It’s hard to imagine what cakes and biscuits would taste and look like if they were made without baking powder, but in fact, baking powder is a recent innovation that did not make its first cookbook appearance until the 1850s. Sourdough or yeast, along with a helping of dregs from the wine casket, was the common way to leaven baked goods before the invention of baking powder. The overtly sour flavor did little to improve a cake’s flavor and pearlash (concentrated potash) was sometimes added. Bakers noticed that sour doughs with potash rose quickly as the potash reacted with the acidic dough to produce carbon dioxide, a discovery that would revolutionize the baking industry and change the way we baked.
Baking Powder and The Acid-Base Reaction
Baking powder produces carbon dioxide gas that tenderizes baked goods by increasing their volume and lightening their texture. Baking powder is used in baked goods where the flavor of fermentation is not desirable and is preferred to yeast because it creates gas faster: where yeast doughs can take 2-3 hours to rise, baking powder can leaven in 15 minutes. (However, flavor is the trade-off and is the reason why yeast continues to be used today.) Baking powder also affects the pH of baked goods which in turn affects color and flavor—as when cakes brown quickly and taste soapy because too much baking powder was used. Because the leavening reaction is chemical, and not biological, use the same amount of baking powder in a recipe and you’ll get the same result every time.
The baking powder we use today is a dry chemical leavener made of an alkali (usually baking soda), an acidic salt (such as cream of tartar), and an inert starch (usually cornstarch). In its simplest form, chemical leavening describes the reaction between an acid and a base, in the presence of heat and moisture, to produce gas. This acid-base reaction is generically represented as:
NaHCO3 (base) + H+(acid) + (heat and moisture) -> Na+ (salt) + CO2 (gas) + H2O (water)
The most common base used in baking powder, and the source of the carbon dioxide gas, is sodium bicarbonate. When mixed with water and an acid, sodium bicarbonate (also known as baking soda) reacts immediately to produce carbon dioxide. Potassium bicarbonate is an expensive alternative to sodium bicarbonate and is used when excessive salt byproducts are not desirable.
The choice of acid in a baking powder blend is much more varied. Predecessors of modern-day baking powders used cream of tartar which reacted and had to be baked quickly. This quick reaction worked well for pancakes and muffins, but not for biscuits that needed to rest before shaping and baking. Today, four acids are used to create commercial baking powder blends. Sodium aluminum phosphate (SALP) is a slow-acting acid that reacts primarily when heated and contributes a springy texture in baked goods. Sodium acid pyrophosphate (SAPP) adds a crunchy, less springy texture but finer crumb in baked goods. It leaves less of an aftertaste than other acids making it well suited for refrigerated biscuit dough. Monocalcium phosphate (MCP) is a fast-acting acid that reacts within minutes when moistened and is usually blended with sodium aluminum phosphate (SALP) which reacts mainly during baking.
Although starch is a filler, it serves important functions in baking powder. It extends shelf life by absorbing moisture and preventing the chemical reaction from happening prematurely in the can. Its moisture-absorbing properties also prevent baking powder from clumping which makes it easier to mix into a batter. The added bulk also makes it easier to measure baking powder as most scales cannot measure in less than 5g increments.
As the various acids and bases can be blended in many combinations, some baking powder blends are more expensive and bakers will sometimes specify a brand in their formulas. However, the basic difference between all baking powders is one of reaction time. Single-acting powders produce most of their gas when mixed with a liquid. Double-acting baking powders release a bit of gas when mixed with a liquid, but generate most of their gas during baking. Most commercial baking powders are double-acting as the blend of baking soda and two acids allows batters to remain unbaked for a relatively long period of time, an advantage that allowed bakers to exert control over when to bake.
Buttery. Salted. Caramel. 
Leave a comment