through biological, chemical, or physical mechanisms.

Biological leaveners rely on living organisms, most commonly yeast. Yeast ferments sugars to produce carbon dioxide and alcohol, gradually inflating doughs in a warm environment. This process also contributes to flavor and aroma, and it is typical in bread and some enriched doughs. Sourdough starters are examples of naturally occurring biological leavening cultures.

Chemical leaveners generate gas through fast chemical reactions. Baking soda (sodium bicarbonate) releases carbon dioxide when combined with an acid. Baking powder contains both an acid and a base and often includes moisture- and heat-activated components; most household baking powders are double-acting. Ammonium compounds such as ammonium carbonate are used in some crackers and cookies for a crisp texture, releasing gas when heated.

Physical leavening relies on air, steam, or both. Air is incorporated into batters by beating or creaming fat and sugar, while steam forms from moisture in the dough or batter during baking, expanding the mixture as it heats.

Practical notes include following recipe proportions, timing, and temperature, since over-leavening can cause a product to rise rapidly and then collapse, while under-leavening yields a dense crumb. Storage of leavening agents should be dry and properly sealed to maintain potency.