Baking powder is a dry chemical leavening agent used to increase the volume and lighten the texture of baked goods such as muffins, cakes, scones and North American biscuits. Baking powder works by releasing carbon dioxide gas into a batter or dough through an acid-base reaction, causing bubbles in the wet mixture to expand and thus leavening the mixture. It is used instead of yeast for end-products where fermentation flavors would be undesirable or where the batter lacks the elastic structure to hold gas bubbles for more than a few minutes. Because carbon dioxide is released at a faster rate through the acid-base reaction than through fermentation, breads made by chemical leavening are called quick breads.
Most commercially-available baking powders are made up of an alkaline component (typically baking soda), one or more acid salts, and an inert starch (cornstarch in most cases, though potato starch may also be used). Baking soda is the source of the carbon dioxide, and the acid-base reaction is more accurately described as an acid-activated decomposition of baking soda, which can be generically represented asNaHCO3 + H+ â†’ Na+ + CO2 + H2O
The inert starch serves several functions in baking powder. Primarily it is used to absorb moisture, and thus prolong shelf life by keeping the powder's alkaline and acidic components from reacting prematurely. A dry powder also flows and mixes more easily. Finally, the added bulk allows for more accurate measurements.
The acid in a baking powder can be either fast-acting or slow-acting. A fast-acting acid reacts in a wet mixture with baking soda at room temperature, and a slow-acting acid will not react until heated in an oven. Baking powders that contain both fast- and slow-acting acids are double acting; those that contain only one acid are single acting. By providing a second rise in the oven, double-acting baking powders increase the reliability of baked goods by rendering the time elapsed between mixing and baking less critical, and this is the type most widely available to consumers today. Common low-temperature acid salts include cream of tartar and monocalcium phosphate (also called calcium acid phosphate). High-temperature acid salts include sodium aluminum sulfate, sodium aluminum phosphate, and sodium acid pyrophosphate.//
Early chemical leavening was accomplished by activating baking soda in the presence of liquid(s) and an acid such as sour milk, vinegar, lemon juice, or cream of tartar. These acidulants all react with baking soda quickly, meaning that retention of gas bubbles was dependent on batter viscosity and that it was critical for the batter to be baked before the gas escaped. The development of baking powder created a system where the gas-producing reactions could be delayed until needed.
While various baking powders were sold in the first half of the 19th century, our modern variants were discovered by Alfred Bird. August Oetker, a German pharmacist, made baking powder very popular when he began selling his mixture to housewives. The same recipe he created in 1891 is still sold as Backin in Germany. Oetker started the mass production of baking powder in 1898 and patented his technique in 1903.
Following the American Civil War Joseph and Cornelius Hoagland developed a baking powder with the help of an employee, and their formula became known as Royal Baking Powder. The small company eventually moved to New York in the 1890s and became the largest manufacturer of baking powder.
Eben Norton Horsford, a student of Justus von Liebig, who began his studies on baking powder in 1856, eventually developed a variety he named in honor of Count Rumford. By the mid-1860s ``Horsford's Yeast Powder`` was on the market as an already-mixed leavening agent, distinct from separate packages of calcium acid phosphate and sodium bicarbonate. This was packaged in bottles, but Horsford was interested in using metal cans for packing; this meant the mixture had to be more moisture resistant. This was accomplished by the addition of corn starch, and in 1869 Rumford began the manufacture of what can truly be considered baking powder.
During World War II, Byron H. Smith, an inventor in Bangor, Maine, created a substitute product for American housewives, who were unable to obtain baking powder, cream of tartar or baking soda due to war food shortages. Named ``Bakewell``, a mixture of sodium pyrophosphate and corn starch, the product is still part of regional culinary history. When combined with baking soda, it is essentially the same as any single-acting baking powder, the only difference being that the acid is sodium pyrophosphate.
In 2006 the development of Rumford Baking Powder was designated an ACS National Historical Chemical Landmark in recognition of its significance for making baking easier, quicker, and more reliable.``
Generally (in countries where the cup is used as a standard measure in cookery) one teaspoon (5ml) of baking powder is used to raise a mixture of one cup (200-250ml) of flour, one cup of liquid, and one egg. However, if the mixture is acidic, baking powder's additional acids will remain unconsumed in the chemical reaction and often lend an unpleasant chemical taste to food. High acidity can be caused by ingredients like buttermilk, lemon, yoghurt, citrus, or honey. When excessive acidity is present, some of the baking powder is replaced with baking soda. For example, one cup of flour, one egg, and one cup of buttermilk requires only Â½ teaspoon of baking powderâ€”the remaining leavening is caused by buttermilk acids reacting with Â¼ teaspoon of baking soda.
Moisture and heat can cause baking powder to lose its effectiveness over time, and commercial varieties have a somewhat arbitrary expiration date printed on the container. Regardless of the expiration date, the effectiveness can be tested by placing a teaspoon of the powder into a small container of hot water. If it fizzes energetically, it's still active and usable.
Baking powder is generally just baking soda mixed with an acid, and a number of kitchen acids may be mixed with baking soda to simulate commercial blends of baking powder. Vinegar (dilute acetic acid), especially white vinegar, is also a common acidifier in baking; for example, many heirloom chocolate cake recipes call for a tablespoon or two of vinegar. Where a recipe already uses buttermilk or yogurt, baking soda can be used without cream of tartar (or with less). Alternatively, lemon juice can be substituted for some of the liquid in the recipe, to provide the required acidity to activate the baking soda. In China, a small amount of powdered coal may be added to baking soda to simulate baking powder.
In older times, when chemically manufactured baking soda was not available, ash water was used instead, especially in confectionery. Wood ash is also weakly alkaline. To prepare ash water, one used a fistful of ash from the fireplace in a big pot of water. Ash from solid woods, such as the olive tree, is preferred, whereas resinous woods, like pine, cannot be used. The ash water is given a boil, then left overnight to settle. The water is then filtered through a cloth and is ready to use. Many traditional recipes call for ash water instead of baking soda, because of some unique qualities: for example, ash water dripped on hot vegetable oils congeals into a gel-like mixture.
Baking powders are available both with and without aluminum compounds. Some people prefer not to use baking powder with aluminum because they believe it gives food a vaguely metallic taste, and because of a possible (but controversial) link between aluminum consumption and