thumb|U.S. consumer-packaged baking powder. [[Eben Norton Horsford|Rumford baking powder contains monocalcium phosphate, sodium bicarbonate, and cornstarch.]]

Baking powder is a dry chemical leavening agent, a mixture of a carbonate or bicarbonate and a weak acid. The base and acid are prevented from reacting prematurely by the inclusion of a desiccant such as cornstarch. Baking powder is used to increase the volume and lighten the texture of baked goods. It 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.

In 1843, the first single-acting baking powder (meaning that it releases all of its carbon dioxide as soon as it is dampened) was developed by pharmacist Alfred Bird in England. In 1856, Eben Norton Horsford, the Rumford Professor at Harvard University, received an American patent, for monocalcium phosphate, for baking powder.

or where the batter lacks the elastic structure to hold gas bubbles for more than a few minutes, and to speed the production of baked goods. 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. The introduction of baking powder was revolutionary in minimizing the time and labor required to make breadstuffs. It led to the creation of new types of cakes, cookies, biscuits, and other baked goods.

:NaHCO<sub>3</sub> + H<sup>+</sup> → Na<sup>+</sup> + CO<sub>2</sub> + H<sub>2</sub>O

The real reactions are more complicated because the acids are complicated. For example, starting with baking soda and monocalcium phosphate, the reaction produces carbon dioxide by the following stoichiometry:

A fast-acting acid reacts in a wet mixture with baking soda at room temperature, and a slow-acting acid does not react until heated. When the chemical reactions in baking powders involve both fast- and slow-acting acids, they are known as "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. This is the type of baking powder most widely available to consumers today. Double-acting baking powders work in two phases; once when cold, and once when hot.

Thus, a double-acting baking powder, with baking soda, uses fast-acting acid that reacts in a cool (room temperature), wet mixture. Later, after heating, the slower-acting acid reacts, with baking soda, in the wet mixture, at the now-high-temperature. Slower-acting acids only react at higher than room temperatures.

However, Rumford Baking Powder is a double-acting product that contains only one leavening acid, monocalcium phosphate. With this acid, about two-thirds of the available gas is released within about two minutes of mixing at room temperature. It then becomes dormant because an intermediate species, dicalcium phosphate, is generated during the initial mixing. A further release of gas requires the batter to be heated above 140&nbsp;°F (60&nbsp;°C).

Common low-temperature acid salts include cream of tartar and monocalcium phosphate (also called calcium acid phosphate). High-temperature acid salts include sodium aluminium sulfate, sodium aluminium phosphate, and sodium acid pyrophosphate.

Starch component

Baking powders also include components to improve their stability and consistency. Cornstarch, flour, or potato starch are often used as desiccants

An inert starch serves several functions in baking powder. Primarily it is used to absorb moisture, and so prolong shelf life of the compound by keeping the powder's alkaline and acidic components dry so as not to react with each other prematurely. A dry powder also flows and mixes more easily. Finally, the added bulk allows for more accurate measurements.

Commonly used bases and acids

Baking powder is made of two main components: an acid and a bicarbonate base. When they are hydrated, an acid–base reaction occurs, releasing carbon dioxide. Commonly used acids and bases for baking powders are:

Bases

  • Sodium bicarbonate
  • Ammonium bicarbonate
  • Potassium bicarbonate

Acids

  • Dicalcium phosphate dihydrate (DCPD) 33 neutralizing value

The ROR of baking powders is impacted by many factors, including: The Oxford English Dictionary credits the first written use of the term "pearl ash" to 1703 and the writing of Abel Boyer.

By the mid-1700s, practical treatises on the calcination of pearlash were available in both England and the United States. Pearlash was the subject of the first patent in the United States, issued in April 1790. Its preparation was time-consuming, but could be accomplished with a cast-iron kettle: it involved soaking fireplace ashes in water to make lye, and then boiling the lye to remove water and obtain "salts".

Once prepared, the white powder was much more stable than yeast. Small amounts could be used on a daily basis, rather than baking a week or two weeks' worth of bread at one time. American Cookery was the first cookbook to call for its use, but by no means the last. With pearlash, cooks were able to create new recipes for new types of cakes, cookies, and biscuits that were quicker and easier to make than yeast-based recipes.

Experimentation

Between the publication of American Cookery in 1796, and the mid-1800s, cooks experimented with a variety of acids, alkalis, and mineral salts as possible chemical leaveners. Many were already available in households as medicinal, cleaning or solvent products. Smelling salts, hartshorn, and sal volatile were all ammonia inhalants, containing forms of ammonium carbonate. The term "saleratus" was applied confusingly to both potassium bicarbonate and to sodium bicarbonate (NaHCO<sub>3</sub>, what we now call baking soda). Because these acidulants react with baking soda quickly, retention of gas bubbles was dependent on batter viscosity. It was critical for the batter to be baked quickly, before the gas escaped. The next step, the development of baking powder, created a system where the gas-producing reactions could be delayed until needed.

Market history

thumb|right|Advertisement for DeLand & Co's Chemical Baking Powder. Earliest possible date: 1877; latest possible date: 1893

The creation of shelf-stable chemical combinations of sodium bicarbonate and cream of tartar is seen as marking the true introduction of baking powder. a baking powder, later, Alfred Bird's Baking Powder, reacted as soon as it became damp.

Bird focused on selling his baking powder to the British Army during the Crimean War,

Nonetheless, Bird's creation of baking powder enabled cooks to take recipes for cakes such as the patriotically named Victoria sponge and make them rise higher.

He did not patent his discovery, and others such as Henry Jones of Bristol soon produced and patented similar products. In 1845, Jones patented "A new preparation of flour" (self-raising flour) that included sodium bicarbonate and tartaric acid to obtain a leavening effect.

Eben Norton Horsford

thumb|right| The Rumford Cook Book, 1910, back cover

thumb|right|Prof. Horsford's Phosphatic Baking Powder,

In America, Eben Norton Horsford, a student of Justus von Liebig, set out to create a flour fortifier and leavening agent. In 1856, he was awarded a patent for "pulverulent phosphoric acid", a process for extracting monocalcium pyrophosphate extracted from bones. Horsford's use of monocalcium pyrophosphate eliminated the need for cream of tartar, which was expensively imported from France and required separate storage.

Combined with baking soda, monocalcium pyrophosphate provided a double-acting form of leavening. Its initial reaction, when exposed to water, released carbon dioxide and produced dicalcium phosphate, which then reacted under heat to release second-stage carbon dioxide.

In the 1860s, Horsford shared his formula for baking powder with his former teacher, Justus von Liebig, who in turn shared it with Ludwig Clamor Marquart and Carl Zimmer in Germany. Baking powders based on Horsford's formula were sold in England as "Horsford-Liebig Baking Powder". They were also sold by several companies in Germany, beginning with Marquart and with Zimmer. However, baking powder was not successful in Germany at that time. Much of German baking occurred in guild-based bakeries, rather than in private homes, and the guilds were not interested in replacing centuries-old craft skills with a new technology. Dr. Oetker Baking Powder continues to be sold, currently listing its ingredients as sodium acid pyrophosphate, sodium bicarbonate and corn starch.

Royal Baking Powder

In the U.S., in 1866, Joseph C. Hoagland and his brother Cornelius developed a baking powder product with the help of Thomas M. Biddle.

Initially in partnership as Biddle & Hoagland, the Hoaglands moved from Fort Wayne, Indiana, to Chicago, leaving Biddle behind, and then to New York. They incorporated there as the Royal Baking Powder Company in 1868. Various battles for control ensued between the Hoagland brothers and their one-time employee William Ziegler. Finally, on March 2, 1899, Ziegler established the New Jersey–based Royal Baking Powder Corporation which combined the three major cream of tartar baking powder companies then in existence in the United States: Dr. Price (Ziegler), Royal (Joseph Hoagland) and Cleveland (Cornelius Nevius Hoagland).

Alum-based baking powders

Cream of tartar was an expensive ingredient in the United States, since it had to be imported from France. In the 1880s, several companies developed double-action baking powders containing cheaper alternative acids known as alums, a class of compounds involving double sulfates of aluminium.

However, the actual composition of alum was not determined until 1798, when Louis Vauquelin demonstrated that common alum is a double salt, composed of sulfuric acid, alumina, and potash. and Jean-Antoine Chaptal published the analysis of four different kinds of alum.

In 1888, William Monroe Wright (a former salesman for Dr. Price) and George Campbell Rew in Chicago introduced a new form of baking powder, which they called Calumet. Calumet Baking Powder contained baking soda, a cornstarch desiccant,

The idea that aluminium in baking powder is dangerous can be traced to Ziegler's attack advertising, and has little if any scientific support. Aluminium is a commonly-found metal that appears in trace quantities in most foods.

By the 1970s Royal had ceased to produce a cream of tartar baking powder. For those who wanted something similar, James Beard suggested combining two parts cream of tartar to one part baking soda just before using it, since the mixture would not keep. It contained sodium acid pyrophosphate and cornstarch and was labeled as a leavening agent. It could be substituted for cream of tartar or mixed with baking soda to replace baking powder.

Smith also sold a baking powder replacement, in which sodium acid pyrophosphate was already mixed with bicarbonate of soda and cornstarch. Somewhat confusingly, it was marketed as "Bakewell Baking Powder" or "Bakewell Cream Baking Powder". Some packaging uses the phrase "The Original Bakewell Cream". A product labelled "Bakewell Cream" may be either the cream of tartar substitute or the baking powder substitute depending on whether it is additionally identified as "Double acting" "Baking Powder". A modern version containing acid sodium pyrophosphate, sodium bicarbonate and redried starch, is sold as being both aluminium-free and gluten-free.

Original preparations

thumb|right|Baking powder with sodium acid pyrophosphate, New Zealand, 1950s

Over time, most baking powder manufacturers have experimented with their products, combining or even replacing what were once key ingredients. Information in the following table reflects the original ingredients as introduced by different individuals and companies. The ingredients used may be very different from later formulations and current products. Where an ingredient had multiple names, they are all listed together in the first occurrence, and the most common name listed thereafter. (Davis baking powder is commonly found in the northeastern United States.)

How much to use

thumb|125px|Effective baking powder foams when placed in hot water.

Generally, one teaspoon (5 g or 1/6 oz) of baking powder is used to raise a mixture of one cup (120&nbsp;g or 4oz) of flour, one cup of liquid, and one egg.

On a sachet of Dr. Oetker's baking powder it is written that it contains 15 grams and is for use with 500 grams flour .

However, if the mixture is acidic, baking powder's additional acids remain unconsumed in the chemical reaction and often lend an unpleasant taste to food. High acidity can be caused by ingredients such as buttermilk, lemon juice, yogurt, citrus, or honey. When excessive acid is present, some of the baking powder should be replaced with baking soda. For example, one cup of flour, one egg, and one cup of buttermilk requires only teaspoon of baking powder—the remaining leavening is caused by buttermilk acids reacting with teaspoon of baking soda.

However, with baking powders that contain sodium acid pyrophosphate, excess alkaline substances can sometimes deprotonate the acid in two steps instead of the one that normally occurs, resulting in an offensive bitter taste to baked goods. Calcium compounds and aluminium compounds do not have that problem, though, since calcium compounds that deprotonate twice are insoluble and aluminium compounds do not deprotonate in that fashion.

Expiration data

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 bubbles vigorously, it is still active and usable.

Comparisons

Different brands of baking powder can perform quite differently in the oven. Early baking powder companies published their own cookbooks, to promote their new products, to educate cooks about exactly how and when to use them, and because cooks could not easily adapt recipes that were developed using different types of baking powder. Baking powders using cream-of-tartar, phosphates, or alums could behave very differently, and required different amounts for a desired rising effect.

Substituting in recipes

Substitute acids

As described above, baking powder is mainly just baking soda mixed with an acid. In principle, a number of kitchen acids may be combined with baking soda to simulate commercial baking powders. 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. The main variable with the use of these kitchen acids is the rate of leavening.

See also

  • Bakewell Cream
  • Calumet Baking Powder Company
  • Clabber Girl, also owns the Rumford, Davis, Hearth Club and Royal brands
  • Dr. Oetker
  • Irish soda bread

References

  • Cook's Thesaurus: Leavens Descriptions of various chemical leavening agents and substitutions.
  • Baking Powder Contains list of aluminium-free baking powders available in the US.