Leavening agent
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In
cooking Cooking, also known as cookery or professionally as the culinary arts, is the art, science and craft of using heat to make food more palatable, digestible, nutritious, or Food safety, safe. Cooking techniques and ingredients vary widely, from ...
, 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 malleable, sometimes elastic paste made from flour (which itself is 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 ...
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 In cooking (and more specifically baking), kneading is a process in the making of bread or dough, used to mix the ingredients and add strength to the final product. It allows the process of baking to be shortened by developing the gluten more qu ...
). 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 is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
, or occasionally
hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
. 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 diet ...
in the flour and the water in the dough form a
matrix Matrix (: matrices or matrixes) or MATRIX may refer to: Science and mathematics * Matrix (mathematics), a rectangular array of numbers, symbols or expressions * Matrix (logic), part of a formula in prenex normal form * Matrix (biology), the m ...
(often supported further by
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
s like
gluten Gluten is a structural protein naturally found in certain Cereal, cereal grains. The term ''gluten'' usually refers to the elastic network of a wheat grain's proteins, gliadin and glutenin primarily, that forms readily with the addition of water ...
or
polysaccharides Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wat ...
, such as pentosans 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 fungal microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have be ...
'' producing
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
found in: ** baker's yeast ** Beer barm (unpasteurised—live yeast) ** ginger beer **
kefir Kefir ( ; alternative spellings: kephir or kefier; ; ; ) is a Fermented milk products, fermented milk drink similar to a thin yogurt or ayran that is made from kefir grains, a specific type of mesophilic SCOBY, symbiotic culture. It is prep ...
** sourdough starter * '' Clostridium perfringens'' producing
hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
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 In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...
of
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 bioche ...
. After they act, these compounds leave behind a chemical salt. Chemical leavens are used in
quick bread Quick bread is any bread leavened with a chemical leavening agent rather than a biological one like Baker's yeast, yeast or Sourdough#Starter, sourdough starter. An advantage of quick breads is their ability to be prepared quickly and reliably, w ...
s and
cake Cake is a flour confection usually 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 elabor ...
s, as well as cookies and numerous other applications where a long biological
fermentation Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduce ...
is impractical or undesirable.


History

Chemical leavening using pearl ash as a leavening agent was mentioned by Amelia Simmons in her '' American Cookery'', 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 powders. Sour milk and carbonates were used in the 1800s. The breakthrough in chemical leavening agents occurred in the 1930s with the introduction of
monocalcium phosphate Monocalcium phosphate is an inorganic compound with the chemical formula Ca(H2PO4)2 ("AMCP" or "CMP-A" for anhydrous monocalcium phosphate). It is commonly found as the monohydrate ("MCP" or "MCP-M"), Ca(H2PO4)2·H2O. Both salts are colourless so ...
s . Other leavening agents developed include sodium aluminium sulfate , disodium pyrophosphate , and sodium aluminium phosphates . These compounds combine with sodium bicarbonate to give
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
in a predictable manner.


Other leavens

Steam Steam is water vapor, often mixed with air or an aerosol of liquid water droplets. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization. Saturated or superheated steam is inv ...
and
air An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
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 products having one large cavity, such as popovers, Yorkshire puddings, pita, and most preparations made from
choux pastry Choux pastry, or (), is a delicate pastry dough used in many pastries. The essential ingredients are butter, water, flour and eggs. Instead of a raising agent, choux pastry employs its high moisture content to create steam, as the water in ...
. The effect is also seen to a lesser extent in tempura.


Mechanical leavening

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 proces ...
or
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 a ...
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.


See also

* Aerated Bread Company, bakeries started in 1862 in the UK that made carbon dioxide leavened bread * Baking powder *
Chametz ''Chametz'' (also ''chometz'', ', ''ḥameṣ'', ''ḥameç'' and other spellings Transliteration, transliterated from ; ) are foods with leavening agents that are forbidden to Jews on the holiday of Passover. ''Chametz'' is a product that is b ...
* Parable of the Leaven *
Passover Passover, also called Pesach (; ), is a major Jewish holidays, Jewish holiday and one of the Three Pilgrimage Festivals. It celebrates the Exodus of the Israelites from slavery in Biblical Egypt, Egypt. According to the Book of Exodus, God in ...
* Unleavened bread


References


Further reading

* Matz, S (1972). "Bakery Technology and Engineering", AVI Publishing Co.


External links

* Wikibooks
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 (food), course (appetize ...
has a recipe/module on '' Leavening agent'' {{DEFAULTSORT:Leavening Agent Fermentation in food processing