cooking Cooking, cookery, or culinary arts is the art, science and craft of using heat to prepare food for consumption. Cooking techniques and ingredients vary widely, from grilling food over an open fire to using electric stoves, to baking in vario ...

, a leavening agent () or raising agent, also called a leaven () or leavener, is any one of a number of substances used in

dough Dough is a thick, malleable, sometimes elastic paste made from grains or from leguminous or chestnut crops. Dough is typically made by mixing flour with a small amount of water or other liquid and sometimes includes yeast or other leavenin ...

s and batters that cause a foaming action (gas bubbles) that lightens and softens the mixture. An alternative or supplement to leavening agents is mechanical action by which air is incorporated (i.e. kneading). Leavening agents can be biological or synthetic

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

s. The gas produced is often

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

, or occasionally

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...

. When a dough or batter is mixed, the

starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human die ...

in the flour and the water in the dough form a

matrix Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** '' The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchi ...

(often supported further by

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

s like

gluten Gluten is a structural protein naturally found in certain cereal grains. Although "gluten" often only refers to wheat proteins, in medical literature it refers to the combination of prolamin and glutelin proteins naturally occurring in all grai ...

or polysaccharides, such as

pentosan Pentosans are polymers composed of pentoses. In contrast to cellulose, which is composed of hexose (glucose) monomers, pentosans are derived from five-carbon sugars such as xylose. Pentosan-rich biomass is the precursor to furfural. The pentosan c ...

s or xanthan gum). The starch then gelatinizes and sets, leaving gas bubbles that remain.

Biological leavening agents

* ''

Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have b ...

'' producing

found in: ** baker's yeast **

Beer barm Barm is the foam or scum formed on the top of a fermenting liquid, such as beer, wine, or feedstock for spirits or industrial ethanol distillation. It is used to leaven bread, or set up fermentation in a new batch of liquor. Barm, as a leaven ...

(unpasteurised—live yeast) ** ginger beer **

kefir Kefir ( ; also spelled as kephir or kefier; ; ; ) is a fermented milk drink similar to a thin yogurt or ayran that is made from kefir grains, a specific type of mesophilic symbiotic culture. The drink originated in the North Caucasus, in p ...

sourdough starter Sourdough or sourdough bread is a bread made by the fermentation of dough using wild lactobacillaceae and yeast. Lactic acid from fermentation imparts a sour taste and improves keeping qualities. History In the ''Encyclopedia of Food Microbiolo ...

* '' Clostridium perfringens'' producing

found in salt-rising bread

Chemical leavening agents

Chemical leavens are mixtures or compounds that release gases when they react with each other, with moisture, or with heat. Most are based on a combination of acid (usually a low molecular weight organic acid) and a

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

bicarbonate In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula . Bicarbonate serves a crucial biochemi ...

. After they act, these compounds leave behind a chemical salt. Chemical leavens are used in quick breads and

cake Cake is a flour confection made from flour, sugar, and other ingredients, and is usually baked. In their oldest forms, cakes were modifications of bread, but cakes now cover a wide range of preparations that can be simple or elaborate ...

s, as well as

cookie A cookie is a baked or cooked snack or dessert that is typically small, flat and sweet. It usually contains flour, sugar, egg, and some type of oil, fat, or butter. It may include other ingredients such as raisins, oats, chocolate chips, nu ...

s and numerous other applications where a long biological

fermentation Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food p ...

is impractical or undesirable.

History

Chemical leavening using pearl ash as a leavening agent was mentioned by

Amelia Simmons Amelia Simmons is an American writer noted for publishing the '' American Cookery''. This cookbook is considered an important text that provided insights into the language and culinary practices of former colonists, helping shape American identit ...

in her ''

American Cookery ''American Cookery'', by Amelia Simmons, is the first known cookbook written by an American, published in Hartford, Connecticut, in 1796. Until then, the cookbooks printed and used in the Thirteen Colonies were British. Its full title is: ''Am ...

'', published in 1796. Since chemical expertise is required to create a functional chemical leaven without producing off-flavors from the chemical precursors involved, such substances are often mixed into premeasured combinations for maximum results. These are generally referred to as

baking powder 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 buffer such as cornstarch. Baking powder is used to increas ...

s. Sour milk and carbonates were used in the 1800s. The breakthrough in chemical leavening agents occurred in the 1930s with the introduction of monocalcium phosphates . Other leavening agents developed include

sodium aluminium sulfate Sodium aluminium sulfate is the inorganic compound with the chemical formula NaAl(SO4)2·12H2O (sometimes written Na2SO4·Al2(SO4)3·24H2O). Also known as soda alum, sodium alum, or SAS, this white solid is used in the manufacture of baking pow ...

, disodium pyrophosphate , and sodium aluminium phosphates . These compounds combine with sodium bicarbonate to give

in a predictable manner.

Other leavens

Steam Steam is a substance containing water in the gas phase, and sometimes also an aerosol of liquid water droplets, or air. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporizatio ...

and air are used as leavening agents when they expand upon heating. To take advantage of this style of leavening, the baking must be done at high enough temperatures to flash the water to steam, with a batter that is capable of holding the steam in until set. This effect is typically used in

popover A popover is a light roll made from an egg batter similar to that of Yorkshire pudding, typically baked in muffin tins or dedicated popover pans, which have straight-walled sides rather than angled. Popovers may be served either as a sweet, t ...

Yorkshire pudding Yorkshire pudding is a baked pudding made from a batter of eggs, flour, and milk or water. A common British side dish, it is a versatile food that can be served in numerous ways depending on its ingredients, size, and the accompanying compon ...

s, and to a lesser extent in

tempura is a typical Japanese dish usually consisting of seafood, meat and vegetables that have been battered and deep fried. The dish was introduced by the Portuguese in Nagasaki through fritter-cooking techniques in the 16th century. The word ...

Mechanical leavening

Creaming is the process of beating sugar crystals and solid fat (typically

butter Butter is a dairy product made from the fat and protein components of churned cream. It is a semi-solid emulsion at room temperature, consisting of approximately 80% butterfat. It is used at room temperature as a spread, melted as a condim ...

) together in a

mixer Mixer may refer to: Electronics * DJ mixer, a type of audio mixing console used by disc jockeys * Electronic mixer, electrical circuit for adding signal voltages * Frequency mixer, electrical circuit that creates new frequencies from two signals ...

. This integrates tiny air bubbles into the mixture, since the sugar crystals physically cut through the structure of the fat. Creamed mixtures are usually further leavened by a chemical leaven like baking soda. This is often used in

cookies A cookie is a baked or cooked snack or dessert that is typically small, flat and sweet. It usually contains flour, sugar, egg, and some type of oil, fat, or butter. It may include other ingredients such as raisins, oats, chocolate chi ...

. Using a whisk on certain liquids, notably

cream Cream is a dairy product composed of the higher-fat layer skimmed from the top of milk before homogenization. In un-homogenized milk, the fat, which is less dense, eventually rises to the top. In the industrial production of cream, this process ...

egg white Egg white is the clear liquid (also called the albumen or the glair/glaire) contained within an egg. In chickens it is formed from the layers of secretions of the anterior section of the hen's oviduct during the passage of the egg. It forms ar ...

s, can also create foams through mechanical action. This is the method employed in the making of sponge cakes, where an egg protein matrix produced by vigorous whipping provides almost all the structure of the finished product. The Chorleywood bread process uses a mix of biological and mechanical leavening to produce bread; while it is considered by food processors to be an effective way to deal with the soft wheat flours characteristic of British Isles agriculture, it is controversial due to a perceived lack of quality in the final product. The process has nevertheless been adapted by industrial bakers in other parts of the world.

References

External links

Wikibooks Wikibooks (previously called ''Wikimedia Free Textbook Project'' and ''Wikimedia-Textbooks'') is a wiki-based Wikimedia project hosted by the Wikimedia Foundation for the creation of free content digital textbooks and annotated texts that any ...

Cookbook A cookbook or cookery book is a kitchen reference containing recipes. Cookbooks may be general, or may specialize in a particular cuisine or category of food. Recipes in cookbooks are organized in various ways: by course (appetizer, first cour ...

has a recipe/module on '' Leavening agent'' {{DEFAULTSORT:Leavening Agent Fermentation in food processing