Baking powder is a dry chemical leavening agent

Leavening agent

A leavening agent is any one of a number of substances used in doughs and batters that cause a foaming action which lightens and softens the finished product...

 used to increase the volume and lighten the texture of baked goods such as muffin

Muffin

A muffin is an American English name for a type of quick bread that is baked in small portions. Many forms are somewhat like small cakes or cupcakes in shape, although they usually are not as sweet as cupcakes and generally lack frosting. Savory varieties, such as cornbread muffins, also exist...

s, cake

Cake

Cake is a form of bread or bread-like food. In its modern forms, it is typically a sweet and enriched baked dessert. In its oldest forms, cakes were normally fried breads or cheesecakes, and normally had a disk shape...

s, scones

Scone (bread)

The scone is a small Scottish quick bread especially popular in the United Kingdom, the United States, Canada, Australia, New Zealand,Belgium and Ireland, but are also eaten in many other countries. They are usually made of wheat, barley or oatmeal, with baking powder as a leavening agent...

 and American-style biscuits

Biscuit (bread)

A biscuit in the United States, and widely used in popular American English, is a small bread made with baking powder or baking soda as a chemical leavening agent rather than yeast....

. Baking powder works by releasing carbon dioxide

Carbon dioxide

Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 gas into a batter or dough through an acid-base reaction, causing bubbles in the wet mixture to expand and thus leavening

Leavening agent

A leavening agent is any one of a number of substances used in doughs and batters that cause a foaming action which lightens and softens the finished product...

 the mixture. It is used instead of yeast

Yeast

Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...

 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 bread

Quick bread

Quick bread is an American term used to denote a type of bread which is leavened with leavening agents other than yeast. Quick breads includes many cakes, brownies and cookies, as well as banana bread, beer bread, cornbread, biscuits, muffins, pancakes, scones, and soda bread.-History::"Quick...

s.

Most commercially-available baking powders are made up of an alkaline component (typically sodium bicarbonate

Sodium bicarbonate

Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . The natural mineral form is...

, also known as baking soda), one or more acid salt

Acid salt

Acid salt is a somewhat obscure term for a class of salts formed by the partial neutralization of diprotic or polyprotic acids. Because the parent acid is only partially neutralized, one or more replaceable hydrogen atoms remain. Typical acid salts have one or more alkali metal ions as well as one...

s, and an inert starch (cornstarch

Cornstarch

Corn starch, cornstarch, cornflour or maize starch is the starch of the corn grain obtained from the endosperm of the corn kernel.-History:...

 in most cases, though potato starch

Potato starch

Potato starch is starch extracted from potatoes. The cells of the root tubers of the potato plant contain starch grains . To extract the starch, the potatoes are crushed; the starch grains are released from the destroyed cells...

 may also be used). Baking soda is the source of the carbon dioxide, and the acid-base reaction can be generically represented as

NaHCO₃ + H⁺ → 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. Double-acting baking powders work in two phases; once when cold, and once when hot. Common low-temperature acid salts include cream of tartar and monocalcium phosphate

Monocalcium phosphate

Monocalcium phosphate is a chemical compound with the formula Ca2. It is commonly found as the monohydrate, Ca2·H2O.-Fertilizer:Phosphorus is an essential nutrient and therefore is a common component of agricultural fertilizers...

 (also called calcium acid phosphate). High-temperature acid salts include sodium aluminum sulfate, sodium aluminum phosphate, and sodium acid pyrophosphate.

History

Early chemical leavening was accomplished by activating baking soda in the presence of liquid(s) and an acid such as sour milk, vinegar

Vinegar

Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...

, 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

Alfred Bird

Alfred Bird was a British food manufacturer and chemist. He was born in Nympsfield, Gloucestershire, England in 1811 was the inventor of a series of food products mostly now taken for granted...

 in 1843. August Oetker

August Oetker

Dr. August Oetker was born in Obernkirchen, Germany and died in Bielefeld, Germany. He invented baking powder, although Alfred Bird of England is also credited with inventing baking powder in 1843...

, a German pharmacist, made baking powder very popular when he began selling his mixture to housewives. The 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

Eben Norton Horsford

Eben Norton Horsford was an American scientist who is best known for his reformulation of baking powder, his interest in Viking settlements in America, and the monuments he built to Leif Erikson.-Life and work:...

, a student of Justus von Liebig

Justus von Liebig

Justus von Liebig was a German chemist who made major contributions to agricultural and biological chemistry, and worked on the organization of organic chemistry. As a professor, he devised the modern laboratory-oriented teaching method, and for such innovations, he is regarded as one of the...

, 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 cream of tartar or baking powder due to war food shortages. Under the name "Bakewell", Smith marketed a mixture of sodium pyrophosphate mixed with corn starch to replace the acid cream of tartar component of baking powder. When mixed with baking soda, the product behaved like a single-acting baking powder, the only difference being that the acid is sodium pyrophosphate. He named the product "Bakewell" and the product is still part of regional culinary history.

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."

Use

Generally (in countries where the cup

Cup (unit)

The cup is a customary unit of measurement for volume, used in cooking to measure liquids and bulk foods such as granulated sugar...

 is used as a standard measure in cookery) one teaspoon

Teaspoon

A teaspoon, an item of cutlery, is a small spoon, commonly part of a silverware place setting, suitable for stirring and sipping the contents of a cup of tea or coffee...

 (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

Buttermilk

Buttermilk refers to a number of dairy drinks. Originally, buttermilk was the liquid left behind after churning butter out of cream. It also refers to a range of fermented milk drinks, common in warm climates where unrefrigerated fresh milk otherwise sours quickly...

, lemon

Lemon juice

The lemon fruit, from a citrus plant, provides a useful liquid when squeezed. Lemon juice, either in natural strength or concentrated, is sold as a bottled product, usually with the addition of preservatives and a small amount of lemon oil.-Uses:...

, yoghurt

Yoghurt

Yoghurt, yogurt or yogourt is a dairy product produced by bacterial fermentation of milk. The bacteria used to make yoghurt are known as "yoghurt cultures"...

, citrus

Citrus

Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...

, or honey

Honey

Honey is a sweet food made by bees using nectar from flowers. The variety produced by honey bees is the one most commonly referred to and is the type of honey collected by beekeepers and consumed by humans...

. 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 ½ teaspoon of baking powder—the remaining leavening is caused by buttermilk acids reacting with ¼ teaspoon of baking soda.

The opposite is sometimes true, too. In baking powders that contain sodium acid pyrophosphate, excess alkaline substances can sometimes deprotonate

Deprotonation

Deprotonation is the removal of a proton from a molecule, forming the conjugate base.The relative ability of a molecule to give up a proton is measured by its pKa value. A low pKa value indicates that the compound is acidic and will easily give up its proton to a base...

 the acid in two steps instead of the one that normally occurs, resulting in an offensive bitter taste to baked goods. Calcium compounds and aluminum compounds do not have that problem though, since calcium compounds that deprotonate twice are insoluble and aluminum compounds do not deprotonate in that fashion.

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.

Substituting in recipes

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

Vinegar

Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...

 (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

Buttermilk

Buttermilk refers to a number of dairy drinks. Originally, buttermilk was the liquid left behind after churning butter out of cream. It also refers to a range of fermented milk drinks, common in warm climates where unrefrigerated fresh milk otherwise sours quickly...

 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 times past, 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.

Usage of aluminum compounds

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 possible negative long term health effects such as bone degeneration and Alzheimer's disease

Alzheimer's disease

Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...

 (see Aluminum).

External links

• How Products Are Made: Baking Powder Background, history, and production
• Cook's Thesaurus: Leavens Descriptions of various chemical leavening agents and substitutions.
• Baking Powder Contains list of aluminum-free baking powders available in the US.