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In cooking, a leavening agent (/ˈlɛvənɪŋ/) or raising agent, also called a leaven (/ˈlɛvən/) or leavener, is any one of a number of substances used in doughs 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 compounds. The gas produced is often carbon dioxide, or occasionally hydrogen.

When a dough or batter is mixed, the starch in the flour and the water in the dough form a matrix (often supported further by proteins like gluten or polysaccharides, such as pentosans or xanthan gum). The starch then gelatinizes and sets, leaving gas bubbles that remain.

Biological leavening agents

• Saccharomyces cerevisiae producing carbon dioxide found in:
  • baker's yeast
  • Beer barm (unpasteurised—live yeast)
  • ginger beer
  • kefir
  • sourdough starter
• Clostridium perfringens producing hydrogen 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 of bicarbonate (HCO₃). After they act, these compounds leave behind a chemical salt. Chemical leavens are used in quick breads and cakes, as well as cookies and numerous other applications where a long biological fermentation 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 phosphates (Ca(H₂PO₄)₂). Other leavening agents developed include sodium aluminium sulfate (NaAl(SO₄)₂·12H₂O), disodium pyrophosphate (Na₂H₂P₂O₇), and sodium aluminium phosphates (NaH₁₄Al₃(PO₄)₈·4H₂O and Na₃H₁₅Al₂(PO₄)₈). These compounds combine with sodium bicarbonate to give carbon dioxide in a predictable manner.

Other leavens

Steam 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 products having one large cavity, such as popovers, Yorkshire puddings, pita, and most preparations made from choux pastry. The effect is also seen to a lesser extent in tempura.

Mechanical leavening

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Using a whisk on certain liquids, notably cream or egg whites, 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
• Parable of the Leaven
• Passover
• Unleavened bread

References

1. Jacobs, Morris Boris (1951). The Chemistry and Technology of Food and Food Products. Hoboken, NJ: Interscience Publishers. p. 1932.
2. Hanft, Steven L. (2016). Fachenglisch für Laborberufe. Weinheim: John Wiley & Sons. p. 208. ISBN 978-3-527-33512-1.
3. Simmons, Amelia; Mary Tolford Wilson (1984) . The First American Cookbook (1984 reprint ed.). Mineola, NY: Dover. ISBN 0-486-24710-4.
4. Smith, Andrew F. (2007-05-01). The Oxford Companion to American Food and Drink. Oxford University Press. ISBN 978-0-19-988576-3.
5. John Brodie, John Godber "Bakery Processes, Chemical Leavening Agents" in Kirk-Othmer Encyclopedia of Chemical Technology 2001, John Wiley & Sons. doi:10.1002/0471238961.0308051303082114.a01.pub2
6. Ensminger, Marion Eugene; Ensminger, Audrey H. (1993). Foods & Nutrition Encyclopedia, Two Volume Set. Boca Raton, FL: CRC Press. p. 249. ISBN 0-8493-8980-1.

Further reading

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

External links

• Wikibooks Cookbook has a recipe/module on Leavening agent

v t e Bread
Types	Brown bread Bun Flatbread Multigrain Quick Rye bread Salt-rising Sandwich bread Soda bread Sourdough Sprouted Unleavened White bread Whole wheat
Ingredients	Baker's yeast Barm Calcium propanoate Dough conditioner Eggs Fat Flour Leavening agent Milk Salt Sugar Water
Equipment	Oven Bread machine Bread pan Dough scraper Farinograph Lame Peel Stand mixer Warmer Toaster Weighing scales
Processes and techniques	Autolysis Baking Biga Chorleywood bread process Kneading Leavening Maillard reaction No-knead bread Proofing Pre-ferment Pre-slicing Sponge and dough Steaming Straight dough Vienna process
Uses	Breadcrumbs Bread bowl Bread pakora Bread pudding Croutons French toast Rusks Stuffing Sandwiches Toast
Other	Bakery Breadmaking Baker percentage Bread and salt Bread in Europe Bread clip History of bread
List articles	American breads Brand name breads Bread dishes Bread rolls British breads Buns French breads Indian breads Pakistani breads Quick breads Sourdough breads Sweet breads Swiss breads Toast dishes
Category

• Leavening agents
• Fermentation in food processing